linsky

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Author name code: linsky
ADS astronomy entries on 2022-09-14
author:"Linsky, Jeffrey L."

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Title: Inhomogeneity within Local Interstellar Clouds
Authors: Linsky, Jeffrey L.; Redfield, Seth; Ryder, Diana;
Chasan-Taber, Adina
2022AJ....164..106L Altcode: 2022arXiv220402428L
Analysis of interstellar absorption lines observed in high-resolution
Hubble Space Telescope spectra of nearby stars provides temperatures,
turbulent velocities, and kinetic properties of warm interstellar
clouds. A new analysis of 97 interstellar-velocity components reveals
a wide range of temperatures and turbulent velocities within the
Local Interstellar Cloud (LIC) and the nearby Cluster of Interstellar
Clouds (CLIC). These variations appear to be random with Gaussian
distributions. We find no trends of these properties with stellar
distance or angles from the Galactic Center, magnetic field, the
main source of extreme-UV radiation (the star ϵ CMa), the center of
the LIC, or the direction of inflowing interstellar matter into the
heliosphere. The spatial scale for temperature variations in the LIC is
likely smaller than 5100 au, a distance that the Sun will traverse in
1000 yr. Essentially all velocity components align with known warm
clouds. We find that within 4 pc of the Sun, space is completely
filled with partially ionized clouds, but at larger distances space
is only partially filled with partially ionized clouds. We find that
the neutral hydrogen number density in the LIC and likely other warm
clouds in the CLIC is about 0.10 cm-3 rather than the 0.20
cm-3 density that may be representative of only the immediate
environment of the LIC. The ≤3000-12,000 K temperature range for the
gas is wider than the predictions of thermal equilibrium theoretical
models of the warm neutral medium and warm ionized medium, and the
high degree of inhomogeneity within clouds argues against simple
theoretical models. *All of the data presented in this paper were
obtained from the Mikulski Archive for Space Telescopes (MAST) at the
Space Telescope Science Institute. The specific observations analyzed
can be accessed via https://doi.org/10.17909/gabn-m136. STScI is
operated by the Association of Universities for Research in Astronomy,
Inc., under NASA contract NAS5-26555. Support to MAST for these data
is provided by the NASA office of Space Science via grant No. NAG5-7584
and by other grants and contracts.

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Title: To Boldly Go, Where No One Has Gone Before: Overview of the
Science Discoveries Enabled by an Interstellar Probe in the 2030's
Authors: Brandt, Pontus; Roelof, Edmond; Kurth, William; Provornikova,
Elena; Opher, Merav; McNutt, Ralph; Galli, Andre; Hill, Matthew; Wurz,
Peter; Bale, Stuart; Lisse, Carey; Kollmann, Peter; Demajistre, Robert;
Zemcov, Michael; Mandt, Kathleen; Rymer, Abi; Beichman, Charles;
Linsky, Jeffrey; Runyon, Kirby; Mostafavi, Parisa; Redfield, Seth;
Turner, Drew
2022cosp...44.3194B Altcode:
For the past 60, 000 years our Sun and its protective heliosphere
have been plowing through the Local Interstellar Cloud (LIC), but is
now in a historic transition region towards the G-cloud that could
have dramatic consequences for the global heliospheric structure. An
Interstellar Probe mission to the Very Local Interstellar Medium (VLISM)
would bring new scientific discoveries of the mechanisms upholding our
vast heliosphere and directly sample the Local Interstellar Clouds to
allow us, not only to understand the current dynamics and shielding,
but also how the heliosphere responded in the past and how it will
respond in the new interstellar environment. An international team
of scientists and experts have now completed a NASA-funded study led
by The Johns Hopkins University Applied Physics Laboratory (APL) to
develop pragmatic example mission concepts for an Interstellar Probe
with a nominal design lifetime of 50 years. The team has analyzed dozens
of launch configurations and demonstrated that asymptotic speeds in
excess of 7.5 Astronomical Units (AU) per year can be achieved using
existing or near-term propulsion stages with a powered or passive
Jupiter Gravity Assist (JGA). These speeds are more than twice that
of the fastest escaping man-made spacecraft to date, which is Voyager
1 currently at 3.59 AU/year. An Interstellar Probe would therefore
reach the Termination Shock (TS) in less than 12 years and cross
the Heliopause into the VLISM after about 16 years from launch. In
this presentation we provide an overview of the study, the science
mission concept, discuss the compelling discoveries that await, and
the associated example science payload, measurements and operations
ensuring a historic data return that would push the boundaries of
space exploration by going where no one has gone before.

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Title: The Cross-Divisional Pathfinder: New Horizons in the Second
Extended Mission
Authors: Brandt, Pontus; Spencer, John; Provornikova, Elena; McNutt,
Ralph; Hill, Matthew; Weaver, Harold; Gladstone, Randy; Bagenal,
Fran; Poppe, Andrew; Kollmann, Peter; Horanyi, Mihaly; Singer, Kelsi;
Elliott, Heather; Stern, Alan; McComas, David; Linsky, Jeffrey;
Redfield, Seth
2022cosp...44.1305B Altcode:
This presentation provides an overview of the science opportunities and
observations that await in New Horizons' second Kuiper Belt extended
mission (KEM2) with an emphasis on the growing helio- and astrophysics
opportunities. Examples are given that illustrate how New Horizons'
continued exploration of the outer Kuiper Belt, the outer heliosphere,
the interstellar medium (ISM) and cosmos, inevitably goes beyond the
stove pipes of disciplines, simultaneously benefitting three of the NASA
divisions. Our solar system has evolved through accretion of dust and
gas as the Sun and its protective magnetic bubble - "the heliosphere" -
have plowed through the ISM on its journey through the galaxy. Over the
course of twenty revolutions around the galactic core the dramatically
different ISM properties and nearby supernovae have resulted in a
severely compressed heliosphere leading to periods of full exposures
of interstellar gas, plasma, dust and galactic cosmic rays (GCRs) that
all have contributed to the evolution of our habitable system. After
the paradigm-shifting discoveries at Pluto and Arrokoth, New Horizons
will now traverse a heliocentric distance from 54 to 63 astronomical
units (au) during KEM2. Here, well beyond the densest region of the
KB, New Horizons will be breaking new ground in understanding the
formation of our solar system by observing multiple "hot" KB and
scattered disk objects and dwarf planets that are different than the
cold classical KBOs observed previously, not only revealing their
shape and rotational states, but also their surface microphysical
properties, and possible small satellites. Entering the outer edge
of the Sun's enormous dust disk, the Student Dust Counter (SDC) will
continue to provide the only in-situ constraints on the large-scale
structure of the dust disk, and the dust measurements during KEM2
will be critical to differentiate between leading theories of dust
production. New Horizons is now also entering an important region of
the outer heliosphere, where the processes responsible for upholding
its boundary are becoming more pronounced. The Solar Wind Around Pluto
(SWAP) and Pluto Energetic Particle Spectrometer Science Investigation
(PEPSSI) instruments measure, for the first time, interstellar proton
and He$^+$ PUIs in the outer heliosphere and how these interact with the
solar wind to later become the dominant pressure in the heliospheric
boundary region. GCRs that penetrate the magnetic boundary of the
heliosphere scatter strongly in the wavy structure of the "ballerina
skirt" of the solar magnetic field and presents an opportunity to
understand this strong modulation as part of the heliospheric GCR
shielding. As New Horizons continues to travel outward, opportunities
emerge to measure dust grains of interstellar origin to shed light on
how they interact with the heliosphere. Recent modeling of the ISD
interaction reveals a far more complicated picture, where not only
solar radiation pressure and interactions at the magnetic heliospheric
boundary are important, but also where the solar magnetic polarity
appears to play a decisive role. Now beyond the infrared and UV haze
of the circumsolar dust and hydrogen gas, New Horizons is also in a
unique position to make remote observations using Alice and the Long
Range Reconnaissance Imager (LORRI) of heliospheric and astrophysical
features beyond the heliopause.

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Title: Intrinsic Lyman alpha Profiles of High-Velocity G, K, and
M Dwarfs
Authors: Youngblood, Allison; Pineda, J. Sebastian; Ayres, Thomas;
France, Kevin; Linsky, Jeffrey; Wood, Brian; Redfield, Seth; Schlieder,
Joshua
2022AAS...24011801Y Altcode:
Observations of H I Lyman alpha, the brightest UV emission line of
late-type stars, are critical for understanding stellar chromospheres
and transition regions, modeling photochemistry in exoplanet
atmospheres, and measuring the abundances of neutral hydrogen and
deuterium in the interstellar medium. Yet, Lyman alpha observations are
notoriously challenging due to severe attenuation from interstellar gas,
hindering our understanding of this important emission line's basic
morphology. We present high-resolution far- and near-UV spectroscopy
of five G, K, and M dwarfs with radial velocities large enough to
Doppler shift the stellar Lyman alpha emission line away from much of
the interstellar attenuation, allowing the line core to be directly
observed. We detect self-reversal in the Lyman alpha emission line core
for all targets, and we show that the self-reversal depth decreases with
increasing surface gravity. Mg II self-reversed emission line profiles
provide some useful information to constrain the Lyman alpha line core,
but the differences are significant enough that Mg II cannot be used
directly as an intrinsic Lyman alpha template during reconstructions. We
show that reconstructions that neglect self-reversal could overestimate
intrinsic Lyman alpha fluxes by 60-100% for G and K dwarfs and 40-170%
for M dwarfs.

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Title: Astrospheres of Planet-Hosting Cool Stars and Beyond ⋅ When
Modeling Meets Observations
Authors: Herbst, Konstantin; Baalmann, Lennart R.; Bykov, Andrei;
Engelbrecht, N. Eugene; Ferreira, Stefan E. S.; Izmodenov, Vladislav
V.; Korolkov, Sergey D.; Levenfish, Ksenia P.; Linsky, Jeffrey L.;
Meyer, Dominique M. -A.; Scherer, Klaus; Strauss, R. Du Toit
2022SSRv..218...29H Altcode:
Thanks to dedicated long-term missions like Voyager and GOES over the
past 50 years, much insight has been gained on the activity of our
Sun, the solar wind, its interaction with the interstellar medium,
and, thus, about the formation, the evolution, and the structure of
the heliosphere. Additionally, with the help of multi-wavelength
observations by the Hubble Space Telescope, Kepler, and TESS,
we not only were able to detect a variety of extrasolar planets
and exomoons but also to study the characteristics of their host
stars, and thus became aware that other stars drive bow shocks and
astrospheres. Although features like, e.g., stellar winds, could
not be measured directly, over the past years several techniques
have been developed allowing us to indirectly derive properties like
stellar mass-loss rates and stellar wind speeds, information that can
be used as direct input to existing astrospheric modeling codes. In
this review, the astrospheric modeling efforts of various stars will be
presented. Starting with the heliosphere as a benchmark of astrospheric
studies, investigating the paleo-heliospheric changes and the Balmer
Hα projections to 1 pc, we investigate the surroundings of cool and
hot stars, but also of more exotic objects like neutron stars. While
pulsar wind nebulae (PWNs) might be a source of high-energy galactic
cosmic rays (GCRs), the astrospheric environments of cool and hot
stars form a natural shield against GCRs. Their modulation within
these astrospheres, and the possible impact of turbulence, are also
addressed. This review shows that all of the presented modeling efforts
are in excellent agreement with currently available observations.

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Title: The Early History of Heliospheric Science and the Spacecraft
That Made It Possible
Authors: Zank, G. P.; Sterken, V.; Giacalone, J.; Möbius, E.;
von Steiger, R.; Stone, E. S.; Krimigis, S. M.; Richardson, J. D.;
Linsky, J.; Izmodenov, V.; Heber, B.
2022SSRv..218...34Z Altcode:
Our understanding of the interaction of the large-scale heliosphere with
the local interstellar medium (LISM) has undergone a profound change
since the very earliest analyses of the problem. In part, the revisions
have been a consequence of ever-improving and widening observational
results, especially those that identified the entrance of interstellar
material and gas into the heliosphere. Accompanying these observations
was the identification of the basic underlying physics of how neutral
interstellar gas and interstellar charged particles of different
energies, up to and including interstellar dust grains, interacted with
the temporal flows and electromagnetic fields of the heliosphere. The
incorporation of these various basic effects into global models of the
interaction, whether focused on neutral interstellar gas and pickup
ions, energetic particles such as anomalous and galactic cosmic rays,
or magnetic fields and large-scale flows, has profoundly changed our
view of how the heliosphere and LISM interact. This article presents
a brief history of the conceptual and observation evolution of our
understanding of the interaction of the heliosphere with the local
interstellar medium, up until approximately 1996.

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Title: Inhomogeneity in the Local ISM and Its Relation to the
Heliosphere
Authors: Linsky, Jeffrey; Redfield, Seth; Ryder, Diana; Moebius,
Eberhard
2022SSRv..218...16L Altcode: 2022arXiv220313280L
This paper reviews past research and new studies underway of the
local interstellar environment and its changing influence on the
heliosphere. The size, shape, and physical properties of the heliosphere
outside of the heliopause are determined by the surrounding environment
- now the outer region of the Local Interstellar Cloud (LIC). The
temperature, turbulence, and velocity vector of neutral atoms and ions
in the LIC and other partially ionized interstellar clouds are measured
from high-resolution spectra of interstellar absorption lines observed
with the STIS instrument on the HST. Analysis of such spectra led to
a kinematic model with many interstellar clouds defined by velocity
vectors derived from radial velocity measurements. This analysis
identified fifteen clouds located within about 10 pc of the Sun and
their mean temperatures, turbulence, and velocity vectors. With
the increasing number of sight lines now being analyzed, we find
that temperatures and turbulent velocities have spatial variations
within the LIC and other nearby clouds much larger than measurement
uncertainties, and that these spatial variations appear to be randomly
distributed and can be fit by Gaussians. The inhomogeneous length scale
is less than 4,000 AU, a distance that the heliosphere will traverse
in less than 600 years. The temperatures and turbulent velocities
do not show significant trends with stellar distance or angle from
the LIC center. If/when the Sun enters an inter-cloud medium, the
physical properties of the future heliosphere will be very different
from the present. For the heliosheath and the very local interstellar
medium (VLISM) just outside of the heliopause, the total pressures are
approximately equal to the gravitational pressure of overlying material
in the Galaxy. The internal pressure in the LIC is far below that in
the VLISM, but there is an uncertain ram pressure term produced by
the flow of the LIC with respect to its environment.

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Title: Are the Skumanich relations the same for chromospheric and
coronal diagnostics?
Authors: Linsky, J.
2022fysr.confE..10L Altcode:
The age dependence of stellar chromospheric and coronal emission
has been measured in optical and UV emission lines and in X-ray
emission. Although all of these diagnostics share a common pattern of
saturation for young stars and logarithmic decay for older stars, the
detailed patterns are not the same for the different diagnostics and
different spectral types. I will show that the ratio of chromospheric
emission as measured by Lyman-alpha flux to coronal emission as
measured by X-ray flux is the same for F, G, and K stars. However the
pattern is different for M stars and especially late-M stars where
the Lyman-alpha emission is relatively weak compared to the X-ray
emission. As shown in an analysis of 79 stars observed by HST and
Chandra or XMM, the L(Lyman-alpha)/L(bol) ratio increases steadily
with decreasing effective temperature for stars younger than 450 Myr,
but the L(X)/L(bol) saturates at 70-90 Myr for stars cooler than 5400
K. For older stars both L(X)/L(bol) and L(Lyman-alpha)/L(bol) increase
steadily to lower effective temperatures. The different saturation times
and coronal/chromospheric flux ratios with spectral type are essential
input when evaluating Skumanich relations among different stars.

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Title: Intrinsic Lyα Profiles of High-velocity G, K, and M Dwarfs
Authors: Youngblood, Allison; Pineda, J. Sebastian; Ayres, Thomas;
France, Kevin; Linsky, Jeffrey L.; Wood, Brian E.; Redfield, Seth;
Schlieder, Joshua E.
2022ApJ...926..129Y Altcode: 2022arXiv220101315Y
Observations of H I Lyman α, the brightest UV emission line of
late-type stars, are critical for understanding stellar chromospheres
and transition regions, modeling photochemistry in exoplanet
atmospheres, and measuring the abundances of neutral hydrogen and
deuterium in the interstellar medium. Yet Lyα observations are
notoriously challenging owing to severe attenuation from interstellar
gas, hindering our understanding of this important emission line's basic
morphology. We present high-resolution far- and near-UV spectroscopy
of five G, K, and M dwarfs with radial velocities large enough
to Doppler-shift the stellar Lyα emission line away from much of
the interstellar attenuation, allowing the line core to be directly
observed. We detect self-reversal in the Lyα emission-line core for
all targets, and we show that the self-reversal depth decreases with
increasing surface gravity. Mg II self-reversed emission-line profiles
provide some useful information to constrain the Lyα line core,
but the differences are significant enough that Mg II cannot be used
directly as an intrinsic Lyα template during reconstructions. We show
that reconstructions that neglect self-reversal could overestimate
intrinsic Lyα fluxes by as much as 60%-100% for G and K dwarfs and
40%-170% for M dwarfs. The five stars of our sample have low magnetic
activity and subsolar metallicity; a larger sample size is needed to
determine how sensitive these results are to these factors.

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Title: Extreme-ultraviolet Stellar Characterization for Atmospheric
Physics and Evolution mission: motivation and overview
Authors: France, Kevin; Fleming, Brian; Youngblood, Allison; Mason,
James; Drake, Jeremy J.; Amerstorfer, Ute V.; Barstow, Martin;
Bourrier, Vincent; Champey, Patrick; Fossati, Luca; Froning, Cynthia
S.; Green, James C.; Grisé, Fabien; Gronoff, Guillaume; Hellickson,
Timothy; Jin, Meng; Koskinen, Tommi T.; Kowalski, Adam F.; Kruczek,
Nicholas; Linsky, Jeffrey L.; Lipscy, Sarah J.; McEntaffer, Randall
L.; McKenzie, David E.; Miles, Drew M.; Patton, Tom; Savage, Sabrina;
Siegmund, Oswald; Spittler, Constance; Unruh, Bryce W.; Volz, Máire
2022JATIS...8a4006F Altcode: 2022arXiv220113219F
The Extreme-ultraviolet Stellar Characterization for Atmospheric
Physics and Evolution (ESCAPE) mission is an astrophysics Small
Explorer employing ultraviolet spectroscopy (EUV: 80 to 825 Å and FUV:
1280 to 1650 Å) to explore the high-energy radiation environment
in the habitable zones around nearby stars. ESCAPE provides the
first comprehensive study of the stellar EUV and coronal mass
ejection environments that directly impact the habitability of rocky
exoplanets. In a 20-month science mission, ESCAPE will provide the
essential stellar characterization to identify exoplanetary systems
most conducive to habitability and provide a roadmap for NASA's
future life-finder missions. ESCAPE accomplishes this goal with
roughly two-order-of-magnitude gains in EUV efficiency over previous
missions. ESCAPE employs a grazing incidence telescope that feeds an
EUV and FUV spectrograph. The ESCAPE science instrument builds on
previous ultraviolet and x-ray instrumentation, grazing incidence
optical systems, and photon-counting ultraviolet detectors used on
NASA astrophysics, heliophysics, and planetary science missions. The
ESCAPE spacecraft bus is the versatile and high-heritage Ball Aerospace
BCP-Small spacecraft. Data archives will be housed at the Mikulski
Archive for Space Telescopes.

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Title: Interactions between the heliosphere and its environment -
important questions for Interstellar Probe
Authors: Linsky, Jeffrey
2021AGUFMSH11B..07L Altcode:
The interstellar environment plays a key role in determining the
structure and physical properties of the heliosphere. The outer
heliosphere called the very local interstellar medium (VLISM)
extends from the heliopause (120 AU) to about 700 AU in the upwind
direction. The VLISM consists of interstellar neutrals, ions, and
magnetic fields modified by charge exchange and other interactions
with solar wind particles and magnetic fields. Beyond the VLISM, there
are at least 15 partially ionized warm clouds including the Local
Interstellar Cloud (LIC), which the heliosphere is now leaving. The
warm clouds are in turn embedded in the ionized warm and hot gas
of the Local Cavity. We will list some important questions that the
Interstellar Probe and other future space missions should address,
and evaluate whether the heliosphere is in approximate total pressure
balance with its environment. Total pressure balance with the LIC and
Local Cavity can indicate which pressure components need to be further
studied in the VLISM.

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Title: Interplanetary Hydrogen Properties as Probes into the
Heliospheric Interface
Authors: Mayyasi, Majd; Clarke, John; Quemerais, Eric; Katushkina,
Olga; Izmodenov, Vladislav; Provornikova, Elena; Sokol, Justyna;
Brandt, Pontus; Galli, Andre; Opher, Merav; Kornbleuth, Marc; Linsky,
Jeffrey; Wood, Brian
2021AGUFMSH15F2069M Altcode:
A NASA sponsored study conducted at John Hopkins University Applied
Physics Lab culminated in a community-inspired heliospheric mission
concept called the Interstellar Probe (ISP). The ISP's science goals
include understanding our habitable astrosphere by investigating
its interactions with the interstellar medium, and determining the
structure, composition, and variability of its constituents. A suite
of instruments were proposed to achieve these and other science
objectives. The instruments include a Lyman-a spectrograph for
velocity-resolved measurements of neutral H atoms. The capability to
address key components of the ISP's science objectives by utilizing
high spectral resolution Lyman-a measurements are described in this
presentation. These findings have been submitted as a community White
Paper to the recent Heliophysics decadal survey.

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Title: Could the Local Cavity be an Irregularly Shaped Strömgren
Sphere?
Authors: Linsky, Jeffrey L.; Redfield, Seth
2021ApJ...920...75L Altcode:
Extending for 50-200 pc in all directions from the Sun, the Local
Cavity has been characterized as an old supernova bubble consisting
of low-density million-degree plasma heated by supernova shocks. We
summarize the arguments for and against this model and conclude that
hydrogen in the Local Cavity is fully ionized, and the plasma near
the Galactic plane is mostly warm (10,000-20,000 K) rather than
hot (106 K). The brightest extreme-ultraviolet source
detected in the EUVE all-sky survey is the star ϵ CMa. Its EUV
radiation photoionizes the outer layers of the Local Interstellar
Cloud and other nearby warm interstellar clouds despite the star's
124 pc distance. Pulsar dispersion measures indicate an electron
density of 0.012 cm-3 in the Local Cavity itself. At this
density the Strömgren sphere of ϵ CMa is as large as the Local
Cavity. We propose that the Local Cavity is an irregularly shaped
Strömgren sphere containing a small percentage of hot gas likely in
many filamentary structures. We also propose that shocks from recent
supernovae encountered pre-existing Strömgren sphere gas, and that
the partially ionized Local Interstellar Cloud and other nearby clouds
could have been formed when supernova shocks encountered regions with
relatively weak magnetic fields producing compression, higher density,
and recombining hydrogen. * Based on observations made with
the NASA/ESA Hubble Space Telescope obtained from the Data Archive
at the Space Telescope Science Institute, which is operated by the
Association of Universities for Research in Astronomy, Inc., under
NASA contract NAS AR-09525.01A. These observations are associated with
programs #12475, 12596.

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Title: The ESCAPE mission overview: exploring the stellar drivers
of exoplanet habitability
Authors: France, Kevin; Fleming, Brian; Youngblood, Allison; Mason,
James; Drake, Jeremy J.; Amerstorfer, Ute; Barstow, Martin; Bourrier,
Vincent; Champey, Patrick; Fossati, Luca; Froning, Cynthia; Green,
James C.; Grisé, Fabien; Gronoff, Guillaume; Hellickson, Timothy;
Jin, Meng; Koskinen, Tommi T.; Kowalski, Adam F.; Kruczek, Nicholas;
Linsky, Jeffrey L.; Lipscy, Sarah J.; McEntaffer, Randall L.; Miles,
Drew M.; Patton, Tom; Savage, Sabrina L.; Siegmund, Oswald; Spittler,
Constance; Unruh, Bryce; Volz, Márie
2021SPIE11821E..03F Altcode:
The Extreme-ultraviolet Stellar Characterization for Atmospheric
Physics and Evolution (ESCAPE) mission is an astrophysics Small
Explorer employing ultraviolet spectroscopy (EUV: 80 - 825 Å and FUV:
1280 - 1650 Å) to explore the high-energy radiation environment in
the habitable zones around nearby stars. ESCAPE provides the first
comprehensive study of the stellar EUV and coronal mass ejection
environments which directly impact the habitability of rocky
exoplanets. In a 20 month science mission, ESCAPE will provide the
essential stellar characterization to identify exoplanetary systems
most conducive to habitability and provide a roadmap for NASA's
future life-finder missions. ESCAPE accomplishes this goal with
roughly two-order-of-magnitude gains in EUV efficiency over previous
missions. ESCAPE employs a grazing incidence telescope that feeds an
EUV and FUV spectrograph. The ESCAPE science instrument builds on
previous ultraviolet and X-ray instrumentation, grazing incidence
optical systems, and photon-counting ultraviolet detectors used on
NASA astrophysics, heliophysics, and planetary science missions. The
ESCAPE spacecraft bus is the versatile and high-heritage Ball Aerospace
BCP-Small spacecraft. Data archives will be housed at the Mikulski
Archive for Space Telescopes (MAST). ESCAPE is currently completing
a NASA Phase A study, and if selected for Phase B development would
launch in 2025.

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Title: New Observational Constraints on the Winds of M dwarf Stars
Authors: Wood, Brian E.; Müller, Hans-Reinhard; Redfield, Seth;
Konow, Fallon; Vannier, Hunter; Linsky, Jeffrey L.; Youngblood,
Allison; Vidotto, Aline A.; Jardine, Moira; Alvarado-Gómez, Julián
D.; Drake, Jeremy J.
2021ApJ...915...37W Altcode: 2021arXiv210500019W
High-resolution UV spectra of stellar H I Lyα lines from the Hubble
Space Telescope (HST) provide observational constraints on the winds
of coronal main-sequence stars, thanks to an astrospheric absorption
signature created by the interaction between the stellar winds and the
interstellar medium. We report the results of a new HST survey of M
dwarf stars, yielding six new detections of astrospheric absorption. We
estimate mass-loss rates for these detections and upper limits for
nondetections. These new constraints allow us to characterize the
nature of M dwarf winds and their dependence on coronal activity for
the first time. For a clear majority of the M dwarfs, we find winds
that are weaker than or comparable in strength to that of the Sun, i.e.,
$\dot{M}\leqslant 1\,{\dot{M}}_{\odot }$ . However, two of the M dwarfs
have much stronger winds: YZ CMi (M4 Ve; $\dot{M}=30\,{\dot{M}}_{\odot
}$ ) and GJ 15AB (M2 V+M3.5 V; $\dot{M}=10\,{\dot{M}}_{\odot }$ ). Even
these winds are much weaker than expectations if the solar relation
between flare energy and coronal mass ejection (CME) mass extended
to M dwarfs. Thus, the solar flare/CME relation does not appear to
apply to M dwarfs, with important ramifications for the habitability
of exoplanets around M dwarfs. There is evidence for some increase in
$\dot{M}$ with coronal activity as quantified by X-ray flux, but with
much scatter. One or more other factors must be involved in determining
wind strength besides spectral type and coronal activity, with magnetic
topology being one clear possibility. * Based on observations made with
the NASA/ESA Hubble Space Telescope, obtained at the Space Telescope
Science Institute, which is operated by the Association of Universities
for Research in Astronomy, Inc., under NASA contract NAS 5-26555. These
observations are associated with program GO-15326.

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Title: Reconstructing the Extreme Ultraviolet Emission of Cool Dwarfs
Using Differential Emission Measure Polynomials
Authors: Duvvuri, Girish M.; Sebastian Pineda, J.; Berta-Thompson,
Zachory K.; Brown, Alexander; France, Kevin; Kowalski, Adam F.;
Redfield, Seth; Tilipman, Dennis; Vieytes, Mariela C.; Wilson, David
J.; Youngblood, Allison; Froning, Cynthia S.; Linsky, Jeffrey; Parke
Loyd, R. O.; Mauas, Pablo; Miguel, Yamila; Newton, Elisabeth R.;
Rugheimer, Sarah; Christian Schneider, P.
2021ApJ...913...40D Altcode: 2021arXiv210208493D
Characterizing the atmospheres of planets orbiting M dwarfs requires
understanding the spectral energy distributions of M dwarfs over
planetary lifetimes. Surveys like MUSCLES, HAZMAT, and FUMES have
collected multiwavelength spectra across the spectral type's range
of Teff and activity, but the extreme ultraviolet (EUV,
100-912 Å) flux of most of these stars remains unobserved because
of obscuration by the interstellar medium compounded with limited
detector sensitivity. While targets with observable EUV flux exist,
there is no currently operational facility observing between 150 and 912
Å. Inferring the spectra of exoplanet hosts in this regime is critical
to studying the evolution of planetary atmospheres because the EUV
heats the top of the thermosphere and drives atmospheric escape. This
paper presents our implementation of the differential emission measure
technique to reconstruct the EUV spectra of cool dwarfs. We characterize
our method's accuracy and precision by applying it to the Sun and AU
Mic. We then apply it to three fainter M dwarfs: GJ 832, Barnard's star,
and TRAPPIST-1. We demonstrate that with the strongest far-ultraviolet
(FUV, 912-1700 Å) emission lines, observed with the Hubble Space
Telescope and/or Far Ultraviolet Spectroscopic Explorer, and a coarse
X-ray spectrum from either the Chandra X-ray Observatory or XMM-Newton,
we can reconstruct the Sun's EUV spectrum to within a factor of 1.8,
with our model's formal uncertainties encompassing the data. We report
the integrated EUV flux of our M dwarf sample with uncertainties of
a factor of 2-7 depending on available data quality.

---------------------------------------------------------
Title: Unique heliophysics science opportunities along the
Interstellar Probe journey up to 1000 AU from the Sun
Authors: Provornikova, Elena; Brandt, Pontus C.; McNutt, Ralph L.,
Jr.; DeMajistre, Robert; Roelof, Edmond C.; Mostafavi, Parisa; Turner,
Drew; Hill, Matthew E.; Linsky, Jeffrey L.; Redfield, Seth; Galli,
Andre; Lisse, Carey; Mandt, Kathleen; Rymer, Abigail; Runyon, Kirby
2021EGUGA..2310504P Altcode:
The Interstellar Probe is a space mission to discover physical
interactions shaping globally the boundary of our Sun`s heliosphere and
its dynamics and for the first time directly sample the properties of
the local interstellar medium (LISM). Interstellar Probe will go through
the boundary of the heliosphere to the LISM enabling for the first time
to explore the boundary with a dedicated instrumentation, to take the
image of the global heliosphere by looking back and explore in-situ
the unknown LISM. The pragmatic concept study of such mission with a
lifetime 50 years that can be implemented by 2030 was funded by NASA and
has been led by the Johns Hopkins University Applied Physics Laboratory
(APL). The study brought together a diverse community of more than 400
scientists and engineers spanning a wide range of science disciplines
across the world.Compelling science questions for the Interstellar Probe
mission have been with us for many decades. Recent discoveries from a
number of space missions exploring the heliosphere raised new questions
strengthening the science case. The very shape of the heliosphere, a
manifestation of complex global interactions between the solar wind and
the LISM, remains the biggest mystery. Interpretations of imaging the
heliosphere in energetic neutral atoms (ENAs) in different energy ranges
on IBEX and Cassini/INCA from inside show contradictory pictures. Global
physics-based models also do not agree on the global shape. Interstellar
Probe on outbound trajectory will image the heliosphere from outside
for the first time and will provide a unique determination of the
global shape.The LISM is a completely new area for exploration and
discovery. We have a crude understanding of the LISM inferred from
in-situ measurements inside the heliosphere of interstellar helium,
pick-up-ions, ENAs, remote observations of solar backscattered
Lyman-alpha emission and absorption line spectroscopy in the lines
of sight of stars. We have no in-situ measurements of most LISM
properties, e.g. ionization, plasma and neutral gas, magnetic field,
composition, dust, and scales of possible inhomogeneities. Voyagers with
limited capabilities have explored 30 AU beyond the heliosphere which
appeared to be a region of significant heliospheric influence. The LISM
properties are among the key unknowns to understand the Sun`s galactic
neighborhood and how it shapes our heliosphere. Interstellar Probe will
be the first NASA mission to discover the very nature of the LISM and
shed light on whether the Sun enters a new region in the LISM in the
near future.In this presentation we give an overview of heliophysics
science for the Interstellar Probe mission focusing on the critical
science questions of the three objectives for the mission. We will
discuss in more details a need for direct measurements in the LISM
uniquely enabled by the Interstellar Probe.

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Title: The Mega-MUSCLES Spectral Energy Distribution of TRAPPIST-1
Authors: Wilson, David J.; Froning, Cynthia S.; Duvvuri, Girish
M.; France, Kevin; Youngblood, Allison; Schneider, P. Christian;
Berta-Thompson, Zachory; Brown, Alexander; Buccino, Andrea P.; Hawley,
Suzanne; Irwin, Jonathan; Kaltenegger, Lisa; Kowalski, Adam; Linsky,
Jeffrey; Parke Loyd, R. O.; Miguel, Yamila; Pineda, J. Sebastian;
Redfield, Seth; Roberge, Aki; Rugheimer, Sarah; Tian, Feng; Vieytes,
Mariela
2021ApJ...911...18W Altcode: 2021arXiv210211415W
We present a 5 Å-100 μm spectral energy distribution (SED)
of the ultracool dwarf star TRAPPIST-1, obtained as part of
the Mega-MUSCLES Treasury Survey. The SED combines ultraviolet
and blue-optical spectroscopy obtained with the Hubble Space
Telescope, X-ray spectroscopy obtained with XMM-Newton, and models
of the stellar photosphere, chromosphere, transition region, and
corona. A new differential emission measure model of the unobserved
extreme-ultraviolet spectrum is provided, improving on the Lyα-EUV
relations often used to estimate the 100-911 Å flux from low-mass
stars. We describe the observations and models used, as well as the
recipe for combining them into an SED. We also provide a semiempirical,
noise-free model of the stellar ultraviolet spectrum based on our
observations for use in atmospheric modeling of the TRAPPIST-1 planets.

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Title: Semiempirical Modeling of the Atmospheres of the M Dwarf
Exoplanet Hosts GJ 832 and GJ 581
Authors: Tilipman, Dennis; Vieytes, Mariela; Linsky, Jeffrey L.;
Buccino, Andrea P.; France, Kevin
2021ApJ...909...61T Altcode: 2020arXiv201211738T
Stellar ultraviolet (UV) radiation drives photochemistry, and
extreme-ultraviolet (EUV) radiation drives mass loss in exoplanet
atmospheres. However, the UV flux is partly unobservable due to
interstellar absorption, particularly in the EUV range (100-912 Å). It
is therefore necessary to reconstruct the unobservable spectra in order
to characterize the radiation environment of exoplanets. In the present
work, we use a radiative transfer code SSRPM to build one-dimensional
semiempirical models of two M dwarf exoplanet hosts, GJ 832 and GJ 581,
and synthesize their spectra. SSRPM is equipped with an extensive atomic
and molecular database and full-NLTE capabilities. We use observations
in the visible, ultraviolet, and X-ray ranges to constrain atmospheric
structures of the modeled stars. The synthesized integrated EUV fluxes
are found to be in good agreement with other reconstruction techniques,
but the spectral energy distributions disagree significantly across
the EUV range. More than two-thirds of the EUV flux is formed above
105 K. We find that the far-ultraviolet (FUV) continuum
contributes 42%-54% of the entire FUV flux between 1450 and 1700 Å. The
comparison of stellar structures of GJ 832 and GJ 581 suggests that
GJ 832 is a more magnetically active star, which is corroborated by
other activity indicators.

---------------------------------------------------------
Title: What M dwarf models reveal about their UV spectra?
Authors: Tilipman, Dennis; Vieytes, Mariela; Linsky, Jeffrey L.;
Buccino, Andrea; France, Kevin
2021csss.confE.294T Altcode:
Stellar ultraviolet (UV) radiation has significant implications
on habitability of their exoplanets, yet this radiation is partly
unobservable due to interstellar medium absorption. We used the
radiative transfer code SSRPM to build stellar models of two M dwarfs
and synthesize their UV spectra, particularly focusing on the far-UV and
extreme-UV spectra. Our most important findings are that 1) the coronae
of two M dwarfs are responsible for more than half of their respective
EUV fluxes, and 2) the continuum in the FUV band between 145 and 170
nm is responsible for about half of total emission in this band. Here,
we discuss the significance of these results and outline future projects
aimed to improve our understanding of solar and stellar UV emission.

---------------------------------------------------------
Title: The Relative Emission from Chromospheres and Coronae:
Dependence on Spectral Type and Age
Authors: Linsky, Jeffrey; Wood, Brian E.; Youngblood, Allison;
Brown, Alexander; Froning, Cynthia S.; France, Kevin; Buccino,
Andrea P.; Cranmer, Steven S.; Mauas, Pablo; Miguel, Yamila; Pineda,
J. Sebastian; Rugheimer, Sarah; Vieytes, Mariela; Wheatley, Peter J.;
Wilson, David J.
2021csss.confE.257L Altcode:
We present a comprehensive picture of the relative emission and heating
of the chromospheres and coronae of stars with spectral types F2 -
M7.5 V as a function of effective temperature and age. At chromospheric
temperatures the dominant emission is in the Lyman-alpha line, which
we take as representative of the total emission from chromospheres. At
coronal temperatures the dominant emission is by X-rays, which we take
a representative of the total emission from coronae. We include in this
study 79 dwarf stars for which there are X-ray fluxes and Lyman-alpha
fluxes corrected for interstellar absorption. The Lyman-alpha fluxes
are from HST/STIS spectra obtained with the MUSCLES, Mega-MUSCLES,
and other surveys and programs. The X-ray fluxes are from XMM-Newton,
Chandra, and ROSAT.We find that Lyman-alpha and X-ray fluxes for
F, G, and K stars lie on the same trend line with active stars
near the top and inactive stars near the bottom. As stars evolve,
they systematically descend the trend line. M stars depart from
the FGK trend line in the sense of relatively weak Lyman-alpha
emission. The ratio of the Lyman-alpha to bolometric luminosity,
L(Lya)/L(bol), increases to lower effective temperature for stars at
all ages. The ratio of X-ray to bolometric luminosity, L(X)/L(bol),
follows a different pattern with young stars (t&lt;450 Myr) showing
X-ray saturation for effective temperatures less than 5200 K and
stronger L(X)/L(bol) than L(Lya/L(bol). For older stars (t&gt;4 Gyr),
L(Lya)/L(bol) exceeds L(X)/L(bol), but L(X)/L(bol) increases to lower
effective temperatures much faster than L(Lya)/L(bol). We discuss the
implications of these results concerning the relative heating rates at
coronal and chromospheric temperatures.This work is supported by grants
from the Space Telescope Science Institute for programs HST-GO-12475,
12596, 13650, 14640, and 15071.

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Title: A Multiwavelength Look at the GJ 9827 System: No Evidence of
Extended Atmospheres in GJ 9827b and d from HST and CARMENES Data
Authors: Carleo, Ilaria; Youngblood, Allison; Redfield, Seth;
Casasayas Barris, Nuria; Ayres, Thomas R.; Vannier, Hunter; Fossati,
Luca; Palle, Enric; Livingston, John H.; Lanza, Antonino F.; Niraula,
Prajwal; Alvarado-Gómez, Julián D.; Chen, Guo; Gandolfi, Davide;
Guenther, Eike W.; Linsky, Jeffrey L.; Nagel, Evangelos; Narita,
Norio; Nortmann, Lisa; Shkolnik, Evgenya L.; Stangret, Monika
2021AJ....161..136C Altcode: 2021arXiv210106277C
GJ 9827 is a bright star hosting a planetary system with three
transiting planets. As a multiplanet system with planets that sprawl
within the boundaries of the radius gap between terrestrial and gaseous
planets, GJ 9827 is an optimal target to study the evolution of the
atmospheres of close-in planets with a common evolutionary history
and their dependence from stellar irradiation. Here we report on the
Hubble Space Telescope (HST) and CARMENES transit observations of GJ
9827 planets b and d. We performed a stellar and ISM characterization
from the ultraviolet HST spectra, obtaining fluxes for Lyα and Mg
II of F(Lyα) = (5.42 ${}_{-0.75}^{+0.96}$ ) × 10-13
erg cm-2 s-1 and F(MgII) = (5.64 ± 0.24)
× 10-14 erg cm-2 s-1. We also
investigated a possible absorption signature in Lyα in the atmosphere
of GJ 9827b during a transit event from HST spectra, as well as Hα
and He I signature for the atmosphere of GJ 9827b and d from CARMENES
spectra. We found no evidence of an extended atmosphere in either
of the planets. This result is also supported by our analytical
estimations of mass loss based on the measured radiation fields for
all three planets of this system, which led to a mass-loss rate of
0.4, 0.3, and 0.1 planetary masses per Gyr for GJ 9827b, c, and d,
respectively. These values indicate that the planets could have lost
their volatiles quickly in their evolution and probably do not retain
an atmosphere at the current stage.

---------------------------------------------------------
Title: The Relative Emission from Chromospheres and Coronae:
Dependence on Spectral Type and Age
Authors: Linsky, J.; Wood, B.; Youngblood, A.; Brown, A.; France,
K.; Buccino, A.; Froning, C.; Cranmer, S.; Mauas, P.; Miguel, Y.;
Pineda, J.; Rugheimer, S.; Vieytes, M.; Wheatley, P.; Wilson, D.
2021AAS...23714110L Altcode:
Extreme-UV and X-ray emissions from stellar coronae drive mass loss
from exoplanet atmospheres, and UV emission from stellar chromospheres
drives photo-chemistry in exoplanet atmospheres. Comparisons of the
spectral energy distributions of host stars are, therefore, essential
for understanding the evolution and habitability of exoplanets. The
large number of stars observed with the MUSCLES, Mega-MUSCLES, and
other recent HST observing programs has provided for the first time
a large sample (79 stars) of reconstructed Lyman-alpha fluxes that
we compare with X-ray fluxes to identify significant patterns in the
relative emission from these two atmospheric regions as a function of
stellar age and effective temperature. We find that as stars age on
the main sequence, a single trend line slope describes the pattern of
X-ray vs. Lyman-alpha emission for F, G and K dwarfs, but the different
trend lines for M dwarf stars show that the Lyman-alpha fluxes of M
stars are significantly smaller than warmer stars with the same X-ray
flux. The X-ray and Lyman-alpha luminosities divided by the stellar
bolometric luminosities show different patterns depending on stellar
age. The L(Lyα)/L(bol) ratios increase smoothly to cooler stars
of all ages, but the L(X)/L(bol) ratios show different trends. For
older stars, the increase in coronal emission with decreasing T(eff)
is much steeper than chromospheric emission. We suggest a fundamental
link between atmospheric properties and trend lines relating coronal
and chromospheric heating. See paper in ApJ volume 902 (2020).

---------------------------------------------------------
Title: Ultraviolet investigations of the interstellar medium from
astrospheres to the local cavity
Authors: Linsky, Jeffrey L.
2021uaqo.book...85L Altcode:
Ultraviolet spectroscopy plays a critical role in our understanding
of the interstellar medium. This chapter describes how the analysis
of resonance lines of abundant neutrals and ions leads to physical
and morphological models of interstellar gas facilitated by innovative
satellites and instruments. The neutral hydrogen Lyman-α line probes
hydrogen walls in the heliosphere and astrospheres where stellar winds
interact with inflowing neutral hydrogen from the local ISM. Doppler
shifts and line widths of interstellar gas in the lines of sight to
nearby stars identify warm neutral clouds within 15 pc of the Sun,
their vector velocities, and column densities. The Sun is likely
at the edge of one of these clouds, the Local Interstellar Cloud
(LIC). Surrounding the warm clouds is the Local Cavity, which is
proposed to be an irregularly shaped Strömgren sphere produced by
the extreme-ultraviolet radiation from the star ε CMa and nearby hot
white dwarfs. The strengths and weaknesses of very different models of
the ISM are discussed in terms of insights obtained from the analysis
of UV interstellar spectra.

---------------------------------------------------------
Title: Testing the apparent steep decline in the chromospheric
emission of very late M dwarfs
Authors: Wheatley, Peter J.; Bourrier, Vincent; Burgasser, Adam J.;
King, George; Linsky, Jeffrey L.; Wood, Brian Erland; Youngblood,
Allison
2020hst..prop16487W Altcode:
We recently published evidence for a steep decline in chromospheric
ultraviolet emission compared with coronal X-ray emission for
mid-to-late M dwarfs. Very late M dwarfs appear to be underluminous
in the ultraviolet by two orders of magnitude. If confirmed,
this chromospheric decline will have profound implications for
the habitability of exoplanet systems similar to TRAPPIST-1. The
chromospheric decline may also point to a change in stellar dynamo
mechanism at the fully convective boundary. We propose XMM-Newton and
HST observations of three very late M dwarfs in order to test that
the chromospheric decline is a common feature of the class.

---------------------------------------------------------
Title: A Look at the Local Interstellar Medium that Encompassed the
Sun in Our Recent Past in order to Understand Our Current and Future
Interstellar Surroundings
Authors: Redfield, S.; Vannier, H. N. N.; Linsky, J. L.
2020AGUFMSH019..07R Altcode:
The Local Interstellar Medium (LISM) is a rich and complex suite of
clouds in the immediate vicinity of the Sun. The Sun is located at the
edge of the Local Interstellar Cloud (LIC), the interstellar structure
that is thought to directly surround the solar system. We present
a global three-dimensional model of the LISM, based on ultraviolet
absorption line spectroscopy of hundreds of nearby stars, including a
dense survey of stars along the historical solar trajectory. Our 3D
model is based on assuming constant neutral hydrogen number density
for all clouds, and a tight packing that ensures a warm, partially
ionized cloud surrounds stars with known astrospheric detections. We
explore the distribution, kinematics, and physical properties of the
LIC and other nearby clouds in order to understand how the heliosphere
has evolved in our most recent past (e.g., within the last 5 Myr),
the properties of the LISM that currently encompass our solar system,
and the conditions we may expect to encounter in the immediate
future. These measurements provide an invaluable global view of the
pristine interstellar material that Interstellar Probe, for the first
time, will be traversing. However, our measurements are averaged over
the entire line of sight. We will discuss the possible measurements by
Interstellar Probe that will provide unique insights into the detailed
structure of LISM clouds that determine the heliospheric morphology
and evolution.

---------------------------------------------------------
Title: EUV spectroscopy with the ESCAPE mission: exploring the
stellar drivers of exoplanet habitability
Authors: France, Kevin; Fleming, Brian; Youngblood, Allison; Mason,
James; Patton, Tom; Kruczek, Nick; Hellickson, Timothy; Fossati, Luca;
McEntaffer, Randall L.; Miles, Drew M.; Barstow, Martin; Green, James
C.; Gronoff, Guillaume; Froning, C. S.; Amerstorfer, Ute V.; Jin, M.;
Bourrier, V.; Linsky, Jeffrey L.; Siegmund, Oswald; Drake, Jeremy J.
2020SPIE11444E..05F Altcode:
The Extreme-ultraviolet Stellar Characterization for Atmospheric
Physics and Evolution (ESCAPE) mission is an astrophysics Small
Explorer employing ultraviolet spectroscopy (EUV: 80 - 825 Å and FUV:
1280 - 1650 Å) to explore the high-energy radiation environment in
the habitable zones around nearby stars. ESCAPE provides the first
comprehensive study of the stellar EUV and coronal mass ejection
environments which directly impact the habitability of rocky
exoplanets. In a 21 month science mission, ESCAPE will provide
the essential stellar characterization to identify exoplanetary
systems most conducive to habitability and provide a roadmap for
future life-finder missions. ESCAPE accomplishes this goal with
roughly two-order-of-magnitude gains in EUV efficiency over previous
missions. ESCAPE employs a grazing incidence telescope that feeds an
EUV and FUV spectrograph, building on experience with ultraviolet
and X-ray instrumentation, grazing incidence optical systems, and
photon-counting ultraviolet detectors. The instrument builds on design
and hardware heritage from numerous NASA UV astrophysics, heliophysics,
and planetary science missions. The ESCAPE spacecraft bus is the
versatile and high-heritage Ball Aerospace BCP-Smallspacecraft. Data
archives are housed at the Mikulski Archive for Space Telescopes (MAST).

---------------------------------------------------------
Title: Estimating the Ultraviolet Emission of M Dwarfs with Exoplanets
from Ca II and Hα
Authors: Melbourne, Katherine; Youngblood, Allison; France, Kevin;
Froning, C. S.; Pineda, J. Sebastian; Shkolnik, Evgenya L.; Wilson,
David J.; Wood, Brian E.; Basu, Sarbani; Roberge, Aki; Schlieder,
Joshua E.; Cauley, P. Wilson; Loyd, R. O. Parke; Newton, Elisabeth R.;
Schneider, Adam; Arulanantham, Nicole; Berta-Thompson, Zachory; Brown,
Alexander; Buccino, Andrea P.; Kempton, Eliza; Linsky, Jeffrey L.;
Logsdon, Sarah E.; Mauas, Pablo; Pagano, Isabella; Peacock, Sarah;
Redfield, Seth; Rugheimer, Sarah; Schneider, P. Christian; Teal,
D. J.; Tian, Feng; Tilipman, Dennis; Vieytes, Mariela
2020AJ....160..269M Altcode: 2020arXiv200907869M
M dwarf stars are excellent candidates around which to search for
exoplanets, including temperate, Earth-sized planets. To evaluate
the photochemistry of the planetary atmosphere, it is essential to
characterize the UV spectral energy distribution of the planet's
host star. This wavelength regime is important because molecules
in the planetary atmosphere such as oxygen and ozone have highly
wavelength-dependent absorption cross sections that peak in the UV
(900-3200 Å). We seek to provide a broadly applicable method of
estimating the UV emission of an M dwarf, without direct UV data, by
identifying a relationship between noncontemporaneous optical and UV
observations. Our work uses the largest sample of M dwarf star far- and
near-UV observations yet assembled. We evaluate three commonly observed
optical chromospheric activity indices—Hα equivalent widths and
log10 LHα/Lbol, and the Mount Wilson
Ca II H&amp;K S and ${R}_{\mathrm{HK}}^{{\prime} }$ indices—using
optical spectra from the HARPS, UVES, and HIRES archives and new HIRES
spectra. Archival and new Hubble Space Telescope COS and STIS spectra
are used to measure line fluxes for the brightest chromospheric and
transition region emission lines between 1200 and 2800 Å. Our results
show a correlation between UV emission-line luminosity normalized to the
stellar bolometric luminosity and Ca II ${R}_{\mathrm{HK}}^{{\prime} }$
with standard deviations of 0.31-0.61 dex (factors of ∼2-4) about the
best-fit lines. We also find correlations between normalized UV line
luminosity and Hα log10 LHα/Lbol
and the S index. These relationships allow one to estimate the average
UV emission from M0 to M9 dwarfs when UV data are not available.

---------------------------------------------------------
Title: The High-energy Radiation Environment around a 10 Gyr M Dwarf:
Habitable at Last?
Authors: France, Kevin; Duvvuri, Girish; Egan, Hilary; Koskinen, Tommi;
Wilson, David J.; Youngblood, Allison; Froning, Cynthia S.; Brown,
Alexander; Alvarado-Gómez, Julián D.; Berta-Thompson, Zachory K.;
Drake, Jeremy J.; Garraffo, Cecilia; Kaltenegger, Lisa; Kowalski,
Adam F.; Linsky, Jeffrey L.; Loyd, R. O. Parke; Mauas, Pablo J. D.;
Miguel, Yamila; Pineda, J. Sebastian; Rugheimer, Sarah; Schneider,
P. Christian; Tian, Feng; Vieytes, Mariela
2020AJ....160..237F Altcode: 2020arXiv200901259F
Recent work has demonstrated that high levels of X-ray and UV activity
on young M dwarfs may drive rapid atmospheric escape on temperate,
terrestrial planets orbiting within the habitable zone. However,
secondary atmospheres on planets orbiting older, less active M
dwarfs may be stable and present more promising candidates for
biomarker searches. In order to evaluate the potential habitability
of Earth-like planets around old, inactive M dwarfs, we present new
Hubble Space Telescope and Chandra X-ray Observatory observations of
Barnard&amp;'s Star (GJ 699), a 10 Gyr old M3.5 dwarf, acquired as part
of the Mega-MUSCLES program. Despite the old age and long rotation
period of Barnard&amp;'s Star, we observe two FUV (δ130
≍ 5000 s; E130 ≍ 1029.5 erg each) and one
X-ray (EX ≍ 1029.2 erg) flares, and we estimate
a high-energy flare duty cycle (defined here as the fraction of the
time the star is in a flare state) of ∼25%. A publicly available
5 Å to 10 μm spectral energy distribution of GJ 699 is created
and used to evaluate the atmospheric stability of a hypothetical,
unmagnetized terrestrial planet in the habitable zone (rHZ
∼ 0.1 au). Both thermal and nonthermal escape modeling indicate (1)
the quiescent stellar XUV flux does not lead to strong atmospheric
escape: atmospheric heating rates are comparable to periods of high
solar activity on modern Earth, and (2) the flare environment could
drive the atmosphere into a hydrodynamic loss regime at the observed
flare duty cycle: sustained exposure to the flare environment of GJ
699 results in the loss of ≍87 Earth atmospheres Gyr-1
through thermal processes and ≍3 Earth atmospheres Gyr-1
through ion loss processes. These results suggest that if rocky planet
atmospheres can survive the initial ∼5 Gyr of high stellar activity,
or if a second-generation atmosphere can be formed or acquired, the
flare duty cycle may be the controlling stellar parameter for the
stability of Earth-like atmospheres around old M stars.

---------------------------------------------------------
Title: The Relative Emission from Chromospheres and Coronae:
Dependence on Spectral Type and Age
Authors: Linsky, Jeffrey L.; Wood, Brian E.; Youngblood, Allison;
Brown, Alexander; Froning, Cynthia S.; France, Kevin; Buccino,
Andrea P.; Cranmer, Steven R.; Mauas, Pablo; Miguel, Yamila; Pineda,
J. Sebastian; Rugheimer, Sarah; Vieytes, Mariela; Wheatley, Peter J.;
Wilson, David J.
2020ApJ...902....3L Altcode: 2020arXiv200901958L
Extreme-ultraviolet and X-ray emission from stellar coronae drives
mass loss from exoplanet atmospheres, and ultraviolet emission
from stellar chromospheres drives photochemistry in exoplanet
atmospheres. Comparisons of the spectral energy distributions of host
stars are, therefore, essential for understanding the evolution and
habitability of exoplanets. The large number of stars observed with
the MUSCLES, Mega-MUSCLES, and other recent Hubble Space Telescope
observing programs has provided for the first time a large sample
(79 stars) of reconstructed Lyα fluxes that we compare with X-ray
fluxes to identify significant patterns in the relative emission
from these two atmospheric regions as a function of stellar age and
effective temperature. We find that as stars age on the main sequence,
the emissions from their chromospheres and coronae follow a pattern
in response to the amount of magnetic heating in these atmospheric
layers. A single trend-line slope describes the pattern of X-ray versus
Lyα emission for G and K dwarfs, but the different trend lines for
M dwarf stars show that the Lyα fluxes of M stars are significantly
smaller than those of warmer stars with the same X-ray flux. The X-ray
and Lyα luminosities divided by the stellar bolometric luminosities
show different patterns depending on stellar age. The L(Lyα)/L(bol)
ratios increase smoothly to cooler stars of all ages, but the
L(X)/L(bol) ratios show different trends. For older stars, the increase
in coronal emission with decreasing ${T}_{\mathrm{eff}}$ is much steeper
than that of chromospheric emission. We suggest a fundamental link
between atmospheric properties and trend lines relating coronal and
chromospheric heating, * Based on observations made with the NASA/ESA
Hubble Space Telescope, obtained from the Mikulski Archive for Space
Telescopes (MAST) at the Space Telescope Science Institute, which is
operated by the Association of Universities for Research in Astronomy,
Inc., under NASA contract NAS AR-09525.01A. These observations are
associated with program Nos. 12475, 12596, 13650, 14640, and 15071.

---------------------------------------------------------
Title: New results concerning the environment of the heliosphere,
nearby interstellar clouds, and physical processes in the inter-cloud
medium
Authors: Linsky, Jeffrey L.; Redfield, Seth; Wood, Brian E.
2020JPhCS1620a2010L Altcode:
We present our new results concerning the interface between the
outer heliosphere and the local interstellar medium (LISM). The three
dimensional shape of the Local Interstellar Cloud (LIC) based on 62
sightlines to nearby stars shows a region of very low neutral hydrogen
density in the direction of the star ɛ CMa, the brightest source
of extreme-UV (EUV) radiation. This “hydrogen hole” with very
weak neutral hydrogen absorption by the LIC and Blue clouds results
from photoionization by the EUV radiation from ɛ CMa. The LIC likely
surrounds the heliosphere, but in the direction of the hydrogen hole
its neutral hydrogen column density is too low to be measured. Upper
limits to this column density and the direction of the Sun’s motion
through space indicate that the Sun will leave the outer edge of the
LIC in less than 1, 900 years. The measured difference between the
speed and direction of incoming neutral hydrogen atoms (measured by
IBEX and Ulysses) and the flow vector of the LIC indicate that the
plasma at the edge of the LIC has a different flow vector than the LIC
core. The inter-cloud plasma and much of the Local Cavity are inside the
Str¨omgren sphere (also called an H II region) surrounding ɛ CMa. The
outer edges of the LIC and other clouds are Str¨omgren shells that are
partially ionized by the EUV radiation from ɛ CMa and white dwarfs. The
Local Cavity could be a Str¨omgren sphere plasma photoionized by ɛ
CMa and hot white dwarfs that contains low density ionized gas that
is not hot. An interstellar probe should measure magnetic field and
plasma properties in the VLISM between the heliopause and 600-700 au
from the Sun and then enter what is likely the Str¨omgren shell outer
edge of the LIC. When the Sun leaves the LIC, it will either enter
the G cloud, a transition region between the LIC and the G cloud,
or ionized Str¨omgren sphere plasma.

---------------------------------------------------------
Title: What lies immediately outside of the heliosphere in the very
local interstellar medium (VLISM): What will ISP detect?
Authors: Linsky, Jeffrey; Redfield, Seth
2020EPSC...14...68L Altcode:
The Interstellar Probe (ISP) will provide the first directmeasurements
of interstellar gas and dust when it travels far beyond theheliopause
where the solar wind no longer influences the ambient medium.We
summarize in this presentation what we have been learning about the
VLISMfrom 20 years of remote observations with the high-resolution
spectrographson the Hubble Space Telescope. Radial velocity measurements
of interstellarabsorption lines seen in the lines of sight to nearby
stars allow us tomeasure the kinematics of gas flows in the VLISM. We
find that the heliosphereis passing through a cluster of warm partially
ionized interstellar clouds.The heliosphere is now at the edge of
the Local Interstellar Cloud (LIC) andheading in the direction of
the slighly cooler G cloud. Two other warm clouds(Blue and Aql) are
very close to the heliosphere. We find that there is alarge region
of the sky with very low neutral hydrogen column density, whichwe
call the hydrogen hole. In the direction of the hydrogen hole is
thebrightest photoionizing source, the star Epsilon Canis Majoris
(CMa). Extremeultraviolet photons from this star produce a Stromgren
sphere region ofionized gas as large as the Local Cavity (extending
to 100-200 parsecs)and produce Stromgren shells at the outer regions
of the local warm cloudsincluding the LIC.When the ISP passes beyond
the hydrogen wall at a distance of about 500 AU,it will likely enter
the outer edge of the LIC where photoionization fromEpsilon CMa plays
an important role. Analysis of Hubble observations ofinterstellar
absorption proves estimates of the densities, temperature,pressure,
and flow properties of the main portion of the LIC, but we havelittle
informtion on these properties at the LIC's edge. Comparison with
theinflow vector of neutral helium measured by IBEX and Ulysses
indicates aslightly different flow speed and direction than the mean
flow of the LIC gas.ISP will provide direct measurements of the flow
and gas properties of thispoorly understood region. In particular,
ISP will provide information onhow photoionization from Epsilon CMa
influences warm clouds through ionization,heating, and perhaps pressure
balance. This information may resolve questionsconcerning the magnetic
field surrounding the heliosphere.

---------------------------------------------------------
Title: A SNAP Survey of the Local Interstellar Medium: New NUV
Observations of Stars with Archived FUV Observations
Authors: Redfield, Seth; Konow, Fallon; Linsky, Jeffrey L.; Wood,
Brian Erland; Youngblood, Allison
2020hst..prop16225R Altcode:
We propose to obtain high-resolution STIS E230H SNAP observations of
MgII and FeII interstellar absorption lines toward stars within 100
parsecs that already have moderate or high-resolution far-UV (FUV),
900-1700 A, observations available in the MAST Archive. Fundamental
properties, such as temperature, turbulence, ionization, abundances,
and depletions of gas in the local interstellar medium (LISM) can be
measured by coupling such observations. Due to the wide spectral range
of STIS, observations to study nearby stars also contain important
data about the LISM embedded within their spectra. However, unlocking
this information from the intrinsically broad and often saturated FUV
absorption lines of low-mass ions, (DI, CII, NI, OI), requires first
understanding the kinematic structure of the gas along the line of
sight. This can be achieved with high resolution spectra of high-mass
ions, (FeII, MgII), which have narrow absorption lines, and can resolve
each individual velocity component (interstellar cloud). Obtaining short
(~10 minute) E230H observations of FeII and MgII, for stars that already
have moderate or high-resolution FUV spectra, will increase the sample
of LISM specta, and enable new measurements of the physical properties
of the gas in our galactic neighborhood. STIS is the only instrument
capable of obtaining the required high resolution UV spectra now or
in the foreseeable future.

---------------------------------------------------------
Title: What lies immediately outside of the heliosphere in the
very local interstellar medium (VLISM): morphology of the Local
Interstellar Cloud, its hydrogen hole, Stromgren Shells, and 60Fe
accretion
Authors: Linsky, Jeffrey
2020EGUGA..22.1410L Altcode:
We describe the very local interstellar medium (VLISM)immediately
outside of the outer heliosphere. The VLISM consists of four partially
ionized clouds - the Local Interstellar Cloud (LIC), G cloud, Blue
cloud, and Aql cloud that are in contact with the outer heliosphere,
and ionized gas produced by extreme-UV radiation primarily from the
star Epsilon CMa. We construct the three-dimensional shape of the LIC
based on interstellar line absorption along 62 sightlines and show
that in the direction of Epsilon CMa, Beta CMa, and Sirius B the
neutral hydrogen column density from the center of the LIC looking
outward is a minimum. We call this region the “hydrogen hole". In this
direction, the presence of Blue cloud absorption and the absence of
LIC absorption can be simply explained by the Blue cloud lying just
outside of the heliosphere. We propose that the outer edge of the
Blue cloud is a Strömgren shell driven toward the heliosphere by high
pressures in the H II region. The outer edges of other clouds facing
Epsilon CMa are likely also Stromgren shells. Unlike previous models,
the LICsurrounds less than half of the heliosphere.We find that the
vectors of neutral and ionized helium flowingthrough the heliosphere
are inconsistent with the mean LIC flow vector and describe several
possible explanations. The ionizationof nearby intercloud gas is
consistent with photo-ionization by Epsilon CMa and hot white dwarfs
without requiring additional sources of ionization or million degree
plasma. In the upwind direction, the heliosphere is passing through
an environment of several LISM clouds, which may explain the recent
influx of interstellar grains containing 60Fe from supernova ejecta
measured in Antarctica snow. The Sun will leave the outer partof the
LIC in less than 1900 years, perhaps this year, to either enter the
partially ionized G cloud or a highly ionized intercloud layer. The
heliosphere will change in either scenario. An instrumented deep space
probe sending back in situ plasma and magnetic field measurements from
500-1,000 AU is needed to understand the heliosphere environment rather
than integrated data along the sightlines to stars.

---------------------------------------------------------
Title: Constructing a Survey of the Local Interstellar Medium using
Hubble Spectra
Authors: Konow, F.; Redfield, S.; Linsky, J.
2020AAS...23536807K Altcode:
Light from distant objects transverses through interstellar clouds
comprised of warm, partially ionized gas causing extinction. The Sun
itself is embedded in a complex amalgamation of these clouds that
can be observed only through sensitive absorption studies in the
ultraviolet. We analyze high resolution spectra obtained by the Space
Telescope Imaging Spectrograph (STIS) on the Hubble Space Telescope
(HST) for 37 local (≪100 pc) stars with the intention to categorize
absorption features caused by local interstellar medium (LISM) clouds
along the line of sight. In particular, we analyze the absorption
features of MgII, FeII, and MnII due to their relatively high abundance
in the LISM and particularly strong absorption. We detect one to five
discrete LISM features for each individual sightline; the higher the
number of features correlating to the longer distance transversed by
the sightline. Each component's spectral absorption feature is fit
with a Voigt profile that determines the cloud's radial velocity,
column density, and Doppler parameter, the final values of which are
compared to a dynamical model of the LISM by Redfield and Linsky (2008)
in an attempt to produce a more complete survey of all LISM clouds. The
results of this survey will significantly improve our understanding
of the three-dimensional morphology of the LISM, and support future
investigations into the fundamental measurements of the LISM. We
acknowledge support for this project through NASA HST Grant GO-13332
awarded by the Space Telescope Science Institute, which is operated
by the Association of Universities for Research in Astronomy, Inc.,
for NASA, under contract NAS 5-26555, and a student research grant
from the Wesleyan Math and Science Scholars (WesMaSS).

---------------------------------------------------------
Title: Semi-Empirical Modeling of the M Dwarf Exoplanet Hosts GJ
832, GJ 581, and GJ 876: UV Radiation and Implications for Exoplanet
Atmospheres
Authors: Tilipman, D.; Vieytes, M.; Linsky, J. L.
2020AAS...23535208T Altcode:
We constructed 1-D atmospheric semi-empirical models of the M dwarf
exoplanet hosts GJ 832 (M2), GJ 581 (M3), and GJ 876 (M5), with the
primary goal of synthesizing ultraviolet (UV) spectra of these stars. UV
radiation drives photochemical processes in exoplanet atmospheres and
can lead to atmospheric escape via hydrodynamic outflow. We compute
our models in full non-LTE using the radiative transfer code SSRPM
(Stellar-Solar Radiation Physical Modelling), and our model atmospheres
extend from the photosphere to the corona. We use spectral data from the
MUSCLES Treasury Survey and the 2.15 m telescope CASLEO in San Juan,
Argentina. Our models fit spectra in the range from X-ray to visible,
including key chromospheric lines such as Lyman alpha, Ca II h &amp; k,
Mg II h &amp; k, C II (133.3 nm), and Si IV (140.0 nm). Thus, we can
synthesize in a self-consistent manner the parts of electromagnetic
spectra that are usually not available due to interstellar hydrogen
absorption, specifically, far-UV (110 - 170 nm) continuum and all
extreme-UV (10 - 91.2 nm) radiation. The output of our models can,
therefore, be used as input for exoplanet atmosphere models.

---------------------------------------------------------
Title: The interface between the outer heliosphere and the inner
LISM: Morphology of the LIC, its hydrogen hole, Stromgren shells,
and 60Fe accretion
Authors: Linsky, J.; Redfield, S.; Tilipman, D.
2020AAS...23544201L Altcode:
We describe the interface between the outer heliosphere and the local
interstellar medium (LISM) surrounding the Sun. The components of the
inner LISM are the four partially ionized clouds [the Local Interstellar
Cloud (LIC), G cloud, Blue cloud, and Aql cloud] that are in contact
with the outer heliosphere, and ionized gas produced by EUV radiation
primarily from Epsilon CMa. We construct the three-dimensional shape of
the LIC based on interstellar absorption along 62 sightlines and show
that in the direction of Epsilon CMa, β CMa, and Sirius B the neutral
hydrogen density from the center of the LIC in a minimum. We call this
region the "hydrogen hole". In this direction, the presence of the
Blue cloud absorption and the absence of LIC absorption can be simply
explained by the Blue cloud lying just outside of the heliosphere. We
propose that the outer edge of the Blue cloud is a Stromgren shell
driven toward the heliosphere by high pressures in the H II region. We
find that the vectors of neutral and ionized helium flowing through
the heliosphere are inconsistent with the LIC flow vector, and that
the nearby intercloud gas in consistent with ionization by Epsilon
CMa and other stellar sources without requiring additional sources
of ionization or million degree plasma. In the upwind direction, the
heliosphere is passing through an environment of several LISM clouds,
which may explain the recent influx of interstellar grains containing
60Fe from supernova ejecta measured in Antarctica snow.

---------------------------------------------------------
Title: Mapping the Local Interstellar Medium: Using Hubble to Look
Back at the ISM Along the Sun's Historical Trajectory
Authors: Vannier, H. N.; Redfield, S.; Wood, B. E.; Mueller, H. R.;
Linsky, J. L.; Frisch, P. C.
2019AGUFMSH51E3323V Altcode:
The local interstellar medium (LISM) is a complex environment,
comprised of a suite of interstellar clouds extending tens of parsecs
and surrounding the nearest stars. On our journey through the Milky
Way, our solar system's heliosphere may have been significantly
compressed by a dense cloud of gas and dust. The properties of
the LISM are critically important in understanding the interaction
between the Sun and other stars with their surrounding interstellar
environments. Using high-resolution UV data obtained from the Space
Telescope Imaging Spectrograph aboard the Hubble Space Telescope, we
focus on eight sight lines along the Sun's historical trajectory. Of
the eight targets, each of which is within 50 pc, we see interstellar
absorption in almost every one, primarily Mg II and Fe II. Two distinct
clouds are clearly identified in all analyzed sight lines, and in at
least one sight line a third cloud is detected. In three of the targets,
additional ions are observed in the shorter wavelength range including
HI, DI, CII, OI, and SiII, providing more access to additional physical
properties of our past environment, such as depletion, temperature,
turbulent velocity, and ionization structure. Utilizing ground-based
observations of more distant ISM and in turn a more distant time
scale, Wyman and Redfield (2013) found the heliosphere could have been
compressed to within 21 AU. These observations will provide the best
opportunity to characterize the interstellar properties just exterior to
the heliosphere and estimate the heliospheric response to interstellar
environments in our recent past and for our immediate future.

---------------------------------------------------------
Title: The Interface between the Outer Heliosphere and the Inner Local
ISM: Morphology of the Local Interstellar Cloud, Its Hydrogen Hole,
Strömgren Shells, and 60Fe Accretion
Authors: Linsky, Jeffrey L.; Redfield, Seth; Tilipman, Dennis
2019ApJ...886...41L Altcode: 2019arXiv191001243L
We describe the interface between the outer heliosphere and the local
interstellar medium (LISM) surrounding the Sun. The components of the
inner LISM are the four partially ionized clouds (the Local Interstellar
Cloud (LIC), G cloud, Blue cloud, and Aql cloud) that are in contact
with the outer heliosphere, and ionized gas produced by EUV radiation
primarily from ɛ CMa. We construct the three-dimensional shape of
the LIC based on interstellar line absorption along 62 sightlines and
show that in the directions of ɛ CMa, β CMa, and Sirius B the neutral
hydrogen column density from the center of the LIC is a minimum. We call
this region the “hydrogen hole.” In this direction, the presence of
Blue cloud absorption and the absence of LIC absorption can be simply
explained by the Blue cloud lying just outside the heliosphere. We
propose that the outer edge of the Blue cloud is a Strömgren shell
driven toward the heliosphere by high pressures in the H II region. We
find that the vectors of neutral and ionized helium flowing through
the heliosphere are inconsistent with the LIC flow vector, and that
the nearby intercloud gas is consistent with ionization by ɛ CMa and
other stellar sources without requiring additional sources of ionization
or million-degree plasma. In the upwind direction, the heliosphere is
passing through an environment of several LISM clouds, which may explain
the recent influx of interstellar grains containing 60Fe from
supernova ejecta measured in Antarctic snow. Based on observations
made with the NASA/ESA Hubble Space Telescope obtained from the Data
Archive at the Space Telescope Science Institute, which is operated
by the Association of Universities for Research in Astronomy, Inc.,
under NASA contract NAS AR-09525.01A. These observations are associated
with programs #12475, 12596.

---------------------------------------------------------
Title: Stars at High Spatial Resolution
Authors: Carpenter, Kenneth G.; van Belle, Gerard; Brown, Alexander;
Cranmer, Steven R.; Drake, Jeremy; Dupree, Andrea K.; Creech-Eakman,
Michelle; Evans, Nancy R.; Grady, Carol A.; Guinan, Edward F.; Harper,
Graham; Karovska, Margarita; Kolenberg, Katrien; Labeyrie, Antoine;
Linsky, Jeffrey; Peters, Geraldine J.; Rau, Gioia; Ridgway, Stephen;
Roettenbacher, Rachael M.; Saar, Steven H.; Walter, Frederick M.;
Wood, Brian
2019arXiv190805665C Altcode:
We summarize some of the compelling new scientific opportunities
for understanding stars and stellar systems that can be enabled by
sub-milliarcsec (sub-mas) angular resolution, UV-Optical spectral
imaging observations, which can reveal the details of the many dynamic
processes (e.g., evolving magnetic fields, accretion, convection,
shocks, pulsations, winds, and jets) that affect stellar formation,
structure, and evolution. These observations can only be provided
by long-baseline interferometers or sparse aperture telescopes in
space, since the aperture diameters required are in excess of 500 m
(a regime in which monolithic or segmented designs are not and will
not be feasible) and since they require observations at wavelengths
(UV) not accessible from the ground. Such observational capabilities
would enable tremendous gains in our understanding of the individual
stars and stellar systems that are the building blocks of our Universe
and which serve as the hosts for life throughout the Cosmos.

---------------------------------------------------------
Title: Measurements of the Ultraviolet Spectral Characteristics of
Low-mass Exoplanetary Systems (Mega-MUSCLES)
Authors: Wilson, David John; Froning, Cynthia; France, Kevin;
Youngblood, Allison; Duvvuri, Girish M.; Brown, Alexander; Schneider,
P. Christian; Kowalski, Adam; Loyd, R. O. Parke; Berta-Thompson,
Zachory Berta-; Pineda, J. Sebastian; Linsky, Jeffrey; Rugheimer,
Sarah; Newton, Elizabeth; Miguel, Yamila; Roberge, Aki; Buccino,
Andrea P.; Irwin, Jonathan; Kaltenegger, Lisa; Vieytes, Mariela;
Mauas, Pablo; Redfield, Seth; Hawley, Suzanne; Tian, Feng
2019ESS.....431906W Altcode:
M dwarf stars have emerged as ideal targets for exoplanet
observations. Their small radii aids planetary discovery, their
close-in habitable zones allow short observing campaigns, and their
red spectra provide opportunities for transit spectroscopy with
JWST. The potential of M dwarfs has been underlined by the discovery
of remarkable systems such as the seven Earth-sized planets orbiting
TRAPPIST-1 and the habitable-zone planet around the closest star to
the Sun. However, to accurately assess the conditions in these
systems requires a firm understanding of how M dwarfs differ from the
Sun, beyond just their smaller size and mass. Of particular importance
are the time-variable, high-energy ultraviolet and x-ray regions of
the M dwarf spectral energy distribution (SED), which can influence
the chemistry and lifetime of exoplanet atmospheres, as well as their
surface radiation environments. The Measurements of the Ultraviolet
Spectral Characteristics of Low-mass Exoplanetary Systems (Mega-MUSCLES)
Treasury project, together with the precursor MUSCLES project, aims to
produce full SEDs of a representative sample of M dwarfs, covering a
wide range of stellar mass, age, and planetary system architecture. We
have obtained x-ray and ultraviolet data for 13 stars using the Hubble,
Chandra and XMM space telescopes, along with ground-based data in the
optical and state-of-the-art DEM modelling to fill in the unobservable
extreme ultraviolet regions. Our completed SEDs will be available as a
community resource, with the aim that a close MUSCLES analogue should
exist for most M dwarfs of interest. In this presentation I will
overview the Mega-MUSCLES project, describing our choice of targets,
observation strategy and SED production methodology. I will also
discuss notable targets such as the TRAPPIST-1 host star, comparing
our observations with previous data and model predictions. Finally,
I will present an exciting by-product of the Mega-MUSCLES project:
time-resolved ultraviolet spectroscopy of stellar flares at multiple
targets, spanning a range of stellar types, ages and flare energies.

---------------------------------------------------------
Title: Properties of the Interstellar Medium along Sight Lines to
Nearby Planet-hosting Stars
Authors: Edelman, Eric; Redfield, Seth; Linsky, Jeffrey L.; Wood,
Brian E.; Müller, Hans
2019ApJ...880..117E Altcode: 2019arXiv190805375E
We analyze the high-resolution ultraviolet spectra of three nearby
exoplanet host stars (HD 192310, HD 9826, and HD 206860) to study
interstellar properties along their lines of sight and to search
for the presence of astrospheric absorption. Using the Hubble Space
Telescope/Space Telescope Imaging Spectrograph spectra of the Lyα,
Mg II, and Fe II lines, we identify three interstellar velocity
components in the lines of sight to each star. We can reliably assign
eight of the nine components to partially ionized clouds found by
Redfield &amp; Linsky (2008) on the basis of the star’s location in
Galactic coordinates and agreement of measured radial velocities with
velocities predicted from the cloud velocity vectors. None of the stars
show blueshifted absorption indicative of an astrosphere, implying
that the stars are in regions of ionized interstellar gas. Coupling
astrospheric and local interstellar medium measurements is necessary
to evaluate the host star electromagnetic and particle flux, which
have profound impacts on the atmospheres of their orbiting planets. We
present a table of all known exoplanets located within 20 pc of the
Sun, listing their interstellar properties and velocities predicted
from the local cloud velocity vectors. Based on observations
made with the NASA/ESA Hubble Space Telescope obtained from the Data
Archive at the Space Telescope Science Institute, which is operated
by the Association of Universities for Research in Astronomy, Inc.,
under NASA contract NAS AR-09525.01A. These observations are associated
with programs #12475, 12596.

---------------------------------------------------------
Title: Cool, evolved stars: results, challenges, and promises for
the next decade
Authors: Rau, Gioia; Montez, Rodolfo, Jr.; Carpenter, Kenneth;
Wittkowski, Markus; Bladh, Sara; Karovska, Margarita; Airapetian,
Vladimir; Ayres, Tom; Boyer, Martha; Chiavassa, Andrea; Clayton,
Geoffrey; Danchi, William; De Marco, Orsola; Dupree, Andrea K.;
Kaminski, Tomasz; Kastner, Joel H.; Kerschbaum, Franz; Linsky,
Jeffrey; Lopez, Bruno; Monnier, John; Montargès, Miguel; Nielsen,
Krister; Ohnaka, Keiichi; Ramstedt, Sofia; Roettenbacher, Rachael;
ten Brummelaar, Theo; Paladini, Claudia; Sarangi, Arkaprabha; van
Belle, Gerard; Ventura, Paolo
2019BAAS...51c.241R Altcode: 2019arXiv190304585R; 2019astro2020T.241R
This White Paper identifies compelling scientific opportunities in
the field of Cool, Evolved Stars, describing the observational and
theoretical challenges to our understanding, and the key advancements
made. We portray the pathway towards understanding, and identify,
through recommendations, which advancements are necessary in 2020-2030
&amp; beyond.

---------------------------------------------------------
Title: Advancing Understanding of Star-Planet Ecosystems in the Next
Decade: The Radio Wavelength Perspective
Authors: Osten, Rachel; Bastian, Tim; Bower, Geoff; Forbrich, Jan;
Gudel, Manuel; Kao, Melodie M.; Lazio, Joseph; Linsky, Jeffrey;
MacGregor, Meredith; Moschou, Sofia P.; Pineda, J. Sebastian; Rupen,
Michael P.; Villadsen, Jackie; White, Stephen; Williams, Peter K. G.;
Wolk, Scott J.
2019BAAS...51c.434O Altcode: 2019astro2020T.434O
In this white paper we advocate for stellar radio observations as a way
to advance understanding of stars in service of a better understanding
of star- planet ecosystems. Specific key advances needed are sensitivity
and access to a broader range of frequency space to make progress in
understanding the space weather environments of exoplanets.

---------------------------------------------------------
Title: High-Energy Photon and Particle Effects on Exoplanet
Atmospheres and Habitability
Authors: Drake, Jeremy; Alvarado-Gómez, Julián D.; Airapetian,
Vladimir; Argiroffi, Costanza; Browning, Matthew K.; Christian,
Damian J.; Cohen, Ofer; Corrales, Lia; Danchi, William; de Val-Borro,
Miguel; Dong, Chuanfei; Forman, William; France, Kevin; Gallo, Elena;
Garcia-Sage, Katherine; Garraffo, Cecilia; Gelino, Dawn M.; Gronoff,
Guillaume; Günther, H. Moritz; Harper, Graham M.; Haywood, Raphaëlle
D.; Karovska, Margarita; Kashyap, Vinay; Kastner, Joel; Kim, Jinyoung
Serena; Leutenegger, Maurice A.; Linsky, Jeffrey; López-Morales,
Mercedes; Micela, Giusi; Moschou, Sofia-Paraskevi; Oskinova, Lidia;
Osten, Rachel A.; Owen, James E.; Poppenhaeger, Katja; Principe,
David A.; Pye, John P.; Sciortino, Salvatore; Tzanavaris, Panayiotis;
Wargelin, Brad; Wheatley, Peter J.; Williams, Peter K. G.; Winston,
Elaine; Wolk, Scott J.; Cauley, P. Wilson
2019BAAS...51c.113D Altcode: 2019astro2020T.113D; 2019arXiv190312338D
Energetic stellar photon and particle radiation evaporates
and erodes planetary atmospheres and controls upper atmospheric
chemistry. Understanding of exoplanet atmospheres, their evolution
and determination of habitability requires a powerful high-resolution
X-ray imaging and spectroscopic observatory to characterize stellar
energetic radiation.

---------------------------------------------------------
Title: Reconstructing Extreme Space Weather From Planet Hosting Stars
Authors: Airapetian, Vladimir; Adibekyan, V.; Ansdell, M.; Alexander,
D.; Barklay, T.; Bastian, T.; Boro Saikia, S.; Cohen, O.; Cuntz,
M.; Danchi, W.; Davenport, J.; DeNolfo, G.; DeVore, R.; Dong, C. F.;
Drake, J. J.; France, K.; Fraschetti, F.; Herbst, K.; Garcia-Sage,
K.; Gillon, M.; Glocer, A.; Grenfell, J. L.; Gronoff, G.; Gopalswamy,
N.; Guedel, M.; Hartnett, H.; Harutyunyan, H.; Hinkel, N. R.; Jensen,
A. G.; Jin, M.; Johnstone, C.; Kahler, S.; Kalas, P.; Kane, S. R.;
Kay, C.; Kitiashvili, I. N.; Kochukhov, O.; Kondrashov, D.; Lazio, J.;
Leake, J.; Li, G.; Linsky, J.; Lueftinger, T.; Lynch, B.; Lyra, W.;
Mandell, A. M.; Mandt, K. E.; Maehara, H.; Miesch, M. S.; Mickaelian,
A. M.; Mouschou, S.; Notsu, Y.; Ofman, L.; Oman, L. D.; Osten, R. A.;
Oran, R.; Petre, R.; Ramirez, R. M.; Rau, G.; Redfield, S.; Réville,
V.; Rugheimer, S.; Scheucher, M.; Schlieder, J. E.; Shibata, K.;
Schnittman, J. D.; Soderblom, David; Strugarek, A.; Turner, J. D.;
Usmanov, A.; Van Der Holst, B.; Vidotto, A.; Vourlidas, A.; Way, M. J.;
Wolk, Scott J.; Zank, G. P.; Zarka, P.; Kopparapu, R.; Babakhanova,
S.; Pevtsov, A. A.; Lee, Y.; Henning, W.; Colón, K. D.; Wolf, E. T.
2019BAAS...51c.564A Altcode: 2019astro2020T.564A; 2019arXiv190306853A
The goal of this white paper is to identify and describe promising key
research goals to aid the theoretical characterization and observational
detection of ionizing radiation from quiescent and flaring upper
atmospheres of planet hosts as well as properties of stellar coronal
mass ejections (CMEs) and stellar energetic particle (SEP) events.

---------------------------------------------------------
Title: Stars at High Spatial Resolution
Authors: Carpenter, Kenneth; van Belle, Gerard; Brown, Alexander;
Cranmer, Steven R.; Drake, Jeremy; Dupree, Andrea K.; Creech-Eakman,
Michelle; Evans, Nancy R.; Grady, Carol A.; Guinan, Edward F.; Harper,
Graham; Karovska, Margarita; Kolenberg, Katrien; Labeyrie, Antoine;
Linsky, Jeffrey; Peters, Geraldine J.; Rau, Gioia; Ridgway, Stephen;
Roettenbacher, Rachael M.; Saar, Steven H.; Walter, Frederick M.;
Wood, Brian
2019BAAS...51c..56C Altcode: 2019astro2020T..56C
We summarize compelling new scientific opportunities for understanding
stars and stellar systems that can be enabled by sub-milliarcsec angular
resolution, UV/Optical spectral imaging observations. These can reveal
details of many dynamic processes that affect stellar formation,
structure, and evolution.

---------------------------------------------------------
Title: A Hot Ultraviolet Flare on the M Dwarf Star GJ 674
Authors: Froning, Cynthia S.; Kowalski, Adam; France, Kevin; Loyd,
R. O. Parke; Schneider, P. Christian; Youngblood, Allison; Wilson,
David; Brown, Alexander; Berta-Thompson, Zachory; Pineda, J. Sebastian;
Linsky, Jeffrey; Rugheimer, Sarah; Miguel, Yamila
2019ApJ...871L..26F Altcode:
As part of the Mega-Measurements of the Ultraviolet Spectral
Characteristics of Low-Mass Exoplanetary Systems Hubble Space Telescope
(HST) Treasury program, we obtained time-series ultraviolet spectroscopy
of the M2.5V star, GJ 674. During the far-ultraviolet (FUV) monitoring
observations, the target exhibited several small flares and one large
flare (E FUV = 1030.75 erg) that persisted
over the entirety of an HST orbit and had an equivalent duration
&gt;30,000 s, comparable to the highest relative amplitude event
previously recorded in the FUV. The flare spectrum exhibited enhanced
line emission from chromospheric, transition region, and coronal
transitions and a blue FUV continuum with an unprecedented color
temperature of TC ≃ 40,000 ± 10,000 K. In this Letter,
we compare the flare FUV continuum emission with parameterizations of
radiative hydrodynamic model atmospheres of M star flares. We find that
the observed flare continuum can be reproduced using flare models but
only with the ad hoc addition of a hot, dense emitting component. This
observation demonstrates that flares with hot FUV continuum temperatures
and significant extreme-ultraviolet/FUV energy deposition will continue
to be of importance to exoplanet atmospheric chemistry and heating, even
as the host M dwarfs age beyond their most active evolutionary phases.

---------------------------------------------------------
Title: A Hot Ultraviolet Flare on the M Dwarf Star GJ 674
Authors: Froning, C. S.; Kowalski, A.; France, K.; Loyd, R. O. Parke;
Schneider, P. Christian; Youngblood, A.; Wilson, D.; Brown, A.;
Berta-Thompson, Z.; Pineda, J. Sebastian; Linsky, J.; Rugheimer, S.;
Miguel, Y.
2019arXiv190108647F Altcode:
As part of the Mega MUSCLES Hubble Space Telescope (HST) Treasury
program, we obtained time-series ultraviolet spectroscopy of the
M2.5V star, GJ~674. During the FUV monitoring observations, the
target exhibited several small flares and one large flare (E_FUV =
10^{30.75} ergs) that persisted over the entirety of a HST orbit
and had an equivalent duration &gt;30,000 sec, comparable to the
highest relative amplitude event previously recorded in the FUV. The
flare spectrum exhibited enhanced line emission from chromospheric,
transition region, and coronal transitions and a blue FUV continuum
with an unprecedented color temperature of T_c ~ 40,000+/-10,000
K. In this paper, we compare the flare FUV continuum emission with
parameterizations of radiative hydrodynamic model atmospheres of M star
flares. We find that the observed flare continuum can be reproduced
using flare models but only with the ad hoc addition of hot, dense
emitting component. This observation demonstrates that flares with hot
FUV continuum temperatures and significant EUV/FUV energy deposition
will continue to be of importance to exoplanet atmospheric chemistry
and heating even as the host M dwarfs age beyond their most active
evolutionary phases.

---------------------------------------------------------
Title: Host Stars and their Effects on Exoplanet Atmospheres
Authors: Linsky, Jeffrey
2019LNP...955.....L Altcode:
No abstract at ADS

---------------------------------------------------------
Title: Comparison between panchromatic spectra of early- and late-M
stars
Authors: Tilipman, Dennis; Linsky, Jeffrey L.; Vieytes, Mariela;
France, Kevin
2019AAS...23336507T Altcode:
We have begun computing panchromatic spectra of M dwarfs that
are known to host exoplanets. We are particularly interested in
ultraviolet radiation that drives photochemical processes in exoplanet
atmospheres. Here we present revised results on GJ 832, a relatively
quiet M2 V dwarf, and a tentative model for GJ 876, an active M5 V
dwarf. The model atmospheres are computed with the SSRPM radiative
transfer code developed by Dr. Juan Fontenla. The code solves for the
non-LTE statistical equilibrium populations of 18,538 levels of 52
atomic and ion species and computes the radiation from all species
(435,986 spectral lines) and about 20,000,000 spectral lines of 20
diatomic species.

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Title: The MUSCLES Treasury Survey. V. FUV Flares on Active and
Inactive M Dwarfs
Authors: Loyd, R. O. Parke; France, Kevin; Youngblood, Allison;
Schneider, Christian; Brown, Alexander; Hu, Renyu; Segura, Antígona;
Linsky, Jeffrey; Redfield, Seth; Tian, Feng; Rugheimer, Sarah; Miguel,
Yamila; Froning, Cynthia S.
2018ApJ...867...71L Altcode: 2018arXiv180907322L
M dwarf stars are known for their vigorous flaring. This flaring
could impact the climate of orbiting planets, making it important
to characterize M dwarf flares at the short wavelengths that drive
atmospheric chemistry and escape. We conducted a far-ultraviolet
flare survey of six M dwarfs from the recent MUSCLES (Measurements of
the Ultraviolet Spectral Characteristics of Low-mass Exoplanetary
Systems) observations, as well as four highly active M dwarfs
with archival data. When comparing absolute flare energies, we
found the active-M-star flares to be about 10× more energetic than
inactive-M-star flares. However, when flare energies were normalized
by the star’s quiescent flux, the active and inactive samples
exhibited identical flare distributions, with a power-law index of
-{0.76}-0.1+0.09 (cumulative distribution). The
rate and distribution of flares are such that they could dominate the
FUV energy budget of M dwarfs, assuming the same distribution holds
to flares as energetic as those cataloged by Kepler and ground-based
surveys. We used the observed events to create an idealized model
flare with realistic spectral and temporal energy budgets to be used
in photochemical simulations of exoplanet atmospheres. Applied to our
own simulation of direct photolysis by photons alone (no particles),
we find that the most energetic observed flares have little effect
on an Earth-like atmosphere, photolyzing ∼0.01% of the total
O3 column. The observations were too limited temporally (73
hr cumulative exposure) to catch rare, highly energetic flares. Those
that the power-law fit predicts occur monthly would photolyze ∼1%
of the O3 column and those it predicts occur yearly would
photolyze the full O3 column. Whether such energetic flares
occur at the rate predicted is an open question.

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Title: Computing Models of M-Type Host Stars and Their Panchromatic
Spectral Output
Authors: Tilipman, D.; Linsky, J. L.; Vieytes, M.; France, K.
2018LPICo2065.2034T Altcode:
We compute semi-empirical models of low-mass stars that are known
to host exoplanets in order to obtain high-resolution panchromatic
spectra. Here we present the first model of an active M5 V dwarf GJ
876 and compare it with our model of GJ 832.

---------------------------------------------------------
Title: Computing Models of M-type Host Stars and their Panchromatic
Spectral Output
Authors: Linsky, Jeffrey; Tilipman, Dennis; France, Kevin
2018AAS...23231703L Altcode:
We have begun a program of computing state-of-the-art model
atmospheres from the photospheres to the coronae of M stars that are
the host stars of known exoplanets. For each model we are computing
the emergent radiation at all wavelengths that are critical for
assessingphotochemistry and mass-loss from exoplanet atmospheres. In
particular, we are computing the stellar extreme ultraviolet radiation
that drives hydrodynamic mass loss from exoplanet atmospheres and is
essential for determing whether an exoplanet is habitable. The model
atmospheres are computed with the SSRPM radiative transfer/statistical
equilibrium code developed by Dr. Juan Fontenla. The code solves for
the non-LTE statistical equilibrium populations of 18,538 levels of
52 atomic and ion species and computes the radiation from all species
(435,986 spectral lines) and about 20,000,000 spectral lines of 20
diatomic species.The first model computed in this program was for the
modestly active M1.5 V star GJ 832 by Fontenla et al. (ApJ 830, 152
(2016)). We will report on a preliminary model for the more active M5
V star GJ 876 and compare this model and its emergent spectrum with
GJ 832. In the future, we will compute and intercompare semi-empirical
models and spectra for all of the stars observed with the HST MUSCLES
Treasury Survey, the Mega-MUSCLES Treasury Survey, and additional stars
including Proxima Cen and Trappist-1.This multiyear theory program is
supported by a grant from the Space Telescope Science Institute.

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Title: Measuring the Local ISM along the Sight Lines of the Two
Voyager Spacecraft with HST/STIS
Authors: Zachary, Julia; Redfield, Seth; Linsky, Jeffrey L.; Wood,
Brian E.
2018ApJ...859...42Z Altcode: 2018arXiv180607979Z
In 2012 August, Voyager 1 crossed the heliopause, becoming the first
human-made object to exit the solar system. This milestone signifies the
beginning of an important new era for local interstellar medium (LISM)
exploration. We present measurements of the structure and composition
of the LISM in the immediate path of the Voyager spacecraft by using
high-resolution Hubble Space Telescope (HST) spectra of nearby stars
that lie along the same lines of sight. We provide a comprehensive
inventory of LISM absorption in the near-ultraviolet (2600-2800 Å)
and far-ultraviolet (1200-1500 Å). The LISM absorption profiles are
used to make comparisons between each pair of closely spaced (&lt;15°)
sight lines. With fits to several absorption lines, we make measurements
of the physical properties of the LISM. We estimate electron density
along the Voyager 2 sight line, and our values are consistent with
recent measurements by Voyager 1. Excess absorption in the H I Lyα
line displays the presence of both the heliosphere and an astrosphere
around GJ 780. This is only the 14th detection of an astrosphere,
and the large mass-loss rate (\dot{M}=10 {\dot{M}}⊙ )
is consistent with other subgiant stars. The heliospheric absorption
matches the predicted strength for a sight line 58° from the upwind
direction. As both HST and Voyager reach the end of their lifetimes,
we have the opportunity to synthesize their respective observations,
combining in situ measurements with the shortest possible line-of-sight
measurements to study the Galactic ISM surrounding the Sun.

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Title: UV astronomy throughout the ages: a historical perspective
Authors: Linsky, Jeffrey L.
2018Ap&SS.363..101L Altcode:
Astronomers have long recognized the critical need for ultraviolet
imaging, photometry and spectroscopy of stars, planets, and galaxies,
but this need could not be satisfied without access to space and
the development of efficient instrumentation. When UV measurements
became feasible, first with rockets and then with satellites, major
discoveries came rapidly. It is true in the UV spectral region as
in all others, that significant increases in sensitivity, spectral
resolution, and time domain coverage have led to significant new
understanding of astrophysical phenomena. I will describe a selection
of these discoveries made in each of three eras: (1) the early history
of rocket instrumentation and Copernicus, the first UV satellite, (2)
the discovery phase pioneered by the IUE, FUSE and EUVE satellites, and
(3) the full flowering of UV astronomy with the successful operation
of HST and its many instruments. I will also mention a few areas
where future UV instrumentation could lead to new discoveries. This
review concentrates on developments in stellar and interstellar UV
spectroscopy; the major discoveries in galactic, extragalactic, and
solar system research are beyond the scope of this review. The important
topic of UV technologies and detectors, which enable the remarkable
advances in UV astronomy are also not included in this review.

---------------------------------------------------------
Title: The ngVLA's Role in Exoplanet Science: Constraining Exo-Space
Weather
Authors: Osten, Rachel A.; Crosley, Michael K.; Gudel, Manuel;
Kowalski, Adam F.; Lazio, Joe; Linsky, Jeffrey; Murphy, Eric; White,
Stephen
2018arXiv180305345O Altcode:
Radio observations are currently the only way to explore accelerated
particles in cool stellar environments. We describe how a next
generation VLA can contribute to the understanding of the stellar
contribution to exo-space weather. This area holds both academic and
popular interest, and is expected to grow in the next several decades.

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Title: VizieR Online Data Catalog: MUSCLES Treasury Survey. IV. M
dwarf UV fluxes (Youngblood+, 2017)
Authors: Youngblood, A.; France, K.; Loyd, R. O. P.; Brown, A.;
Mason, J. P.; Schneider, P. C.; Tilley, M. A.; Berta-Thompson, Z. K.;
Buccino, A.; Froning, C. S.; Hawley, S. L.; Linsky, J.; Mauas,
P. J. D.; Redfield, S.; Kowalski, A.; Miguel, Y.; Newton, E. R.;
Rugheimer, S.; Segura, A.; Roberge, A.; Vieytes, M.
2018yCat..18430031Y Altcode:
We selected stars with HST UV spectra and ground-based optical spectra
either obtained directly by us or available in the VLT/XSHOOTER or
Keck/HIRES public archives. Several targets have spectroscopic
data obtained with the Dual Imaging Spectrograph (DIS) on the
ARC 3.5m telescope at Apache Point Observatory (APO), R~2500, or
the REOSC echelle spectrograph on the 2.15m telescope at Complejo
Astronomico El Leoncito (CASLEO), R~12000, within a day or two of
the HST observations. We also gathered spectra of GJ1132, GJ1214,
and Proxima Cen on the nights of 2016 March 7-9 using the MIKE echelle
spectrograph on the Magellan Clay telescope. (2 data files).

---------------------------------------------------------
Title: Chromospheric and Transition Region Emission Properties of G,
K, and M dwarf Exoplanet Host Stars
Authors: France, Kevin; Arulanantham, Nicole; Fossati, Luca; Lanza,
A. F.; Linsky, Jeffrey L.; Redfield, Seth; Loyd, Robert; Schneider,
Christian
2018AAS...23134906F Altcode:
Exoplanet magnetic fields have proven notoriously hard to detect,
despite theoretical predictions of substantial magnetic field strengths
on close-in extrasolar giant planets. It has been suggested that
stellar and planetary magnetic field interactions can manifest as
enhanced stellar activity relative to nominal age-rotation-activity
relationships for main sequence stars or enhanced activity on stars
hosting short-period massive planets. In a recent study of M and K
dwarf exoplanet host stars, we demonstrated a significant correlation
between the relative luminosity in high-temperature stellar emission
lines (L(ion)/L_Bol) and the “star-planet interaction strength”,
M_plan/a_plan. Here, we expand on that work with a survey of G, K, and
M dwarf exoplanet host stars obtained in two recent far-ultraviolet
spectroscopic programs with the Hubble Space Telescope. We have
measured the relative luminosities of stellar lines C II, Si III,
Si IV, and N V (formation temperatures from 30,000 - 150,000 K) in a
sample of ~60 exoplanet host stars and an additional ~40 dwarf stars
without known planets. We present results on star-planet interaction
signals as a function of spectral type and line formation temperature,
as well as a statistical comparison of stars with and without planets.

---------------------------------------------------------
Title: The Development of New Atmospheric Models for K and M
DwarfStars with Exoplanets
Authors: Linsky, Jeffrey L.
2018AAS...23142405L Altcode:
The ultraviolet and X-ray emissions of host stars play critical roles
in the survival and chemical composition of the atmospheres of their
exoplanets. The need to measure and understand this radiative output,
in particular for K and M dwarfs, is the main rationale for computing
a new generation of stellar models that includes magnetically heated
chromospheres and coronae in addition to their photospheres. We describe
our method for computing semi-empirical models that includes solutions
of the statistical equilibrium equations for 52 atoms and ions and of
the non-LTE radiative transfer equations for all important spectral
lines. The code is an offspring of the Solar Radiation Physical
Modelling system (SRPM) developed by Fontenla et al. (2007--2015)
to compute one-dimensional models in hydrostatic equilibrium to
fit high-resolution stellar X-ray to IR spectra. Also included
are 20 diatomic molecules and their more than 2 million spectral
lines. Our-proof-of-concept model is for the M1.5 V star GJ 832
(Fontenla et al. ApJ 830, 154 (2016)). We will fit the line fluxes and
profiles of X-ray lines and continua observed by Chandra and XMM-Newton,
UV lines observed by the COS and STIS instruments on HST (N V, C IV, Si
IV, Si III, Mg II, C II, and O I), optical lines (including H$\alpha$,
Ca II, Na I), and continua. These models will allow us to compute
extreme-UV spectra, which are unobservable but required to predict the
hydrodynamic mass-loss rate from exoplanet atmospheres, and to predict
panchromatic spectra of new exoplanet host stars discovered after the
end of the HST mission.This work is supported by grant HST-GO-15038
from the Space Telescope Science Institute to the Univ. of Colorado

---------------------------------------------------------
Title: Model Atmospheres and Spectral Irradiance Library of the
Exoplanet Host Stars Observed in the MUSCLES Survey
Authors: Linsky, Jeffrey
2017hst..prop15038L Altcode:
We propose to compute state-of-the-art model atmospheres (photospheres,
chromospheres, transition regions and coronae) of the 4 K and 7 M
exoplanet host stars observed by HST in the MUSCLES Treasury Survey, the
nearest host star Proxima Centauri, and TRAPPIST-1. Our semi-empirical
models will fit theunique high-resolution panchromatic (X-ray to
infrared) spectra of these stars in the MAST High-Level Science Products
archive consisting of COS and STIS UV spectra and near-simultaneous
Chandra, XMM-Newton, and ground-based observations. We will compute
models with the fully tested SSRPM computer software incorporating 52
atoms and ions in full non-LTE (435,986 spectral lines) and the 20
most-abundant diatomic molecules (about 2 million lines). This code
has successfully fit the panchromatic spectrum of the M1.5 V exoplanet
host star GJ 832 (Fontenla et al. 2016), the first M star with such
a detailed model, and solar spectra. Our models will (1) predict the
unobservable extreme-UV spectra, (2) determine radiative energy losses
and balancing heating rates throughout these atmospheres, (3) compute a
stellar irradiance library needed to describe the radiation environment
of potentially habitable exoplanets to be studied by TESS and JWST, and
(4) in the long post-HST era when UV observations will not be possible,
the stellar irradiance library will be a powerful tool for predicting
the panchromatic spectra of host stars that have only limited spectral
coverage, in particular no UV spectra. The stellar models and spectral
irradiance library will be placed quickly in MAST.

---------------------------------------------------------
Title: Stellar Model Chromospheres and Spectroscopic Diagnostics
Authors: Linsky, Jeffrey L.
2017ARA&A..55..159L Altcode:
The discovery of exoplanets and the desire to understand their
atmospheric chemical composition and habitability provides a
new rationale for understanding the radiation from X-rays to radio
wavelengths emitted by their host stars. Semiempirical models of stellar
atmospheres that include accurate treatment of radiative transfer of
all important atoms, ions, and molecules provide the essential basis
for understanding a star's emitted radiation that is our main data
source for characterizing a star and the radiation environment of its
exoplanets. In Solar-type and cooler stars, the ultraviolet and extreme
ultraviolet radiation formed in their chromospheres and transition
regions drive the photochemistry in exoplanet atmospheres. In this
review, I describe and critique the development of semiempirical static
and time-dependent models of the chromospheres and transition regions of
the Sun and cooler stars as well as the spectroscopic diagnostics upon
which these models are based. The related topics of stellar coronae and
winds and their theoretical bases are beyond the scope of this review.

---------------------------------------------------------
Title: The MUSCLES Treasury Survey. IV. Scaling Relations for
Ultraviolet, Ca II K, and Energetic Particle Fluxes from M Dwarfs
Authors: Youngblood, Allison; France, Kevin; Loyd, R. O. Parke; Brown,
Alexander; Mason, James P.; Schneider, P. Christian; Tilley, Matt A.;
Berta-Thompson, Zachory K.; Buccino, Andrea; Froning, Cynthia S.;
Hawley, Suzanne L.; Linsky, Jeffrey; Mauas, Pablo J. D.; Redfield,
Seth; Kowalski, Adam; Miguel, Yamila; Newton, Elisabeth R.; Rugheimer,
Sarah; Segura, Antígona; Roberge, Aki; Vieytes, Mariela
2017ApJ...843...31Y Altcode: 2017arXiv170504361Y
Characterizing the UV spectral energy distribution (SED) of
an exoplanet host star is critically important for assessing its
planet’s potential habitability, particularly for M dwarfs, as they
are prime targets for current and near-term exoplanet characterization
efforts and atmospheric models predict that their UV radiation can
produce photochemistry on habitable zone planets different from that
on Earth. To derive ground-based proxies for UV emission for use when
Hubble Space Telescope (HST) observations are unavailable, we have
assembled a sample of 15 early to mid-M dwarfs observed by HST and
compared their nonsimultaneous UV and optical spectra. We find that
the equivalent width of the chromospheric Ca II K line at 3933 Å, when
corrected for spectral type, can be used to estimate the stellar surface
flux in ultraviolet emission lines, including H I Lyα. In addition,
we address another potential driver of habitability: energetic particle
fluxes associated with flares. We present a new technique for estimating
soft X-ray and &gt;10 MeV proton flux during far-UV emission line flares
(Si IV and He II) by assuming solar-like energy partitions. We analyze
several flares from the M4 dwarf GJ 876 observed with HST and Chandra as
part of the MUSCLES Treasury Survey and find that habitable zone planets
orbiting GJ 876 are impacted by large Carrington-like flares with peak
soft X-ray fluxes ≥10-3 W m-2 and possible
proton fluxes ∼102-103 pfu, approximately four
orders of magnitude more frequently than modern-day Earth.

---------------------------------------------------------
Title: What Can TRAPPIST-1 Tell Us About Radiation From M-Dwarf
Chromospheres And Coronae
Authors: Linsky, Jeffrey
2017reph.conf20103L Altcode:
The recent discovery of 7 planets orbiting the nearby star TRAPPIST-1
(Gillon et al. Nature 2017) and the discovery that this M8 V host star
has very weak chromospheric compared to coronal emission (Bourrier
et al. A+A 2017) raises the broader question of the relation of
chromospheres to coronae in host stars. This question is important
because chromospheric emission, primarily in the Lyman-alpha line,
controls photochemical reactions in the outer atmospheres of exoplanets,
whereas coronal X-ray emission and associated coronal mass ejections
play critical roles in atmospheric mass loss. Both chromospheric and
coronal emission from the host star can, therefore, determine whether
a planet is habitable. I will show that the amount of emission in the
Lyman-alpha line is proportional to that in X-rays for F-K dwarf stars,
but that chromospheric emission becomes relatively weak in the early
M dwarfs and very weak in the late-M dwarfs such as TRAPPIST-1.Stellar
emission lines formed in a star's chromosphere and transition region can
be separated into narrow and broad Gaussian components with the broad
components formed by microflaring events or high speed flows. I will
show how the broad component activity indicator depends on stellar
effective temperature and age.I will also describe the results
concerning star-planet interactions obtained by MUSCLES Treasury
Survey team.

---------------------------------------------------------
Title: Measuring the local ISM along the sight lines of the two
Voyager spacecraft with HST/STIS
Authors: Zachary, Julia; Redfield, Seth; Linsky, Jeffrey
2017AAS...22934034Z Altcode:
In August 2012, Voyager 1 crossed the heliopause, becoming the first
human-made object to exit the Solar System. This milestone signifies the
beginning of an important new era for local interstellar medium (LISM)
discoveries. We present measurements of the structure and composition
of the LISM by using high-resolution Hubble Space Telescope spectra of
nearby stars that lie along the same lines of sight as the respective
paths of the Voyager spacecraft. We provide a comprehensive inventory
of LISM absorption in the near-ultraviolet (2600-2800Å) and the
far-ultraviolet (1200-1500Å). The LISM absorption profiles are used
to make comparisons between each pair of closely spaced (&lt;15°)
sight lines. With these fits, we can make measurements of the physical
properties of the LISM, including temperature, turbulence, electron
density, and dust composition. As both HST and Voyager reach the end
of their lifetimes, we now have the opportunity to synthesize their
respective independent and complementary observations, combining in-situ
measurements with the shortest possible line-of-sight measurements
to provide an unprecedented study of the galactic ISM surrounding
the Sun.We would like to acknowledge NASA HST Grant GO-13658 awarded
by the Space Telescope Science Institute, which is operated by the
Association of Universities for Research in Astronomy, Inc., for NASA,
under contract NAS 5-26555.

---------------------------------------------------------
Title: Semi-empirical Modeling of the Photosphere, Chromosphere,
Transition Region, and Corona of the M-dwarf Host Star GJ 832
Authors: Fontenla, J. M.; Linsky, Jeffrey L.; Witbrod, Jesse; France,
Kevin; Buccino, A.; Mauas, Pablo; Vieytes, Mariela; Walkowicz,
Lucianne M.
2016ApJ...830..154F Altcode:
Stellar radiation from X-rays to the visible provides the energy
that controls the photochemistry and mass loss from exoplanet
atmospheres. The important extreme ultraviolet (EUV) region (10-91.2
nm) is inaccessible and should be computed from a reliable stellar
model. It is essential to understand the formation regions and
physical processes responsible for the various stellar emission
features to predict how the spectral energy distribution varies with
age and activity levels. We compute a state-of-the-art semi-empirical
atmospheric model and the emergent high-resolution synthetic spectrum
of the moderately active M2 V star GJ 832 as the first of a series
of models for stars with different activity levels. We construct
a one-dimensional simple model for the physical structure of the
star’s chromosphere, chromosphere-corona transition region, and
corona using non-LTE radiative transfer techniques and many molecular
lines. The synthesized spectrum for this model fits the continuum
and lines across the UV-to-optical spectrum. Particular emphasis is
given to the emission lines at wavelengths that are shorter than 300 nm
observed with the Hubble Space Telescope, which have important effects
on the photochemistry of the exoplanet atmospheres. The FUV line ratios
indicate that the transition region of GJ 832 is more biased to hotter
material than that of the quiet Sun. The excellent agreement of our
computed EUV luminosity with that obtained by two other techniques
indicates that our model predicts reliable EUV emission from GJ 832. We
find that the unobserved EUV flux of GJ 832, which heats the outer
atmospheres of exoplanets and drives their mass loss, is comparable
to the active Sun. Based on observations made with the NASA/ESA
Hubble Space Telescope obtained from the Data Archive at the Space
Telescope Science Institute, which is operated by the Association of
Universities for Research in Astronomy, Inc., under NASA contract NAS
AR-09525.01A. These observations are associated with programs #12034,
12035, 12464.

---------------------------------------------------------
Title: Semi-empirical Modeling of the Photosphere, Chromosphere,
Transition Region, and Corona of the M-dwarf Host Star GJ 832
Authors: Fontenla, J. M.; Linsky, Jeffrey L.; Witbrod, Jesse;
France, Kevin; Buccino, A.; Mauas, Pablo; Vietes, Mariela; Walkowicz,
Lucianne M.
2016arXiv160800934F Altcode:
Stellar radiation from X-rays to the visible provides the energy
that controls the photochemistry and mass loss from exoplanet
atmospheres. The important extreme ultraviolet (EUV) region
(10--91.2~nm) is inaccessible and should be computed from a reliable
stellar model. It is essential to understand the formation regions and
physical processes responsible for the various stellar emission features
in order to predict how the spectral energy distribution varies with
age and activity levels. We compute a state-of-the-art semi-empirical
atmospheric model and the emergent high-resolution synthetic spectrum
of the moderately active M2~V star GJ~832 as the first of a series
of models for stars with different activity levels. Using non-LTE
radiative transfer techniques and including many molecular lines, we
construct a one-dimensional simple model for the physical structure
of the star's chromosphere, chromosphere-corona transition region, and
corona. The synthesized spectrum for this model fits the continuum and
lines across the UV to optical spectrum. Particular emphasis is given
to the emission lines at wavelengths shorter than 300~nm observed
with {\em HST}, which have important effects on the photochemistry
in the exoplanet atmospheres. The FUV line ratios indicate that the
transition region of GJ~832 is more biased to hotter material than
that of the quiet Sun. The excellent agreement of our computed EUV
luminosity with that obtained by two other techniques indicates that
our model predicts reliable EUV emission from GJ~832. We find that
unobserved EUV flux of GJ~832, which heats the outer atmospheres of
exoplanets and drives their mass loss, is comparable to the active Sun.

---------------------------------------------------------
Title: Prospects for ALMA Studies of the Solar-Stellar Connection
Authors: Linsky, Jeffrey
2016csss.confE..81L Altcode:
ALMA provides a splendid opportunity to observe a wide range of star
types at millimeter wavelengths to investigate the solar-stellar
connection. I will compare the sensitivities and wavelength coverages
of ALMA and the JVLA to highlight the discovery space that ALMA has
for stellar astronomy. At millimeter wavelengths, ALMA will be able
to detect thermal and gyroresonance emission from nearby stellar
chromospheres and transition regions. Comparison of millimeter fluxes
from ALMA with centimeter fluxes from JVLA may be able to separate
thermal from gyrosynchrotron emission from stellar coronae and thereby
measure magnetic field strengths in stellar coronae. Measurements of
stellar wind mass-loss rates are feasible with ALMA for giants but
will be difficult for main sequence stars. The study of stellar flares
should be an active area of research with ALMA.

---------------------------------------------------------
Title: The MUSCLES Treasury Survey. III. X-Ray to Infrared Spectra
of 11 M and K Stars Hosting Planets
Authors: Loyd, R. O. P.; France, Kevin; Youngblood, Allison; Schneider,
Christian; Brown, Alexander; Hu, Renyu; Linsky, Jeffrey; Froning,
Cynthia S.; Redfield, Seth; Rugheimer, Sarah; Tian, Feng
2016ApJ...824..102L Altcode: 2016arXiv160404776P
We present a catalog of panchromatic spectral energy distributions
(SEDs) for 7 M and 4 K dwarf stars that span X-ray to infrared
wavelengths (5 Å -5.5 μm). These SEDs are composites of Chandra
or XMM-Newton data from 5-∼50 Å, a plasma emission model from
∼50-100 Å, broadband empirical estimates from 100-1170 Å, Hubble
Space Telescope data from 1170-5700 Å, including a reconstruction of
stellar Lyα emission at 1215.67 Å, and a PHOENIX model spectrum from
5700-55000 Å. Using these SEDs, we computed the photodissociation
rates of several molecules prevalent in planetary atmospheres
when exposed to each star’s unattenuated flux (“unshielded”
photodissociation rates) and found that rates differ among stars by
over an order of magnitude for most molecules. In general, the same
spectral regions drive unshielded photodissociations both for the
minimally and maximally FUV active stars. However, for O3
visible flux drives dissociation for the M stars whereas near-UV
flux drives dissociation for the K stars. We also searched for an
far-UV continuum in the assembled SEDs and detected it in 5/11 stars,
where it contributes around 10% of the flux in the range spanned
by the continuum bands. An ultraviolet continuum shape is resolved
for the star ɛ Eri that shows an edge likely attributable to Si II
recombination. The 11 SEDs presented in this paper, available online
through the Mikulski Archive for Space Telescopes, will be valuable
for vetting stellar upper-atmosphere emission models and simulating
photochemistry in exoplanet atmospheres.

---------------------------------------------------------
Title: The MUSCLES Treasury Survey. II. Intrinsic LYα and Extreme
Ultraviolet Spectra of K and M Dwarfs with Exoplanets*
Authors: Youngblood, Allison; France, Kevin; Loyd, R. O. Parke; Linsky,
Jeffrey L.; Redfield, Seth; Schneider, P. Christian; Wood, Brian E.;
Brown, Alexander; Froning, Cynthia; Miguel, Yamila; Rugheimer, Sarah;
Walkowicz, Lucianne
2016ApJ...824..101Y Altcode: 2016arXiv160401032Y
The ultraviolet (UV) spectral energy distributions (SEDs) of
low-mass (K- and M-type) stars play a critical role in the heating
and chemistry of exoplanet atmospheres, but are not observationally
well-constrained. Direct observations of the intrinsic flux of the
Lyα line (the dominant source of UV photons from low-mass stars)
are challenging, as interstellar H I absorbs the entire line core
for even the closest stars. To address the existing gap in empirical
constraints on the UV flux of K and M dwarfs, the MUSCLES Hubble Space
Telescope Treasury Survey has obtained UV observations of 11 nearby
M and K dwarfs hosting exoplanets. This paper presents the Lyα and
extreme-UV spectral reconstructions for the MUSCLES targets. Most
targets are optically inactive, but all exhibit significant UV
activity. We use a Markov Chain Monte Carlo technique to correct the
observed Lyα profiles for interstellar absorption, and we employ
empirical relations to compute the extreme-UV SED from the intrinsic
Lyα flux in ∼100 Å bins from 100-1170 Å. The reconstructed Lyα
profiles have 300 km s-1 broad cores, while &gt;1% of the
total intrinsic Lyα flux is measured in extended wings between 300
and 1200 km s-1. The Lyα surface flux positively correlates
with the Mg II surface flux and negatively correlates with the stellar
rotation period. Stars with larger Lyα surface flux also tend to
have larger surface flux in ions formed at higher temperatures, but
these correlations remain statistically insignificant in our sample
of 11 stars. We also present H I column density measurements for 10
new sightlines through the local interstellar medium. Based on
observations made with the NASA/ESA Hubble Space Telescope, obtained
from the data archive at the Space Telescope Science Institute. STScI is
operated by the Association of Universities for Research in Astronomy,
Inc. under NASA contract NAS 5-26555.

---------------------------------------------------------
Title: A SNAP UV Spectroscopic Study of Star-Planet Interactions
Authors: France, Kevin; Arulanantham, Nicole; Fossati, Luca; Lanza,
Antonino; Linsky, Jeffrey L.; Loyd, R. O. Parke; Redfield, Seth;
Schneider, Christian
2016hst..prop14633F Altcode:
We propose a SNAP spectroscopic program to survey G and K dwarf
exoplanet host stars in the solar neighborhood to characterize
the interaction of these stars with their orbiting planetary
systems. Stellar and planetary fields may interact for close-in planets,
resulting in enhanced stellar activity of the host star and potentially
affecting the habitability of planets in the system. A recent study
of low-mass stars (France et al. 2016) found evidence for star-planet
interactions (SPI) between the stellar transition region/corona and
the planets. This work showed a correlation between high-temperature
(T_{form} &gt;~ 10^{5} K) stellar emission lines (N V, C IV, and Si
IV) and the ratio of planetary mass to the orbital semi-major axis,
M_{plan}/a_{plan}. However, that work focused on a limited number of M
and K stars. We propose to observe a large number of exoplanet hosting G
and K dwarfs to expand the parameter space to a wider range of stellar
mass and M_{plan}/a_{plan}. Given the combination of spectroscopic
sensitivity and the rich suite of spectral diagnostics in the COS
G130M band, this program can be carried out with ~1800 second SNAP
observations of G and K dwarf host stars within 50 pc.

---------------------------------------------------------
Title: A semi-empirical model for the M star GJ832 using modeling
tools developed for computing semi-empirical solar models
Authors: Linsky, Jeffrey; Fontenla, Juan; France, Kevin
2016SPD....47.0105L Altcode:
We present a semi-empirical model of the photosphere, chromosphere,
transition region, and corona for the M2 dwarf star GJ832, which
hosts two exoplanets. The atmospheric model uses a modification of
the Solar Radiation Physical Modeling tools developed by Fontenla
and collaborators. These computer codes model non-LTE spectral line
formation for 52 atoms and ions and include a large number of lines
from 20 abundant diatomic molecules that are present in the much
cooler photosphere and chromosphere of this star. We constructed the
temperature distribution to fit Hubble Space Telescope observations of
chromospheric lines (e.g., MgII), transition region lines (CII, CIV,
SiIV, and NV), and the UV continuum. Temperatures in the coronal portion
of the model are consistent with ROSAT and XMM-Newton X-ray observations
and the FeXII 124.2 nm line. The excellent fit of the model to the
data demonstrates that the highly developed model atmosphere code
developed to explain regions of the solar atmosphere with different
activity levels has wide applicability to stars, including this M star
with an effective temperature 2200 K cooler than the Sun. We describe
similarities and differences between the M star model and models of
the quiet and active Sun.

---------------------------------------------------------
Title: Astrospheres, stellar winds, and the interstellar medium
Authors: Wood, Brian E.; Linsky, Jeffrey L.
2016hasa.book...56W Altcode:
No abstract at ADS

---------------------------------------------------------
Title: The MUSCLES Treasury Survey. I. Motivation and Overview
Authors: France, Kevin; Loyd, R. O. Parke; Youngblood, Allison;
Brown, Alexander; Schneider, P. Christian; Hawley, Suzanne L.;
Froning, Cynthia S.; Linsky, Jeffrey L.; Roberge, Aki; Buccino,
Andrea P.; Davenport, James R. A.; Fontenla, Juan M.; Kaltenegger,
Lisa; Kowalski, Adam F.; Mauas, Pablo J. D.; Miguel, Yamila; Redfield,
Seth; Rugheimer, Sarah; Tian, Feng; Vieytes, Mariela C.; Walkowicz,
Lucianne M.; Weisenburger, Kolby L.
2016ApJ...820...89F Altcode: 2016arXiv160209142F
Ground- and space-based planet searches employing radial velocity
techniques and transit photometry have detected thousands
of planet-hosting stars in the Milky Way. With so many planets
discovered, the next step toward identifying potentially habitable
planets is atmospheric characterization. While the Sun-Earth system
provides a good framework for understanding the atmospheric chemistry
of Earth-like planets around solar-type stars, the observational
and theoretical constraints on the atmospheres of rocky planets in
the habitable zones (HZs) around low-mass stars (K and M dwarfs) are
relatively few. The chemistry of these atmospheres is controlled by the
shape and absolute flux of the stellar spectral energy distribution
(SED), however, flux distributions of relatively inactive low-mass
stars are poorly understood at present. To address this issue, we
have executed a panchromatic (X-ray to mid-IR) study of the SEDs of
11 nearby planet-hosting stars, the Measurements of the Ultraviolet
Spectral Characteristics of Low-mass Exoplanetary Systems (MUSCLES)
Treasury Survey. The MUSCLES program consists visible observations from
Hubble and ground-based observatories. Infrared and astrophysically
inaccessible wavelengths (EUV and Lyα) are reconstructed using
stellar model spectra to fill in gaps in the observational data. In
this overview and the companion papers describing the MUSCLES survey,
we show that energetic radiation (X-ray and ultraviolet) is present from
magnetically active stellar atmospheres at all times for stars as late
as M6. The emission line luminosities of C IV and Mg II are strongly
correlated with band-integrated luminosities and we present empirical
relations that can be used to estimate broadband FUV and XUV (≡X-ray +
EUV) fluxes from individual stellar emission line measurements. We find
that while the slope of the SED, FUV/NUV, increases by approximately
two orders of magnitude form early K to late M dwarfs (≈0.01-1), the
absolute FUV and XUV flux levels at their corresponding HZ distances
are constant to within factors of a few, spanning the range 10-70 erg
cm-2 s-1 in the HZ. Despite the lack of strong
stellar activity indicators in their optical spectra, several of the
M dwarfs in our sample show spectacular UV flare emission in their
light curves. We present an example with flare/quiescent ultraviolet
flux ratios of the order of 100:1 where the transition region
energy output during the flare is comparable to the total quiescent
luminosity of the star Eflare(UV) ∼ 0.3 L*Δt
(Δt = 1 s). Finally, we interpret enhanced L(line)/LBol
ratios for C IV and N v as tentative observational evidence for the
interaction of planets with large planetary mass-to-orbital distance
ratios (Mplan/aplan) with the transition regions
of their host stars. Based on observations made with the NASA/ESA
Hubble Space Telescope, obtained from the data archive at the Space
Telescope Science Institute. STScI is operated by the Association
of Universities for Research in Astronomy, Inc. under NASA contract
NAS 5-26555.

---------------------------------------------------------
Title: Quiescent and flaring lyman-α radiation of host stars and
effects on exoplanets
Authors: Linsky, Jeffrey L.; France, Kevin; Miguel, Yamila;
Kaltenegger, Lisa
2016IAUS..320..391L Altcode:
Lyman-α radiation dominates the ultraviolet spectra of G, K, and M
stars and is a major photodissociation source for H2O,
CO2, and CH4 in the upper atmospheres of
exoplanets. We obtain intrinsic Lyman-α line fluxes for late-type
stars by correcting for interstellar absorption or by scaling from
other spectroscopic observables. When stars flare, all emission
lines brighten by large factors as shown by HST spectra. We describe
photochemical models of the atmosphere of the mini-Neptune GJ 436b
(Miguel et al. 2015) that show the effects of flaring Lyman-α fluxes
on atmospheric chemical abundances.

---------------------------------------------------------
Title: An Empirically-derived non-LTE XUV-Visible Spectral Synthesis
Model of the M1 V Exoplanet Host Star GJ832
Authors: Linsky, Jeffrey; Fontenla, Juan; Witbrod, Jesse; France, Kevin
2016AAS...22712106L Altcode:
GJ832 (HD 204961) is a nearby M1 V host star with two exoplanets:
a Jovian mass planet and a super-Earth. We have obtained near-UV and
far-UV spectra of GJ832 with the STIS and COS instruments on HST as
part of the Cycle 19 MUSCLES pilot program (France et al. 2013). Our
objective is to obtain the first accurate physical model for a
representative M-dwarf host star in order to understand the stellar
radiative emission at all wavelengths and to infer the radiation
environment of their exoplanets that drives their atmospheric
photochemistry.We have calculated a full non-LTE model for GJ 832
including the photosphere, chromosphere, transition region, and
corona to fit the observed emission lines formed over a wide range of
temperatures and the X-ray flux. Our one-dimensional semi-empirical
model uses the Solar-Stellar Physical Modelling tools that are an
offspring of the tools used by Fontenla and collaborators for computing
solar models. For this model of GJ832, we calculate the populations of
52 atoms and ions and 20 molecules with 2 million spectral lines. We
find excellent agreement with the observed H-alpha, CaII, MgII, CII,
SiIV, CIV, and NV lines. Our model for GJ832 has a temperature minimum
in the lower chromosphere much cooler than the Sun and then a steep
temperature rise different from the Sun. The different thermal structure
of GJ832 compared to the Sun results in the formation regions of the
emission lines being different for the two stars. We also compute
theradiative cooling rates as a function of height and temperature in
the atmosphere of GJ832.This work is supported by grants from STScI
to the University of Colorado.

---------------------------------------------------------
Title: The MUSCLES Treasury Survey: Temporally- and
Spectrally-Resolved Irradiance from Low-mass Exoplanet Host Stars
Authors: France, Kevin; Loyd, R. O. Parke; Youngblood, Allison;
Linsky, Jeffrey; MUSCLES Treasury Survey Team
2016AAS...22712107F Altcode:
The spectral and temporal behavior of exoplanet host stars is a
critical input to models of the chemistry and evolution of planetary
atmospheres. High-energy photons (X-ray to near-UV; 5 - 3200 Ang)
from these stars regulate the atmospheric temperature profiles and
photochemistry on orbiting planets, influencing the production of
potential "biomarker" gases. It has been shown that the atmospheric
signatures of potentially habitable planets around low-mass stars may
be significantly different from planets orbiting Sun-like stars owing
to the different UV spectral energy distribution. I will present
results from a panchromatic survey (Hubble/Chandra/XMM/optical)
of M and K dwarf exoplanet hosts, the MUSCLES Treasury Survey
(Measurements of the Ultraviolet Spectral Characteristics of Low-mass
Exoplanetary Systems). We reconstruct the Lyman-alpha and extreme-UV
(100-900 Ang) radiation lost to interstellar attenuation and create
5 Angstrom to 5 micron stellar irradiance spectra; these data will
be publically available as a High-Level Science Product on MAST. We
find that all low-mass exoplanet host stars exhibit significant
chromospheric/transition region/coronal emission -- no "UV inactive"
M dwarfs are observed. The F(far-UV)/F(near-UV) flux ratio, a driver
for possible abiotic production of the suggested biomarkers O2 and
O3, increases by ~3 orders of magnitude as the habitable zone moves
inward from 1 to 0.1 AU, while the incident far-UV (912 - 1700 Ang)
and XUV (5 - 900 Ang) radiation field strengths decrease by factors of
a few across this range. Far-UV flare activity is common in 'optically
inactive' M dwarfs; statistics from the entire sample indicate that
large UV flares (E(300 - 1700 Ang) &gt;= 10^31 erg) occur several
times per day on typical M dwarf exoplanet hosts.

---------------------------------------------------------
Title: Connecting Earth with its Galactic Environment: Probing Our
Interstellar Past Along the Historical Solar Trajectory
Authors: Redfield, Seth; Cauley, Paul Wilson; Frisch, Priscilla C.;
Linsky, Jeffrey L.; Mueller, Hans-Reinhard; Wyman, Katherine
2015hst..prop14084R Altcode:
We propose to observe a sample of stars along the historical solar
trajectory to probe the physical properties of our past interstellar
environments. For more than 90 years there has been speculation
surrounding the relationship between the interstellar medium, its
influence on our heliosphere, and ultimately on variations in the
atmosphere and even organism evolution here on Earth. By looking
locally, at our most recent interstellar history, we can minimize many
of the complications that have made establishing such a relationship
difficult. The low column densities require high resolution spectroscopy
of the strongest resonance lines, which are in the UV. This program
will complement a ground-based survey that utilized the two strongest
transitions in the optical, CaII and NaI, but was unable detect the
lowest interstellar column densities within 100 pc. Therefore, this is
necessarily a UV program and the strength of UV transitions will ensure
detection of this material. The observations will be used to measure the
number of clouds, their distances, densities, and velocities along this
special line of sight. These measurements will be used to reconstruct
the recent variations in heliospheric structure and Galactic cosmic ray
flux as a result of passing through these clouds. Our observational
results can be compared with existing geological tracers of cosmic
rays. If these observations support a relationship between our past
interstellar surroundings and the cosmic ray flux at 1 AU, it would
have important implications for the history of the Earth's biosphere,
as well as a new context to evaluate the interstellar environments of
nearby stars with planetary systems.

---------------------------------------------------------
Title: Evaluating the Morphology of the Local Interstellar Medium:
Using New Data to Distinguish between Multiple Discrete Clouds and
a Continuous Medium
Authors: Redfield, Seth; Linsky, Jeffrey L.
2015ApJ...812..125R Altcode: 2015arXiv150902517R
Ultraviolet and optical spectra of interstellar gas along the lines
of sight to nearby stars have been interpreted by Redfield &amp;
Linsky and previous studies as a set of discrete warm, partially
ionized clouds each with a different flow vector, temperature, and
metal depletion. Recently, Gry &amp; Jenkins proposed a fundamentally
different model consisting of a single cloud with nonrigid flows filling
space out to 9 pc from the Sun that they propose better describes the
local ISM. Here we test these fundamentally different morphological
models against the spatially unbiased Malamut et al. spectroscopic
data set, and find that the multiple cloud morphology model provides a
better fit to both the new and old data sets. The detection of three or
more velocity components along the lines of sight to many nearby stars,
the presence of nearby scattering screens, the observed thin elongated
structures of warm interstellar gas, and the likely presence of strong
interstellar magnetic fields also support the multiple cloud model. The
detection and identification of intercloud gas and the measurement of
neutral hydrogen density in clouds beyond the Local Interstellar Cloud
could provide future morphological tests. Based on observations
made with the NASA/ESA Hubble Space Telescope, obtained from the Data
Archive at the Space Telescope Science Institute, which is operated
by the Association of Universities for Research in Astronomy, Inc.,
under NASA contract NAS AR-09525.01A. These observations are associated
with programs #11568.

---------------------------------------------------------
Title: Observations of Strong Magnetic Fields in Nondegenerate Stars
Authors: Linsky, Jeffrey L.; Schöller, Markus
2015SSRv..191...27L Altcode: 2015SSRv..tmp...16L
We review magnetic-field measurements of nondegenerate stars across
the Hertzprung-Russell diagram for main sequence, premain sequence,
and postmain sequence stars. For stars with complex magnetic-field
morphologies, which includes all G-M main sequence stars, the analysis
of spectra obtained in polarized vs unpolarized light provides very
different magnetic measurements because of the presence or absence
of cancellation by oppositely directed magnetic fields within the
instrument's spatial resolution. This cancellation can be severe, as
indicated by the spatially averaged magnetic field of the Sun viewed
as a star. These averaged fields are smaller by a factor of 1000
or more compared to spatially resolved magnetic-field strengths. We
explain magnetic-field terms that characterize the fields obtained with
different measurement techniques. Magnetic fields typically control
the structure of stellar atmospheres in and above the photosphere,
the heating rates of stellar chromospheres and coronae, mass and
angular momentum loss through stellar winds, chemical peculiarity,
and the emission of high energy photons, which is critically important
for the evolution of protoplanetary disks and the habitability of
exoplanets. Since these effects are governed by the star's magnetic
energy, which is proportional to the magnetic-field strength squared
and its fractional surface coverage, it is important to measure or
reliably infer the true magnetic-field strength and filling factor
across a stellar disk. We summarize magnetic-field measurements obtained
with the different observing techniques for different types of stars
and estimate the highest magnetic-field strengths. We also comment
on the different field morphologies observed for stars across the H-R
diagram, typically inferred from Zeeman-Doppler imaging and rotational
modulation observations,

---------------------------------------------------------
Title: New Insights Concerning the Local Interstellar medium
Authors: Linsky, Jeffrey L.; Redfield, Seth
2015IAUGA..2247097L Altcode:
We have been analyzing HST high-resolution ultraviolet spectra of
nearby stars to measure the radial velocities, turbulence, temperature,
and depletions on warm diffuse interstellar gas within a few parsecs
of the Sun. These data reveal a picture of many partially-ionized
warm gas clouds, each with their own vector velocity and physical
characteristics. This picture has been recently challenged by Gry
and Jenkins (2014), who argue for a single nonrigid cloud surrounding
the Sun. We present a test of these two very different morphological
structure by checking how well each predicts the radial velocities
in a new data set (Malamut et al. 2014) that was not available when
both models were constructed. We find that the multicloud model
(Redfield &amp; Linsky 2008) provides a much better fit to the new
data. We compare the new IBEX results for the temperature and velocity
of inflowing He gas (McComas et al. 2015) with the properties of the
Local Interstellar Cloud and the G cloud. We also show a preliminary
three-dimensional model for the local interstellar medium.

---------------------------------------------------------
Title: Effect of UV Radiation on the Spectral Fingerprints of
Earth-like Planets Orbiting M Stars
Authors: Rugheimer, S.; Kaltenegger, L.; Segura, A.; Linsky, J.;
Mohanty, S.
2015ApJ...809...57R Altcode: 2015arXiv150607202R
We model the atmospheres and spectra of Earth-like planets orbiting
the entire grid of M dwarfs for active and inactive stellar models
with Teff = 2300 K to Teff = 3800 K and for
six observed MUSCLES M dwarfs with UV radiation data. We set the
Earth-like planets at the 1 AU equivalent distance and show spectra
from the visible to IR (0.4-20 μm) to compare detectability of
features in different wavelength ranges with the James Webb Space
Telescope and other future ground- and spaced-based missions to
characterize exo-Earths. We focus on the effect of UV activity
levels on detectable atmospheric features that indicate habitability
on Earth, namely, H2O, O3, CH4,
N2O, and CH3Cl. To observe signatures of
life—O2/O3 in combination with reducing
species like CH4—we find that early and active M dwarfs
are the best targets of the M star grid for future telescopes. The
O2 spectral feature at 0.76 μm is increasingly difficult
to detect in reflected light of later M dwarfs owing to low stellar
flux in that wavelength region. N2O, another biosignature
detectable in the IR, builds up to observable concentrations in our
planetary models around M dwarfs with low UV flux. CH3Cl
could become detectable, depending on the depth of the overlapping
N2O feature. We present a spectral database of Earth-like
planets around cool stars for directly imaged planets as a framework
for interpreting future light curves, direct imaging, and secondary
eclipse measurements of the atmospheres of terrestrial planets in the
habitable zone to design and assess future telescope capabilities.

---------------------------------------------------------
Title: Quiescent and Flaring Lyman-alpha Radiation of Host Stars
and Effects on Exoplanet Atmospheres
Authors: Linsky, Jeffrey L.; France, Kevin; Miguel, Yamila;
Kaltenegger, Lisa
2015IAUGA..2246040L Altcode:
Lyman-alpha radiation dominates the ultraviolet spectra of stars
with spectral types G, K, and M, and is a major contributor to the
photodissociation of important molecules including water, CO2, and CH4
in the upper atmospheres of exoplanets. We obtain intrinsic Lyman-alpha
line fluxes for late-type stars by either correcting for interstellar
absorption or by scaling from other spectroscopic observables and
broadband fluxes. When stars flare, all emission lines brighten by
large factors (Parke Loyd &amp; France ApJS 211, 9 (2014)) as shown by
HST spectra of G-M dwarf stars. We estimate the enhancement factors
in the Lyman-alpha flux during M dwarf flares by scaling from the
observed flux in C II and other UV emission lines. We then describe
photochemical models of the atmosphere of the miniNeptune GJ 436b
(Miguel et al. MNRAS 446, 345 (2015)) that show the effects of flaring
Lyman-alpha fluxes on atmospheric chemical abundances.

---------------------------------------------------------
Title: Poster: Quiescent and Flaring Lyma-a Radiation of Host Stars
and Effects on Exoplanet Atmopsheres
Authors: Linsky, Jeffrey L.; France, Kevin; Miguel, Yamila; Rugheimer,
Sarah; Kaltenegger, Lisa
2015pthp.confE..37L Altcode:
No abstract at ADS

---------------------------------------------------------
Title: Characterizing the Habitable Zones of Exoplanetary Systems
with a Large Ultraviolet/Visible/Near-IR Space Observatory
Authors: France, Kevin; Shkolnik, Evgenya; Linsky, Jeffrey; Roberge,
Aki; Ayres, Thomas; Barman, Travis; Brown, Alexander; Davenport,
James; Desert, Jean-Michel; Domagal-Goldman, Shawn; Fleming, Brian;
Fontenla, Juan; Fossati, Luca; Froning, Cynthia; Hallinan, Gregg;
Hawley, Suzanne; Hu, Renyu; Kaltenegger, Lisa; Kasting, James;
Kowlaski, Adam; Loyd, Parke; Mauas, Pablo; Miguel, Yamila; Osten,
Rachel; Redfield, Seth; Rugheimer, Sarah; Schneider, Christian; Segura,
Antigona; Stocke, John; Tian, Feng; Tumlinson, Jason; Vieytes, Mariela;
Walkowicz, Lucianne; Wood, Brian; Youngblood, Allison
2015arXiv150501840F Altcode:
Understanding the surface and atmospheric conditions of Earth-size,
rocky planets in the habitable zones (HZs) of low-mass stars is
currently one of the greatest astronomical endeavors. Knowledge of
the planetary effective surface temperature alone is insufficient
to accurately interpret biosignature gases when they are observed
in the coming decades. The UV stellar spectrum drives and regulates
the upper atmospheric heating and chemistry on Earth-like planets,
is critical to the definition and interpretation of biosignature
gases, and may even produce false-positives in our search for biologic
activity. This white paper briefly describes the scientific motivation
for panchromatic observations of exoplanetary systems as a whole (star
and planet), argues that a future NASA UV/Vis/near-IR space observatory
is well-suited to carry out this work, and describes technology
development goals that can be achieved in the next decade to support
the development of a UV/Vis/near-IR flagship mission in the 2020s.

---------------------------------------------------------
Title: Characterising exoplanets and their environment with UV
transmission spectroscopy
Authors: Fossati, L.; Bourrier, V.; Ehrenreich, D.; Haswell, C. A.;
Kislyakova, K. G.; Lammer, H.; Lecavelier des Etangs, A.; Alibert,
Y.; Ayres, T. R.; Ballester, G. E.; Barnes, J.; Bisikalo, D. V.;
Collier, A.; Cameron; Czesla, S.; Desert, J. -M.; France, K.; Guedel,
M.; Guenther, E.; Helling, Ch.; Heng, K.; Homstrom, M.; Kaltenegger,
L.; Koskinen, T.; Lanza, A. F.; Linsky, J. L.; Mordasini, C.; Pagano,
I.; Pollacco, D.; Rauer, H.; Reiners, A.; Salz, M.; Schneider, P. C.;
Shematovich, V. I.; Staab, D.; Vidotto, A. A.; Wheatley, P. J.; Wood,
B. E.; Yelle, R. V.
2015arXiv150301278F Altcode:
Exoplanet science is now in its full expansion, particularly after
the CoRoT and Kepler space missions that led us to the discovery of
thousands of extra-solar planets. The last decade has taught us that
UV observations play a major role in advancing our understanding of
planets and of their host stars, but the necessary UV observations can
be carried out only by HST, and this is going to be the case for many
years to come. It is therefore crucial to build a treasury data archive
of UV exoplanet observations formed by a dozen "golden systems" for
which observations will be available from the UV to the infrared. Only
in this way we will be able to fully exploit JWST observations for
exoplanet science, one of the key JWST science case.

---------------------------------------------------------
Title: Characterizing Transiting Planet Atmospheres through 2025
Authors: Cowan, N. B.; Greene, T.; Angerhausen, D.; Batalha, N. E.;
Clampin, M.; Colón, K.; Crossfield, I. J. M.; Fortney, J. J.;
Gaudi, B. S.; Harrington, J.; Iro, N.; Lillie, C. F.; Linsky, J. L.;
Lopez-Morales, M.; Mandell, A. M.; Stevenson, K. B.
2015PASP..127..311C Altcode: 2015arXiv150200004C
[Abridged] We have only been able to comprehensively characterize
the atmospheres of a handful of transiting planets, because most
orbit faint stars. TESS will discover transiting planets orbiting the
brightest stars, enabling, in principle, an atmospheric survey of 10^2
to 10^3 bright hot Jupiters and warm sub-Neptunes. Uniform observations
of such a statistically significant sample would provide leverage to
understand---and learn from---the diversity of short-period planets. We
argue that the best way to maximize the scientific returns of TESS is
with a follow-up space mission consisting of a ~1 m telescope with an
optical--NIR spectrograph: it could measure molecular absorption for
non-terrestrial planets, as well as eclipses and phase variations for
the hottest jovians. Such a mission could observe up to 10^3 transits
per year, thus enabling it to survey a large fraction of the bright
(J&lt;11) TESS planets. JWST could be used to perform detailed
atmospheric characterization of the most interesting transiting
targets (transit, eclipse, and---when possible---phase-resolved
spectroscopy). TESS is also expected to discover a few temperate
terrestrial planets transiting nearby M-Dwarfs. Characterizing these
worlds will be time-intensive: JWST will need months to provide
tantalizing constraints on the presence of an atmosphere, planetary
rotational state, clouds, and greenhouse gases. Future flagship missions
should be designed to provide better constraints on the habitability
of M-Dwarf temperate terrestrial planets.

---------------------------------------------------------
Title: Predicting the Extreme-UV and Lyman-α Fluxes Received by
Exoplanets from their Host Stars
Authors: Linsky, Jeffrey L.; France, Kevin; Ayres, Thomas R.
2015csss...18..831L Altcode:
Extreme-UV (EUV) radiation from the chromospheres, transition
regions, and coronae of host stars (spectral types F, G, K, and
M) ionize and heat the outer atmospheres of exoplanets leading
to mass loss that is observed during transits and can change the
exoplanet's atmosphere. Lyman-α emission from host stars controls
the photochemistry in the upper layers of planetary atmospheres by
photodissociating important molecules including H_2O, CO_2, CH_4,
thereby increasing the oxygen and ozone mixing ratios important for
habitability. Both the EUV and strong Lyman-α radiation are largely
absorbed by the interstellar medium and must be reconstructed or
estimated to understand the radiation environment of exoplanets. In two
recent papers, tet{Linsky2013} and tet{Linsky2014}, we have presented
robust methods for predicting the intrinsic Lyman-α and EUV fluxes from
main sequence cool stars. Solar models and satellite observations (HST,
FUSE, and EUVE) provide tests for the feasibility of these methods.

---------------------------------------------------------
Title: What is the morphology of the local interstellar medium and
its importance in the GAIA era?
Authors: Linsky, Jeffrey L.; Redfield, Seth
2015MmSAI..86..606L Altcode:
High-resolution studies of interstellar absorption lines that appear
in the spectra of nearby stars provide essential information on the
physical properties and inhomogeneous structure of interstellar gas
along short lines of sight. These absorption lines are primarily in the
ultraviolet as observed with the Space Telescope Imaging Spectrograph
(STIS) and Cosmic Origins Spectrograph (COS) instruments on the Hubble
Space Telescope (HST), but very sensitive ground-based spectra also are
important. The local interstellar medium (LISM) within a few pc of the
Sun provides a basis for testing the assumptions underlying theoretical
models before these models can be applied reliably to understanding
interstellar gas in more distant regions of the Galaxy where GAIA will
be providing information on the stellar structure. We address here
the critical question of whether the inhomogeneous properties of the
LISM are more realistically characterized by a morphology consisting
of many distinct structures, each with their own physical and kinematic
properties, or by a continuous medium with nonrigid flows and spatially
variable properties. We test these two models using a new data set with
lines of sight randomly distributed in the sky. An expanded version
of this paper is available \citep{Redfield2015}.

---------------------------------------------------------
Title: Exoplanet Host Star Radiation and Plasma Environment
Authors: Linsky, Jeffrey L.; Güdel, Manuel
2015ASSL..411....3L Altcode:
Radiation from host stars controls the planetary energy budget,
photochemistry in planetary atmospheres, and mass loss from the
outer layers of these atmospheres. Stellar optical and infrared
radiation, the major source of energy for the lower atmosphere
and planetary surfaces, increases slowly as stars evolve from
the Zero-Age-Main-Sequence&lt;IndexTerm&gt; . Ultraviolet
radiation&lt;IndexTerm&gt; , including the Lyman-α emission
line that dominates the UV spectrum of M dwarf stars, controls
photochemical reactions of important molecules, including
H2O, CO2, and CH4. Extreme
ultraviolet and X-radiation from host stars ionizes and heats the
outer layers of planetary atmospheres driving mass loss that is rapid
for close-in Jupiter-like planets. The strength of the stellar UV,
EUV&lt;IndexTerm&gt; , and X-radiation depends on stellar activity,
which decays with time as stellar rotation decreases. As a result,
the evolution of an exoplanet's atmosphere depends on the evolution of
its host star. We summarize the available techniques for measuring or
estimating the X-ray&lt;IndexTerm&gt; , EUV, and UV radiation of host
stars with different spectral types and ages.

---------------------------------------------------------
Title: The effect of Lyman α radiation on mini-Neptune atmospheres
around M stars: application to GJ 436b
Authors: Miguel, Yamila; Kaltenegger, Lisa; Linsky, Jeffrey L.;
Rugheimer, Sarah
2015MNRAS.446..345M Altcode: 2014arXiv1410.2112M
Mini-Neptunes orbiting M stars are a growing population of known
exoplanets. Some of them are located very close to their host star,
receiving large amounts of UV radiation. Many M stars emit strong
chromospheric emission in the H I Lyman α line (Lyα) at 1215.67 Å,
the brightest far-UV emission line. We show that the effect of incoming
Lyα flux can significantly change the photochemistry of mini-Neptunes'
atmospheres. We use GJ 436b as an example, considering different
metallicities for its atmospheric composition. For solar composition,
H2O-mixing ratios show the largest change because of Lyα
radiation. H2O absorbs most of this radiation, thereby
shielding CH4, whose dissociation is driven mainly by
radiation at other far-UV wavelengths (∼1300 Å). H2O
photolysis also affects other species in the atmosphere, including H,
H2, CO2, CO, OH and O. For an atmosphere with high
metallicity, H2O- and CO2-mixing ratios show the
biggest change, thereby shielding CH4. Direct measurements
of the UV flux of the host stars are important for understanding the
photochemistry in exoplanets' atmospheres. This is crucial, especially
in the region between 1 and 10-6 bars, which is the part of
the atmosphere that generates most of the observable spectral features.

---------------------------------------------------------
Title: Observations of Exoplanet Atmospheres and Surrounding
Environments
Authors: Fossati, Luca; Haswell, Carole A.; Linsky, Jeffrey L.;
Kislyakova, Kristina G.
2015ASSL..411...59F Altcode:
The study of exoplanets is arguably the most exciting and
fastest-growing field in astrophysics. Given the youth of exoplanet
science, the field is strongly driven by observations. Here we summarise
current knowledge of the atmospheres and wider environments of the known
exoplanets giving particular emphasis on the upper atmospheres and the
surrounding environment, rather than on the deeper atmospheric layers.

---------------------------------------------------------
Title: Understanding the Morphology and Kinematics of the Local
Interstellar Medium
Authors: Linsky, Jeffrey
2015AAS...22514210L Altcode:
In our 2008 paper (Redfield and Linsky ApJ 673, 283), we proposed
a model of the local interstellar medium (LISM) containing 15
warm partially ionized clouds, each with its own velocity vector,
located within 15 pc of the Sun. Since then we have obtained many new
high-resolution spectra from HST and optical spectra of nearby stars
containing a large number of interstellar absorption lines (see Malamut
et al. ApJ 787, 75 (2014)). With this large increase in interstellar
data, we have developed a new three-dimensional model of the LISM
consisting of a larger number of partially ionized clouds, revised
cloud shapes, and including constraints of Stromgren spheres surrounding
hot white dwarfs and the location of stars with detected astrospheres
inside of clouds with neutral gas. We discuss which clouds are likely
to be filamentary and where cloud-cloud interactions likely occur. We
present a new model for the shape of the Local Interstellar Cloud and
show that its irregular shape may be determined by the directions of
bright sources of extreme-UV radiation. We consider whether the LISM
is best described by a complex of distinct partially ionized clouds
each a different velocity vector or a continuous medium with a complex
velocity structure.This work is supported by grants and HST observing
time from the Space Telescope Science Institute

---------------------------------------------------------
Title: Stellar Winds in Time
Authors: Wood, Brian E.; Linsky, Jeffrey L.; Güdel, Manuel
2015ASSL..411...19W Altcode:
Exposure to stellar winds&lt;IndexTerm&gt; can have significant long
term consequences for planetary atmospheres. Estimating the effects of
these winds requires knowledge of how they evolve with time. Determining
this empirically requires the ability to study the winds of stars of
various ages and activity levels, but this is not easy to do as the
coronal winds of solar-like stars are very hard to detect. Relevant
observations are here reviewed, as well as more theoretical methods
of addressing the problem.

---------------------------------------------------------
Title: The local ISM in three dimensions: kinematics, morphology
and physical properties
Authors: Linsky, Jeffrey L.; Redfield, Seth
2014Ap&SS.354...29L Altcode:
We summarize the results of our long-term program to study the
kinematics, morphology, and physical properties of warm partially
ionized interstellar gas located within 100 pc of the Sun. Using the
Space Telescope Imaging Spectrograph (STIS) and other spectrographs
on the Hubble Space Telescope (HST), we measure radial velocities
of neutral and singly ionized atoms that identify comoving structures
(clouds) of warm interstellar gas. We have identified 15 of these clouds
located within 15 pc of the Sun. Each of them moves with a different
velocity vector, and they have narrow ranges of temperature, turbulence,
and metal depletions. We compute a three-dimensional model for the Local
Interstellar Cloud (LIC), in which the Sun is likely embedded near its
edge, and the locations and shapes of the other nearby clouds. These
clouds are likely separated by ionized Strömgren sphere gas produced
by ɛ CMa, Sirius B, and other hot white dwarfs. We propose that some
of these partially ionized clouds are shells of the Strömgren spheres.

---------------------------------------------------------
Title: The ultraviolet radiation environment in the habitable zones
around low-mass exoplanet host stars
Authors: France, Kevin; Linsky, Jeffrey L.; Loyd, R. O. Parke
2014Ap&SS.354....3F Altcode:
The EUV (200-911 Å), FUV (912-1750 Å), and NUV (1750-3200 Å) spectral
energy distribution of exoplanet host stars has a profound influence
on the atmospheres of Earth-like planets in the habitable zone. The
stellar EUV radiation drives atmospheric heating, while the FUV (in
particular, Ly α) and NUV radiation fields regulate the atmospheric
chemistry: the dissociation of H2O and CO2,
the production of O2 and O3, and may determine
the ultimate habitability of these worlds. Despite the importance of
this information for atmospheric modeling of exoplanetary systems,
the EUV/FUV/NUV radiation fields of cool (K and M dwarf) exoplanet host
stars are almost completely unconstrained by observation or theory. We
present observational results from a Hubble Space Telescope survey of
M dwarf exoplanet host stars, highlighting the importance of realistic
UV radiation fields for the formation of potential biomarker molecules,
O2 and O3. We conclude by describing preliminary
results on the characterization of the UV time variability of these
sources.

---------------------------------------------------------
Title: The Radiation Environment of Exoplanet Atmospheres
Authors: Linsky, Jeffrey
2014Chall...5..351L Altcode:
Exoplanets are born and evolve in the radiation and particle
environment created by their host star. The host star's optical
and infrared radiation heats the exoplanet's lower atmosphere and
surface, while the ultraviolet, extreme ultraviolet and X-radiation
control the photochemistry and mass loss from the exoplanet's upper
atmosphere. Stellar radiation, especially at the shorter wavelengths,
changes dramatically as a host star evolves leading to changes in the
planet's atmosphere and habitability. This paper reviews the present
state of our knowledge concerning the time-dependent radiation emitted
by stars with convective zones, that is stars with spectral types F,
G, K, and M, which comprise nearly all of the host stars of detected
exoplanets.

---------------------------------------------------------
Title: Lyman-α observations of astrospheres
Authors: Linsky, J. L.; Wood, B. E.
2014ASTRP...1...43L Altcode: 2014arXiv1408.5934L
Charge-exchange reactions between outflowing stellar wind protons and
interstellar neutral hydrogen atoms entering a stellar astrosphere
produce a region of piled-up-decelerated neutral hydrogen called the
hydrogen wall. Absorption by this gas, which is observed in stellar
Lyman-α emission lines, provides the only viable technique at this time
for measuring the mass-loss rates of F-M dwarf stars. We describe this
technique, present an alternative way for understanding the relation
of mass-loss rate with X-ray emission, and identify several critical
issues.

---------------------------------------------------------
Title: The Structure of the Local Interstellar Medium. VI. New Mg II,
Fe II, and Mn II Observations toward Stars within 100 pc
Authors: Malamut, Craig; Redfield, Seth; Linsky, Jeffrey L.; Wood,
Brian E.; Ayres, Thomas R.
2014ApJ...787...75M Altcode: 2014arXiv1403.8096M
We analyze high-resolution spectra obtained with the Space Telescope
Imaging Spectrograph onboard the Hubble Space Telescope toward 34 nearby
stars (&lt;=100 pc) to record Mg II, Fe II, and Mn II absorption due
to the local interstellar medium (LISM). Observations span the entire
sky, probing previously unobserved regions of the LISM. The heavy
ions studied in this survey produce narrow absorption features that
facilitate the identification of multiple interstellar components. We
detected one to six individual absorption components along any given
sight line, and the number of absorbers roughly correlates with the
pathlength. This high-resolution near-ultraviolet (NUV) spectroscopic
survey was specifically designed for sight lines with existing far-UV
(FUV) observations. The FUV spectra include many intrinsically broad
absorption lines (i.e., of low atomic mass ions) and are often observed
at medium resolution. The LISM NUV narrow-line absorption component
structure presented here can be used to more accurately interpret the
archival FUV observations. As an example of this synergy, we present a
new analysis of the temperature and turbulence along the line of sight
toward epsilon Ind. The new observations of LISM velocity structure
are also critical in the interpretation of astrospheric absorption
derived from fitting the saturated H I Lyα profile. As an example, we
reanalyze the spectrum of λ And and find that this star likely does
have an astrosphere. Two stars in the sample that have circumstellar
disks (49 Cet and HD141569) show evidence for absorption due to disk
gas. Finally, the substantially increased number of sight lines is
used to test and refine the three-dimensional kinematic model of the
LISM and search for previously unidentified clouds within the Local
Bubble. We find that every prediction made by the Redfield &amp; Linsky
kinematic model of the LISM is confirmed by an observed component in
the new lines of sight.

---------------------------------------------------------
Title: VizieR Online Data Catalog: HST far-UV survey of H2 emission
of T Tau stars (France+, 2012)
Authors: France, K.; Schindhelm, E.; Herczeg, G. J.; Brown, A.;
Abgrall, H.; Alexander, R. D.; Bergin, E. A.; Brown, J. M.; Linsky,
J. L.; Roueff, E.; Yang, H.
2014yCat..17560171F Altcode:
Our sample of 34 T Tauri Stars (TTSs) was assembled from new and
archival observations with HST-COS and -STIS. The majority of the
targets were observed as part of the DAO of Tau guest observing program
(PID 11616; PI: G. Herczeg) and the COS Guaranteed Time Observing
program (PIDs 11533 and 12036; PI: J. Green). Additional observations
of the transitional disk HD 135344B and weak-lined systems TWA 13A
and TWA 13B (PIDs 11828 and 12361; PI: A. Brown) are presented. A
subset of the H2 survey observations have been presented previously
in the literature. Finally, we have included archival Space Telescope
Imaging Spectrograph (STIS) observations of the well-studied Classical
T Tauri Star (CTTS) TW Hya, obtained through StarCAT (Ayres, 2010,
Cat. J/ApJS/187/149). Most of the targets were observed with
the medium-resolution far-UV modes of COS (G130M and G160M). These
observations were acquired between 2009 December and 2011 September. (3 data files).

---------------------------------------------------------
Title: Reconstructing the Stellar UV and EUV Emission that Controls
the Chemistry of Exoplanet Atmospheres
Authors: Linsky, Jeffrey L.; France, Kevin; Ayres, Tom
2014IAUS..293..309L Altcode:
Lyman-α and extreme-ultraviolet radiation from exoplanet host stars are
critically important for evaluating the phototchemistry of planetary
atmospheres, but these emissions are largely or completely absorbed
by hydrogen in the interstellar medium. We describe a new technique
for estimating the intrinsic Lyman-α and EUV fluxes of F, G, K,
and M stars using correlations with observable emission lines.

---------------------------------------------------------
Title: Influence of UV activity on the Spectral Fingerprints of
Earth-like Planets around M dwarfs
Authors: Rugheimer, S.; Kaltenegger, L.; Linsky, J.; Mohanty, S.
2014ebi..conf..2.6R Altcode:
A wide range of potentially rocky transiting planets in the habitable
zone (HZ) have been detected by Kepler as well as ground-based
searches. The spectral type of the host star will influence our
ability to detect atmospheric features with future space and ground
based missions like JWST, GMT and E-ELT. Particularly the active and
inactive M stars are a stellar class that covers a wide range of UV
luminosity that influence the detectability of habitable conditions. The
UV emission from a planet's host star dominates the photochemistry and
thus the resultant observable spectral features. Using the latest UV
spectra obtained by Hubble as well as IUE, we Earth-like planets over
a wide range of M-stars host stars from M0 to M9 for both active and
inactive stars. These planets are the first ones that should become
available to observations with JWST and E-ELT. A wide range of such
targets will soon be identified in our Solar Neighborhood by the TESS
mission that will launch in 2017.

---------------------------------------------------------
Title: The solar-exoplanet-host-star connection: measurements,
reconstruction, and estimates of the UV, Lyman-alpha, and EUV
radiation emitted by exoplanet host stars
Authors: Linsky, J.
2014ebi..confP2.35L Altcode:
One of the important ways in which host stars influence their exoplanets
is through photochemistry in their atmospheres. For example, the
photodissociation of such important molecules in exoplanet atmospheres
as H2O, CO2, and CH4 is primarily controlled by Lymanalpha and FUV
radiation from the host stars. Photochemistry of oxygen and ozone
is controlled by NUV radiation. EUV radiation photoionizes H and other
atoms, heats the outer atmospheres, and thereby drives mass loss from
exoplanets. Photodissociation of H2O and CO2 liberates oxygen without
the need for life forms and thus complicates the use of oxygen and
ozone as biosignatures. The COS instrument on HST has now obtained
UV spectra of a number of M dwarfs host stars. The Lyman-alpha line,
which is important for G stars but completely dominates the UV emission
of M dwarfs, is attenuated by interstellar absorption. I will present
techniques for reconstructing or estimating the stellar emission
in this line. The EUV emission can be estimated by comparison with
Lymanalpha and other emission lines. These recent developments now
make it feasible to evaluate the radiation received by exoplanets and
to compute realistic models of the chemistry of exoplanet atmospheres.

---------------------------------------------------------
Title: High stellar FUV/NUV ratio and oxygen contents in the
atmospheres of potentially habitable planets
Authors: Tian, Feng; France, Kevin; Linsky, Jeffrey L.; Mauas, Pablo
J. D.; Vieytes, Mariela C.
2014E&PSL.385...22T Altcode: 2013arXiv1310.2590T
Recent observations of several planet-hosting M dwarfs show that
most have FUV/NUV flux ratios 1000 times greater than that of the
Sun. Here we show that the atmospheric oxygen contents (O2
and O3) of potentially habitable planets in this type
of UV environment could be 2-3 orders of magnitude greater than
those of their counterparts around Sun-like stars as a result of
decreased photolysis of O3, H2O2,
and HO2. Thus detectable levels of atmospheric oxygen, in
combination with the existence of H2O and CO2,
may not be the most promising biosignatures on planets around stars
with high FUV/NUV ratios such as the observed M dwarfs.

---------------------------------------------------------
Title: The Intrinsic EUV, Lyman-alpha, and UV Emission from Exoplanet
Host Stars
Authors: Linsky, Jeffrey; France, K.; Fontenla, J.
2014AAS...22323002L Altcode:
The chemical composition and mass loss from exoplanet atmospheres
is driven largely by the ultraviolet and extreme ultraviolet (EUV)
radiation from their host stars. In particular, such important
molecules as H2O, CO2, and CH4 are photodissociated primarily by
radiation in the Lyman-alpha line, and planetary exospheres are heated
primarily by EUV radiation from the host star, producing expansion
and mass loss. Unfortunately, most of the host star radiation in the
Lyman-alpha line is removed by hydrogen in the interstellar medium,
and the EUV emission between 400 and 912 Angstroms is absorbed by
interstellar hydrogen. We have developed a variety of techniques for
inferring the intrinsic Lyman-alpha and EUV emission from main sequence
stars with spectral types F5 to M5. We find that the ratios of the
EUV flux to Lyman-alpha and the Lyman-alpha flux to other emission
lines are relatively insensitive to spectral type and activity. We
therefore propose formulae for estimating the intrinsic emission from
exoplanet host stars. We present results from our HST observing program
MUSCLES that provides near-UV and far-UV spectra of M dwarf exoplanet
host stars. We also present a preliminary non-LTE chromosphere model
for an M dwarf host star. This combination of HST spectra, host star
models, and estimated intrinsic Lyman-alpha and EUV emission provides
essential input for the computation of photochemical models of exoplanet
atmospheres. This work is supported by the Space Telescope Science
Institute and NASA grants.

---------------------------------------------------------
Title: The Intrinsic Extreme Ultraviolet Fluxes of F5 V TO M5 V Stars
Authors: Linsky, Jeffrey L.; Fontenla, Juan; France, Kevin
2014ApJ...780...61L Altcode: 2013arXiv1310.1360L
Extreme ultraviolet (EUV) radiations (10-117 nm) from host stars play
important roles in the ionization, heating, and mass loss from exoplanet
atmospheres. Together with the host star's Lyα and far-UV (117-170
nm) radiation, EUV radiation photodissociates important molecules,
thereby changing the chemistry in exoplanet atmospheres. Since stellar
EUV fluxes cannot now be measured and interstellar neutral hydrogen
completely obscures stellar radiation between 40 and 91.2 nm, even
for the nearest stars, we must estimate the unobservable EUV flux
by indirect methods. New non-LTE semiempirical models of the solar
chromosphere and corona and solar irradiance measurements show that the
ratio of EUV flux in a variety of wavelength bands to the Lyα flux
varies slowly with the Lyα flux and thus with the magnetic heating
rate. This suggests and we confirm that solar EUV/Lyα flux ratios
based on the models and observations are similar to the available 10-40
nm flux ratios observed with the Extreme Ultraviolet Explorer (EUVE)
satellite and the 91.2-117 nm flux observed with the Far Ultraviolet
Spectroscopic Explorer (FUSE) satellite for F5 V-M5 V stars. We provide
formulae for predicting EUV flux ratios based on the EUVE and FUSE
stellar data and on the solar models, which are essential input for
modeling the atmospheres of exoplanets.

---------------------------------------------------------
Title: Measurements of the Stellar Wind Strengths of Planet-Hosting G-
and K-Type Stars
Authors: Edelman, Eric; Redfield, S.; Wood, B.; Linsky, J.; Mueller,
H. R.
2014AAS...22315110E Altcode:
Voyager 1 has recently crossed the heliosphere, where the solar wind
meets the material of the interstellar medium. With line of sight
spectral information provided by the STIS on Hubble, the analogous
boundary around other stars, which is known as an astrosphere, can
be detected. We are conducting a thorough analysis of MgII, FeII, DI,
and HI Lyman-alpha absorption along the lines of sight to a sample of
nearby K and G stars in order to obtain and use astrospheric detections
to estimate stellar wind strengths, and to study their effects upon
exoplanetary atmospheres. Each astrospheric measurement is obtained
by careful examination and reconstruction of the Lyman-alpha emission
feature, which ultimately provides an estimate of the neutral hydrogen
column density associated with a star’s astrosphere. The amount of
neutral hydrogen in that region is highly dependent on the stellar wind
strength of the host star, and is one of the scant few methods available
today for measuring that quantity. If stellar winds are strong enough,
they can be responsible for stripping a nearby planet of its atmosphere,
as was potentially the case with Mars and our Sun approximately 4
billion years ago. Increasing the sample size of measurements of
stellar wind strengths for K and G type stars will allow for us to
more accurately determine the influence of solar-type host stars on
their respective exoplanetary systems. Included in our sample are the
stars HD9826 and HD192310, which both have confirmed exoplanets in
orbit. This project includes the reconstructions of the Lyman-alpha
emission feature along the lines of sight to a sample of nearby stars,
with a determination of whether or not astrospheric or heliospheric
absorption is detected in each instance, with hydrogen column densities
for positive detections. We would like to acknowledge NASA HST Grant
GO-12475 awarded by the Space Telescope Science Institute, which is
operated by the Association of Universities for Research in Astronomy,
Inc., for NASA, under contract NAS 5-26555, and a student fellowship
from the Connecticut Space Grant Consortium for their support of this
research, as well as the Astronomy faculty and students at Wesleyan
University.

---------------------------------------------------------
Title: The Science of Exoplanets and Their Systems
Authors: Lammer, Helmut; Blanc, Michel; Benz, Willy; Fridlund,
Malcolm; Foresto, Vincent Coudé du; Güdel, Manuel; Rauer, Heike;
Udry, Stephane; Bonnet, Roger-Maurice; Falanga, Maurizio; Charbonneau,
David; Helled, Ravit; Kley, Willy; Linsky, Jeffrey; Elkins-Tanton,
Linda T.; Alibert, Yann; Chassefière, Eric; Encrenaz, Therese;
Hatzes, Artie P.; Lin, Douglas; Liseau, Rene; Lorenzen, Winfried;
Raymond, Sean N.
2013AsBio..13..793L Altcode:
No abstract at ADS

---------------------------------------------------------
Title: Hot Gas Lines in T Tauri Stars
Authors: Ardila, David R.; Herczeg, Gregory J.; Gregory, Scott G.;
Ingleby, Laura; France, Kevin; Brown, Alexander; Edwards, Suzan;
Johns-Krull, Christopher; Linsky, Jeffrey L.; Yang, Hao; Valenti,
Jeff A.; Abgrall, Hervé; Alexander, Richard D.; Bergin, Edwin;
Bethell, Thomas; Brown, Joanna M.; Calvet, Nuria; Espaillat, Catherine;
Hillenbrand, Lynne A.; Hussain, Gaitee; Roueff, Evelyne; Schindhelm,
Rebecca N.; Walter, Frederick M.
2013ApJS..207....1A Altcode: 2013arXiv1304.3746A
For Classical T Tauri Stars (CTTSs), the resonance doublets of N V, Si
IV, and C IV, as well as the He II 1640 Å line, trace hot gas flows and
act as diagnostics of the accretion process. In this paper we assemble
a large high-resolution, high-sensitivity data set of these lines in
CTTSs and Weak T Tauri Stars (WTTSs). The sample comprises 35 stars:
1 Herbig Ae star, 28 CTTSs, and 6 WTTSs. We find that the C IV, Si IV,
and N V lines in CTTSs all have similar shapes. We decompose the C
IV and He II lines into broad and narrow Gaussian components (BC and
NC). The most common (50%) C IV line morphology in CTTSs is that of a
low-velocity NC together with a redshifted BC. For CTTSs, a strong BC
is the result of the accretion process. The contribution fraction of
the NC to the C IV line flux in CTTSs increases with accretion rate,
from ~20% to up to ~80%. The velocity centroids of the BCs and NCs
are such that V BC &gt;~ 4 V NC, consistent with
the predictions of the accretion shock model, in at most 12 out of 22
CTTSs. We do not find evidence of the post-shock becoming buried in
the stellar photosphere due to the pressure of the accretion flow. The
He II CTTSs lines are generally symmetric and narrow, with FWHM and
redshifts comparable to those of WTTSs. They are less redshifted than
the CTTSs C IV lines, by ~10 km s-1. The amount of flux in
the BC of the He II line is small compared to that of the C IV line,
and we show that this is consistent with models of the pre-shock
column emission. Overall, the observations are consistent with the
presence of multiple accretion columns with different densities or
with accretion models that predict a slow-moving, low-density region
in the periphery of the accretion column. For HN Tau A and RW Aur
A, most of the C IV line is blueshifted suggesting that the C IV
emission is produced by shocks within outflow jets. In our sample,
the Herbig Ae star DX Cha is the only object for which we find a
P-Cygni profile in the C IV line, which argues for the presence of a
hot (105 K) wind. For the overall sample, the Si IV and N
V line luminosities are correlated with the C IV line luminosities,
although the relationship between Si IV and C IV shows large scatter
about a linear relationship and suggests that TW Hya, V4046 Sgr, AA
Tau, DF Tau, GM Aur, and V1190 Sco are silicon-poor, while CV Cha,
DX Cha, RU Lup, and RW Aur may be silicon-rich.

---------------------------------------------------------
Title: Computing Intrinsic LYα Fluxes of F5 V to M5 V Stars
Authors: Linsky, Jeffrey L.; France, Kevin; Ayres, Tom
2013ApJ...766...69L Altcode: 2013arXiv1301.5711L
The Lyα emission line dominates the far-ultraviolet spectra of
late-type stars and is a major source for photodissociation of important
molecules including H2O, CH4, and CO2
in exoplanet atmospheres. The incident flux in this line illuminating
an exoplanet's atmosphere cannot be measured directly as neutral
hydrogen in the interstellar medium (ISM) attenuates most of the flux
reaching the Earth. Reconstruction of the intrinsic Lyα line has been
accomplished for a limited number of nearby stars, but is not feasible
for distant or faint host stars. We identify correlations connecting
the intrinsic Lyα flux with the flux in other emission lines formed
in the stellar chromosphere, and find that these correlations depend
only gradually on the flux in the other lines. These correlations,
which are based on Hubble Space Telescope spectra, reconstructed
Lyα line fluxes, and irradiance spectra of the quiet and active Sun,
are required for photochemical models of exoplanet atmospheres when
intrinsic Lyα fluxes are not available. We find a tight correlation of
the intrinsic Lyα flux with stellar X-ray flux for F5 V to K5 V stars,
but much larger dispersion for M stars. We also show that knowledge
of the stellar effective temperature and rotation rate can provide
reasonably accurate estimates of the Lyα flux for G and K stars,
and less accurate estimates for cooler stars.

---------------------------------------------------------
Title: The Ultraviolet Radiation Environment around M dwarf Exoplanet
Host Stars
Authors: France, Kevin; Froning, Cynthia S.; Linsky, Jeffrey L.;
Roberge, Aki; Stocke, John T.; Tian, Feng; Bushinsky, Rachel; Désert,
Jean-Michel; Mauas, Pablo; Vieytes, Mariela; Walkowicz, Lucianne M.
2013ApJ...763..149F Altcode: 2012arXiv1212.4833F
The spectral and temporal behavior of exoplanet host stars is a
critical input to models of the chemistry and evolution of planetary
atmospheres. Ultraviolet photons influence the atmospheric temperature
profiles and production of potential biomarkers on Earth-like planets
around these stars. At present, little observational or theoretical
basis exists for understanding the ultraviolet spectra of M dwarfs,
despite their critical importance to predicting and interpreting the
spectra of potentially habitable planets as they are obtained in the
coming decades. Using observations from the Hubble Space Telescope, we
present a study of the UV radiation fields around nearby M dwarf planet
hosts that covers both far-UV (FUV) and near-UV (NUV) wavelengths. The
combined FUV+NUV spectra are publicly available in machine-readable
format. We find that all six exoplanet host stars in our sample (GJ 581,
GJ 876, GJ 436, GJ 832, GJ 667C, and GJ 1214) exhibit some level of
chromospheric and transition region UV emission. No "UV-quiet" M dwarfs
are observed. The bright stellar Lyα emission lines are reconstructed,
and we find that the Lyα line fluxes comprise ~37%-75% of the total
1150-3100 Å flux from most M dwarfs; gsim103 times the
solar value. We develop an empirical scaling relation between Lyα and
Mg II emission, to be used when interstellar H I attenuation precludes
the direct observation of Lyα. The intrinsic unreddened flux ratio
is F(Lyα)/F(Mg II) = 10 ± 3. The F(FUV)/F(NUV) flux ratio, a driver
for abiotic production of the suggested biomarkers O2 and
O3, is shown to be ~0.5-3 for all M dwarfs in our sample,
&gt;103 times the solar ratio. For the four stars with
moderate signal-to-noise Cosmic Origins Spectrograph time-resolved
spectra, we find UV emission line variability with amplitudes of
50%-500% on 102-103 s timescales. This effect
should be taken into account in future UV transiting planet studies,
including searches for O3 on Earth-like planets. Finally,
we observe relatively bright H2 fluorescent emission from
four of the M dwarf exoplanetary systems (GJ 581, GJ 876, GJ 436, and
GJ 832). Additional modeling work is needed to differentiate between
a stellar photospheric or possible exoplanetary origin for the hot
(T(H2) ≈ 2000-4000 K) molecular gas observed in these
objects. Based on observations made with the NASA/ESA Hubble
Space Telescope, obtained from the data archive at the Space Telescope
Science Institute. STScI is operated by the Association of Universities
for Research in Astronomy, Inc., under NASA contract NAS 5-26555.

---------------------------------------------------------
Title: Hot Gas Flows in T Tauri Stars
Authors: Ardila, David R.; Herczeg, G.; Gregory, S. G.; Ingleby, L.;
France, K.; Brown, A.; Edwards, S.; Linsky, J.; Yang, H.; Valenti,
J. A.; Johns-Krull, C. M.; Alexander, R.; Bergin, E. A.; Bethell,
T.; Brown, J.; Calvet, N.; Espaillat, C.; Hervé, A.; Hillenbrand,
L.; Hussain, G.; Roueff, E.; Schindhelm, R.; Walter, F. M.
2013AAS...22111704A Altcode:
We describe observations of the hot gas 1e5 K) ultraviolet lines C IV
and He II, in Classical and Weak T Tauri Stars (CTTSs, WTTSs). Our goal
is to provide observational constraints for realistic models. Most of
the data for this work comes from the Hubble proposal “The Disks,
Accretion, and Outflows (DAO) of T Tau stars” (PI Herczeg). The DAO
program is the largest and most sensitive high resolution spectroscopic
survey of young stars in the UV ever undertaken and it provides a rich
source of information for these objects. The sample of high resolution
COS and STIS spectra presented here comprises 35 stars: one Herbig
Ae star, 28 CTTSs, and 6 WTTSs. For CTTSs, the lines consist of two
kinematic components. The relative strengths of the narrow and broad
components (NC, BC) are similar in C IV but in He II the NC is stronger
than the BC, and dominates the line profile. We do not find correlations
between disk inclination and the velocity centroid, width, or shape
of the CIV line profile. The NC of the C IV line in CTTSs increases in
strength with accretion rate, and its contribution to the line increases
from ∼20% to ∼80%, for the accretion rates considered here (1e-10
to 1e-7 Msun/yr). The CTTSs C IV lines are redshifted by ∼20 km/s
while the CTTSs He II are redshifted by ∼10 km/s. Because the He
II line and the C IV NC have the same width in CTTSs and in WTTSs,
but are correlated with accretion, we suggest that they are produced
in the stellar transition region. The accretion shock model predicts
that the velocity of the post-shock emission should be 4x smaller than
the velocity of the pre-shock emission. Identifying the post-shock
emission with the NC and the pre-shock with the BC, we find that this is
approximately the case in 11 out of 23 objects. The model cannot explain
11 systems in which the velocity of the NC is smaller than the velocity
of the BC, or systems in which one of the velocities is negative (five
CTTSs). The hot gas lines in some systems such as HN Tau, RW Aur A, AK
Sco, DK Tau, T Tau N, and V1190 Sco require an outflow contribution,
which may come from jet shocks in the observed outflows. We suggest
that a hot wind is being launched by the Herbig Ae star DX Cha.

---------------------------------------------------------
Title: Ultraviolet and Extreme Ultraviolet Emission of Host Stars
and Effects on Exoplanet Atmospheres
Authors: Linsky, Jeffrey; France, K.; Ayres, T. R.
2013AAS...22132105L Altcode:
The chemistry and mass-loss rates of exoplanet atmospheres are
controlled by the radiative and particle emission of their host
star. The host star's ultraviolet radiation, and especially the
Lyman-alpha emission, photodissociate important molecules in exoplanet
atmospheres including water, CO2, and methane. The intrinsic Lyman-alpha
emission cannot be observed because of attenuation by neutral hydrogen
in the interstellar medium and must therefore be reconstructed. We
describe a new reconstruction method based on correlations of
Lyman-alpha flux with the fluxes in other emission lines formed at
similar temperatures in the stellar chromosphere. Except for low metal
abundance stars, this technique provides estimates of the Lyman-alpha
flux within 20 percent of the values obtained by Wood et al. (2005)
for stars of spectral type F5 V to M5 V. We also show that the EUV flux
in 100 A wide spectral bands from 300 to 1170 A is well correlated
with the Lyman-alpha flux and therefore can be accurately estimated
for these stars. This work is based on observations with the COS and
STIS instruments on HST, and is supported by NASA grants to the Space
Telescope Science Institute and the University of Colorado.

---------------------------------------------------------
Title: Mapping the Local Interstellar Medium Using High-Resolution
UV Absorption Spectroscopy
Authors: Malamut, Craig; Redfield, S.; Linsky, J.
2013AAS...22134935M Altcode:
Observations using the Space Telescope Imaging Spectrograph aboard
the Hubble Space Telescope have provided high-resolution near
ultraviolet spectra showing MgII, FeII and MnII absorption in the local
interstellar medium (LISM). The sample includes sight lines towards
over 30 stars within 100 parsecs and across a wide range of spectral
types. Observations span the entire sky, probing previously unobserved
regions of the LISM. The heavy ions studied in this survey produce
narrow absorption features that make possible the identification of
multiple interstellar components. Our simultaneous fits of the MgII,
FeII, and MnII doublets reveal anywhere from one to six individual
absorption components in a particular sight line, where the number of
absorbers roughly correlates with the length of the sight line. The
simultaneous fitting procedure reduces the systematic errors involved
in continuum placement and number of absorbers. Already, sight lines
show evidence of previously unidentified clouds within the Local
Bubble. These measurements will be added to a growing data set of 81
near UV sight lines. The increase in the number of sight lines will
test and improve a three dimensional kinematic model of the local
interstellar medium. With an improved understanding of the LISM's
kinematical structure, it will be possible to distinguish blended
components within the absorption features of lighter ions. Specifically,
the MAST Archive contains FUV observations of interstellar absorption
by low mass ions (DI, CII, NI, OI) along the the same sight lines. The
combination of these data will constrain properties of the LISM such
as temperature, turbulence, ionization, abundances and depletions. We
acknowledge support for this project through NASA HST Grant GO-11568
awarded by the Space Telescope Science Institute, which is operated
by the Association of Universities for Research in Astronomy, Inc.,
for NASA, under contract NAS 5-26555, and a student research fellowship
from the Connecticut Space Grant Consortium.

---------------------------------------------------------
Title: Lyα Dominance of the Classical T Tauri Far-ultraviolet
Radiation Field
Authors: Schindhelm, Rebecca; France, Kevin; Herczeg, Gregory J.;
Bergin, Edwin; Yang, Hao; Brown, Alexander; Brown, Joanna M.; Linsky,
Jeffrey L.; Valenti, Jeff
2012ApJ...756L..23S Altcode: 2012arXiv1208.2271S
Far-ultraviolet (FUV) radiation plays an important role in determining
chemical abundances in protoplanetary disks. H I Lyman α (Lyα)
is suspected to be the dominant component of the FUV emission from
Classical T Tauri Stars (CTTSs), but is difficult to measure directly
due to circumstellar and interstellar H I absorption. To better
characterize the intrinsic Lyα radiation, we present FUV spectra of 14
CTTSs taken with the Hubble Space Telescope Cosmic Origins Spectrograph
and Space Telescope Imaging Spectrograph instruments. H2
fluorescence, commonly seen in the spectra of CTTSs, is excited by Lyα
photons, providing an indirect measure of the Lyα flux incident upon
the warm disk surface. We use observed H2 progression fluxes
to reconstruct the CTTS Lyα profiles. The Lyα flux correlates with
total measured FUV flux, in agreement with an accretion-related source
of FUV emission. With a geometry-independent analysis, we confirm that
in accreting T Tauri systems Lyα radiation dominates the FUV flux
(~1150 Å -1700 Å). In the systems surveyed this one line comprises
70%-90% of the total FUV flux.

---------------------------------------------------------
Title: A Hubble Space Telescope Survey of H2 Emission in
the Circumstellar Environments of Young Stars
Authors: France, Kevin; Schindhelm, Rebecca; Herczeg, Gregory J.;
Brown, Alexander; Abgrall, Hervé; Alexander, Richard D.; Bergin, Edwin
A.; Brown, Joanna M.; Linsky, Jeffrey L.; Roueff, Evelyne; Yang, Hao
2012ApJ...756..171F Altcode: 2012arXiv1207.4789F
The formation timescale and final architecture of exoplanetary
systems are closely related to the properties of the molecular disks
from which they form. Observations of the spatial distribution and
lifetime of the molecular gas at planet-forming radii (a &lt; 10 AU) are
important for understanding the formation and evolution of exoplanetary
systems. Toward this end, we present the largest spectrally resolved
survey of H2 emission around low-mass pre-main-sequence
stars compiled to date. We use a combination of new and archival
far-ultraviolet spectra from the Cosmic Origins Spectrograph and Space
Telescope Imaging Spectrograph instruments on the Hubble Space Telescope
to sample 34 T Tauri stars (27 actively accreting Classical T Tauri
Stars and 7 non-accreting Weak-lined T Tauri Stars) with ages ranging
from ~1 to 10 Myr. We observe fluorescent H2 emission,
excited by Lyα photons, in 100% of the accreting sources, including
all of the transitional disks in our sample (CS Cha, DM Tau, GM Aur,
UX Tau A, LkCa 15, HD 135344B, and TW Hya). The spatial distribution of
the emitting gas is inferred from spectrally resolved H2 line
profiles. Some of the emitting gas is produced in outflowing material,
but the majority of H2 emission appears to originate in
a rotating disk. For the disk-dominated targets, the H2
emission originates predominately at a &lt;~ 3 AU. The emission line
widths and inner molecular radii are found to be roughly consistent
with those measured from mid-IR CO spectra. Based on observations
made with the NASA/ESA Hubble Space Telescope, obtained from the data
archive at the Space Telescope Science Institute. STScI is operated by
the Association of Universities for Research in Astronomy, Inc. under
NASA contract NAS 5-26555.

---------------------------------------------------------
Title: From Protoplanetary Disks to Extrasolar Planets: Understanding
the Life Cycle of Circumstellar Gas with Ultraviolet Spectroscopy
Authors: France, Kevin; Beasley, Matthew; Ardila, David R.; Bergin,
Edwin A.; Brown, Alexander; Burgh, Eric B.; Calvet, Nuria; Chiang,
Eugene; Cook, Timothy A.; Désert, Jean-Michel; Ebbets, Dennis;
Froning, Cynthia S.; Green, James C.; Hillenbrand, Lynne A.;
Johns-Krull, Christopher M.; Koskinen, Tommi T.; Linsky, Jeffrey L.;
Redfield, Seth; Roberge, Aki; Schindhelm, Rebecca; Scowen, Paul A.;
Stapelfeldt, Karl R.; Tumlinson, Jason
2012arXiv1208.2270F Altcode:
Few scientific discoveries have captured the public imagination like the
explosion of exoplanetary science during the past two decades. This work
has fundamentally changed our picture of Earth's place in the Universe
and led NASA to make significant investments towards understanding
the demographics of exoplanetary systems and the conditions that
lead to their formation. The story of the formation and evolution of
exoplanetary systems is essentially the story of the circumstellar gas
and dust that are initially present in the protostellar environment;
in order to understand the variety of planetary systems observed,
we need to understand the life cycle of circumstellar gas from its
initial conditions in protoplanetary disks to its endpoint as planets
and their atmospheres. In this white paper response to NASA's Request
for Information "Science Objectives and Requirements for the Next
NASA UV/Visible Astrophysics Mission Concepts (NNH12ZDA008L)", we
describe scientific programs that would use the unique capabilities
of a future NASA ultraviolet (UV)/visible space observatory to make
order-of-magnitude advances in our understanding of the life cycle of
circumstellar gas.

---------------------------------------------------------
Title: Unexpected Advice for Beginning Graduate Students in
Astrophysics
Authors: Linsky, Jeffrey L.
2012opsa.book..143L Altcode:
My experience is that beginning graduate students in astrophysics
have unrealistic views of how to negotiate the complexities of
graduate school and to prepare themselves for a professional career in
astrophysics or some other field. This chapter describes my unexpected
advice to students beginning with why they should not plan to write
a thesis. Other advice concerns how to find and work with a research
supervisor, writing and other skills needed for their research, and
the need to be creative and when necessary controversial.

---------------------------------------------------------
Title: The solar wind in time
Authors: Linsky, Jeffrey L.; Wood, Brian E.; Redfield, Seth
2012IAUS..286..286L Altcode:
We describe our method for measuring mass loss rates of F-M main
sequence stars with high-resolution Lyman-α line profiles. Our
diagnostic is the extra absorption on the blue side the interstellar
hydrogen absorption produced by neutral hydrogen gas in the hydrogen
walls of stars. For stars with low X-ray fluxes, the correlation of
observed mass loss rate with X-ray surface flux and age predicts the
solar wind mass flux between 700 Myr and the present.

---------------------------------------------------------
Title: Ultraviolet Spectroscopy of Rapidly Rotating Solar-Mass Stars:
Emission-line Redshifts as a Test of the Solar-Stellar Connection
Authors: Linsky, Jeffrey L.; Bushinsky, Rachel; Ayres, Tom; France,
Kevin
2012ApJ...754...69L Altcode: 2012arXiv1205.6498L
We compare high-resolution ultraviolet spectra of the Sun and
thirteen solar-mass main-sequence stars with different rotational
periods that serve as proxies for their different ages and magnetic
field structures. In this, the second paper in the series, we study
the dependence of ultraviolet emission-line centroid velocities on
stellar rotation period, as rotation rates decrease from that of the
Pleiades star HII314 (P rot = 1.47 days) to α Cen A (P
rot = 28 days). Our stellar sample of F9 V to G5 V stars
consists of six stars observed with the Cosmic Origins Spectrograph
on the Hubble Space Telescope (HST) and eight stars observed with the
Space Telescope Imaging Spectrograph on HST. We find a systematic
trend of increasing redshift with more rapid rotation (decreasing
rotation period) that is similar to the increase in line redshift
between quiet and plage regions on the Sun. The fastest-rotating
solar-mass star in our study, HII314, shows significantly enhanced
redshifts at all temperatures above log T = 4.6, including the corona,
which is very different from the redshift pattern observed in the
more slowly rotating stars. This difference in the redshift pattern
suggests that a qualitative change in the magnetic-heating process
occurs near P rot = 2 days. We propose that HII314 is an
example of a solar-mass star with a magnetic heating rate too large
for the physical processes responsible for the redshift pattern to
operate in the same way as for the more slowly rotating stars. HII314
may therefore lie above the high activity end of the set of solar-like
phenomena that is often called the "solar-stellar connection."

---------------------------------------------------------
Title: An analysis of the rapidly rotating Bp star HD 133880
Authors: Bailey, J. D.; Grunhut, J.; Shultz, M.; Wade, G.; Landstreet,
J. D.; Bohlender, D.; Lim, J.; Wong, K.; Drake, S.; Linsky, J.
2012MNRAS.423..328B Altcode: 2012MNRAS.tmp.2947B; 2012arXiv1203.5277B
HD 133880 is a rapidly rotating chemically peculiar B-type (Bp)
star (v sin i≃ 103 km s-1) and is host to one of the
strongest magnetic fields of any Ap/Bp star. A member of the Upper
Centaurus Lupus association, it is a star with a well-determined age
of 16 Myr. 12 new spectra, four of which are polarimetric, obtained
from the FEROS, ESPaDOnS and HARPS instruments, provide sufficient
material from which to re-evaluate the magnetic field and obtain a
first approximation to the atmospheric abundance distributions of He,
O, Mg, Si, Ti, Cr, Fe, Ni, Pr and Nd. An abundance analysis was
carried out using ZEEMAN, a program which synthesizes spectral line
profiles for stars with permeating magnetic fields. The magnetic field
structure was characterized by a colinear multipole expansion from
the observed variations of the longitudinal and surface fields with
rotational phase. Both magnetic hemispheres are clearly visible during
the stellar rotation, and thus a three-ring abundance distribution
model encompassing both magnetic poles and magnetic equator with
equal spans in colatitude was adopted. Using the new magnetic
field measurements and optical photometry together with previously
published data, we refine the period of HD 133880 to P= 0.877 476 ±
0.000 009 d. Our simple axisymmetric magnetic field model is based on
a predominantly quadrupolar component that roughly describes the field
variations. Using spectrum synthesis, we derived mean abundances for O,
Mg, Si, Ti, Cr, Fe and Pr. All elements, except Mg, are overabundant
compared to the Sun. Mg appears to be approximately uniform over
the stellar surface, while all other elements are more abundant
in the negative magnetic hemisphere than in the positive magnetic
hemisphere. In contrast to most Ap/Bp stars which show an underabundance
in O, in HD 133880 this element is clearly overabundant compared to
the solar abundance ratio. In studying the Hα and Paschen lines
in the optical spectra, we could not unambiguously detect information
about the magnetosphere of HD 133880. However, radio emission data
at both 3 and 6 cm suggest that the magnetospheric plasma is held
in rigid rotation with the star by the magnetic field and further
supported against collapse by the rapid rotation. Subtle differences
in the shapes of the optically thick radio light curves at 3 and 6 cm
suggest that the large-scale magnetic field is not fully axisymmetric at
large distances from the star. Based in part on observations made with
the European Southern Observatory (ESO) telescopes under ESO programmes
082.D-0061(A), 083.D-0034(A), 085.D-0296(A) and 086.D-0449(A), obtained
from the ESO/ST-ECF Science Archive Facility. It is also based in
part on observations carried out at the Canada-France-Hawaii Telescope
(CFHT) which is operated by the National Research Council of Canada,
the Institut National des Science de l'Univers of the Centre National
de la Recherche Scientifique of France and the University of Hawaii.

---------------------------------------------------------
Title: Time-resolved Ultraviolet Spectroscopy of the GJ 876
Exoplanetary System
Authors: France, Kevin; Tian, F.; Linsky, J. L.; Froning, C. S.;
Roberge, A.; Stocke, J. T.
2012AAS...22012907F Altcode:
Extrasolar planets orbiting M-stars may represent our best chance
to discover habitable worlds in the coming decade. The ultraviolet
spectrum incident upon both Earth-like and Jovian planets is critically
important for proper modeling of their atmospheric heating and
chemistry. In order to provide a more realistic input for atmospheric
models of planets orbiting low-mass stars, we present new near- and
far-ultraviolet spectroscopy of the M-dwarf exoplanet host GJ 876
(M4V). Using the COS and STIS spectrographs aboard the Hubble Space
Telescope, we have characterized the 1150-3140A spectrum of GJ 876. We
have reconstructed the stellar HI LyA emission line profile, and find
that the integrated LyA flux is roughly twice the rest of the integrated
flux in the 1150-3140A ultraviolet bandpass (F(LyA)/F(FUV+NUV) 2). This
LyA/(FUV+NUV) ratio is approximately four orders of magnitude greater
than the solar value. We present a description of the ultraviolet line
spectrum and report surprisingly strong fluorescent emission from hot
H2 (T &gt; 2000 K). We describe the light-curve of a chromospheric +
transition region flare observed in several far-UV emission lines,
with flare/quiescent ratios &gt; 10. The strong far-ultraviolet
radiation field of an M-star (and specifically LyA) may be important
for determining the abundance of O2 in the lower atmosphere, and the
formation of biomarkers, for Earth-like planets in the habitable zones
of low-mass stars.

---------------------------------------------------------
Title: Time-resolved Ultraviolet Spectroscopy of the M-dwarf GJ 876
Exoplanetary System
Authors: France, Kevin; Linsky, Jeffrey L.; Tian, Feng; Froning,
Cynthia S.; Roberge, Aki
2012ApJ...750L..32F Altcode: 2012arXiv1204.1976F
Extrasolar planets orbiting M-stars may represent our best chance
to discover habitable worlds in the coming decade. The ultraviolet
spectrum incident upon both Earth-like and Jovian planets is critically
important for proper modeling of their atmospheric heating and
chemistry. In order to provide more realistic inputs for atmospheric
models of planets orbiting low-mass stars, we present new near- and
far-ultraviolet (NUV and FUV) spectroscopy of the M-dwarf exoplanet
host GJ 876 (M4V). Using the COS and STIS spectrographs on board the
Hubble Space Telescope, we have measured the 1150-3140 Å spectrum
of GJ 876. We have reconstructed the stellar H I Lyα emission line
profile, and find that the integrated Lyα flux is roughly equal to
the rest of the integrated flux (1150-1210 Å + 1220-3140 Å) in the
entire ultraviolet bandpass (F(Lyα)/F(FUV+NUV) ≈ 0.7). This ratio is
~2500× greater than the solar value. We describe the ultraviolet line
spectrum and report surprisingly strong fluorescent emission from hot
H2 (T(H2) &gt; 2000 K). We show the light curve
of a chromospheric + transition region flare observed in several far-UV
emission lines, with flare/quiescent flux ratios &gt;=10. The strong
FUV radiation field of an M-star (and specifically Lyα) is important
for determining the abundance of O2—and the formation
of biomarkers—in the lower atmospheres of Earth-like planets in
the habitable zones of low-mass stars. Based on observations
made with the NASA/ESA Hubble Space Telescope, obtained from the data
archive at the Space Telescope Science Institute. STScI is operated
by the Association of Universities for Research in Astronomy, Inc.,
under NASA contract NAS 5-26555.

---------------------------------------------------------
Title: The Cosmic Origins Spectrograph
Authors: Green, James C.; Froning, Cynthia S.; Osterman, Steve; Ebbets,
Dennis; Heap, Sara H.; Leitherer, Claus; Linsky, Jeffrey L.; Savage,
Blair D.; Sembach, Kenneth; Shull, J. Michael; Siegmund, Oswald H. W.;
Snow, Theodore P.; Spencer, John; Stern, S. Alan; Stocke, John; Welsh,
Barry; Béland, Stéphane; Burgh, Eric B.; Danforth, Charles; France,
Kevin; Keeney, Brian; McPhate, Jason; Penton, Steven V.; Andrews,
John; Brownsberger, Kenneth; Morse, Jon; Wilkinson, Erik
2012ApJ...744...60G Altcode: 2011arXiv1110.0462G
The Cosmic Origins Spectrograph (COS) is a moderate-resolution
spectrograph with unprecedented sensitivity that was installed into the
Hubble Space Telescope (HST) in 2009 May, during HST Servicing Mission
4 (STS-125). We present the design philosophy and summarize the key
characteristics of the instrument that will be of interest to potential
observers. For faint targets, with flux F λ ≈ 1.0 ×
10-14 erg cm-2 s-1 Å-1,
COS can achieve comparable signal to noise (when compared to Space
Telescope Imaging Spectrograph echelle modes) in 1%-2% of the observing
time. This has led to a significant increase in the total data volume
and data quality available to the community. For example, in the
first 20 months of science operation (2009 September-2011 June) the
cumulative redshift pathlength of extragalactic sight lines sampled by
COS is nine times than sampled at moderate resolution in 19 previous
years of Hubble observations. COS programs have observed 214 distinct
lines of sight suitable for study of the intergalactic medium as of
2011 June. COS has measured, for the first time with high reliability,
broad Lyα absorbers and Ne VIII in the intergalactic medium, and
observed the He II reionization epoch along multiple sightlines. COS
has detected the first CO emission and absorption in the UV spectra of
low-mass circumstellar disks at the epoch of giant planet formation,
and detected multiple ionization states of metals in extra-solar
planetary atmospheres. In the coming years, COS will continue its
census of intergalactic gas, probe galactic and cosmic structure,
and explore physics in our solar system and Galaxy.

---------------------------------------------------------
Title: CO and H2 Absorption in the AA Tauri Circumstellar
Disk
Authors: France, Kevin; Burgh, Eric B.; Herczeg, Gregory J.;
Schindhelm, Rebecca; Yang, Hao; Abgrall, Hervé; Roueff, Evelyne;
Brown, Alexander; Brown, Joanna M.; Linsky, Jeffrey L.
2012ApJ...744...22F Altcode: 2011arXiv1109.1831F
The direct study of molecular gas in inner protoplanetary disks is
complicated by uncertainties in the spatial distribution of the gas,
the time variability of the source, and the comparison of observations
across a wide range of wavelengths. Some of these challenges can be
mitigated with far-ultraviolet spectroscopy. Using new observations
obtained with the Hubble Space Telescope Cosmic Origins Spectrograph,
we measure column densities and rovibrational temperatures for
CO and H2 observed on the line of sight through the AA
Tauri circumstellar disk. CO A - X absorption bands are observed
against the far-UV continuum. The CO absorption is characterized by
log10(N(12CO)) = 17.5 ± 0.5 cm-2 and T
rot(CO) = 500+500 -200 K, although this
rotational temperature may underestimate the local kinetic temperature
of the CO-bearing gas. We also detect 13CO in absorption with
an isotopic ratio of ~20. We do not observe H2 absorption
against the continuum; however, hot H2 (v &gt; 0) is detected
in absorption against the Lyα emission line. We measure the column
densities in eight individual rovibrational states, determining
a total log10(N(H2)) = 17.9+0.6
-0.3 cm-2 with a thermal temperature of
T(H2) = 2500+800 -700 K. The high
temperature of the molecules, the relatively small H2
column density, and the high inclination of the AA Tauri disk suggest
that the absorbing gas resides in an inner disk atmosphere. If the
H2 and CO are cospatial within a molecular layer ~0.6 AU
thick, this region is characterized by \langle n_{H_{2}} \rangle ~
105 cm-3 with an observed langCO/H2rang
ratio of ~0.4. We also find evidence for a departure from a purely
thermal H2 distribution, suggesting that excitation by
continuum photons and H2 formation may be altering the
level populations in the molecular gas. Based on observations
made with the NASA/ESA Hubble Space Telescope, obtained from the data
archive at the Space Telescope Science Institute. STScI is operated by
the Association of Universities for Research in Astronomy, Inc. under
NASA contract NAS 5-26555.

---------------------------------------------------------
Title: Far-ultraviolet Continuum Emission: Applying This Diagnostic
to the Chromospheres of Solar-mass Stars
Authors: Linsky, Jeffrey L.; Bushinsky, Rachel; Ayres, Tom; Fontenla,
Juan; France, Kevin
2012ApJ...745...25L Altcode: 2011arXiv1109.5653L
The far-ultraviolet (FUV) continuum flux is recognized as a very
sensitive diagnostic of the temperature structure of the Sun's
lower chromosphere. Until now analysis of the available stellar FUV
data has shown that solar-type stars must also have chromospheres,
but quantitative analyses of stellar FUV continua require far higher
quality spectra and comparison with new non-LTE chromosphere models. We
present accurate far-ultraviolet (FUV, 1150-1500 Å) continuum flux
measurements for solar-mass stars, made feasible by the high throughput
and very low detector background of the Cosmic Origins Spectrograph on
the Hubbble Space Telescope. We show that the continuum flux can be
measured above the detector background even for the faintest star in
our sample. We find a clear trend of increasing continuum brightness
temperature at all FUV wavelengths with decreasing rotational period,
which provides an important measure of magnetic heating rates in stellar
chromospheres. Comparison with semiempirical solar flux models shows
that the most rapidly rotating solar-mass stars have FUV continuum
brightness temperatures similar to the brightest faculae seen on the
Sun. The thermal structure of the brightest solar faculae therefore
provides a first-order estimate of the thermal structure and heating
rate for the most rapidly rotating solar-mass stars in our sample.

---------------------------------------------------------
Title: A Far-ultraviolet Atlas of Low-resolution Hubble Space
Telescope Spectra of T Tauri Stars
Authors: Yang, Hao; Herczeg, Gregory J.; Linsky, Jeffrey L.; Brown,
Alexander; Johns-Krull, Christopher M.; Ingleby, Laura; Calvet, Nuria;
Bergin, Edwin; Valenti, Jeff A.
2012ApJ...744..121Y Altcode: 2012arXiv1205.4789Y
We present a far-ultraviolet (FUV) spectral atlas consisting of
spectra of 91 pre-main-sequence stars. Most stars in this sample
were observed with the Space Telescope Imaging Spectrograph and
Advanced Camera for Surveys on the Hubble Space Telescope (HST). A
few archival spectra from the International Ultraviolet Explorer
and the Goddard High Resolution Spectrograph on HST are included for
completeness. We find strong correlations among the O I λ1304 triplet,
the Si IV λλ1394/1403 doublet, the C IV λ1549 doublet, and the He
II λ1640 line luminosities. For classical T Tauri stars (CTTSs), we
also find strong correlations between these lines and the accretion
luminosity, suggesting that these lines form in processes related to
accretion. These FUV line fluxes and X-ray luminosity correlate loosely
with large scatters. The FUV emission also correlates well with Hα,
Hβ, and Ca II K line luminosities. These correlations between FUV and
optical diagnostics can be used to obtain rough estimates of FUV line
fluxes from optical observations. Molecular hydrogen (H2)
emission is generally present in the spectra of actively accreting
CTTSs but not the weak-lined T Tauri stars that are not accreting. The
presence of H2 emission in the spectrum of HD 98800 N
suggests that the disk should be classified as actively accreting
rather than a debris disk. We discuss the importance of FUV radiation,
including the hydrogen Lyα line, on the photoevaporation of exoplanet
atmospheres. We find that the Ca II/C IV flux ratios for more evolved
stars are lower than those for less evolved accretors, indicating
preferential depletion of refractory metals into dust grains. Based
on observations made with the NASA/ESA Hubble Space Telescope, obtained
from the data archive at the Space Telescope Science Institute. STScI is
operated by the Association of Universities for Research in Astronomy,
Inc., under NASA contract NAS 5-26555. This work also contains results
from Chandra projects 09200763 and 10200804 supported by SAO grants
GO8-9024X and GO9-0020B to the University of Colorado. This work was
supported in part by NASA Swift grants NNX09AL59G and NNX10AK88G,
and Smithsonian Institution Chandra grants GO8-9024X, GO9-0020B,
GO0-11042X, and GO1-12031X to the University of Colorado.

---------------------------------------------------------
Title: Voyagers of Discovery
Authors: Linsky, Jeffrey L.
2011Sci...334.1647L Altcode:
No abstract at ADS

---------------------------------------------------------
Title: Revealing the Spectral Type Dependence of the Coronal FIP
Effect
Authors: Wood, B.; Linsky, J. L.
2011ASPC..448.1325W Altcode: 2011csss...16.1325W
The most widely studied coronal abundance anomaly is the so-called "FIP
effect", where the abundances of elements with low First Ionization
Potential (FIP) are enhanced relative to the photosphere. Many studies
in the past have reported a tendency for more active stars to have less
of a FIP effect, and for particularly active stars to even exhibit an
inverse FIP effect, where low FIP elements are depleted in the corona
instead of enhanced. However, we find that this activity dependence
is nonexistent among main sequence stars when the most active stars
with log LX &gt; 29 are excluded. Extremely active stars
normally dominate coronal surveys since active stars are brighter
and more easily observed in X-rays, but by avoiding such extremes and
focusing solely on more normal stars we find a very different empirical
view of the FIP effect, one in which FIP bias is dependent on spectral
type instead of activity. This dependence indicates a strong connection
between coronal abundance and basic photospheric characteristics.

---------------------------------------------------------
Title: The Radio-X-ray Relation in Cool Stars: Are We Headed Toward
a Divorce?
Authors: Forbrich, J.; Wolk, S. J.; Güdel, M.; Benz, A.; Osten, R.;
Linsky, J. L.; McLean, M.; Loinard, L.; Berger, E.
2011ASPC..448..455F Altcode: 2011csss...16..455F; 2010arXiv1012.1626F
This splinter session was devoted to reviewing our current knowledge
of correlated X-ray and radio emission from cool stars in order
to prepare for new large radio observatories such as the EVLA. A
key interest was to discuss why the X-ray and radio luminosities of
some cool stars are in clear breach of a correlation that holds for
other active stars, the so-called Güdel-Benz relation. This article
summarizes the contributions whereas the actual presentations can be
accessed on the splinter website.

---------------------------------------------------------
Title: HST/COS Spectra of DF Tau and V4046 Sgr: First Detection of
Molecular Hydrogen Absorption Against the Lyman α Emission Line
Authors: Yang, H.; Linsky, J. L.; France, K.
2011ASPC..448...69Y Altcode: 2011csss...16...69Y
We present moderate-resolution (16,000 - 18,000) far-UV spectra of
two classical T Tauri stars, DF Tau and V4046 Sgr, obtained with the
Cosmic Origins Spectrograph (COS) on the Hubble Space Telescope (HST),
and report for the first time detection of absorption in the Lyman-α
profile produced by the H2 pumping transitions. For most
absorption features, the absorbed energy in the H2 pumping
transitions is significantly smaller than the amount of energy in the
resulting fluorescent emission, indicative of additional absorption
in the H I Lyman-α profile along our light of sight. We model the
additional H I absorption and are able to correct the H2
absorption/emission ratios close to unity. The required H I absorption
for DF Tau is at a velocity close to the radial velocity of the star,
consistent with H I absorption in the interstellar medium and the
edge-on disk. For V4046 Sgr, a nearly face-on system, the required
absorption is near +290 km s-1, most likely resulting from
H I gas in the accretion columns falling onto the star.

---------------------------------------------------------
Title: Near-ultraviolet Excess in Slowly Accreting T Tauri Stars:
Limits Imposed by Chromospheric Emission
Authors: Ingleby, Laura; Calvet, Nuria; Bergin, Edwin; Herczeg,
Gregory; Brown, Alexander; Alexander, Richard; Edwards, Suzan;
Espaillat, Catherine; France, Kevin; Gregory, Scott G.; Hillenbrand,
Lynne; Roueff, Evelyne; Valenti, Jeff; Walter, Frederick; Johns-Krull,
Christopher; Brown, Joanna; Linsky, Jeffrey; McClure, Melissa; Ardila,
David; Abgrall, Hervé; Bethell, Thomas; Hussain, Gaitee; Yang, Hao
2011ApJ...743..105I Altcode: 2011arXiv1110.6312I
Young stars surrounded by disks with very low mass accretion rates
are likely in the final stages of inner disk evolution and therefore
particularly interesting to study. We present ultraviolet (UV)
observations of the ~5-9 Myr old stars RECX-1 and RECX-11, obtained
with the Cosmic Origins Spectrograph and Space Telescope Imaging
Spectrograph on the Hubble Space Telescope, as well as optical and
near-infrared spectroscopic observations. The two stars have similar
levels of near-UV emission, although spectroscopic evidence indicates
that RECX-11 is accreting and RECX-1 is not. The line profiles of
Hα and He I λ10830 in RECX-11 show both broad and narrow redshifted
absorption components that vary with time, revealing the complexity of
the accretion flows. We show that accretion indicators commonly used
to measure mass accretion rates, e.g., U-band excess luminosity or the
Ca II triplet line luminosity, are unreliable for low accretors, at
least in the middle K spectral range. Using RECX-1 as a template for the
intrinsic level of photospheric and chromospheric emission, we determine
an upper limit of 3 × 10-10 M ⊙ yr-1
for RECX-11. At this low accretion rate, recent photoevaporation models
predict that an inner hole should have developed in the disk. However,
the spectral energy distribution of RECX-11 shows fluxes comparable to
the median of Taurus in the near-infrared, indicating that substantial
dust remains. Fluorescent H2 emission lines formed in the
innermost disk are observed in RECX-11, showing that gas is present
in the inner disk, along with the dust. This paper includes data
gathered with the 6.5 m Magellan Telescopes located at Las Campanas
Observatory, Chile.

---------------------------------------------------------
Title: Understanding physical processes in the diffuse ISM using
high-resolution UV spectroscopy
Authors: Linsky, Jeffrey L.
2011Ap&SS.335..177L Altcode: 2011Ap&SS.tmp..285L; 2011Ap&SS.tmp..405L
Our understanding of the important physical processes operating in the
diffuse interstellar medium (ISM) has advanced in recent years from
the analysis of high-resolution ultraviolet (UV) spectra obtained with
the Hubble Space Telescope (HST) and the Far-Ultraviolet Spectrograph
Explorer (FUSE) and from high-fidelity simulations of the kinematics
and energetics of the ISM. Nevertheless, much remains to be learned
from observations with the Space Telescope Imaging Spectrograph (STIS)
instrument on HST and spectrographs on the World Space Observatory
(WSO). I will describe several major unanswered questions and
suggest how future UV observations can answer these questions. I will
also summarize the instrument requirements needed for a future UV
spectroscopic mission and recommend how to achieve a successful mission.

---------------------------------------------------------
Title: HST-COS observations of the transiting extrasolar planetary
system HD 209458b
Authors: France, Kevin; Linsky, Jeffrey L.; Yang, Hao; Stocke, John
T.; Froning, Cynthia S.
2011Ap&SS.335...25F Altcode: 2011Ap&SS.tmp..262F; 2011Ap&SS.tmp..382F
We summarize results from deep spectroscopic observations
of the HD 209458 planetary system, carried out with the Hubble
Space Telescope—Cosmic Origins Spectrograph. Orbitally resolved
observations are used to show that hot gas emission lines, arising only
in the stellar atmosphere, are not variable, while lower ionizations
species found in the upper atmosphere of the hot Jupiter HD 209458b
absorb stellar photons during transit. For both C II and Si III,
we find mean transit attenuation of ∼8%. The firm detection of
silicon is in direct conflict with previous low-resolution studies,
which we attribute to long-term variability in the system. We also
use these observations to search for auroral emission from the planet,
detecting a statistically significant emission feature at 1582 Å that
is consistent with H2 photoexcited by stellar O I photons.

---------------------------------------------------------
Title: The Far-ultraviolet "Continuum" in Protoplanetary Disk
Systems. II. Carbon Monoxide Fourth Positive Emission and Absorption
Authors: France, Kevin; Schindhelm, Rebecca; Burgh, Eric B.; Herczeg,
Gregory J.; Harper, Graham M.; Brown, Alexander; Green, James C.;
Linsky, Jeffrey L.; Yang, Hao; Abgrall, Hervé; Ardila, David R.;
Bergin, Edwin; Bethell, Thomas; Brown, Joanna M.; Calvet, Nuria;
Espaillat, Catherine; Gregory, Scott G.; Hillenbrand, Lynne A.;
Hussain, Gaitee; Ingleby, Laura; Johns-Krull, Christopher M.; Roueff,
Evelyne; Valenti, Jeff A.; Walter, Frederick M.
2011ApJ...734...31F Altcode: 2011arXiv1104.0670F
We exploit the high sensitivity and moderate spectral resolution
of the Hubble Space Telescope Cosmic Origins Spectrograph to detect
far-ultraviolet (UV) spectral features of carbon monoxide (CO) present
in the inner regions of protoplanetary disks for the first time. We
present spectra of the classical T Tauri stars HN Tau, RECX-11, and
V4046 Sgr, representative of a range of CO radiative processes. HN
Tau shows CO bands in absorption against the accretion continuum. The
CO absorption most likely arises in warm inner disk gas. We measure
a CO column density and rotational excitation temperature of N(CO) =
(2 ± 1) × 1017 cm-2 and T rot(CO)
500 ± 200 K for the absorbing gas. We also detect CO A-X band emission
in RECX-11 and V4046 Sgr, excited by UV line photons, predominantly H
I Lyα. All three objects show emission from CO bands at λ &gt; 1560
Å, which may be excited by a combination of UV photons and collisions
with non-thermal electrons. In previous observations these emission
processes were not accounted for due to blending with emission from the
accretion shock, collisionally excited H2, and photo-excited
H2, all of which appeared as a "continuum" whose components
could not be separated. The CO emission spectrum is strongly dependent
upon the shape of the incident stellar Lyα emission profile. We find
CO parameters in the range: N(CO) ~ 1018-1019
cm-2, T rot(CO) &gt;~ 300 K for the Lyα-pumped
emission. We combine these results with recent work on photo-excited
and collisionally excited H2 emission, concluding that the
observations of UV-emitting CO and H2 are consistent with a
common spatial origin. We suggest that the CO/H2 ratio (≡
N(CO)/N(H2)) in the inner disk is ~1, a transition between
the much lower interstellar value and the higher value observed in solar
system comets today, a result that will require future observational
and theoretical study to confirm. Based on observations made
with the NASA/ESA Hubble Space Telescope, obtained from the data
archive at the Space Telescope Science Institute. STScI is operated
by the Association of Universities for Research in Astronomy, Inc.,
under NASA contract NAS 5-26555.

---------------------------------------------------------
Title: The Joys of Applying UV Spectroscopy to Understanding the
Solar-Stellar Connection and Related Topics in Astrophysics
Authors: Linsky, Jeffrey
2011AAS...21821301L Altcode: 2011BAAS..43G21301L
For more than 40 years a central theme of my research has been the
application of spectroscopy mostly at ultraviolet wavelengths to a
clearer understanding of phenomena and physical processes occuring in
the outer atmospheres of the Sun, cool stars, premain sequence stars,
and the interstellar medium near the Sun. The sensitivity and spectral
resolution available for this work has increased enormously over
time. My thesis involved the analysis of solar chromosphere spectra of
the Ca II H and K lines using the McMath-Pierce solar telescope on Kitt
Peak. Then with spectra from the Copernicus and IUE satellites and the
GHRS, STIS, and COS instruments on HST, I extended this research to the
study of stellar chromospheres. The availability of X-ray observations
and spectra with HEAO-1, Einstein, XMM-Newton, and Chandra observatories
opened up the study of stellar coronae. Absorption lines observed
against stellar emission lines are not noise but important signals
leading to a better understanding of the local interstellar medium,
deuterium in the Galaxy, and even mass loss from a transiting planet. In
all of these research areas, I have had the pleasure of working with
and learning from many stimulating graduate students and postdocs. In this talk I will select several key discoveries in the above
topics, summarize our present understanding of these topics, identify
what we need to understand better, and suggest what observational and
theoretical advances should be pursued to improve our understanding.

---------------------------------------------------------
Title: HST/COS Spectra of DF Tau and V4046 Sgr: First Detection of
Molecular Hydrogen Absorption Against the Lyα Emission Line
Authors: Yang, Hao; Linsky, Jeffrey L.; France, Kevin
2011ApJ...730L..10Y Altcode: 2011arXiv1102.3659Y
We report the first detection of molecular hydrogen (H2)
absorption in the Lyα emission line profiles of two classical T
Tauri stars (CTTSs), DF Tau and V4046 Sgr, observed by the Hubble
Space Telescope/Cosmic Origins Spectrograph. This absorption is the
energy source for many of the Lyman-band H2 fluorescent
lines commonly seen in the far-ultraviolet spectra of CTTSs. We find
that the absorbed energy in the H2 pumping transitions from
a portion of the Lyα line significantly differ from the amount of
energy in the resulting fluorescent emission. By assuming additional
absorption in the H I Lyα profile along our light of sight, we can
correct the H2 absorption/emission ratios so that they
are close to unity. The required H I absorption for DF Tau is at a
velocity close to the radial velocity of the star, consistent with H I
absorption in the edge-on disk and interstellar medium. For V4046 Sgr,
a nearly face-on system, the required absorption is between +100 km
s-1 and +290 km s-1, most likely resulting from
H I gas in the accretion columns falling onto the star. Based on
observations made with the NASA/ESA Hubble Space Telescope, obtained
from the data archive at the Space Telescope Science Institute. STScI is
operated by the Association of Universities for Research in Astronomy,
Inc. under NASA contract NAS 5-26555.

---------------------------------------------------------
Title: The Far-ultraviolet "Continuum" in Protoplanetary Disk
Systems. I. Electron-impact H2 and Accretion Shocks
Authors: France, Kevin; Yang, Hao; Linsky, Jeffrey L.
2011ApJ...729....7F Altcode: 2011arXiv1101.0165F
We present deep spectroscopic observations of the classical T
Tauri stars DF Tau and V4046 Sgr in order to better characterize
two important sources of far-ultraviolet continuum emission in
protoplanetary disks. These new Hubble Space Telescope-Cosmic Origins
Spectrograph observations reveal a combination of line and continuum
emission from collisionally excited H2 and emission from
accretion shocks. H2 is the dominant emission in the
1400 Å &lt;~ λ &lt;~ 1650 Å band spectrum of V4046 Sgr, while an
accretion continuum contributes strongly across the far-ultraviolet
spectrum of DF Tau. We compare the spectrum of V4046 Sgr to models
of electron-impact-induced H2 emission to constrain the
physical properties of the emitting region, after making corrections
for attenuation within the disk. We find reasonable agreement with the
broad spectral characteristics of the H2 model, implying
N(H2) ~ 1018 cm-2, T(H2) =
3000+1000 -500 K, and a characteristic electron
energy in the range of ~50-100 eV. We propose that self-absorption and
hydrocarbons provide the dominant attenuation for H2 line
photons originating within the disk. For both DF Tau and V4046 Sgr, we
find that a linear fit to the far-UV data can reproduce near-UV/optical
accretion spectra. We discuss outstanding issues concerning how these
processes operate in protostellar/protoplanetary disks, including the
effective temperature and absolute strength of the radiation field
in low-mass protoplanetary environments. We find that the 912-2000
Å continuum in low-mass systems has an effective temperature of
~104 K with fluxes 105-107 times the
interstellar level at 1 AU. Based on observations made with the
NASA/ESA Hubble Space Telescope, obtained from the data archive at the
Space Telescope Science Institute. STScI is operated by the Association
of Universities for Research in Astronomy, Inc., under NASA contract
NAS 5-26555.

---------------------------------------------------------
Title: The Far-uv “continuum” In Protoplanetary Disks: Accretion,
H2, And Co
Authors: France, Kevin; Yang, H.; Linsky, J. L.; Harper, G. M.;
Schindhelm, R.; Brown, A.; Herczeg, G. J.
2011AAS...21733913F Altcode: 2011BAAS...4333913F
We present new far-UV spectroscopic observations of a sample
of classical T Tauri stars obtained with the HST-Cosmic Origins
Spectrograph. The combination of very low background and moderate
spectral resolution allow us to unambiguously measure the processes
that contribute to the far-UV continuum emission in these systems:
hot chromospheric accretion, electron-excited H2, and CO A-X band
emission. Previous observations have lacked the sensitivity to detect
this faint emission or the spectral resolution to study the composition
of this “continuum” in detail. We show that the accretion spectrum
can be fit in a continuous manner from the far-UV to the optical in
some systems. The far-UV spectrum of CO has been identified and modeled
for the first time in a protostellar/protoplanetary disk. The electron
impact spectrum of H2 has been modeled, and results indicate that the
red far-UV color ratio and attenuation of discrete Werner band features
is consistent with absorption by hydrocarbons in the inner disk.

---------------------------------------------------------
Title: New Detections Of Werner-band Molecular Hydrogen Lines In
Classical T Tauri Stars With Hst/cos
Authors: Yang, Hao; Linsky, J. L.; France, K.
2011AAS...21725811Y Altcode: 2011BAAS...4325811Y
We present identification of atmoic and molecular hydrogen lines
shortward of 1200 A in the far ultraviolet in the spectra of two
classical T Tauri stars, DF Tau and V4046 Sgr. These lines have not been
observed in a protostellar/protoplanetary envelope and such observations
have just recently become possible, thanks to the high sensitivity and
very low background noise of the Cosmic Origins Spectrograph (COS)
newly installed on the Hubble Space Telescope (HST). The molecular
hydrogen lines below 1250 A are mostly Werner band lines, and we discuss
their photoexcitation routes. A comparison of the spectra indicates
that the observed lines are not common to all disks, possibly due
to differences in disk inclination, ground-state H2 population, and
shape of the pumping radiation field in the two objects. This work is
supported by a NASA grant to the University of Colorado.

---------------------------------------------------------
Title: First Detection of Both Absorption and Emission of Molecular
Hydrogen in Classical T Tauri Stars
Authors: Linsky, Jeffrey; Yang, H.; France, K.
2011AAS...21733918L Altcode: 2011BAAS...4333918L
Classical T Tauri stars (CTTSs) show bright emission lines of molecular
hydrogen in their ultraviolet spectra. These fluorescent emission
lines are pumped by molecular hydrogen transitions coincident with the
hydrogen Lyman-alpha emission line and other UV emission lines. While
these emission lines have been studied in the UV spectra of many CTTSs,
the pumping transitions have never been detected in absorption against
the Lyman alpha emission line. Spectra obtained with the excellent
sensitivity and low background of the new Cosmic Origin Spectrograph
(COS) on HST now show absorption by the pumping transitions in two
CTTSs, V4046 Sag and DF Tau. We compare the energy absorbed in each
pumping transition to the energy emitted in the resulting fluorescent
emission lines. The absorption/emission ratios are very different from
unity, but the ratios at different wavelengths across the Lyman-alpha
emission line of each star can be brought close to unity by assuming
additional Lyman-alpha absorption along the line of sight. For V4046
Sag, a CTTS observed nearly face-on, the required absorption is near
+290 km/s most likely due to hydrogen accreting onto the star. For
DF Tau, a CTTS observed nearly edge-on, the line of sight absorption
is near 0 km/s, indicating absorption in the disk. We shows models
for both stars. This work is supported by a NASA grant to the
University of Colorado.

---------------------------------------------------------
Title: Stellar Imager (SI): developing and testing a predictive
dynamo model for the Sun by imaging other stars
Authors: Carpenter, Kenneth G.; Schrijver, Carolus J.; Karovska,
Margarita; Kraemer, Steve; Lyon, Richard; Mozurkewich, David;
Airapetian, Vladimir; Adams, John C.; Allen, Ronald J.; Brown, Alex;
Bruhweiler, Fred; Conti, Alberto; Christensen-Dalsgaard, Joergen;
Cranmer, Steve; Cuntz, Manfred; Danchi, William; Dupree, Andrea; Elvis,
Martin; Evans, Nancy; Giampapa, Mark; Harper, Graham; Hartman, Kathy;
Labeyrie, Antoine; Leitner, Jesse; Lillie, Chuck; Linsky, Jeffrey L.;
Lo, Amy; Mighell, Ken; Miller, David; Noecker, Charlie; Parrish, Joe;
Phillips, Jim; Rimmele, Thomas; Saar, Steve; Sasselov, Dimitar; Stahl,
H. Philip; Stoneking, Eric; Strassmeier, Klaus; Walter, Frederick;
Windhorst, Rogier; Woodgate, Bruce; Woodruff, Robert
2010arXiv1011.5214C Altcode:
The Stellar Imager mission concept is a space-based UV/Optical
interferometer designed to resolve surface magnetic activity and
subsurface structure and flows of a population of Sun-like stars,
in order to accelerate the development and validation of a predictive
dynamo model for the Sun and enable accurate long-term forecasting of
solar/stellar magnetic activity.

---------------------------------------------------------
Title: Observations of Mass Loss from the Transiting Exoplanet
HD 209458b
Authors: Linsky, Jeffrey L.; Yang, Hao; France, Kevin; Froning,
Cynthia S.; Green, James C.; Stocke, John T.; Osterman, Steven N.
2010ApJ...717.1291L Altcode: 2010arXiv1005.1633L
Using the new Cosmic Origins Spectrograph on the Hubble Space Telescope,
we obtained moderate-resolution, high signal/noise ultraviolet spectra
of HD 209458 and its exoplanet HD 209458b during transit, both orbital
quadratures, and secondary eclipse. We compare transit spectra with
spectra obtained at non-transit phases to identify spectral features
due to the exoplanet's expanding atmosphere. We find that the mean
flux decreased by 7.8% ± 1.3% for the C II 1334.5323 Å and 1335.6854
Å lines and by 8.2% ± 1.4% for the Si III 1206.500 Å line during
transit compared to non-transit times in the velocity interval -50 to
+50 km s-1. Comparison of the C II and Si III line depths
and transit/non-transit line ratios shows deeper absorption features
near -10 and +15 km s-1 and less certain features near -40
and +30-70 km s-1, but future observations are needed to
verify this first detection of velocity structure in the expanding
atmosphere of an exoplanet. Our results for the C II lines and the
non-detection of Si IV 1394.76 Å absorption are in agreement with
Vidal-Madjar et al., but we find absorption during transit in the Si
III line contrary to the earlier result. The 8% ± 1% obscuration of
the star during transit is far larger than the 1.5% obscuration by
the exoplanet's disk. Absorption during transit at velocities between
-50 and +50 km s-1 in the C II and Si III lines requires
high-velocity ion absorbers. Assuming hydrodynamic model values for
the gas temperature and outflow velocity at the limb of the outflow
as seen in the C II lines, we find mass-loss rates in the range
(8-40)×1010 g s-1. These rates assume that the
carbon abundance is solar, which is not the case for the giant planets
in the solar system. Our mass-loss rate estimate is consistent with
theoretical hydrodynamic models that include metals in the outflowing
gas. Based on observations made with the NASA/ESA Hubble Space
Telescope, obtained from the Data Archive at the Space Telescope Science
Institute. STScI is operated by the Association of Universities for
Research in Astronomy, Inc., under NASA contract NAS 5-26555. These
observations are associated with the HST GTO program 11534.

---------------------------------------------------------
Title: Resolving the ξ Boo Binary with Chandra, and Revealing the
Spectral Type Dependence of the Coronal "FIP Effect"
Authors: Wood, Brian E.; Linsky, Jeffrey L.
2010ApJ...717.1279W Altcode: 2010arXiv1005.3281W
On 2008 May 2, Chandra observed the X-ray spectrum of ξ Boo (G8 V+K4
V), resolving the binary for the first time in X-rays and allowing
the coronae of the two stars to be studied separately. With the
contributions of ξ Boo A and B to the system's total X-ray emission
now observationally established (88.5% and 11.5%, respectively),
consideration of mass loss measurements for GK dwarfs of various
activity levels (including one for ξ Boo) leads to the surprising
conclusion that ξ Boo B may dominate the wind from the binary, with ξ
Boo A's wind being very weak despite its active corona. Emission measure
(EM) distributions and coronal abundances are computed for both stars
and compared with Chandra measurements of other moderately active stars
with G8-K5 spectral types, all of which exhibit a narrow peak in EM
near log T = 6.6, indicating that the coronal heating process in these
stars has a strong preference for this temperature. As is the case
for the Sun and many other stars, our sample of stars shows coronal
abundance anomalies dependent on the first ionization potential (FIP)
of the element. We see no dependence of the degree of "FIP effect" on
activity, but there is a dependence on spectral type, a correlation that
becomes more convincing when moderately active main-sequence stars with
a broader range of spectral types are considered. This clear dependence
of coronal abundances on spectral type weakens if the stellar sample
is allowed to be contaminated by evolved stars, interacting binaries,
or extremely active stars with log LX &gt;29, explaining
why this correlation has not been recognized in the past.

---------------------------------------------------------
Title: Metal Depletion and Warm H2 in the Brown Dwarf
2M1207 Accretion Disk
Authors: France, Kevin; Linsky, Jeffrey L.; Brown, Alexander; Froning,
Cynthia S.; Béland, Stéphane
2010ApJ...715..596F Altcode: 2010arXiv1004.1186F
We present new far-ultraviolet observations of the young M8 brown dwarf
2MASS J12073346-3932539, which is surrounded by an accretion disk. The
data were obtained using the Hubble Space Telescope-Cosmic Origins
Spectrograph. Moderate-resolution spectra (R≈ 17,000-18,000) obtained
in the 1150-1750 Å and 2770-2830 Å bandpasses reveal H2
emission excited by H I Lyα photons, several ionization states of
carbon (C I-C IV), and hot gas emission lines of He II and N V (T ≈
104-105 K). Emission from some species that would
be found in a typical thermal plasma at this temperature (Si II, Si III,
Si IV, and Mg II) is not detected. The non-detections indicate that
these refractory elements are depleted into grains, and that accretion
shocks dominate the production of the hot gas observed on 2MASS
J12073346-3932539. We use the observed C IV luminosity to constrain the
mass accretion rate in this system. We use the kinematically broadened
H2 profile to confirm that the majority of the molecular
emission arises in the disk, measure the radius of the inner hole of the
disk (R hole ≈ 3R *), and constrain the physical
conditions of the warm molecular phase of the disk (T(H2) ≈
2500-4000 K). A second, most likely unresolved H2 component
is identified. This feature is either near the stellar surface in the
region of the accretion shock or in a molecular outflow, although the
possibility that this Jovian-like emission arises on the dayside disk
of a 6 MJ companion (2M1207b) cannot be conclusively ruled
out. In general, we find that this young brown dwarf disk system is a
low-mass analog to classical T Tauri stars that are observed to produce
H2 emission from a warm layer in their disks, such as the
well-studied TW Hya and DF Tau systems. Based on observations
made with the NASA/ESA Hubble Space Telescope, obtained from the data
archive at the Space Telescope Science Institute. STScI is operated
by the Association of Universities for Research in Astronomy, Inc.,
under NASA contract NAS 5-26555.

---------------------------------------------------------
Title: The total deuterium abundance in the local Galactic disk:
decisions and implications
Authors: Linsky, Jeffrey L.
2010IAUS..268...53L Altcode:
Analyses of FUSE spacecraft spectra have provided measurements of
D/H in the gas phase of the interstellar medium for many lines of
sight extending to several kpc from the Sun. These measurements,
together with the earlier Copernicus, HST, and IMAPS data, show
a wide range of D/H values that have challenged both observers and
chemical evolution modellers. I believe that the best explanation for
the diverse D/H measurements is that deuterium can be sequestered on
to carbonaceous grains and PAH molecules and thereby removed from the
interstellar gas. Grain destruction can raise the gas phase D/H value
to approximately the total D/H value. Supernovae and stellar winds,
however, can decrease the total D/H value along lines of sight on time
scales less than mixing time scales. I will summarize the theoretical
and observational arguments for this model and estimate the most likely
range for the total D/H in the local Galactic disk. This range in total
D/H presents a constraint on realistic Galactic chemical evolution
models or the primordial value of D/H or both.

---------------------------------------------------------
Title: Searching for Far-ultraviolet Auroral/Dayglow Emission from
HD 209458b
Authors: France, Kevin; Stocke, John T.; Yang, Hao; Linsky, Jeffrey
L.; Wolven, Brian C.; Froning, Cynthia S.; Green, James C.; Osterman,
Steven N.
2010ApJ...712.1277F Altcode: 2010arXiv1002.3218F
We present recent observations from the Hubble Space Telescope-Cosmic
Origins Spectrograph aimed at characterizing the auroral emission
from the extrasolar planet HD 209458b. We obtained medium-resolution
(R ~ 20,000) far-ultraviolet (1150-1700 Å) spectra at both the Phase
0.25 and Phase 0.75 quadrature positions as well as a stellar baseline
measurement at secondary eclipse. This analysis includes a catalog of
stellar emission lines and a star-subtracted spectrum of the planet. We
present an emission model for planetary H2 emission,
and compare this model to the planetary spectrum. No unambiguously
identifiable atomic or molecular features are detected, and upper
limits are presented for auroral/dayglow line strengths. An orbital
velocity cross-correlation analysis finds a statistically significant
(3.8σ) feature at +15(± 20) km s-1 in the rest frame of
the planet, at λ1582 Å. This feature is consistent with emission
from H2 B-X (2-9) P(4) (λrest = 1581.11 Å)
however, the physical mechanism required to excite this transition
is unclear. We compare limits on relative line strengths seen in the
exoplanet spectrum with models of ultraviolet fluorescence to constrain
the atmospheric column density of neutral hydrogen between the star
and the planetary surface. These results support models of short-period
extrasolar giant planets with weak magnetic fields and extended atomic
atmospheres. Based on observations made with the NASA/ESA Hubble
Space Telescope, obtained from the data archive at the Space Telescope
Science Institute. STScI is operated by the Association of Universities
for Research in Astronomy, Inc. under NASA contract NAS 5-26555.

---------------------------------------------------------
Title: Chandra and HST Observations of the High Energy (X-ray/UV)
Radiation Fields for an Evolutionary Sequence of Pre-Main-Sequence
Stars
Authors: Brown, Alexander; Herczeg, G. J.; Brown, J. M.; Walter,
F. M.; Valenti, J.; Ardila, D.; Hillenbrand, L. A.; Edwards, S.;
Johns-Krull, C. M.; Alexander, R.; Bergin, E. A.; Calvet, N.; Bethell,
T. J.; Ingleby, L.; Bary, J. S.; Audard, M.; Baldovin, C.; Roueff,
E.; Abgrall, H.; Gregory, S. G.; Ayres, T. R.; Linsky, J. L.
2010HEAD...11.1709B Altcode: 2010BAAS...42..684B
Pre-main-sequence (PMS) stars are strong X-ray and UV emitters and the
high energy radiation from the central stars directly influences the
physical and chemical processes in their protoplanetary disks. Gas
and dust in protoplanetary systems are excited by these photons,
which are the dominant ionization source for hundreds of AU around the
star. X-rays penetrate deep into disks and power complex chemistry on
grain surfaces. “Transitional disks” are an important short-lived
evolutionary stage for PMS stars and protoplanetary systems. These disks
have transformed most of the dust and gas in their inner regions into
planetesimals or larger solid bodies. As dust disks disappear after ages
of roughly 5 Myr high levels of stellar magnetic activity persist and
continue to bathe the newly-forming protoplanetary systems with intense
high energy radiation. We present new X-ray and UV spectra for
a sample of PMS stars at a variety of evolutionary stages, including
the classical T Tauri stars DE Tau and DK Tau, the transitional
disk stars GM Aur and HD135344B, the Herbig Ae star HD104237, and
the weak-lined T Tauri star LkCa4, the Eta Cha cluster [age 7 Myr]
members RECX1, RECX-11, and RECX-15, and TW Hya association [age 8 Myr]
member TWA-2. These include the first results from our 111 orbit HST
Large project and associated X-ray data. New and archival Chandra, XMM,
and Swift X-ray spectra and HST COS+STIS FUV spectra are being used to
reconstruct the full high energy (X-ray/EUV/FUV/NUV) spectra of these
stars, thus allowing detailed modeling of the physics and chemistry
of their circumstellar environments. The UV spectra provide improved
emission line profiles revealing details of the magnetically-heated
plasma and accretion and outflow processes. This work is supported
by Chandra grants GO8-9024X, GO9-0015X and GO9-0020B and proposal
11200754 and HST GO grants 11336, 11616, and 11828.

---------------------------------------------------------
Title: First Far-Ultraviolet Observation of HD 199288 in the Arcturus
Moving Group with the Cosmic Origins Spectrograph
Authors: Yang, Hao; Linsky, J.; COS Science Team
2010AAS...21546411Y Altcode: 2010BAAS...42..500Y
We present the first far-ultraviolet spectra of a solar-type star in
the Arcturus moving group, HD 199288, observed with the newly installed
Cosmic Origins Spectrograph (COS) on the HST. The Arcturus moving
group was first identified by Eggen as a group of stars orbiting the
Galactic center with a speed that is 100 km/s slower relative to the
Local Standard Rest. These stars are metal poor ([Fe/H] -0.6) and have
peculiar alpha element abundances. They have been recently suggested
to be captured from a disrupted satellite of our Galaxy. We analyze
the moderate-resolution (R 20,000) spectra to provide new information
on the abundances and discuss how the metal-poor nature affects the
outer atmospheres of these stars.

---------------------------------------------------------
Title: Searching for Far-ultraviolet Auroral/dayglow Emission from
HD209458b with the Cosmic Origins Spectrograph
Authors: France, Kevin; Yang, H.; Stocke, J. T.; Linsky, J. L.;
Froning, C. S.; Green, J. C.; Osterman, S.; Keeney, B. A.
2010AAS...21546406F Altcode: 2010BAAS...42..499F
We present initial results from an HST Cycle 17 program to search for
atomic and molecular emissions from the well-studied transiting planet
HD209458b. HD209248b is a hot-Jupiter (M 0.7 MJ) known
to have a hydrogen-rich atmosphere. We describe recent observations
with the HST/Cosmic Origins Spectrograph aimed at detecting molecular
hydrogen and/or atomic emission from aurorae present in the planet's
atmosphere. We use a total of 12 orbits to acquire moderate resolution
(R 20,000) far-UV (1140 - 1750 A) spectra at both the Phase 0.25 and
Phase 0.75 quadrature positions. We have used high-quality spectra
of a template G0V star (alpha Cen) to identify stellar features that
may overlap with planetary signal. We also describe a model for H2
emission from the Jovian aurora/dayglow that has been adapted for the
interpretation of the COS spectra.

---------------------------------------------------------
Title: HST/COS Observations of the Transit of HD 209458b
Authors: Linsky, Jeffrey; Yang, H.; France, K.; Stocke, J.; Green,
J.; Froning, C.; COS Science Team
2010AAS...21546417L Altcode: 2010BAAS...42..501L
We report on observations of the transiting planet HD 209458b with
the new Cosmic Origins Spectrograph (COS) on HST. The observations
were made with the G130M and G160M gratings on COS that cover the
1150--1750 A region with a resolving power of 20,000. We compare the
transit spectra with spectra obtained at both quadratures and secondary
eclipse to identify spectral features due to the planet's atmosphere
and wind. With the greater sensitivity and spectral resolution of COS
compared to STIS, we will be able to measure absorption and emission
features due to several ions and molecules and infer their locations
from measured Doppler shifts. The observations were obtained between
September 15 and October 10, 2009. This work is supported by NASA
through a grant to the COS Science Team at the University of Colorado.

---------------------------------------------------------
Title: Results from the ISSI Workshop: “From the Outer Heliosphere
to the Local Bubble: Comparison of New Observations with Theory”
Authors: Linsky, Jeffrey L.
2009AIPC.1156..184L Altcode:
On 15-19 October 2007, the International Space Science Institute
(ISSI) in Bern, Switzerland, hosted a workshop that brought together
scientists studying various aspects of the interaction of the solar
wind with the local interstellar medium and the Local Bubble. Recent
results from the Voyager missions and other space-based observatories
have stimulated new understanding and theories concerning phenomena
in these environments. Important questions discussed at the workshop
included the structure and dominant physical processes in the outer
heliosphere and the properties, structures, and origin of the local
interstellar medium. A focus of the workshop was the many roles that
magnetic fields play in the outer heliosphere and Local Bubble. This
review summarizes the important topics discussed at the workshop and
lists some of the important conclusions.

---------------------------------------------------------
Title: The Galactic Environment of the Sun: Interstellar Material
Inside and Outside of the Heliosphere
Authors: Frisch, P. C.; Bzowski, M.; Grün, E.; Izmodenov, V.;
Krüger, H.; Linsky, J. L.; McComas, D. J.; Möbius, E.; Redfield,
S.; Schwadron, N.; Shelton, R.; Slavin, J. D.; Wood, B. E.
2009SSRv..146..235F Altcode:
Interstellar material (ISMa) is observed both inside and outside of the
heliosphere. Relating these diverse sets of ISMa data provides a richer
understanding of both the interstellar medium and the heliosphere. The
galactic environment of the Sun is dominated by warm, low-density,
partially ionized interstellar material consisting of atoms and dust
grains. The properties of the heliosphere are dependent on the pressure,
composition, radiation field, ionization, and magnetic field of ambient
ISMa. The very low-density interior of the Local Bubble, combined
with an expanding superbubble shell associated with star formation in
the Scorpius-Centaurus Association, dominate the properties of the
local interstellar medium (LISM). Once the heliosphere boundaries
and interaction mechanisms are understood, interstellar gas, dust,
pickup ions, and anomalous cosmic rays inside of the heliosphere can be
directly compared to ISMa outside of the heliosphere. Our understanding
of ISMa at the Sun is further enriched when the circumheliospheric
interstellar material is compared to observations of other nearby ISMa
and the overall context of our galactic environment. The IBEX mission
will map the interaction region between the heliosphere and ISMa, and
improve the accuracy of comparisons between ISMa inside and outside
the heliosphere.

---------------------------------------------------------
Title: Structure, Dynamics, and Physical Properties of the Warm LISM
Within the Local Bubble
Authors: Linsky, Jeffrey L.; Redfield, Seth
2009AIPC.1156..174L Altcode:
We describe our empirical model of warm gas in the local interstellar
medium. High-resolution absorption-line spectra of 157 stars provide
radial-velocity and physical parameter data for 270 interstellar
velocity components. This extensive data set allowed us to piece
together a detailed model of the partially ionized warm gas within
the Local Bubble. We have identified velocity vectors and projected
morphologies of 15 warm gas clouds located within 15 parsecs of the
Sun. These clouds have diverse gas temperatures, turbulent velocities,
and metal depletions. Cloud-cloud collisions may be responsible for the
filamentary morphologies found in about 1/3 of the clouds. We explain
the large-amplitude intraday and annular scintillation variability
of several quasars seen at radio wavelengths by turbulent scattering
screens located at cloud boundaries. Collisions between the clouds
could produce the turbulence and ionization at the cloud boundaries. A
nearby cold dense cloud is likely compressed and shielded by surounding
warm clouds.

---------------------------------------------------------
Title: Provocative Questions for the Deuterium Session
Authors: Linsky, Jeffrey L.
2009AIPC.1135...63L Altcode:
Analyses of spectra obtained with the Far Ultraviolet Spectrograph
Explorer (FUSE) satellite, together with spectra from the Copernicus,
Hubble Space Telescope (HST), and Interstellar Medium Absorption
Profile Spectrograph (IMAPS) instruments reveal a very wide range in
the observed deuterium/hydrogen (D/H) ratios for interstellar gas in
the Galactic disk beyond the Local Bubble. For gas located beyond the
Local Bubble but within several hundred parsecs, the observed D/H ratios
differ by a factor of 4-5. A critically important question is what value
or values of D/H in the local region of our Galaxy should be compared
with chemical evolution models of the Galaxy and with the primordial
deuterium abundance. Linsky et al. [Astrophys. J. 647, 1106 (2006)]
argued that spatial variations in the depletion of deuterium onto dust
grains can explain these local variations in the observed gas-phase
D/H ratios. In this provacative introduction to the deuterium session,
I ask six questions concerning analysis techniques and proposed results
from the FUSE D/H program in the hope that the speakers and participants
in this conference will give serious thought to the robustness of our
present understanding of this important topic. In particular, is the
deuterium depletion model valid? Is it only part of the explanation?

---------------------------------------------------------
Title: Solving the mysteries of the diffuse interstellar medium with
high-resolution UV spectroscopy
Authors: Linsky, Jeffrey L.
2009Ap&SS.320...85L Altcode:
Understanding the complex structure, dynamics, and ionization of
gas in the nearby interstellar medium is required before one can
realistically model interstellar gas in other galaxies. High-resolution
ultraviolet spectra provide the essential data for such studies because
the resonance lines of most important atoms, ions, and molecules are
located in the ultraviolet, and high spectral resolution is needed
to resolve line profiles and determine the velocity structure along
a line of sight. I list ten important physical questions concerning
interstellar gas that require a more sensitive spectrometer than STIS
and the desired spectral resolution to answer these questions.

---------------------------------------------------------
Title: Summary of the First NUVA Conference Space Astronomy: the UV
Window to the Universe
Authors: Linsky, Jeffrey L.
2009Ap&SS.320....3L Altcode: 2008Ap&SS.tmp...48L
In this summary of the conference Space Astronomy: the UV Window to
the Universe, held in El Escorial, Spain, May 28 to June 1, 2007, I
identify the important scientific questions posed by the speakers and
the corresponding discoveries that future ultraviolet space instruments
should enable. The science objectives described by the various speakers
naturally fall into groups according to the needed instrumental
requirements: wavelength coverage, spectral resolution, sensitivity,
rapid access to targets, monitoring, and signal/noise. Although most
of the science objectives presented during the conference require
UV spectra in the 1,170-3,200 Å range, there are important science
objectives that require spectra in the 912-1,170 Å range and at shorter
wavelengths. I identify the limitations of present instruments for
meeting these requirements. To avoid the upcoming UV dark age, important
work must be done to properly build the World Space Observatory (WSO)
and to plan future space missions.

---------------------------------------------------------
Title: Foreword
Authors: Linsky, Jeffrey; Izmodenov, Vlad; Möbius, Eberhard
2009SSRv..143....1L Altcode: 2008SSRv..tmp..131L
No abstract at ADS

---------------------------------------------------------
Title: Ionization of Local Interstellar Gas Based on STIS and FUSE
spectra of Nearby Stars
Authors: Redfield, Seth; Linsky, J. L.
2009AAS...21348507R Altcode: 2009BAAS...41..456R
The ultraviolet contains many resonance line transitions that are
sensitive to a range of ionization stages of ions present in the local
interstellar medium (LISM). We couple observations of high resolution
ultraviolet spectrographs, STIS and GHRS on the Hubble Space Telescope
(HST) and the Far-Ultraviolet Spectroscopic Explorer (FUSE) in order
to make a comprehensive survey of the ionization structure of the
local interstellar medium. In particular, we focus on the sight line
toward G191-B2B, a nearby (69 pc) white dwarf. We present interstellar
detections of highly ionized elements (e.g., SiIII, CIII, CIV, etc)
and compare them directly to neutral or singly ionized LISM detections
(e.g., SiII, CII, etc). The extensive observations of G191-B2B
provides an opportunity for a broad study of ionization stages of
several elements, while a survey of several sight lines provides a
comprehensive look at the ionization structure of the LISM. We
acknowledge support for this project through NASA FUSE Grant NNX06AD33G.

---------------------------------------------------------
Title: From the Outer Heliosphere to the Local Bubble
Authors: Linsky, J. L.; Izmodenov, V. V.; Möbius, E.; von Steiger, R.
2009fohl.book.....L Altcode:
No abstract at ADS

---------------------------------------------------------
Title: Foreword
Authors: Linsky, Jeffrey; Izmodenov, Vlad; Möbius, Eberhard
2009fohl.book....1L Altcode:
No abstract at ADS

---------------------------------------------------------
Title: Million Degree Plasmas in Extreme Ultraviolet (EUV)
Astrophysics
Authors: Kowalski, Michael P.; Barstow, Martin; Bruhweiler, Frederick;
Cruddance, Raymond; Dupree, Andrea; Holberg, Jay; Howell, Steve;
Laming, J. Martin; Linsky, Jeffrey; Sion, Edward; Strohmayer, Tod;
Szkody, Paula; Welsh, Barry; Wolff, Michael; Wood, Kent
2009astro2010S.161K Altcode: 2009arXiv0903.5212K
Million degree plasmas are ubiquitous in the Universe, and examples
include the atmospheres of white dwarfs; accretion phenomena in young
stars, cataclysmic variables and active galactic nuclei; the coronae of
stars; and the interstellar medium of our own galaxy and of others. The
bulk of radiation from million degree plasmas is emitted at extreme
ultraviolet (EUV) wavelengths, which includes critical spectral
features containing diagnostic information often not available at
other wavelengths. With underpinning by a mature instrument technology,
there is great opportunity here for exciting discoveries.

---------------------------------------------------------
Title: Mass Transport Processes and their Roles in the Formation,
Structure, and Evolution of Stars and Stellar Systems
Authors: Carpenter, Kenneth G.; Karvovska, Margarita; Schrijver,
Carolus J.; Grady, Carol A.; Allen, Ronald J.; Brown, Alexander;
Cranmer, Steven R.; Dupree, Andrea K.; Evans, Nancy R.; Guinan,
Edward F.; Harper, Graham; Labeyrie, Antoine; Linsky, Jeffrey;
Peters, Geraldine J.; Roberge, Aki; Saar, Steven H.; Sonneborn,
George; Walter, Frederick M.
2009astro2010S..40C Altcode: 2009arXiv0903.2433C
We summarize some of the compelling new scientific opportunities
for understanding stars and stellar systems that can be enabled
by sub-mas angular resolution, UV/Optical spectral imaging
observations, which can reveal the details of the many dynamic
processes (e.g., variable magnetic fields, accretion, convection,
shocks, pulsations, winds, and jets) that affect their formation,
structure, and evolution. These observations can only be provided
by long-baseline interferometers or sparse aperture telescopes in
space, since the aperture diameters required are in excess of 500 m -
a regime in which monolithic or segmented designs are not and will
not be feasible - and since they require observations at wavelengths
(UV) not accessible from the ground. Two mission concepts which could
provide these invaluable observations are NASA's Stellar Imager (SI;
http://hires.gsfc.nasa.gov/si/) interferometer and ESA's Luciola
sparse aperture hypertelescope, which each could resolve hundreds
of stars and stellar systems. These observatories will also open an
immense new discovery space for astrophysical research in general and,
in particular, for Active Galactic Nuclei (Kraemer et al. Decadal
Survey Science Whitepaper). The technology developments needed for
these missions are challenging, but eminently feasible (Carpenter et
al. Decadal Survey Technology Whitepaper) with a reasonable investment
over the next decade to enable flight in the 2025+ timeframe. That
investment would enable tremendous gains in our understanding of the
individual stars and stellar systems that are the building blocks of our
Universe and which serve as the hosts for life throughout the Cosmos.

---------------------------------------------------------
Title: Reverse engineering a spectrum: using fluorescent spectra of
molecular hydrogen to recreate the missing Lyman-α line of pre-main
sequence stars
Authors: Linsky, J. L.; Herczeg, G.; Wood, B. E.
2008PhST..133a4018L Altcode:
The hydrogen Lyman-α (Lyα) line, a major source of ionization
of metals in the circumstellar disks of pre-main sequence (PMS)
stars, is usually not observed due to absorption by interstellar and
circumstellar hydrogen. We have developed a technique to reconstruct the
intrinsic Lyα line using the observed emission in the H2
B-X lines that are fluoresced by Lyα. We describe this technique and
the subsequent analysis of the ultraviolet (UV) spectra of the TW Hya,
RU Lupi and other PMS stars. We find that the reconstructed Lyα lines
are indeed far brighter than any other feature in the UV spectra of
these stars and therefore play an important role in the ionization
and heating of the outer layers of circumstellar disks.

---------------------------------------------------------
Title: The Eagle Nebula: Pillars of Creation, EGGs, and PMS Stars
in NGC 6611
Authors: Linsky, J. L.; Gagné, M.; Mytyk, A.; McCaughrean, M.;
Andersen, M.
2008ASPC..384...59L Altcode: 2008csss...14...59L
We report on Chandra ACIS-I observations of the Eagle Nebula
containing the young Galactic cluster NGC~6611 and the dark columns
called the “Pillars of Creation”. We find that NGC~6611 contains
a rich collection of young X-ray emitting stars, but the EGGs at the
edge of the pillars are not detected at levels below the Orion young
stellar objects.

---------------------------------------------------------
Title: The Origin of Radio Scintillation in the Local Interstellar
Medium
Authors: Linsky, Jeffrey L.; Rickett, Barney J.; Redfield, Seth
2008ApJ...675..413L Altcode: 2007arXiv0711.1144L
We study three quasar radio sources (B1257-326, B1519-273,
and J1819+385) that show large-amplitude intraday and annual
scintillation variability produced by the Earth's motion relative
to turbulent-scattering screens located within a few parsecs of the
Sun. We find that the lines of sight to these sources pass through the
edges of partially ionized warm interstellar clouds where two or more
clouds may interact. From the gas flow vectors of these clouds, we find
that the relative radial and transverse velocities of these clouds are
large and could generate the turbulence that is responsible for the
observed scintillation. For all three sight lines the flow velocities
of nearby warm local interstellar clouds are consistent with the fits
to the transverse flows of the radio scintillation signals.

---------------------------------------------------------
Title: The Structure of the Local Interstellar Medium. IV. Dynamics,
Morphology, Physical Properties, and Implications of Cloud-Cloud
Interactions
Authors: Redfield, Seth; Linsky, Jeffrey L.
2008ApJ...673..283R Altcode: 2008arXiv0804.1802R
We present an empirical dynamical model of the LISM based on 270
radial velocity measurements for 157 sight lines toward nearby
stars. Physical parameter measurements (i.e., temperature, turbulent
velocity, depletions) are available for 90 components, or one-third
of the sample, enabling initial characterizations of the physical
properties of LISM clouds. The model includes 15 warm clouds located
within 15 pc of the Sun, each with a different velocity vector. We
derive projected morphologies of all clouds and estimate the volume
filling factor of warm partially ionized material in the LISM to be
between ~5.5% and 19%. Relative velocities of potentially interacting
clouds are often supersonic, consistent with heating, turbulent, and
metal depletion properties. Cloud-cloud collisions may be responsible
for the filamentary morphologies found in ~\frac{1}{3} of LISM clouds,
the distribution of clouds along the boundaries of the two nearest
clouds (LIC and G), the detailed shape and heating of the Mic Cloud,
the location of nearby radio scintillation screens, and the location
of an LISM cold cloud. Contrary to previous claims, the Sun appears
to be located in the transition zone between the LIC and G Cloud. Based on observations made with the NASA/ESA Hubble Space Telescope,
obtained from the Data Archive at the Space Telescope Science Institute,
which is operated by the Association of Universities for Research in
Astronomy, Inc., under NASA contract NAS 5-26555. These observations
are associated with programs 9525 and 10236.

---------------------------------------------------------
Title: Commission 42: Close Binaries
Authors: Giménez, Alvaro; Rucinski, Slavek M.; Szkody, Paula; Gies,
Douglas R.; Kang, Young-Woon; Linsky, Jeffrey L.; Livio, Mario;
Morrell, Nidia; Hilditch, Ronald W.; Nordström, Birgitta; Ribas,
Ignasi; Ribas, Edward; Vrielmann, Sonja; Scarfe, Colin D.
2007IAUTB..26..171G Altcode:
The president of the Commission welcomed the participants in the
business meeting and provided an overview of the activities carried
out during the past triennium 2002-2005. A good number of meetings
have been held during this period on close binaries, about two per
year, including both classical and interacting systems. One specific
Symposium at the General Assembly in Prague, devoted to binary stars
as astrophysical tools, showed the vitality of the field and the trend
of cooperation between scientists studying close binaries and those
specialized in visual double stars. The study of very low-mass binaries,
including those containing planet-sized components also received much
attention as well as the analysis of massive objects in nearby galaxies.

---------------------------------------------------------
Title: VizieR Online Data Catalog: Fluorescent H2 emission
from T Tauri stars (Herczeg+,
Authors: Herczeg, G. J.; Linsky, J. L.; Walter, F. M.; Gahm, G. F.;
Johns-Krull, C. M.
2007yCat..21650256H Altcode:
We observed the T Tauri stars DF Tau, RU Lupi, T Tau, DG Tau, V836
Tau, V410 Tau, and V819 Tau with HST STIS as part of HST program
GO8157. Each FUV observation consists of 45 orbits using the E140M
echelle spectrograph, spanning 1170-1710{AA}, with the 0.2"x0.06"
aperture to isolate on-source emission. (1 data file).

---------------------------------------------------------
Title: The Structure of the Local Interstellar Medium IV: Dynamics,
Morphology, Physical Properties, and Implications of Cloud-Cloud
Interactions
Authors: Redfield, Seth; Linsky, Jeffrey L.
2007arXiv0709.4480R Altcode:
We present an empirical dynamical model of the local interstellar medium
based on 270 radial-velocity measurements for 157 sight lines toward
nearby stars. Physical-parameter measurements (i.e., temperature,
turbulent velocity, depletions) are available for 90 components,
or one-third of the sample, enabling initial characterizations of
the physical properties of LISM clouds. The model includes 15 warm
clouds located within 15 pc of the Sun, each with a different velocity
vector. We derive projected morphologies of all clouds and estimate
the volume filling factor of warm partially ionized material in the
LISM to be between ~5.5% and 19%. Relative velocities of potentially
interacting clouds are often supersonic, consistent with heating,
turbulent, and metal-depletion properties. Cloud-cloud collisions
may be responsible for the filamentary morphologies found in ~1/3 of
LISM clouds, the distribution of clouds along the boundaries of the
two nearest clouds (LIC and G), the detailed shape and heating of
the Mic Cloud, the location of nearby radio scintillation screens,
and the location of a LISM cold cloud. Contrary to previous claims,
the Sun appears to be located in the transition zone between the LIC
and G Clouds.

---------------------------------------------------------
Title: High-resolution soft x-ray spectroscopy for constellation X
Authors: Lillie, Charles; Cash, Webster; Arav, Nahum; Shull,
J. Michael; Linsky, Jeffrey
2007SPIE.6686E..12L Altcode: 2007SPIE.6686E..33L
The Constellation-X mission, with 5 to 10 times the collecting area
of any previous x-ray observatory, will obtain high-throughput,
high resolution spectroscopic observations of x-ray sources ranging
from super-massive black holes to the disks around young stars in
the 0.25-4.0 keV region of the spectrum. We describe the need for
high resolution X-ray spectroscopy on the Constellation-X mission,
the various options for obtaining it, and the implementation that we
recommend;, e.g. an off-plane grating system that can simultaneously
provide spectral resolutions (λ/δλ) as high as 3000 and substantially
increased throughput in the 0.2 to 2.0 keV region. As a flagship
mission, Constellation-X will be a general purpose facility for the
astronomy community. The reflection grating system we describe will
enable Constellation-X to address the important questions of the next
generation within NASA's current cost target.

---------------------------------------------------------
Title: Structure of the Local ISM
Authors: Linsky, J. L.; Redfield, S.
2007ASPC..365..219L Altcode:
We report preliminary results of our program to determine the structure
and physical properties of warm partially-ionized clouds in the local
interstellar medium. Analysis of ultraviolet absorption lines toward
stars inside the Local Bubble provides 183 interstellar velocity
components and ground-based Ca II spectra provide an additional 87
components. We fit these data with 15 velocity vectors and determine
the shapes of 15 clouds located within 15 pc of the Sun. We find that
four nearby radio scintillation scattering screens are coincident with
the intersections of the LIC, G and other nearby clouds. The cold
cloud mapped by Heiles and Troland may be near the edges of the Leo
and Gem clouds.

---------------------------------------------------------
Title: D/H and Nearby Interstellar Cloud Structures
Authors: Linsky, J. L.
2007SSRv..130..367L Altcode: 2007SSRv..tmp..101L
Analysis of UV spectra obtained with the HST, FUSE and other satellites
provides a new understanding of the deuterium abundance in the
local region of the galactic disk. The wide range of gas-phase D/H
measurements obtained outside of the Local Bubble can now be explained
as due to different amounts of deuterium depletion on carbonaceous
grains. The total D/H ratio including deuterium in the gas and dust
phases is at least 23 parts per million of hydrogen, which is providing
a challenge to models of galactic chemical evolution. Analysis of HST
and ground-based spectra of many lines of sight to stars within the
Local Bubble have identified interstellar velocity components that are
consistent with more than 15 velocity vectors. We have identified the
structures of 15 nearby warm interstellar clouds on the basis of these
velocity vectors and common temperatures and depletions. We estimate
the distances and masses of these clouds and compare their locations
with cold interstellar clouds.

---------------------------------------------------------
Title: Dependence of Heliospheric Lyα Absorption on the Interstellar
Magnetic Field
Authors: Wood, Brian E.; Izmodenov, Vladislav V.; Linsky, Jeffrey L.;
Alexashov, Dmitry
2007ApJ...659.1784W Altcode: 2007astro.ph..1274W
We use newly developed three-dimensional kinetic MHD models of
the heliosphere to predict heliospheric H I Lyα absorption for
various lines of sight. These predictions are compared with actual
Lyα spectra from the Hubble Space Telescope, many of which have
yielded previous detections of heliospheric absorption. We find that
the absorption predicted by the models is weakly affected by both
the magnitude and orientation of the assumed interstellar medium
(ISM) magnetic field. Models with B=1.25-2.5 μG and an angle of
α=15deg-45deg with respect to the upwind
direction of the ISM flow generally provide the best fits to the
data, but the sensitivity of the Lyα absorption to many model input
parameters makes it difficult to fully characterize the region of
parameter space allowed by the data. We also use the models to assess
the degree to which heliospheric asymmetries induced by the ISM field
should be apparent in Lyα absorption. An ISM field that is skewed
with respect to the ISM flow vector results in substantial azimuthal
asymmetries in both the hydrogen wall and heliosheath, but only the
heliosheath asymmetries yield potentially detectable asymmetries in
Lyα absorption; and then only in downwind directions, where comparison
with the data is complicated by few actual absorption detections and
an insufficient model grid extent.

---------------------------------------------------------
Title: Commission 42: Close Binaries
Authors: Giménez, Alvaro; Rucinski, Slavek; Szkody, P.; Gies, D.;
Kang, Y. -W.; Linsky, J.; Livio, M.; Morrell, N.; Hilditch, R.;
Nordström, B.; Ribas, I.; Sion, E.; Vrielman, S.
2007IAUTA..26..259G Altcode:
The triennial report from Commission 42 covers various topics
like massive binaries, contact systems, cataclysmic variables and
low-mass binary stars. We try in a number of sections to provide
an update on the current status of the main research areas in the
field of close binaries. It is not a formal review, even complete
or comprehensive, but an attempt to bring the main topics on recent
research to astronomers working in other fields. References are also not
comprehensive and simply added to the text to help the reader looking
for deeper information on the subject. For this reason, we have chosen
to include references (sometimes incomplete for ongoing work) not in
a list at the end but integrated with the main text body. Complete
references and additional sources can be easily obtained through
web access of ADS or SIMBAD. Furthermore, the summary of papers on
close-binary research contained in the Bibliography of Close Binaries
(BCB) can be accessed from the web site of Commission 42. I would like
to express the gratitude of the commission for the careful work of Colin
Scarfe as Editor-in-Chief of BCB and Andras Holl and Attila Sragli for
maintaining the web pages of the Commission within the structure of
Division V. Finally, K. Olah and J. Jurcsik are gratefully acknowledged
for their continued support as editors of the Information Bulletin on
Variable Stars (IBVS), also accessible through the commission web page.

---------------------------------------------------------
Title: Lyα Absorption from Heliosheath Neutrals
Authors: Wood, Brian E.; Izmodenov, Vladislav V.; Linsky, Jeffrey L.;
Malama, Yury G.
2007ApJ...657..609W Altcode: 2006astro.ph.11927W
We assess the information that HST observations of stellar Lyα
lines can provide on the heliosheath, the region of the heliosphere
between the termination shock and heliopause. To search for evidence
of heliosheath absorption, we conduct a systematic inspection of
stellar Lyα lines reconstructed after correcting for ISM absorption
(and heliospheric/astrospheric absorption, if present). Most of the
stellar lines are well centered on the stellar radial velocity,
as expected, but the three lines of sight with the most downwind
orientations relative to the ISM flow (χ1 Ori, HD 28205,
and HD 28568) have significantly blueshifted Lyα lines. Since it is in
downwind directions that heliosheath absorption should be strongest,
the blueshifts are almost certainly caused by previously undetected
heliosheath absorption. We make an initial comparison between the
heliosheath absorption and the predictions of a pair of heliospheric
models. A model with a complex multicomponent treatment of plasma
within the heliosphere predicts less absorption than a model with a
simple single-fluid treatment, which leads to better agreement with the
data. Finally, we find that nonplanetary energetic neutral atom (ENA)
fluxes measured by the ASPERA-3 instrument on board Mars Express, which
have been interpreted as being from the heliosheath, are probably too
high to be consistent with the relative lack of heliosheath absorption
seen by HST. This would argue for a local interplanetary source for
these ENAs instead of a heliosheath source.

---------------------------------------------------------
Title: D/H and Nearby Interstellar Cloud Structures
Authors: Linsky, J. L.
2007coma.book..367L Altcode:
Analysis of UV spectra obtained with the HST, FUSE and other satellites
provides a new understanding of the deuterium abundance in the
local region of the galactic disk. The wide range of gas-phase D/H
measurements obtained outside of the Local Bubble can now be explained
as due to different amounts of deuterium depletion on carbonaceous
grains. The total D/H ratio including deuterium in the gas and dust
phases is at least 23 parts per million of hydrogen, which is providing
a challenge to models of galactic chemical evolution. Analysis of HST
and ground-based spectra of many lines of sight to stars within the
Local Bubble have identified interstellar velocity components that are
consistent with more than 15 velocity vectors. We have identified the
structures of 15 nearby warm interstellar clouds on the basis of these
velocity vectors and common temperatures and depletions. We estimate
the distances and masses of these clouds and compare their locations
with cold interstellar clouds.

---------------------------------------------------------
Title: Chandra Observations of the Eagle Nebula. I. Embedded Young
Stellar Objects near the Pillars of Creation
Authors: Linsky, Jeffrey L.; Gagné, Marc; Mytyk, Anna; McCaughrean,
Mark; Andersen, Morten
2007ApJ...654..347L Altcode: 2006astro.ph.10279L
We present and analyze the first high-resolution X-ray images ever
obtained of the Eagle Nebula star-forming region. On 2001 July 30 the
Chandra X-Ray Observatory obtained a 78 ks image of the Eagle Nebula
(M16) that includes the core of the young galactic cluster NGC 6611
and the dark columns of dust and cold molecular gas in M16 known as the
“Pillars of Creation.” We find a total of 1101 X-ray sources in the
17'×17' ACIS-I field of view. Most of the X-ray
sources are low-mass pre-main-sequence or high-mass main-sequence stars
in this young cluster. A handful of hard X-ray sources in the pillars
are spatially coincident with deeply embedded young stellar objects
seen in high-resolution near-infrared images recently obtained with
the VLT (McCaughrean &amp; Andersen). In this paper, we focus on the
40 X-ray sources in and around pillars 1-4 at the heart of the Eagle
Nebula. None of the X-ray sources are associated with the evaporating
gaseous globules (EGGs) first observed by Hester and coworkers)
in HST WFPC2 images of M16, implying either that the EGGs do not
contain protostars or that the protostars have not yet become X-ray
active. Eight X-ray counts are coincident with the Herbig-Haro object
HH 216, implying logLX~30.0.

---------------------------------------------------------
Title: The Eagle Nebula: Pillars of Creation, EGGs, and PMS Stars
in NGC 6611
Authors: Linsky, Jeffrey; Gagne, M.; Mytyk, A.; McCaughrean, M.;
Andersen, M.
2006AAS...20921920L Altcode: 2006BAAS...38.1206L
We report on our 78 ks Chandra ACIS-I observation of the Eagle Nebula
(M16) and the young cluster NGC 6611. We detected a total of 1101 X-ray
sources, most of which are PMS stars in the cluster. Near the tip of
the one of the Pillars of Creation, we detect a luminous X-ray source
M16ES-1 which we believe is a high mass embedded protostar perhaps
heated by magnetically channeled wind shocks. We detected no X-rays
from the EGGs, the evaporating gaseous globules first observed in a
WFPC2 image by Hester et al. (1996) near the edges of the Pillars. The
EGGs could contain condensations that are very early stages of low
mass star formation. The nondetection of EGGs with embedded infrared
sources at X-ray luminosities well below the low-mass PMS stars in
Orion indicates either that the EGGs do not contain protostars or
that at the very early stage of evolution low-mass protostars have
not yet become X-ray active. We also report on the X-ray properties
of the YSOs in NGC 6611 and compare their properties to the YSOs in
the Orion Nebula Cluster and other young clusters. This work is
supported by NASA through grant H-04630D to the University of Colorado.

---------------------------------------------------------
Title: The Dynamical Structure of the Local Interstellar Medium
Authors: Redfield, Seth; Linsky, J. L.
2006AAS...209.8409R Altcode: 2006BAAS...38.1011R
We present a dynamical analysis of the largest collection of
local interstellar medium (LISM) absorption velocity component
measurements. High resolution ultraviolet observations with the Hubble
Space Telescope of stars within 100 pc provide 183 interstellar
components and ground-based CaII spectra provide an additional 87
components. We fit these data with 15 rigid velocity vectors and
determine the shapes of the associated clouds located within 15 pc
of the Sun. Assignment of cloud membership is not solely derived
from projected velocity agreement, but also includes comparison of
physical parameters (e.g., temperature, nonthermal velocity, and
depletions) with nearby cloud members. The Local Interstellar Cloud,
the collection of gas that directly surrounds our solar system is
easily identified in more than 75 sightlines. The remaining clouds are
identified with 4 to 21 sightlines. 20% of observed components are not
satisfactorily characterized by the 15 velocity vectors, and possibly
include more distant clouds that subtend much smaller solid angles or
are caused by absorption of circumstellar gas. Several clouds have a
filamentary structure, which may be indicative of shocked or interacting
material. We examine cloud dynamics at boundary regions and search
for evidence of shear flows or cloud-cloud interactions. We find that
several nearby radio scintillation scattering screens are coincident
with the intersections of the LIC, and other nearby clouds. Support
for this work was provided by NASA through Hubble Fellowship grant
HST-HF-01190.01, AR-09525.01A and GO-10236.02 awarded by the Space
Telescope Science Institute, which is operated by the Association of
Universities for Research in Astronomy, Inc., for NASA, under contract
NAS 5-26555.

---------------------------------------------------------
Title: What Is the Total Deuterium Abundance in the Local Galactic
Disk?
Authors: Linsky, Jeffrey L.; Draine, Bruce T.; Moos, H. W.; Jenkins,
Edward B.; Wood, Brian E.; Oliveira, Cristina; Blair, William P.;
Friedman, Scott D.; Gry, Cecile; Knauth, David; Kruk, Jeffrey W.;
Lacour, Sylvestre; Lehner, Nicolas; Redfield, Seth; Shull, J. Michael;
Sonneborn, George; Williger, Gerard M.
2006ApJ...647.1106L Altcode: 2006astro.ph..8308L
Analyses of spectra obtained with the Far Ultraviolet Spectroscopic
Explorer (FUSE) satellite, together with spectra from the Copernicus
and interstellar medium absorption profile spectrograph (IMAPS)
instruments, reveal an unexplained, very wide range in the observed
deuterium/hydrogen (D/H) ratios for interstellar gas in the Galactic
disk beyond the Local Bubble. We argue that spatial variations in
the depletion of deuterium onto dust grains can explain these local
variations in the observed gas-phase D/H ratios. We present a variable
deuterium depletion model that naturally explains the constant measured
values of D/H inside the Local Bubble, the wide range of gas-phase
D/H ratios observed in the intermediate regime [logN(HI)=19.2-20.7],
and the low gas-phase D/H ratios observed at larger hydrogen column
densities. We consider empirical tests of the deuterium depletion
hypothesis: (1) correlations of gas-phase D/H ratios with depletions
of the refractory metals iron and silicon, and (2) correlation with the
H2 rotational temperature. Both of these tests are consistent
with deuterium depletion from the gas phase in cold, not recently
shocked regions of the ISM, and high gas-phase D/H ratios in gas that
has been shocked or otherwise heated recently. We argue that the most
representative value for the total (gas plus dust) D/H ratio within 1
kpc of the Sun is &gt;=23.1+/-2.4(1σ) parts per million (ppm). This
ratio constrains Galactic chemical evolution models to have a very
small deuterium astration factor, the ratio of primordial to total
(D/H) ratio in the local region of the Galactic disk, which we estimate
to be fd&lt;=1.19+0.16-0.15(1σ) or
&lt;=1.12+/-0.14(1σ) depending on the adopted light-element nuclear
reaction rates. Based on observations made with the NASA-CNES-CSA
Far Ultraviolet Spectroscopic Explorer. FUSE is operated for NASA by
the Johns Hopkins University under NASA contract NAS5-32985.

---------------------------------------------------------
Title: Chromospheric and Transition Regions Features in Solar
Like Stars
Authors: Pagano, I.; De Martino, C.; Lanza, A. F.; Spadaro, D.;
Linsky, J. L.
2006ESASP.617E..91P Altcode: 2006soho...17E..91P
No abstract at ADS

---------------------------------------------------------
Title: The Origins of Fluorescent H2 Emission From T
Tauri Stars
Authors: Herczeg, Gregory J.; Linsky, Jeffrey L.; Walter, Frederick
M.; Gahm, Gösta F.; Johns-Krull, Christopher M.
2006ApJS..165..256H Altcode: 2006astro.ph..2404H
We survey fluorescent H2 emission in HST STIS spectra
of the classical T Tauri stars (CTTSs) TW Hya, DF Tau, RU Lupi,
T Tau, and DG Tau, and the weak-lined T Tauri star (WTTS) V836
Tau. From each of those sources we detect between 41 and 209 narrow
H2 emission lines, most of which are pumped by strong
Lyα emission. H2 emission is not detected from the
WTTS V410 Tau. The fluorescent H2 emission appears to
be common to circumstellar environments around all CTTSs, but high
spectral and spatial resolution STIS observations reveal diverse
phenomenon. Blueshifted H2 emission detected from RU Lupi,
T Tau, and DG Tau is consistent with an origin in an outflow. The
H2 emission from TW Hya, DF Tau, and V836 Tau is centered
at the radial velocity of the star and is consistent with an origin in
a warm disk surface. The H 2 lines from RU Lupi, DF Tau,
and T Tau also have excess blueshifted H2 emission that
extends to as much as -100 km s-1. The strength of this
blueshifted component from DF Tau and T Tau depends on the upper level
of the transition. In all cases, the small aperture and attenuation
of H2 emission by stellar winds restricts the H2
emission to be formed close to the star. In the observation of RU Lupi,
the Lyα emission and the H2 emission that is blueshifted
by 15 km s-1 are extended to the SW by ~0.07", although
the faster H2 gas that extends to ~100 km s-1
is not spatially extended. We also find a small reservoir of H
2 emission from TW Hya and DF Tau consistent with an excitation
temperature of ~2.5×104 K.

---------------------------------------------------------
Title: A Cycle-4 Survey of RS CVn Binary Systems
Authors: Redfield, S.; Linsky, J. L.; Ayres, T. R.; Brown, A.; Herczeg,
G. J.
2006ASPC..348..269R Altcode:
RS CVn systems are detached late-type binaries that are very active as
a result of their tidally enforced rapid rotation. They are actively
studied and bright at X-ray and ultraviolet (UV) wavelengths, but very
few have been observed in the far-UV. We present multiple orbital
phase observations of RS CVn systems taken by the Far Ultraviolet
Spectroscopic Explorer (FUSE) through a survey program in Cycle
4. Located in the FUSE spectral range are emission lines formed in
plasma at 50,000--300,000 K (e.g., C III and O VI). We present an
analysis of the strong emission line profiles. By monitoring the
change in the profile shape over the course of an orbital period
we can measure the fractional contributions of each star in the RS
CVn binary system at different plasma temperatures. In addition,
the spectral resolution and wavelength scale of FUSE permit us to
measure the width and velocity shift of the O VI and C III lines,
providing a new window on stellar atmospheric dynamics and structure.

---------------------------------------------------------
Title: Key problems in cool-star astrophysics
Authors: Pagano, Isabella; Ayres, Thomas R.; Lanzafame, Alessandro C.;
Linsky, Jeffrey L.; Montesinos, Benjamín; Marcello-Rodonò
2006Ap&SS.303...17P Altcode:
Selected key problems in cool-star astrophysics are reviewed, with
emphasis on the importance of new ultraviolet missions to tackle the
unresolved issues. UV spectral signatures are an essential probe of
critical physical processes related to the production and transport
of magnetic energy in astrophysical plasmas ranging, for example, from
stellar coronae, to the magnetospheres of magnetars, and the accretion
disks of protostars and Active Galactic Nuclei. From an historical
point of view, our comprehension of such processes has been closely
tied to our understanding of solar/stellar magnetic activity, which
has its origins in a poorly understood convection-powered internal
magnetic dynamo. The evolution of the Sun's dynamo, and associated
magnetic activity, affected the development of planetary atmospheres
in the early solar system, and the conditions in which life arose on
the primitive Earth. The gradual fading of magnetic activity as the
Sun grows old likewise will have profound consequences for the future
heliospheric environment. Beyond the Sun, the magnetic activity of
stars can influence their close-in companions, and vice versa. Cool
star outer atmospheres thus represent an important laboratory in which
magnetic activity phenomena can be studied under a wide variety of
conditions, allowing us to gain insight into the fundamental processes
involved. The UV range is especially useful for such studies because it
contains powerful diagnostics extending from warm (∼ 104 K)
chromospheres out to hot (1 10 MK) coronae, and very high-resolution
spectroscopy in the UV has been demonstrated by the GHRS and STIS
instruments on HST but has not yet been demonstrated in the higher
energy EUV and X-ray bands. A recent example is the use of the hydrogen
Lyα resonance line—at 110 000 resolution with HST STIS—study,
for the first time, coronal winds from cool stars through their
interaction with the interstellar gas. These winds cannot be detected
from the ground, for lack of suitable diagnostics; or in the X-rays,
because the outflowing gas is too thin. A 2m class UV space telescope
with high resolution spectroscopy and monitoring capabilities would
enable important new discoveries in cool-star astronomy among the
stars of the solar neighborhood out to about 150 pc. A larger aperture
facility (4 6 m) would reach beyond the 150 pc horizon to fainter
objects including young brown dwarfs and pre-main sequence stars in
star-forming regions like Orion, and magnetic active stars in distant
clusters beyond the Pleiades and α Persei. This would be essential,
as well, to characterize the outer atmospheres of stars with planets,
that will be discovered by future space missions like COROT, Kepler,
and Darwin.

---------------------------------------------------------
Title: UV Capabilities to Probe the Formation of Planetary Systems:
From the ISM to Planets
Authors: Gómez de Castro, Ana I.; Lecavelier, Alain; D'Avillez,
Miguel; Linsky, Jeffrey L.; Cernicharo, José
2006Ap&SS.303...33G Altcode:
Planetary systems are angular momentum reservoirs generated during
star formation. Solutions to three of the most important problems in
contemporary astrophysics are needed to understand the entire process
of planetary system formation: The physics of the ISM. Stars form from
dense molecular clouds that contain ∼ 30% of the total interstellar
medium (ISM) mass. The structure, properties and lifetimes of molecular
clouds are determined by the overall dynamics and evolution of a very
complex system the ISM. Understanding the physics of the ISM is of
prime importance not only for Galactic but also for extragalactic
and cosmological studies. Most of the ISM volume (∼ 65%) is
filled with diffuse gas at temperatures between 3000 and 300 000 K,
representing about 50% of the ISM mass. The physics of accretion and
outflow. Powerful outflows are known to regulate angular momentum
transport during star formation, the so-called accretion outflow
engine. Elementary physical considerations show that, to be efficient,
the acceleration region for the outflows must be located close to the
star (within 1 AU) where the gravitational field is strong. According to
recent numerical simulations, this is also the region where terrestrial
planets could form after 1 Myr. One should keep in mind that today the
only evidence for life in the Universe comes from a planet located in
this inner disk region (at 1 AU) from its parent star. The temperature
of the accretion outflow engine is between 3000 and 10 7
K. After 1 Myr, during the classical T Tauri stage, extinction is
small and the engine becomes naked and can be observed at ultraviolet
wavelengths. The physics of planet formation. Observations of volatiles
released by dust, planetesimals and comets provide an extremely powerful
tool for determining the relative abundances of the vaporizing species
and for studying the photochemical and physical processes acting in
the inner parts of young planetary systems. This region is illuminated
by the strong UV radiation field produced by the star and the accretion
outflow engine. Absorption spectroscopy provides the most sensitive tool
for determining the properties of the circumstellar gas as well as the
characteristics of the atmospheres of the inner planets transiting the
stellar disk. UV radiation also pumps the electronic transitions of the
most abundant molecules (H 2, CO, etc.) that are observed in
the UV. Here we argue that access to the UV spectral range is essential
for making progress in this field, since the resonance lines of the
most abundant atoms and ions at temperatures between 3000 and 300
000 K, together with the electronic transitions of the most abundant
molecules (H 2, CO, OH, CS, S 2, CO 2
+, C 2, O 2, O3, etc.) are
at UV wavelengths. A powerful UV-optical instrument would provide an
efficient mean for measuring the abundance of ozone in the atmosphere
of the thousands of transiting planets expected to be detected by the
next space missions (GAIA, Corot, Kepler, etc.). Thus, a follow-up UV
mission would be optimal for identifying Earth-like candidates.

---------------------------------------------------------
Title: Opacity in the transition region of cool dwarfs: A powerful
diagnostic
Authors: Mathioudakis, M.; Christian, D. J.; Bloomfield, D. S.;
Keenan, F. P.; Linsky, J. L.; Dupuis, J.
2006ASPC..348..159M Altcode:
A detailed study of the C III 1176Å multiplet in active cool stars
has shown significant deviations of the line flux from the optically
thin approximation. These deviations become more pronounced during
flares. Opacity can be used as a powerful diagnostic to estimate path
lengths in the transition region. Our analysis reveals that stellar
transition regions have very small spatial characteristics typically
in the range of 10 - 100 km. These path lengths are in agreement with
the small scale structure seen in the solar transition region.

---------------------------------------------------------
Title: Coronal Emission Measures and Abundances for Moderately Active
K Dwarfs Observed by Chandra
Authors: Wood, Brian E.; Linsky, Jeffrey L.
2006ApJ...643..444W Altcode: 2006astro.ph..1551W
We have used Chandra to resolve the nearby 70 Oph (K0 V+K5 V) and
36 Oph (K1 V+K1 V) binary systems for the first time in X-rays. The
LETG/HRC-S spectra of all four of these stars are presented and
compared with an archival LETG spectrum of another moderately active
K dwarf, ɛ Eri. Coronal densities are estimated from O VII line
ratios and emission measure distributions are computed for all five
of these stars. We see no substantial differences in coronal density
or temperature among these stars, which is not surprising considering
that they are all early K dwarfs with similar activity levels. However,
we do see significant differences in coronal abundance patterns. Coronal
abundance anomalies are generally associated with the first ionization
potential (FIP) of the elements. On the Sun, low-FIP elements are
enhanced in the corona relative to high-FIP elements, the so-called
FIP effect. Different levels of FIP effect are seen for our stellar
sample, ranging from 70 Oph A, which shows a prominent solar-like FIP
effect, to 70 Oph B, which has no FIP bias at all or possibly even a
weak inverse FIP effect. The strong abundance difference exhibited by
the two 70 Oph stars is unexpected considering how similar these stars
are in all other respects (spectral type, age, rotation period, X-ray
flux). It will be difficult for any theoretical explanation for the
FIP effect to explain how two stars so similar in all other respects
can have coronae with different degrees of FIP bias. Finally, for the
stars in our sample exhibiting a FIP effect, a curious difference from
the solar version of the phenomenon is that the data seem to be more
consistent with the high-FIP elements being depleted in the corona
rather than with a low-FIP enhancement.

---------------------------------------------------------
Title: Optical Structure and Proper-Motion Age of the Oxygen-rich
Supernova Remnant 1E 0102-7219 in the Small Magellanic Cloud
Authors: Finkelstein, Steven L.; Morse, Jon A.; Green, James C.;
Linsky, Jeffrey L.; Shull, J. Michael; Snow, Theodore P.; Stocke,
John T.; Brownsberger, Kenneth R.; Ebbets, Dennis C.; Wilkinson,
Erik; Heap, Sara R.; Leitherer, Claus; Savage, Blair D.; Siegmund,
Oswald H.; Stern, Alan
2006ApJ...641..919F Altcode: 2006astro.ph..1543F
We present new optical emission-line images of the young SNR 1E
0102-7219 in the SMC obtained with the ACS on HST. This object is a
member of the oxygen-rich class of SNRs showing strong oxygen, neon,
and other metal-line emissions in its optical and X-ray spectra, and an
absence of hydrogen and helium. The progenitor of 1E 0102-7219 may have
been a Wolf-Rayet star that underwent considerable mass loss prior to
exploding as a Type Ib/c or IIL/b supernova. The ejecta in this SNR are
generally fast-moving (V&gt;1000 km s-1) and emit as they are
compressed and heated in the reverse shock. In 2003 we obtained optical
[O III], Hα, and continuum images with the ACS Wide Field Camera. The
[O III] image through the F475W filter captures the full velocity range
of the ejecta and shows considerable high-velocity emission projected
in the middle of the SNR that was Doppler-shifted out of the narrow
F502N bandpass of a previous WFPC2 image from 1995. Using these two
epochs separated by ~8.5 yr, we measure the transverse expansion of the
ejecta around the outer rim in this SNR for the first time at visible
wavelengths. From proper-motion measurements of 12 ejecta filaments,
we estimate a mean expansion velocity for the bright ejecta of ~2000 km
s-1 and an inferred kinematic age for the SNR of ~2050+/-600
yr. The age we derive from HST data is about twice that inferred by
Hughes et al. from X-ray data, although our 1 σ error bars overlap. Our
proper-motion age is consistent with an independent optical kinematic
age derived by Eriksen et al. in 2003 using spatially resolved [O III]
radial-velocity data. We derive an expansion center that lies very
close to conspicuous X-ray and radio hot spots, which could indicate
the presence of a compact remnant (neutron star or black hole). Based on observations with the NASA/ESA Hubble Space Telescope (HST),
obtained at the Space Telescope Science Institute (STScI), which is
operated by the Association of Universities for Research in Astronomy
(AURA), Inc., under NASA contract NAS5-26555.

---------------------------------------------------------
Title: An Insider's Perspective on Observing Time Selection Committees
Authors: Linsky, Jeffrey L.
2006ASSL..335..111L Altcode: 2006osa6.book..111L
The process of selecting the best proposals for observing time on
observatories in space and on the ground is vitally important for
astronomy and is generally done well, but the system has problems and
can be improved. I identify four types of bias that enter the process
when the oversubscription of observing time is large. The negative
interaction between the large oversubscription rates and these biases
should be recognized and can be mitigated. I believe that selection
committees provide the most competent and least biased advice when
they are given a modest number of proposals (roughly 50) covering a
coherent but modest range of scientific topics, and the approximate
time allocations among the committees covering the different scientific
topics are driven largely by proposal pressure. There are several
mechanisms for revising when necessary the allocations of observing
time among the various committees.

---------------------------------------------------------
Title: Letters to the Editor of the AAS Newsletter: A Personal Story
Authors: Linsky, Jeffrey L.
2006ASSL..335..175L Altcode: 2006osa6.book..175L
Since 1987 the American Astronomical Society Newsletter has published
some 142 Letters to the Editor that provide the personal statements and
concerns of astronomers about the policies, priorities, and experiences
of being an astronomer. While these Letters do not provide a scientific
sampling of the issues, they do provide an illuminating picture of the
astronomical scene as seen from the perspectives of our colleagues. I
describe the history and policies of the Letters section, then summarize
the issues presented and debated in these Letters. The topics (in order
of numbers of Letters published) are: (1) publishing and refereeing,
(2) how the AAS and IAU conduct their business, (3) jobs and how to
get them, (4) support for astronomy, (5) scientific units and time, (6)
public policy issues, (7) planning for telescopes and space missions,
(8) how astronomers do their work, (9) women in astronomy, (10) the
work environment, and (11) other issues. A chronological list of the
Letters by title and author is included.

---------------------------------------------------------
Title: Stellar magnetic fields and signatures of heating
Authors: Linsky, J. L.
2006cosp...36..716L Altcode: 2006cosp.meet..716L
A great many measurements of stellar X-ray ultraviolet and radio
emission have demonstrated that stars with measured or inferred strong
magnetic fields show evidence for strong heating in their coronal and
chromospheric layers While the qualitative connection between strong
magnetic fields and strong heating is evident quantitative measures
of the correlation and physical models underlying the connection are
less clear I will review the measurements of magnetic field strength
and flux in stars with convective zones and the proposed empirical
relations between magnetic flux and X-ray flux on the Sun and stars
The emerging relationship between magnetic flux and stellar mass loss
rate may indicate an important difference in magnetic geometry between
stars with low and high magnetic flux and thus between old and young
stars Magnetic flux tube geometry which depends on the field filling
factor could play an important role in heating

---------------------------------------------------------
Title: The Radio and X-ray Properties of Magnetic Bp/Ap Stars
Authors: Drake, S. A.; Wade, G. A.; Linsky, J. L.
2006ESASP.604...73D Altcode: 2006xru..conf...73D
No abstract at ADS

---------------------------------------------------------
Title: What is the Total Deuterium Abundance in the Local Galactic
Disk?
Authors: Linsky, J. L.; Draine, B. T.; Moos, H. W.; Jenkins, E. B.;
Wood, B. E.; Oliveira, C.; Blair, W. P.; Friedman, S. D.; Gry, C.;
Knauth, D.; Kruk, J. W.; Lacour, S.; Lehner, N.; Redfield, S.; Shull,
J. M.; Sonneborn, G.; Williger, G. M.
2005AAS...20717503L Altcode: 2005BAAS...37R1444L
Analyses of spectra obtained with the FUSE satellite, together with
spectra from the Copernicus and IMAPS instruments, reveal a very wide
range in the observed deuterium/hydrogen (D/H) ratios for interstellar
gas in the Galactic disk beyond the Local Bubble (the region of space
extending to roughly 100 pc from the Sun). For gas located beyond
the Local Bubble but within several hundred parsecs, the observed D/H
ratios differ by a factor of 4--5, which is difficult to explain solely
on the basis of either: (i) small-scale spatial variations in stellar
nuclear processes that convert deuterium to heavier elements; or (ii)
the infall of deuterium-rich gas from the Galactic halo and the IGM. We
argue instead that spatial variations in the depletion of deuterium
onto dust grains can explain these local variations in the observed
gas-phase D/H ratios. We present a variable deuterium depletion model
that naturally explains the constant measured values of D/H inside the
Local Bubble, the wide range of gas-phase D/H ratios observed in the
intermediate regime (log N(H I) = 19.2--20.7), and the low gas-phase
D/H ratios observed at larger hydrogen column densities. We test the
deuterium depletion hypothesis by: (i) correlations of gas-phase D/H
ratios with depletions of the refractory metals iron and silicon,
and (ii) correlation with HD in heavily reddened lines of sight. Both
of these tests are consistent with deuterium depletion from the gas
phase in cold, not recently shocked, regions of the ISM, and high
gas-phase D/H ratios in gas that has been shocked or otherwise heated
recently. We argue that the total (gas plus dust) D/H ratio within 1
kpc of the Sun has a much larger value than D/H in the gas phase in the
Local Bubble, indicating that over the lifetime of the Galaxy there
has been a relatively small decrease in the total D/H ratio from its
primordial value. This work is based on observations made with
the NASA-CNES-CSA FUSE satellite, which is operated for NASA by the
Johns Hopkins University under NASA contract NAS5-32985.

---------------------------------------------------------
Title: Inferences About the History of the Solar Wind from Stellar
Wind Measurements
Authors: Wood, B. E.; Linsky, J. L.; Müller, H. -R.; Zank, Gary P.
2005ESASP.592..387W Altcode: 2005soho...16E..64W; 2005ESASP.592E..64W
No abstract at ADS

---------------------------------------------------------
Title: New Mass-Loss Measurements from Astrospheric Lyα Absorption
Authors: Wood, B. E.; Müller, H. -R.; Zank, G. P.; Linsky, J. L.;
Redfield, S.
2005ApJ...628L.143W Altcode: 2005astro.ph..6401W
Measurements of stellar mass-loss rates are used to assess how wind
strength varies with coronal activity and age for solar-like stars. Mass
loss generally increases with activity, but we find evidence that
winds suddenly weaken at a certain activity threshold. Very active
stars are often observed to have polar starspots, and we speculate
that the magnetic field geometry associated with these spots may be
inhibiting the winds. Our inferred mass-loss/age relation represents
an empirical estimate of the history of the solar wind. This result is
important for planetary studies as well as solar/stellar astronomy,
since solar wind erosion may have played an important role in the
evolution of planetary atmospheres.

---------------------------------------------------------
Title: Stellar Lyα Emission Lines in the Hubble Space Telescope
Archive: Intrinsic Line Fluxes and Absorption from the Heliosphere
and Astrospheres
Authors: Wood, Brian E.; Redfield, Seth; Linsky, Jeffrey L.; Müller,
Hans-Reinhard; Zank, Gary P.
2005ApJS..159..118W Altcode: 2005astro.ph..3372W
We search the Hubble Space Telescope (HST) archive for previously
unanalyzed observations of stellar H I Lyα emission lines, our primary
purpose being to look for new detections of Lyα absorption from the
outer heliosphere and to also search for analogous absorption from the
astrospheres surrounding the observed stars. The astrospheric absorption
is of particular interest because it can be used to study solar-like
stellar winds that are otherwise undetectable. We find and analyze
33 HST Lyα spectra in the archive. All the spectra were taken with
the E140M grating of the Space Telescope Imaging Spectrograph (STIS)
instrument on board HST. The HST STIS spectra yield four new detections
of heliospheric absorption (70 Oph, ξ Boo, 61 Vir, and HD 165185)
and seven new detections of astrospheric absorption (EV Lac, 70 Oph,
ξ Boo, 61 Vir, δ Eri, HD 128987, and DK UMa), doubling the previous
number of heliospheric and astrospheric detections. When combined
with previous results, 10 of 17 lines of sight within 10 pc yield
detections of astrospheric absorption. This high detection fraction
implies that most of the ISM within 10 pc must be at least partially
neutral, since the presence of H I within the ISM surrounding the
observed star is necessary for an astrospheric detection. In contrast,
the detection percentage is only 9.7% (3 out of 31) for stars beyond 10
pc. Our Lyα analyses provide measurements of ISM H I and D I column
densities for all 33 lines of sight, and we discuss some implications
of these results. Finally, we measure chromospheric Lyα fluxes
from the observed stars. We use these fluxes to determine how Lyα
flux correlates with coronal X-ray and chromospheric Mg II emission,
and we also study how Lyα emission depends on stellar rotation. Based on observations with the NASA/ESA Hubble Space Telescope,
obtained at the Space Telescope Science Institute, which is operated
by the Association of Universities for Research in Astronomy, Inc.,
under NASA contract NAS5-26555.

---------------------------------------------------------
Title: The Loopy Ultraviolet Line Profiles of RU Lupi: Accretion,
Outflows, and Fluorescence
Authors: Herczeg, Gregory J.; Walter, Frederick M.; Linsky, Jeffrey
L.; Gahm, Gösta F.; Ardila, David R.; Brown, Alexander; Johns-Krull,
Christopher M.; Simon, Michal; Valenti, Jeff A.
2005AJ....129.2777H Altcode: 2005astro.ph..4654H
We present far-ultraviolet (FUV) spectra of the classical T Tauri
star RU Lup covering the 912-1710 Å spectral range, as observed by
the Hubble Space Telescope STIS and the Far Ultraviolet Spectroscopic
Explorer satellite. We use these spectra, which are rich in emission
and absorption lines, to probe both the accreting and outflowing
gas. Absorption in the Lyα profile constrains the extinction to
AV~0.07 mag, which we confirm with other diagnostics. We
estimate a mass accretion rate of (5+/-2)×10-8
Msolar yr-1 using the optical-NUV accretion
continuum. The accreting gas is also detected in bright, broad lines of
C IV, Si IV, and N V, which all show complex structures across the line
profile. Many other emission lines, including those of H2
and Fe II, are pumped by Lyα. RU Lup's spectrum varies significantly
in the FUV; our STIS observations occurred when RU Lup was brighter
than several other observations in the FUV, possibly because of a high
mass accretion rate.

---------------------------------------------------------
Title: Monitoring Altair's far-ultraviolet emission lines for
variability over a stellar rotation period
Authors: Redfield, S.; Linsky, J. L.
2005ESASP.560..903R Altcode: 2005csss...13..903R
No abstract at ADS

---------------------------------------------------------
Title: The winds of solar-like main sequence stars
Authors: Wood, B. E.; Redfield, S.; Linsky, J. L.; Müller, H. -R.;
Zank, G. P.
2005ESASP.560..309W Altcode: 2005csss...13..309W
No abstract at ADS

---------------------------------------------------------
Title: A Far-Ultraviolet Spectroscopic Survey of Luminous Cool Stars
Authors: Dupree, A. K.; Lobel, A.; Young, P. R.; Ake, T. B.; Linsky,
J. L.; Redfield, S.
2005ApJ...622..629D Altcode: 2004astro.ph.12539D
The Far Ultraviolet Spectroscopic Explorer (FUSE) ultraviolet spectra
of eight giant and supergiant stars reveal that high-temperature
(3×105 K) atmospheres are common in luminous cool stars
and extend across the color-magnitude diagram from α Car (F0 II)
to the cool giant α Tau (K5 III). Emission present in these spectra
includes chromospheric H Lyβ, Fe II, C I, and transition region lines
of C III, O VI, Si III, and Si IV. Emission lines of Fe XVIII and Fe
XIX signaling temperatures of ~107 K and coronal material
are found in the most active stars, β Cet and 31 Com. A short-term
flux variation, perhaps a flare, was detected in β Cet during our
observation. Stellar surface fluxes of the emission of C III and
O VI are correlated and decrease rapidly toward the cooler stars,
reminiscent of the decay of magnetically heated atmospheres. Profiles
of the C III λ977 lines suggest that mass outflow is underway at
T~80,000 K and the winds are warm. Indications of outflow at higher
temperatures (3×105 K) are revealed by O VI asymmetries and
the line widths themselves. High-temperature species are absent in the
M supergiant α Ori. Narrow fluorescent lines of Fe II appear in the
spectra of many giants and supergiants, apparently pumped by H Lyα,
and formed in extended atmospheres. Instrumental characteristics that
affect cool star spectra are discussed.

---------------------------------------------------------
Title: The relevance and future of the ultraviolet range
Authors: Gómez de Castro, A. I.; Pagano, I.; Linsky, J. L.
2005ESASP.560..155G Altcode: 2005csss...13..155G
No abstract at ADS

---------------------------------------------------------
Title: Summary for Cool Stars 13: internal and external connections
Authors: Linsky, J. L.
2005ESASP.560..367L Altcode: 2005csss...13..367L
No abstract at ADS

---------------------------------------------------------
Title: Introducing Joint Discussion 20: Frontiers of high resolution
spectroscopy
Authors: Linsky, Jeffrey L.
2005HiA....13..781L Altcode:
This paper introduces the rationale and program of Joint Discussion 20,
Frontiers of High Resolution Spectroscopy, which took place on 2003
July 23-24 during the IAU General Assembly in Sydney Australia.

---------------------------------------------------------
Title: Molecular Hydrogen and Lyman-alpha Emission in FUV Spectra
of CTTSs
Authors: Herczeg, Gregory J.; Linsky, J. L.; Wood, B. E.; Walter,
F. M.; Valenti, J.; Johns-Krull, C. M.
2004AAS...20515604H Altcode: 2004BAAS...36.1608H
The presence and structure of gas in circumstellar disks around young
stars has profound implications on the formation and early evolution of
planets. We use HST/STIS and FUSE spectra of a small sample of CTTSs to
study fluorescent H2 emission, pumped by Lyman-alpha. We find
that the H2 traces 2500 K gas at or near the disk surface
within 2 AU of the central star. These H2 lines allow us to
indirectly measure Lyman-alpha emission, which is typically obscured by
H I absorption in our line of sight to the star. Lyman-alpha emission
contributes 80-90% of the total FUV emission from CTTSs, and alters
the disk chemistry.

---------------------------------------------------------
Title: Hydrogen Walls: Mass Loss of Dwarf Stars and the Young Sun
Authors: Linsky, Jeffrey L.; Wood, Brian E.
2004ASSL..317....1L Altcode: 2004shis.conf....1L
No abstract at ADS

---------------------------------------------------------
Title: The Structure of the Local Interstellar
Medium. III. Temperature and Turbulence
Authors: Redfield, Seth; Linsky, Jeffrey L.
2004ApJ...613.1004R Altcode: 2004astro.ph..6464R
We present 50 individual measurements of the gas temperature and
turbulent velocity in the local interstellar medium (LISM) within 100
pc. By comparing the absorption line widths of many ions with different
atomic masses, we can satisfactorily discriminate between the two
dominant broadening mechanisms, thermal broadening and macroscopic
nonthermal, or turbulent, broadening. We find that the successful
use of this technique requires a measurement of a light ion, such as
D I, and an ion at least as heavy as Mg II. However, observations
of more lines provide an important consistency check and can also
improve the precision and accuracy of the measurement. Temperature and
turbulent velocity measurements are vital to understanding the physical
properties of the gas in our local environment and can provide insight
into the three-dimensional morphological structure of the LISM. The
weighted mean gas temperature in the LISM warm clouds is 6680 K and
the dispersion about the mean is 1490 K. The weighted mean turbulent
velocity is 2.24 km s-1 and the dispersion about the mean is
1.03 km s-1. The ratio of the mean thermal pressure to the
mean turbulent pressure is PT/Pξ~26. Turbulent
pressure in LISM clouds cannot explain the difference in the apparent
pressure imbalance between warm LISM clouds and the surrounding hot gas
of the Local Bubble. Pressure equilibrium among the warm clouds may be
the source of a moderately negative correlation between temperature and
turbulent velocity in these clouds. However, significant variations
in temperature and turbulent velocity are observed. The turbulent
motions in the warm partially ionized clouds of the LISM are definitely
subsonic, and the weighted mean turbulent Mach number for clouds in
the LISM is 0.19 with a dispersion of 0.11. These measurements provide
important constraints on models of the evolution and origin of warm
partially ionized clouds in our local environment. Based on
observations made with the NASA/ESA Hubble Space Telescope, obtained
from the Data Archive at the Space Telescope Science Institute, which is
operated by the Association of Universities for Research in Astronomy,
Inc., under NASA contract NAS AR-09525.01A. These observations are
associated with program 9525.

---------------------------------------------------------
Title: A Multiwavelength Perspective of Flares on HR 1099: 4 Years
of Coordinated Campaigns
Authors: Osten, Rachel A.; Brown, Alexander; Ayres, Thomas R.; Drake,
Stephen A.; Franciosini, Elena; Pallavicini, Roberto; Tagliaferri,
Gianpiero; Stewart, Ron T.; Skinner, Stephen L.; Linsky, Jeffrey L.
2004ApJS..153..317O Altcode: 2004astro.ph..2613O
We report on four years of multiple wavelength observations of the RS
CVn system V711 Tau (HR 1099) from 1993, 1994, 1996, and 1998. This
combination of radio, ultraviolet, extreme ultraviolet, and X-ray
observations allows us to view, in the most comprehensive manner
currently possible, the coronal and upper atmospheric variability of
this active binary system. We report on the changing activity state
of the system as recorded in the EUV and radio across the four years
of the observations, and study the high energy variability using an
assemblage of X-ray telescopes. (Longer abstract in paper).

---------------------------------------------------------
Title: Two New Low Galactic D/H Measurements from the Far Ultraviolet
Spectroscopic Explorer
Authors: Wood, Brian E.; Linsky, Jeffrey L.; Hébrard, Guillaume;
Williger, Gerard M.; Moos, H. Warren; Blair, William P.
2004ApJ...609..838W Altcode: 2004astro.ph..3606W
We analyze interstellar absorption observed toward two subdwarf O
stars, JL 9 and LS 1274, using spectra taken by the Far Ultraviolet
Spectroscopic Explorer (FUSE). Column densities are measured
for many atomic and molecular species (H I, D I, C I, N I, O I,
P II, Ar I, Fe II, and H2), but our main focus is on
measuring the D/H ratios for these extended lines of sight, as
D/H is an important diagnostic for both cosmology and Galactic
chemical evolution. We find D/H=(1.00+/-0.37)×10-5
toward JL 9 and D/H=(0.76+/-0.36)×10-5 toward LS 1274
(2 σ uncertainties). With distances of 590+/-160 and 580+/-100
pc, respectively, these two lines of sight are currently among
the longest Galactic lines of sight with measured D/H. With the
addition of these measurements, we see a significant tendency for
longer Galactic lines of sight to yield low D/H values, consistent
with previous inferences about the deuterium abundance from D/O and
D/N measurements. Short lines of sight with H I column densities of
logN(HI)&lt;19.2 suggest that the gas-phase D/H value within the Local
Bubble is (D/H)LBg=(1.56+/-0.04)×10-5. However,
the four longest Galactic lines of sight with measured D/H, which
have d&gt;500 pc and logN(HI)&gt;20.5, suggest a significantly
lower value for the true local disk gas-phase D/H value,
(D/H)LDg=(0.85+/-0.09)×10-5. One
interpretation of these results is that D is preferentially
depleted onto dust grains relative to H and that longer lines of
sight that extend beyond the Local Bubble sample more depleted
material. In this scenario, the higher Local Bubble D/H ratio is
actually a better estimate than (D/H)LDg for the true
local disk D/H, (D/H)LD. However, if (D/H)LDg
is different from (D/H)LBg simply because of variable
astration and incomplete interstellar medium mixing, then
(D/H)LD=(D/H)LDg. Based on observations
made with the NASA-CNES-CSA Far Ultraviolet Spectroscopic Explorer
(FUSE), which is operated for NASA by Johns Hopkins University under
NASA contract NAS5-32985.

---------------------------------------------------------
Title: The Far-Ultraviolet Spectra of TW Hydrae. II. Models of
H2 Fluorescence in a Disk
Authors: Herczeg, Gregory J.; Wood, Brian E.; Linsky, Jeffrey L.;
Valenti, Jeff A.; Johns-Krull, Christopher M.
2004ApJ...607..369H Altcode: 2004astro.ph..2238H
We measure the temperature of warm gas at planet-forming radii in the
disk around the classical T Tauri star (CTTS) TW Hya by modeling the
H2 fluorescence observed in Hubble Space Telescope Space
Telescope Imaging Spectrograph and Far Ultraviolet Spectroscopic
Explorer spectra. Strong Lyα emission irradiates a warm disk surface
within 2 AU of the central star and pumps certain excited levels of
H2. We simulate a one-dimensional plane-parallel atmosphere
to estimate fluxes for the 140 observed H2 emission lines
and to reconstruct the Lyα emission profile incident upon the warm
H2. The excitation of H2 can be determined
from relative line strengths by measuring self-absorption in lines
with low-energy lower levels, or by reconstructing the Lyα profile
incident upon the warm H2 using the total flux from a single
upper level and the opacity in the pumping transition. Based on those
diagnostics, we estimate that the warm disk surface has a column
density of logN(H2)=18.5+1.2-0.8,
a temperature T=2500+700-500 K, and a filling
factor of H2, as seen by the source of Lyα emission,
of 0.25+/-0.08 (all 2 σ error bars). TW Hya produces approximately
10-3 Lsolar in the FUV, about 85% of which is in
the Lyα emission line. From the H I absorption observed in the Lyα
emission, we infer that dust extinction in our line of sight to TW Hya
is negligible. Based on observations with the NASA/ESA Hubble Space
Telescope, obtained at the Space Telescope Science Institute, which is
operated by the Association of Universities for Research in Astronomy,
Inc., under NASA contract NAS5-26555. This work is also based on data
obtained for the FUSE Science Team by the NASA-CNES-CSA FUSE mission,
operated by Johns Hopkins University.

---------------------------------------------------------
Title: The Mystery of the Deuterium Abundance in the Local Galactic
Disk is Solved!
Authors: Linsky, J. L.; Wood, B. E.
2004AAS...204.6117L Altcode: 2004BAAS...36..771L
Analyses of spectra obtained with the Far Ultraviolet Spectroscopic
Explorer (FUSE) satellite, together with previous Copernicus and
IMAPS spectrometer observations, reveal a very wide range in the
deuterium/hydrogen (D/H) ratios for interstellar gas in the Galactic
disk within 1 kpc of the Sun. This result is very difficult to explain
on the basis of nuclear processes in stars that convert deuterium to
3He and 4He and the infall of deuterium rich gas from the Galactic halo
and the intergalactic medium, because the D/H ratios differ greatly
on very short spatial scales. We argue instead that spatial variations
in the depletion of deuterium onto dust grains can explain these local
variations in the gas phase D/H ratios. The D/H measurements appear to
fall into three regimes depending on the line of sight hydrogen column
density. Our dynamic deuterium depletion model naturally explains the
constant D/H measurements for the local Bubble (log N(HI) &lt; 19.2),
the wide range of gas phase D/H ratios found in the intermediate regime
(log N(HI) = 19.2-20.5), and the low gas phase D/H ratios at larger
hydrogen column densities. We argue that the most representative
value for the total (gas plus dust) D/H ratio within 1 kpc of the
Sun is 23 +/- 4 ppm (parts per million), which constrains Galactic
chemical evolution models to have small deuterium astration rates. This work is based on observations made with the NASA-CNES-CSA Far
Ultraviolet Spectroscopic Explorer. FUSE is operated for NASA by the
Johns Hopkins University under NASA contract NAS5-32985.

---------------------------------------------------------
Title: Flares from small to large: X-ray spectroscopy of Proxima
Centauri with XMM-Newton
Authors: Güdel, M.; Audard, M.; Reale, F.; Skinner, S. L.; Linsky,
J. L.
2004A&A...416..713G Altcode: 2003astro.ph.12297G
We report results from a comprehensive study of the nearby M dwarf
Proxima Centauri with the XMM-Newton satellite, using simultaneously
its X-ray detectors and the Optical Monitor with its U band filter. We
find strongly variable coronal X-ray emission, with flares ranging
over a factor of 100 in peak flux. The low-level emission is found
to be continuously variable on at least three time scales (a slow
decay of several hours, modulation on a time scale of 1 hr, and
weak flares with time scales of a few minutes). Several weak flares
are characteristically preceded by an optical burst, compatible with
predictions from standard solar flare models. We propose that the U band
bursts are proxies for the elusive stellar non-thermal hard X-ray bursts
suggested from solar observations. In the course of the observation,
a very large X-ray flare started and was observed essentially in
its entirety. Its peak luminosity reached 3.9× 1028 erg
s-1 [0.15-10 keV], and the total X-ray energy released
in the same band is derived to be 1.5× 1032 ergs. This
flare has for the first time allowed to measure significant density
variations across several phases of the flare from X-ray spectroscopy
of the O VII He-like triplet; we find peak densities reaching up to 4×
1011 cm-3 for plasma of about 1-5 MK. Abundance
ratios show little variability in time, with a tendency of elements
with a high first ionization potential to be overabundant relative
to solar photospheric values. Using Fe XVII lines with different
oscillator strengths, we do not find significant effects due to opacity
during the flare, indicating that large opacity increases are not the
rule even in extreme flares. We model the large flare in terms of an
analytic 2-Ribbon flare model and find that the flaring loop system
should have large characteristic sizes (≈ 1R*) within
the framework of this simplistic model. These results are supported by
full hydrodynamic simulations. Comparing the large flare to flares of
similar size occurring much more frequently on more active stars, we
propose that the X-ray properties of active stars are a consequence of
superimposed flares such as the example analyzed in this paper. Since
larger flares produce hotter plasma, such a model also explains why,
during episodes of low-level emission, more active stars show hotter
plasma than less active stars. Based on observations obtained with
XMM-Newton, an ESA science mission with instruments and contributions
directly funded by ESA Member States and the USA (NASA).

---------------------------------------------------------
Title: HST/STIS high resolution echelle spectra of <ASTROBJ>α
Centauri A</ASTROBJ> (G2 V)
Authors: Pagano, I.; Linsky, J. L.; Valenti, J.; Duncan, D. K.
2004A&A...415..331P Altcode: 2003astro.ph.10901P
We describe and analyze HST/STIS observations of the G2 V star α
Centauri A (<ASTROBJ>α Cen A</ASTROBJ>, <ASTROBJ>HD 128620</ASTROBJ>),
a star similar to the <ASTROBJ>Sun</ASTROBJ>. The high resolution
echelle spectra obtained with the E140H and E230H gratings cover
the complete spectral range 1133-3150 Å with a resolution of 2.6 km
s-1, an absolute flux calibration accurate to ± 5%, and an
absolute wavelength accuracy of 0.6-1.3 km s-1. We present
here a study of the E140H spectrum covering the 1140-1670 Åspectral
range, which includes 671 emission lines representing 37 different
ions and the molecules CO and H_2. For <ASTROBJ>α Cen A</ASTROBJ>
and the quiet and active <ASTROBJ>Sun</ASTROBJ>, we intercompare the
redshifts, nonthermal line widths, and parameters of two Gaussian
representations of transition region lines (e.g., Si IV, C IV), infer
the electron density from the O IV intersystem lines, and compare
their differential emission measure distributions. One purpose of
this study is to compare the <ASTROBJ>α Cen A</ASTROBJ> and solar
UV spectra to determine how the atmosphere and heating processes in
<ASTROBJ>α Cen A</ASTROBJ> differ from the <ASTROBJ>Sun</ASTROBJ>
as a result of the small differences in gravity, age, and chemical
composition of the two stars. A second purpose is to provide an
excellent high resolution UV spectrum of a solar-like star that can
serve as a proxy for the <ASTROBJ>Sun</ASTROBJ> observed as a point
source when comparing other stars to the <ASTROBJ>Sun</ASTROBJ>. Based on observations made with the NASA/ESA Hubble Space Telescope,
obtained at the Space Telescope Science Institute, which is operated
by the Association of Universities for Research in Astronomy, Inc.,
under NASA contract NAS 5-26555. These observations are associated
with proposal GO-07263. Table 4 is only available in electronic
form at the CDS via anonymous ftp to cdsarc.u-strasbg.fr (130.79.128.5)
or via http://cdsweb.u-strasbg.fr/cgi-bin/qcat?J/A+A/415/331

---------------------------------------------------------
Title: The Structure of the Local Interstellar
Medium. II. Observations of D I, C II, N I, O I, Al II, and Si II
toward Stars within 100 Parsecs
Authors: Redfield, Seth; Linsky, Jeffrey L.
2004ApJ...602..776R Altcode: 2003astro.ph.10878R
Moderate- and high-resolution measurements (λ/Δλ&gt;~40,000)
of interstellar resonance lines of D I, C II, N I, O I, Al II, and
Si II (hereafter called light ions) are presented for all available
observed targets located within 100 pc that also have high-resolution
observations of interstellar Fe II or Mg II (heavy ions) lines. All
spectra were obtained with the Goddard High Resolution Spectrograph or
the Space Telescope Imaging Spectrograph instrument aboard the Hubble
Space Telescope. Currently, there are 41 sight lines to targets within
100 pc with observations that include a heavy ion at high resolution
and at least one light ion at moderate or high resolution. We present
new measurements of light ions along 33 of these sight lines and
collect from the literature results for the remaining sight lines
that have already been analyzed. For all of the new observations we
provide measurements of the central velocity, Doppler width parameter,
and column density for each absorption component. We greatly increase
the number of sight lines with useful local interstellar medium (LISM)
absorption-line measurements of light ions by using knowledge of the
kinematic structure along a line of sight obtained from high-resolution
observations of intrinsically narrow absorption lines, such as Fe II and
Mg II. We successfully fit the absorption lines with this technique,
even with moderate-resolution spectra. Because high-resolution
observations of heavy ions are critical for understanding the kinematic
structure of local absorbers along the line of sight, we include
18 new measurements of Fe II and Mg II in an Appendix. We present a
statistical analysis of the LISM absorption measurements, which provides
an overview of some physical characteristics of warm clouds in the LISM,
including temperature and turbulent velocity. This complete collection
and reduction of all available LISM absorption measurements provides an
important database for studying the structure of nearby warm clouds,
including ionization, abundances, and depletions. Subsequent papers
will present models for the morphology and physical properties of
individual structures (clouds) in the LISM. Based on observations
made with the NASA/ESA Hubble Space Telescope, obtained from the Data
Archive at the Space Telescope Science Institute, which is operated
by the Association of Universities for Research in Astronomy, Inc.,
under NASA contract NAS AR-09525.01A. These observations are associated
with program 9525.

---------------------------------------------------------
Title: Mass Loss of Solar-like Dwarf Stars and the Young Sun
Authors: Linsky, J. L.; Wood, B. E.; Müller, H. -R.; Zank, G. P.
2004IAUS..219..898L Altcode: 2003IAUS..219E.217L
The collision of an ionized stellar wind with the partially-ionized warm
gas in the interstellar medium creates a population of hot decelerated
neutral hydrogen atoms. This ""hydrogen wall"" produces a blue-shifted
absorption component in the stellar Lyman alpha emission line that has
now been detected in HST spectra of 6 dwarf stars. Comparisons of the
observed Lyman alpha line profiles with theoretical models lead to the
first very sensitive measurements of mass loss rates as small as 4 x
10-15 solar masses per year for solar-like dwarf stars. Our
program provides the first observational data (other than for the Sun)
with which to test theories for the winds of solar-like dwarf stars. We
find an empirical correlation of stellar mass loss rate with X-ray
surface flux that allows us to predict the mass loss rates of other
stars and to infer the solar wind flux at earlier times when the solar
wind may have been as much as 1000 times more massive. We mention some
important ramifications for the history of planetary atmospheres in our
solar system that of Mars in particular and for exoplanets around stars.

---------------------------------------------------------
Title: The heliospheric hydrogen wall and astrospheres
Authors: Wood, B. E.; Müller, H. -R.; Zank, G. P.; Izmodenov, V. V.;
Linsky, J. L.
2004AdSpR..34...66W Altcode:
Charge exchange processes in the outer heliosphere produce a population
of hot hydrogen gas within the heliosphere, creating a "hydrogen wall"
between the heliopause and bow shock. The heliospheric hydrogen wall
scatters Lyα photons passing through it, producing a detectable
absorption signature in observations of H I Lyα emission from nearby
stars. This heliospheric absorption has been observed using observations
from the Hubble Space Telescope (HST), and these observations have
also yielded detections of analogous "astrospheric" absorption from
material surrounding the observed stars. The astrospheric detections
dramatize the importance of understanding the heliospheric interaction,
since similar interactions exist around other stars and can now be
studied with HST. We review comparisons that have been made between
the observed heliospheric absorption and the predictions of various
models. The astrospheric absorption provides a way to empirically
estimate the mass loss rates of solar-like stars, leading to the first
empirical estimates of how solar-like winds vary with stellar age and
activity. Thus, we also review these astrospheric results and discuss
their ramifications for solar, stellar, and planetary science.

---------------------------------------------------------
Title: The Disk and Accretion Shock of TW Hya
Authors: Herczeg, G. J.; Linsky, J. L.; Wood, B. E.; Valenti, J. A.;
Johns-Krull, C. M.
2004IAUS..219..883H Altcode: 2003IAUS..219E.222L
We analyze the molecular hydrogen emission lines observed in HST/STIS
and FUSE spectra of the nearest premain sequence star TW Hya. The
molecular hydrogen lines are fluoresced by the Lyman alpha emission
that likely comes from an accretion shock. We identify 140 molecular
hydrogen emission lines and the 19 excitation paths that produce
these lines. The molecular hydrogen is located near the inner edge
of the disk with a temperature of 3000 K. The fluorescent emission
allows us to reconstruct the Lyman alpha emission line profile and to
study the properties of the stellar wind. We propose a model for the
disk and accretion column of this star and discuss possible formation
mechanisms of excited molecular hydrogen.

---------------------------------------------------------
Title: D/H as a Measure of Chemical Inhomogeneity in our Galaxy
Authors: Linsky, J. L.
2004oee..sympE..35L Altcode:
Accurate measurements of interstellar deuterium abundances along lines
of sight extending out to several hundred parsecs by FUSE and other
instruments is making D/H a useful tool for understanding Galactic
chemical evolution. We find that the gas inside of the Local Bubble
is chemically homogeneous, but that large variations in D/H beyond
the Local Bubble are real and challenge present concepts of chemical
evolution. A new set of models is needed that will include spatially
dependent infall of relatively unprocessed material, depletion of D
onto grains, and appropriate mixing timescales.

---------------------------------------------------------
Title: Physical structure of the local interstellar medium
Authors: Redfield, S.; Wood, B. E.; Linsky, J. L.
2004AdSpR..34...41R Altcode:
The physical structure and morphology of the interstellar medium that
surrounds our solar system directly effects the heliosphere and the
interplanetary environment. High resolution ultraviolet absorption
spectra of nearby stars and the intervening interstellar medium,
observed by the Hubble Space Telescope, provide important information
about the chemical abundance, ionization, temperature, kinematics,
density, morphology, and turbulent structures of the local interstellar
medium. Fortunately, nearly all observations of nearby stars contain
useful local interstellar medium absorption lines. The number of
useful observations is large enough that we can start analyzing the
local interstellar medium as a three-dimensional object, as opposed
to focusing on individual sightlines. We present the results of
high resolution observations of nearby gas obtained by the Hubble
Space Telescope. Our focus will be on the kinematic, temperature,
and turbulent velocity structures in the Local Interstellar Cloud and
other nearby clouds. Understanding the physical characteristics of
these structures is necessary if we are to discuss the morphology of
the local interstellar medium, its evolution, origin, and impact on
the heliosphere and our solar system.

---------------------------------------------------------
Title: Multi-Wavelength Observations of EV Lacertae
Authors: Osten, R. A.; Hawley, S. L.; Allred, J.; Johns-Krull, C. M.;
Roark, C.; Ambruster, C.; Brown, A.; Ayres, T. R.; Linsky, J. L.
2004IAUS..219..249O Altcode: 2003IAUS..219E.207O
We present an analysis of simultaneous radio optical UV and
X-ray observations of the dMe flare star EV Lacertae taken in 2001
September. The analysis is time-resolved and concentrates on determining
flare-related changes in each spectral region. Temporal correlations
in different wavelength regions are examined. Numerous X-ray flares
were observed; two X-ray flares are accompanied by UV enhancements
in a pattern reminiscent of the Neupert effect seen in solar flares
where UV bursts are interpreted as a product of nonthermal heat input
to the lower atmosphere and soft X-ray emission occurs as a result of
the heating. An extemely large radio flare seen at two frequencies
and representing a factor of 100 increase in quiescent radio flux
density has an optical counterpart with an enhancement of about 3
magnitudes in the U filter. There is no corresponding increase in
soft X-ray flux. We investigate scenarios which could give rise to the
observed multi-wavelength correlations. The run of electron density with
temperature in the outer atmosphere (transition region through corona)
is investigated and implications for coronal structure are given.

---------------------------------------------------------
Title: The Sun as a Star: Comparing Alpha Cen A to UV Solar Spectra
Authors: Linsky, J. L.; Pagano, I.; Valenti, J. A.; Duncan, D.
2004IAUS..219..431L Altcode: 2003IAUS..219E.224L
The Space Telescope Imaging Spectrograph (STIS) obtained high resolution
echelle spectra of the nearby G2 V star Alpha Centauri A covering the
entire 1133-3150 Angstrom region with very high signal/noise. This data
set provides what is likely the best approximation to the spectrum
of the Sun viewed as a star because it is a full disk spectrum with
2.6 km/s resolution accurate absolute fluxs full UV spectral coverage
high S/N and low scattered light. In the 1140-1670 Angstrom region
we identify 671 emission lines from 27 different atoms and ions and
molecular hydrogen. We make a detailed comparison of the solar and Alpha
Cen A spectra in terms of line identification line widths and Doppler
shifts emission measure distribution and electron densities. Although
the two stars are very similar we do identify differences that could be
ascribed to slight differences in gravity age and chemical composition
of the two stars.

---------------------------------------------------------
Title: RU Lupi? A UV spectroanalysis of an adolescent star
Authors: Herczeg, G.; Walter, F.; Linsky, J. L.; Ardila, D.; Brown.,
A.; Gahm, G.; Johns-Krull, C.; Lissauer, J.; Simon, M.; Valenti,
J. A.; Wood, B. E.
2003AAS...20314708H Altcode: 2004BAAS...36Q.593H
We present an HST/STIS E140M spectrum of the CTTS RU Lupi. The UV
spectrum of RU Lupi is dominated by emission lines, including tracers
of hot accreting gas and cool molecular gas. We also detect a strong
continuum and wind absorption features. We analyze 90 fluorescent H2
emission lines, and use them to reconstruct the intrinsic Ly-alpha
profile.

---------------------------------------------------------
Title: Proposed mission concept for the Astrophysical Plasmadynamic
Explorer (APEX): an EUV high-resolution spectroscopic SMEX
Authors: Kowalski, Michael P.; Cruddace, Raymond G.; Wood, Kent S.;
Yentis, Daryl J.; Wolff, Michael T.; Laming, J. M.; Gursky, Herbert;
Carruthers, George R.; Barbee, Troy W., Jr.; Kordas, Joseph F.; Mauche,
Chris W.; Fritz, Gilbert G.; Varlese, Steve J.; Barstow, Martin A.;
Fraser, George W.; Siegmund, Oswald H. W.; Welsh, Barry Y.; Brickhouse,
Nancy S.; Dupree, Andrea K.; Brown, Alex; Bruhweiler, Frederick C.;
Cameron, Andrew C.; Holberg, Jay B.; Howell, Steven B.; Jordan, Carole;
Linsky, Jeffrey L.; Matthews, Sarah A.; Sion, Edward M.; Werner, Klaus
2003SPIE.5164....1K Altcode:
APEX is a proposed mission for a Small Explorer (SMEX) satellite. APEX
will investigate the density, temperature, composition, magnetic field,
structure, and dynamics of hot astrophysical plasmas (log T = ~5-7),
which emit the bulk of their radiation at EUV wavelengths and produce
critical spectral diagnostics not found at other wavelengths. APEX
addresses basic questions of stellar evolution and galactic structure
through high-resolution spectroscopy of white dwarf stars, cataclysmic
variables, the local interstellar medium, and stellar coronae. Thus
APEX complements the Chandra, Newton-XMM, FUSE, and CHIPS missions. The
instrument is a suite of 8 near-normal incidence spectrometers (~90-275
Angstroms, resolving power ~10,000, effective area 30-50 cm2)
each of which employs a multilayer-coated ion-etched blazed diffraction
grating and a microchannel plate detector of high quantum efficiency
and high spatial resolution. The instrument is mounted on a 3-axis
stabilized commercial spacecraft bus with a precision pointing
system. The spacecraft is launched by a Taurus vehicle, and payload
size and weight fit comfortably within limits for the 2210 fairing. Of
order 100 targets will be observed over the baseline mission of 2
years. These are selected carefully to maximize scientific return,
and all were detected in the EUVE and the ROSAT WFC surveys.

---------------------------------------------------------
Title: Coordinated Chandra and HST Observations of Proxima Centauri
Authors: Linsky, J. L.; VanVliet, T.
2003AAS...203.4306L Altcode: 2003BAAS...35R1273L
We describe and analyze coordinated HST/STIS, Chandra ACIS-S and RXTE
observations of the M5.5 Ve flare star Proxima Centauri (α Cen C, GJ
551). The observing program includes three sessions with the Chandra
ACIS-S, one of which includes the HETGS in the beam, and one session
with the HST STIS instrument with the E140M grating. The second Chandra
observation is simultaneous with the HST observation. Since the star was
observed in the continuous viewing zone, we have long, uninterrupted
observing sequences. We observe Prox Cen in quiescence and during
several small and moderate sized flares. We derive an emission measure
distribution for quiescence covering the temperature range log T =
4.3--7.4, and discuss the change in the emission measure distribution
during the flares. We model the moderate-sized flare as a large loop
and infer its physical properties discussing the applicability of the
2-ribbon solar flare model to stellar astronomy. We also discuss the
change in shape of transition region lines (e.g., Si IV, C IV), infer
the electron density from the O IV intersystem lines, and compare the
quiescence and flare emission measure distributions. This work is
supported by grants from NASA and the Space Telescope Science Institute
to the University of Colorado.

---------------------------------------------------------
Title: A Far-Ultraviolet Spectroscopic Survey of RS CVn Binary Systems
Authors: Redfield, S.; Linsky, J. L.; Ayres, T. R.; Brown, A.; Herczeg,
G. J.
2003AAS...203.1218R Altcode: 2003BAAS...35.1224R
RS CVn systems are detached late-type binaries that are very active as
a result of their tidally-enforced rapid rotation. They are actively
studied and bright at X-ray and ultraviolet (UV) wavelengths, but very
few have been observed in the far-UV. We present multiple orbital
phase observations of RS CVn systems taken by the Far Ultraviolet
Spectroscopic Explorer (FUSE). Located in the FUSE spectral range are
emission lines formed in plasma at 50,000-300,000 K (e.g., C III and
O VI). We present an analysis of the strong emission line profiles. By
monitoring the change in the profile shape over the course of an orbital
period we can measure the fractional contributions of each star in the
RS CVn binary system at different plasma temperatures. In addition,
the spectral resolution and wavelength scale of FUSE permit us to
measure the width and velocity shift of the O VI and C III lines,
providing a new window on stellar atmospheric dynamics and structure.

---------------------------------------------------------
Title: VizieR Online Data Catalog: HST/STIS spectra of alpha Cen A
(Pagano+, 2004)
Authors: Pagano, I.; Linsky, J. L.; Valenti, J.; Duncan, D. K.
2003yCat..34150331P Altcode:
This table is part of a paper is which a study of the alpha Cen A
spectrum recorded with the E140 grating by HST/STIS between 1140 and
1670{AA} is presented. In this spectrum the authors have identified a
total of 662 emission features of which 77 are due to blends of two
or more lines, 71 are due to unidentified transitions, and 514 are
identified as due to single emission lines. (1 data file).

---------------------------------------------------------
Title: Chandra Observations of the Pleiades Open Cluster: X-ray
emission from late-B and A type Pleiades members
Authors: Daniel, K. J.; Linsky, J. L.; Gagné, M.
2003csss...12..757D Altcode:
We present the analysis of 38.4 ks and 23.6 ks ACIS-I observations
of the core of the Pleiades open cluster. Of the 101 sources detected
in the 17 arcmin×17 arcmin region, 53 have not been cataloged at any
other wavelength. Eighteen of 23 Pleiades members in the ACIS-I FOV were
detected as X-ray sources with moderate to high time variability. Two
of the early-type Pleiades members, HII 980 (B6 IV) and HII 956 (A7 V),
are very bright X-ray sources, show soft X-ray spectra, and are variable
with no obvious signs of flaring. K- and M-type cluster members with
comparable X-ray luminosities have hard X-ray spectra and display
strong flares. For non-flaring K- and M-type stars, LX is
1--2 orders of magnitude lower. One A-type star, HII 1284 (A9 V), has
X-ray properties comparable to these non-flaring K-type stars. One star,
HII 1338 (F3 V), exhibits an X-ray flare and two others, HII 1362 (A7 V)
and HII 1375 (A0 V) are not detected. Despite the low number statistics,
this pattern among late-B to early-F stars suggests that some early-type
stars like HII 980 and HII 956 are intrinsic X-ray emitters. Some,
like HII 1284 and HII 1338, may have late-type companions and some,
like HII 1362 and HII 1375, may be single, inactive stars. X-ray
spectra and light curves of a larger sample of intermediate-mass stars
are needed to confirm this trend.

---------------------------------------------------------
Title: FUSE Observations of the Active K Dwarf AB Doradus
Authors: Robinson, R. D.; Ake, T. B.; Dupree, A. K.; Linsky, J. L.
2003csss...12..964R Altcode:
In this paper we report on flaring activity observed in high time
resolution FUV observations of the active K dwarf star AB Doradus,
taken with the FUSE satellite. These observations include data on
the C III (λ1175) and O VI (λλ1032,1037) lines as well as the FUV
continuum. During 29 hours of observation, two large flares and &gt;10
smaller events were observed. Here we describe the time history of
these events as well as a search for unresolved microflaring activity.

---------------------------------------------------------
Title: The FUSE Cool Star Survey
Authors: Ake, T. B.; Dupree, A. K.; Linsky, J. L.; FUSE Cool Star Team
2003csss...12..857A Altcode:
As part of the PI-team program, the FUSE cool star group has surveyed
eight coronal, non-coronal, and hybrid stars using the LWRS (30 arcsec
× 30 arcsec) aperture, providing full wavelength coverage in the FUSE
bandpass. Additional stars are being observed with the MDRS (4 arcsec ×
20 arcsec) slit for the team D/H program, primarily to obtain intrinsic
Lyman β profiles. We provide here an overview of the observations to
date, with examples of the types of studies currently in progress.

---------------------------------------------------------
Title: Dynamics of Coronal Iron Lines in Cool Stars based on FUSE
and HST/STIS Observations
Authors: Redfield, S.; Ayres, T. R.; Linsky, J. L.; Guinan, E. F.
2003csss...12..863R Altcode:
We present UV observations of coronal forbidden lines of highly
ionized iron. Fe XXI λ1354 and Fe XII λ1242 have been observed
by spectrographs on board the Hubble Space Telescope (HST), and Fe
XVIII λ975 recently has been identified in spectra taken by the Far
Ultraviolet Spectroscopic Explorer (FUSE). Mass motions of hot gas in
the corona provide information on the heating mechanism and magnetic
field strength in the corona. Observations of forbidden iron lines
with these moderate to high resolution spectrographs provide a unique
opportunity to study high temperature dynamics of the hot coronal
plasmas. We positively detect the forbidden iron line of Fe XVIII
λ975 in five stars. β Ceti shows the strongest Fe XVIII emission,
and since it is a single star system, it is an ideal target to study
stellar coronal dynamics. We find that the hot coronal plasma is
confined, in contrast to observed downflows at the temperatures where
the 105 K lines like C III λ977 form.

---------------------------------------------------------
Title: Mass Loss Rates for Solar-like Stars Measured from Lyα
Absorption
Authors: Wood, B. E.; Müller, H. -R.; Linsky, J. L.
2003csss...12..349W Altcode:
We present a number of mass loss rate measurements for solar-like stars
with coronal winds, computed using a Lyα absorption technique. The
collision between the solar wind and the interstellar wind seen by
the Sun defines the large scale structure of our heliosphere. Similar
structures, “astrospheres,” exist around other solar-like stars. The
deceleration of the interstellar wind at the solar or stellar bow
shock heats the interstellar material. Heated neutral hydrogen in
the outer astrosphere (and/or heliosphere) produces a broad Lyα
absorption profile that is often detectable in high resolution Hubble
Space Telescope spectra. The amount of absorption is dependent upon
the strength of the stellar wind. With guidance from hydrodynamic
models of astrospheres, we use detected astrospheric Lyα absorption
to estimate the stellar mass loss rates. For the solar-like GK stars
in our sample, mass loss appears to increase with stellar activity,
suggesting that young, active stars have stronger winds than old,
inactive stars. However, Proxima Cen (M5.5 Ve) and λ And (G8 IV-III+M
V) appear to be inconsistent with this relation.

---------------------------------------------------------
Title: FUSE Observations of Molecular Hydrogen in PMS Stars
Authors: Herczeg, G. J.; Linsky, J. L.; Brown, A.; Harper, G. M.;
Wilkinson, E.
2003csss...12..717H Altcode:
Pre-main sequence stars exhibit rich molecular hydrogen emission and
absorption spectra in the FUV. We survey four PMS stars that have been
observed with FUSE: the Classical T Tauri Stars TW Hya and V4046 Sgr,
and the Herbig Ae/Be stars AB Aur and DX Cha. The spectrum of TW Hya
and V4046 Sgr show H2 fluorescence in Lyman (B-X) and Werner
(C-X) bands caused by photoexcitation by Lyα, H2 absorption
occurs against line and continuum emission in the spectrum of AB Aur
and DX Cha. We measure column densities of log(NH_2)=20.2 ±
0.2 cm-2 towards AB Aur and log(NH_2)=19.4± 0.2
cm-2 towards DX Cha. The rotational excitation temperature
of the H2 gas around DX Cha varies from 300--500 K for
different rotational levels, compared with 65--450 K the gas around
AB Aur. We discuss the circumstellar origin of H2 emission
and absorption.

---------------------------------------------------------
Title: Measurements of the winds of solar-like stars and their
influence on extrasolar planets
Authors: Linsky, Jeffrey L.; Wood, Brian E.; Müller, Hans-Reinhard;
Zank, Gary P.
2003ESASP.539..507L Altcode: 2003toed.conf..507L
Until recently there have been no reliable measurements of the mass
loss rates for main sequence stars of spectral type F-M. Although such
mass loss rates are generally presumed to be small as in the solar
case, there has been no confirmation of this assumption. We report
on a new method for measuring dwarf star mass loss rates using the
observed absorption on the blue side of the interstellar Lyman-α
absorption feature to study the star's astrosphere. Astrospheres,
which are analogs of the heliosphere are produced when the stellar wind
interacts with the interstellar gas flow. Neutral hydrogen piles up at
the astropause when the interstellar hydrogen atoms charge exchange
with the stellar wind protons. This absorption is blue-shifted with
respect to the interstellar medium flow. Astrosphere models constructed
to be consistent with the absorption features of eight dwarf stars
provide mass loss rates and show a dependence of mass loss rate per
unit surface area on X-ray surface flux and thus stellar age. We
infer a relation of mass loss rate with age for solar-like stars,
and discuss its implications for planets around the Sun and stars.

---------------------------------------------------------
Title: Summary of the Twelfth Cool Stars Workshop: Insights,
Mysteries, and Action Items
Authors: Linsky, J. L.
2003csss...12..583L Altcode:
This paper summarizes the Twelfth Cambridge Workshop on Cool Stars,
Stellar Systems, and the Sun held in Boulder, Colorado on July 30
to August 3, 2001. I describe many of the important new results and
insights presented at the meeting and list the important unanswered
questions that should drive future research in the field. Finally,
I present a set of urgent action items that are needed if we are to
maintain and enhance research opportunities in the field.

---------------------------------------------------------
Title: The α Cen A and Solar FUV Spectra
Authors: Pagano, I.; Linsky, J. L.; Curdt, W.; Valenti, J.; Gagné, M.
2003csss...12..847P Altcode:
We present a comparison of the high-resolution FUV spectrum of α Cen A
(G2 V) acquired by STIS on HST with the solar FUV spectra acquired by
SUMER on SOHO, and by UVSP on SMM, respectively. We compare the line
properties of the strongest lines, and discuss the main peculiarities
of the FUV emission of both stars.

---------------------------------------------------------
Title: Crazy Coronal Abundances
Authors: Linsky, J. L.; Osten, R.; Brown, A.
2003csss...12..869L Altcode:
Closed magnetic structures in the solar corona show enhanced abundances
of elements with first ionization potentials (FIP) less than 10
eV. Analyses of Chandra and XMM-Newton spectra of active stars show
an inverse FIP bias in which the low FIP elements are underabundant
and some high FIP elements are overabundant. We propose an explanation
for both of these abundance anomalies.

---------------------------------------------------------
Title: X-ray coronae of stars: Recent results from Chandra
Authors: Linsky, Jeffrey L.
2003AdSpR..32..917L Altcode:
I summarize and comment upon studies of stellar coronae using the
remarkable spectroscopic and imaging capabilities of the Chandra
X-ray Observatory. Nearly all types of stars are detected as X-ray
sources, except for the late-B to early-A stars and the cool giants
and supergiants. Chandra's high resolution spectroscopy provides
emission measure distributions, electron densities, coronal abundances,
and tantilizing hints about the structure and evolution of stellar
coronae. Chandra's high resolution imaging is resolving the crowded
fields of young clusters into their constituent stars from massive O
stars to brown dwarfs.

---------------------------------------------------------
Title: D/H as a Measure of Chemical Imhomogeneity in our Galaxy
Authors: Linsky, Jeffrey L.
2003astro.ph..9255L Altcode:
Accurate measurements of interstellar deuterium abundances along lines
of sight extending out to several hundred parsecs by FUSE and other
instruments is making D/H a useful tool for understanding Galactic
chemical evolution. We find that the gas inside of the Local Bubble
is chemically homogeneous, but that large variations in D/H beyond
the Local Bubble are real and challenge present concepts of chemical
evolution. A new set of models is needed that will include spatially
dependent infall of relatively unprocessed material, depletion of D
onto grains, and appropriate mixing timescales. $

---------------------------------------------------------
Title: A Search for Lyα Emission from the Astrosphere of 40 Eridani A
Authors: Wood, Brian E.; Linsky, Jeffrey L.; Müller, Hans-Reinhard;
Zank, Gary P.
2003ApJ...591.1210W Altcode:
We report the results of Hubble Space Telescope (HST) observations
of the nearby (d=5.0 pc) K1 V star 40 Eri A, which we use to search
for scattered Lyα emission surrounding the star indicative of the
interaction between the stellar wind and the interstellar medium
(ISM). Absorption from circumstellar hot H I has previously been
detected around many solar-like stars in HST observations of their
Lyα lines, so there is potential for circumstellar Lyα emission
to be detectable as well. There was previously a tentative detection
of absorption for 40 Eri A, but unfortunately, we do not detect any
circumstellar emission around 40 Eri A in our new observations. We
use hydrodynamic models of the stellar “astrosphere” (i.e., the ISM
interaction region) and radiative transfer calculations to demonstrate
that emission should have been detected for assumed mass-loss rates of
M&lt;~2 Msolar, assuming that the star is surrounded by warm,
partially neutral ISM material like that which surrounds the Sun. In
contrast, when the models are compared with the absorption data, we
find consistency with the data only for M&gt;~2 Msolar. We
believe that the most likely explanation for these apparently
contradictory results is that the previous tentative detection of
astrospheric absorption toward 40 Eri A is erroneous and that 40
Eri A probably lies within the hot ionized phase of the ISM. Thus,
there is no interstellar H I within the astrosphere for us to detect
in either absorption or emission, and no meaningful constraints on
the mass-loss rate of 40 Eri A can be derived from the HST data. Based on observations with the NASA/ESA Hubble Space Telescope,
obtained at the Space Telescope Science Institute, which is operated
by the Association of Universities for Research in Astronomy, Inc.,
under NASA contract NAS5-26555.

---------------------------------------------------------
Title: Complex C: A Low-Metallicity, High-Velocity Cloud Plunging
into the Milky Way
Authors: Tripp, Todd M.; Wakker, Bart P.; Jenkins, Edward B.; Bowers,
C. W.; Danks, A. C.; Green, R. F.; Heap, S. R.; Joseph, C. L.; Kaiser,
M. E.; Linsky, J. L.; Woodgate, B. E.
2003AJ....125.3122T Altcode: 2003astro.ph..2534T
We present evidence that high-velocity cloud (HVC) complex C is a
low-metallicity gas cloud that is plunging toward the disk and beginning
to interact with the ambient gas that surrounds the Milky Way. This
evidence begins with a new high-resolution (7 km s-1 FWHM)
echelle spectrum of 3C 351 obtained with the Space Telescope Imaging
Spectrograph (STIS). 3C 351 lies behind the low-latitude edge of complex
C, and the new spectrum provides accurate measurements of O I, Si II,
Al II, Fe II, and Si III absorption lines at the velocity of complex
C; N I, S II, Si IV, and C IV are not detected at 3 σ significance
in complex C proper. However, Si IV and C IV as well as O I, Al II,
Si II and Si III absorption lines are clearly present at somewhat
higher velocities associated with a “high-velocity ridge” (HVR)
of 21 cm emission. This high-velocity ridge has a similar morphology
to and is roughly centered on complex C proper. The similarities
of the absorption-line ratios in the HVR and complex C suggest that
these structures are intimately related. In complex C proper we find
[O/H]=-0.76+0.23-0.21. For other species the
measured column densities indicate that ionization corrections are
important. We use collisional and photoionization models to derive
ionization corrections; in both models we find that the overall
metallicity Z=0.1-0.3 Zsolar in complex C proper, but
nitrogen must be underabundant. The iron abundance indicates that the
complex C contains very little dust. The size and density implied by the
ionization models indicate that the absorbing gas is not gravitationally
confined. The gas could be pressure confined by an external medium,
but alternatively we may be viewing the leading edge of the HVC,
which is ablating and dissipating as it plunges into the Milky Way. O
VI column densities observed with the Far Ultraviolet Spectroscopic
Explorer (FUSE) toward nine QSOs/AGNs behind complex C support this
conclusion: N(O VI) is highest near 3C 351, and the O VI/H I ratio
increases substantially with decreasing latitude, suggesting that the
lower latitude portion of the cloud is interacting more vigorously
with the Galaxy. The other sight lines through complex C show some
dispersion in metallicity, but, with the current uncertainties, the
measurements are consistent with a constant metallicity throughout the
HVC. However, all of the complex C sight lines require significant
nitrogen underabundances. Finally, we compare the 3C 351 data with
high-resolution STIS observations of the nearby QSO H1821+643 to search
for evidence of outflowing Galactic fountain gas that could be mixing
with complex C. We find that the intermediate-velocity gas detected
toward 3C 351 and H1821+643 has a higher metallicity and may well be
a fountain/chimney outflow from the Perseus spiral arm. However, the
results for the higher velocity gas are inconclusive: the HVC detected
toward H1821+643 near the velocity of complex C could have a similar
metallicity to the 3C 351 gas or it could have a significantly higher
Z, depending on the poorly constrained ionization correction. Based on observations with the NASA/ESA Hubble Space Telescope,
obtained at the Space Telescope Science Institute, which is operated
by the Association of Universities for Research in Astronomy, Inc.,
under NASA contract NAS 5-26555.

---------------------------------------------------------
Title: Discovery of a Little Homunculus within the Homunculus Nebula
of η Carinae
Authors: Ishibashi, Kazunori; Gull, Theodore R.; Davidson, Kris;
Smith, Nathan; Lanz, Thierry; Lindler, Don; Feggans, Keith; Verner,
Ekaterina; Woodgate, Bruce E.; Kimble, Randy A.; Bowers, Charles W.;
Kraemer, Steven; Heap, Sarah R.; Danks, Anthony C.; Maran, Stephen
P.; Joseph, Charles L.; Kaiser, Mary Elizabeth; Linsky, Jeffrey L.;
Roesler, Fred; Weistrop, Donna
2003AJ....125.3222I Altcode:
We report long-slit spectroscopic mapping of the η Carinae nebula
obtained using the Space Telescope Imaging Spectrograph. The
observations reveal the presence of a previously unknown bipolar
emission nebula (roughly +/-2" along its major axis) embedded within
the well-known and larger Homunculus Nebula. A preliminary analysis
suggests that this embedded nebula may have originated from a minor
eruption event circa 1890, 50 years after the formation of the larger
Homunculus. Based on observations made with the NASA/ESA Hubble
Space Telescope, and supported by GO grants 7302 and 8327 from the
Space Telescope Science Institute and STIS GTO funding. This paper is a
merger of the HST GO programs (PI: K. Davidson) and STIS IDT Key Project
8483, which used orbits allocated in the shared Guaranteed Telescope
Observations. The STScI is operated by the Association of Universities
for Research in Astronomy, Inc., under NASA contract NAS 5-26555.

---------------------------------------------------------
Title: Atomic Deuterium/Hydrogen in the Galaxy
Authors: Linsky, Jeffrey L.
2003SSRv..106...49L Altcode: 2003astro.ph..9099L
An accurate value of the D/H ratio in the local interstellar medium
(LISM) and a better understanding of the D/H variations with position
in the Galactic disk and halo are vitally important questions as they
provide information on the primordial D/H ratio in the Galaxy at the
time of the protosolar nebula, and the amount of astration and mixing
in the Galaxy over time. Recent measurements have been obtained with
UV spectrographs on FUSE, HST, and IMAPS using hot white dwarfs, OB
stars, and late-type stars as background light sources against which
to measure absorption by D and H in the interstellar medium along
the lines of sight. Recent analyses of FUSE observations of seven
white dwarfs and subdwarfs provide a weighted mean value of D/H =
(1.52±0.08) × 10-5 (15.2 ± 0.8 ppm), consistent with
the value of (1.50 ± 0.10) × 10-5 (15.0 ± 1.0 ppm)
obtained from analysis of lines of sight toward nearby late-type
stars. Both numbers refer to the ISM within about 100 pc of the Sun,
which samples warm clouds located within the Local Bubble. Outside
of the Local Bubble at distances of 200 to 500 pc, analyses of far-UV
spectra obtained with the IMAPS instrument indicate a much wider range
of D/H ratios between 0.8 to 2.2 ppm. This portion of the Galactic
disk provides information on inhomogeneous astration in the Galaxy.

---------------------------------------------------------
Title: A Far Ultraviolet Spectroscopic Explorer Survey of Coronal
Forbidden Lines in Late-Type Stars
Authors: Redfield, Seth; Ayres, Thomas R.; Linsky, Jeffrey L.; Ake,
Thomas B.; Dupree, A. K.; Robinson, Richard D.; Young, Peter R.
2003ApJ...585..993R Altcode: 2002astro.ph.11363R
We present a survey of coronal forbidden lines detected in Far
Ultraviolet Spectroscopic Explorer (FUSE) spectra of nearby stars. Two
strong coronal features, Fe XVIII λ974 and Fe XIX λ1118, are
observed in 10 of the 26 stars in our sample. Various other coronal
forbidden lines, observed in solar flares, also were sought but
not detected. The Fe XVIII feature, formed at logT=6.8 K, appears
to be free of blends, whereas the Fe XIX line can be corrupted by
a C I multiplet. FUSE observations of these forbidden iron lines at
spectral resolution λ/Δλ~15,000 provides the opportunity to study
dynamics of hot coronal plasmas. We find that the velocity centroid
of the Fe XVIII feature deviates little from the stellar rest frame,
confirming that the hot coronal plasma is confined. The observed line
widths generally are consistent with thermal broadening at the high
temperatures of formation and show little indication of additional
turbulent broadening. The fastest rotating stars, 31 Com, α Aur Ab,
and AB Dor, show evidence for excess broadening beyond the thermal
component and the photospheric vsini. The anomalously large widths in
these fast-rotating targets may be evidence for enhanced rotational
broadening, consistent with emission from coronal regions extending
an additional ΔR~0.4-1.3R* above the stellar photosphere,
or represent the turbulent broadening caused by flows along magnetic
loop structures. For the stars in which Fe XVIII is detected, there is
an excellent correlation between the observed Röntgensatellit (ROSAT)
0.2-2.0 keV soft X-ray flux and the coronal forbidden line flux. As
a result, Fe XVIII is a powerful new diagnostic of coronal thermal
conditions and dynamics that can be utilized to study high-temperature
plasma processes in late-type stars. In particular, FUSE provides the
opportunity to obtain observations of important transition region
lines in the far-UV, as well as simultaneous measurements of soft
X-ray coronal emission, using the Fe XVIII coronal forbidden line.

---------------------------------------------------------
Title: Space Telescope Imaging Spectrograph Survey of Far-Ultraviolet
Coronal Forbidden Lines in Late-Type Stars
Authors: Ayres, Thomas R.; Brown, Alexander; Harper, Graham M.; Osten,
Rachel A.; Linsky, Jeffrey L.; Wood, Brian E.; Redfield, Seth
2003ApJ...583..963A Altcode:
We describe an extensive search with the Space Telescope Imaging
Spectrograph (STIS) for ultraviolet coronal (T&gt;106
K) forbidden lines in a sample of 29 F-M dwarfs, giants, and
supergiants. Measuring coronal lines in the 1150-1700 Å band with
STIS has important advantages of superior velocity resolution and an
absolute wavelength calibration compared with using the Chandra or
XMM-Newton grating spectrometers to observe permitted transitions of
the same ion stages in the kilovolt X-ray region. Fe XII λλ1242, 1349
(T~2×106 K) and Fe XXI λ1354 (107 K) are well
known from solar studies and have been reported in previous stellar
work. A search for other coronal forbidden lines in the 1200-1600 Å
region was largely negative. The few candidate identifications (e.g.,
Ar XIII λ1330 and Ca XV λ1375) are too faint to be diagnostically
useful. We add new dwarfs to the list of Fe XII detections, including
the nearby solar twin α Cen A (G2 V). Clear detections of Fe XXI were
obtained in dMe stars, active giants, a short-period RS CVn binary,
and possibly in active solar-type dwarfs. We developed a semiempirical
method for removing the C I blend that partially affects the Fe XXI
λ1354 profile. As discussed recently by Johnson et al., Capella (α
Aur; G8 III+G1 III) displays clear Fe XXI variability between Goddard
High-Resolution Spectograph (GHRS) and STIS observations 4 yr apart,
which is apparently due to a substantial decline in the contribution
from the G8 primary. We present an alternative model of the GHRS and
STIS era profiles using information in the two sets of line shapes
jointly, as well as knowledge of the behavior of Fe XXI profiles of
other late-G “clump” giants similar to Capella G8. The full survey
sample also provides a context for the apparent variability: the Fe
XXI flux of the G8 star in the GHRS spectrum is nearly identical (in
LFeXXI/Lbol) to other clump giants of similar
LX/Lbol, but it had dropped at least a factor
of 6 in the STIS measurement. The He II λ1640 Bα feature-which is
thought to be responsive to coronal irradiation-also showed significant
changes between the GHRS and STIS epochs, but the decrease in the
G8 star was much smaller than Fe XXI. The Fe XII flux displays a
correlation with the ROSAT 0.2-2 keV X-ray flux that can be described
by an α=0.5 power law. Fe XXI exhibits a steeper, perhaps linear
(α=1), correlation with the ROSAT flux down to an activity level of
LX/Lbol~10-5, below which detections
of the coronal forbidden line are rare. There is no evidence of large,
systematic Doppler shifts in either Fe XII λ1242 or Fe XXI λ1354. This
suggests that the emissions arise dominantly in confined structures,
analogous to magnetic loops on the Sun, rather than, say, in a hot
wind. The Fe XII and Fe XXI line widths generally are close to thermal
(FWHM~40-90 km s-1 at T~106.2-107.0
K), except for the Hertzsprung-gap giants 31 Comae (G0 III) and Capella
G1 and the K1 subgiant primary of HR 1099, all of which show evidence
for excess broadening in Fe XXI (Fe XII is obscured in these objects by
broad N V λ1242 features). If the excess broadening is rotational, it
implies that the hot coronae of “X-ray-deficient” 31 Com and Capella
G1 are highly extended, contrary to the compact structures suggested
by recent density estimates in a number of active coronal sources.

---------------------------------------------------------
Title: NLTE Radiative Transfer in the Extended Atmospheres and Winds
of Cool Stars
Authors: Bennett, P. D.; Harper, G. M.; Brown, A.; Linsky, J. L.
2003IAUS..210...93B Altcode:
No abstract at ADS

---------------------------------------------------------
Title: Hydrogen Walls: Mass Loss of Dwarf Stars and the Young Sun
Authors: Linsky, Jeffrey L.; Wood, Brian E.; Muller, Hans-Reinhard;
Zank, Gary
2003IAUJD...7E..39L Altcode:
The collision of an ionized stellar wind with the partially-ionized warm
gas in the interstellar medium creates a population of hot decelerated
neutral hydrogen atoms. This ""hydrogen wall"" produces a blue-shifted
absorption component in the stellar Lyman alpha emission line that has
now been detected in HST spectra of 6 dwarf stars. Comparisons of the
observed Lyman alpha line profiles with theoretical models lead to the
first very sensitive measurements of mass loss rates as small as 4 x
10-15 solar masses per year for solar-like dwarf stars. Our
program provides the first observational data (other than for the Sun)
with which to test theories for the winds of solar-like dwarf stars. We
find an empirical correlation of stellar mass loss rate with X-ray
surface flux that allows us to predict the mass loss rates of other
stars and to infer the solar wind flux at earlier times when the solar
wind may have been as much as 1000 times more massive. We mention some
important ramifications for the history of planetary atmospheres in our
solar system that of Mars in particular and for exoplanets around stars.

---------------------------------------------------------
Title: Models of H2 Fluorescence in the UV spectrum of
the CTTS TW Hya
Authors: Herczeg, Gregory J.; Wood, Brian E.; Linsky, Jeffrey L.;
Valenti, J. A.; Johns-Krull, C. M.
2003cdsf.conf..193H Altcode:
Strong UV emission lines produced in accretion shocks of classical T
Tauri stars significantly affect the chemistry of the circumstellar
disks. The surface layers of the disk close to the star are analgous
to a photo-dissociation region, only controlled by line rather than
continuum emission. A broad Ly-α emission line incident on surface
layers of the disk photoexcites the warm H2, producing
Lyman-band H2 emission. We model this H2
fluorescence to determine the temperature and depth of the warm
molecular layer. We compare these models to H2 fluorescence
observed in the UV spectra of the CTTS TW Hya obtained with HST/STIS
and FUSE. We discuss applications of this model, including disk
truncation, disk height and disk dissipation. See: Paper I:
http://xxx.lanl.gov/abs/astro-ph/0201319, in ApJ 10 June 2002.

---------------------------------------------------------
Title: Constructing Physically Realistic Models of Interstellar Gas
in Galaxies: Start with Understanding the Physics of the Local ISM
Authors: Linsky, J. L.
2003ASPC..291..188L Altcode: 2003hslf.conf..188L
No abstract at ADS

---------------------------------------------------------
Title: Winds of Late-Type Dwarf Stars - Observational Constraints
Authors: Linsky, J. L.; Wood, B. E.; Müller, H. -R.; Zank, G. P.
2003IAUS..210P.F14L Altcode:
No abstract at ADS

---------------------------------------------------------
Title: Atomic Deuterium/Hydrogen in the Galaxy
Authors: Linsky, Jeffrey L.
2003sshi.conf...49L Altcode:
No abstract at ADS

---------------------------------------------------------
Title: Warm UV H2 Emission from the Inner Disks of CTTSs
Authors: Herczeg, G. J.; Linsky, J. L.; Wood, B. E.; Valenti, J. A.;
Johns-Krull, C. M.
2003ASPC..287..307H Altcode: 2003gsfa.conf..307H
We observed Lyman-band H2 emission in the 1150--1700 Åregion
from the classical T Tauri stars TW Hya and DF Tau with HST/STIS using
the E140M grating. In the UV spectra of TW Hya and DF Tau, we detect
146 and 94 H2 lines from 19 and 11 different upper levels,
respectively, that are photoexcited by Lyα. The characteristics
of the H2 emission indicate that it is produced in a
warm layer within 2 AU of the central star. Models of this region
indicate H2 excitation temperatures of about 2300 K. We
present some implications of these results, including comparisons to
photo-dissociation regions.

---------------------------------------------------------
Title: Fluorescence and Excitation of Molecular Hydrogen in the
Circumstellar Environment of PMS Stars
Authors: Linsky, Jeffrey L.
2003fuse.prop.C067L Altcode:
TW Hya will likely have the richest and best exposed far-UV spectrum
of any member of the important class of classical T Tauri stars (CTTS)
because of its uniquely low extinction (A_v approx. 0.0), the face-on
geometry of its disk that minimizes local extinction, absence of a local
molecular cloud, and 50 pc distance (the closest for a CTTS). We request
a deep exposure of TW Hya to improve the model for H_2 fluorescence
(primarily by Lyman-alpha) as demonstrated by our analysis of the
very rich H_2 emission line spectrum in the 1170-1600 A range seen in
HSTSTIS echelle data. Since the FUSE band includes H_2 emission lines
pumped from different rovibrational states in the ground electronic
system, including much lower energy states than are sampled by STIS,
we can study the population of rovibrational states within the ground
electronic state, search for other fluorescent channels, infer the shape
of the stellar Lyman-alpha line, study possible excitation mechanisms,
and derive a lower limit for the amount of H_2 that is located in the
stellar disk. In a short (2.1 ks) test spectrum of TW Hya the probable
detection of the two H_2 emission lines demonstrates the feasibility
of our program. The requested spectrum will also provide excellent
profiles of the OVI emission lines that are needed to set upper limits
on the amount of H_2 present in accretion columns andor outflows and
to compare with models of line formation in accretion flows along
magnetic flux tubes connecting the disk to polar magnetic starspots.

---------------------------------------------------------
Title: X-Rays from Young Stars and Eggs in the Eagle Nebula (M16)
Authors: Linsky, Jeffrey L.; Gagne, Marc; Mytyk, Anna
2003IAUS..221P.207L Altcode:
The Chandra X-ray Observatory observed the Eagle Nebula (M16) a young
star forming region containing the dark columns of dust and cold
molecular gas known as the ""Pillars of Creation"" or ""elephant
trunks"". We identify more than 1000 X-ray sources coincident with
K-band stars that are premain sequence stars ranging in spectral type
from O to M. A handful of the hard X-ray sources in the pillars are
spatially coincident with deeply embedded young stellar objects seen
in JHK images. However none of the X-ray sources are associated with
the evaporating gaseous globules (EGGs) first observed by Hester et
al. (1996).

---------------------------------------------------------
Title: Chandra, Extreme Ultraviolet Explorer, and Very Large Array
Observations of the Active Binary System σ2 Coronae
Borealis
Authors: Osten, Rachel A.; Ayres, Thomas R.; Brown, Alexander; Linsky,
Jeffrey L.; Krishnamurthi, Anita
2003ApJ...582.1073O Altcode:
We present the results of a coordinated observing campaign on the
short-period RS CVn binary σ2 Coronae Borealis (F6V+G0V
Porb=1.14 days) with the Very Large Array, the Extreme
Ultraviolet Explorer, and the Chandra X-Ray Observatory High-Energy
Transmission Grating Spectrometer. The radio emission is consistent with
previously determined quiescent gyrosynchrotron properties. Multiple
flares were seen with Extreme Ultraviolet Explorer, five occurring
within two consecutive orbital periods. The first of these flares
was observed with Chandra. The Chandra observations of σ2
CrB showed no systematic variations of line fluxes, widths, or Doppler
shifts with orbital phase, nor any response in line width or offset
due to the flare. This is consistent with both stars being equally
active coronal emitters. We have developed a self-consistent method of
spectral analysis to derive information from the line and continuum
emissions concerning the distribution of plasma with temperature and
elemental abundances. A bimodal temperature distribution is appropriate
for both quiescent and flare intervals, with a stable peak at 6-8 MK and
another variable enhancement at higher temperatures, with evidence for
significant contribution from temperatures up to 50 MK during the flare,
compared to 30 MK during quiescence. The iron abundance is subsolar
during quiescence but is enriched by about a factor of 2 during a
large flare seen with Chandra. The noble gas elements neon and argon
show elevated abundances with respect to iron, but there is no clear
evidence for any first ionization potential-based abundance pattern
during quiescence or the flare. We have determined coronal electron
densities from the helium-like ions O VII, Ne IX, Mg XI, and Si XIII,
which imply densities &gt;=1010 cm-3. There is
a small enhancement in the electron densities derived for the flare,
but it is not statistically significant. We call attention to electron
temperature constraints provided by the ratios of 1s2
1S0-1snp 1P1 transitions
of the helium-like ions O VII, Ne IX, Mg XI, and Si XIII. The derived
coronal electron pressures change by 1-2 orders of magnitude over a 25%
change in temperature, implying nonisobaric coronal conditions. We
find no evidence for significant departures from the effectively
thin coronal assumption. The electron densities inferred from the
soft X-ray spectra are inconsistent with cospatial gyrosynchrotron
emission; further observations are necessary to discriminate the
relative locations of the radio and soft X-ray-emitting plasma.

---------------------------------------------------------
Title: Elemental Abundances and Ionization States within the Local
Interstellar Cloud Derived from Hubble Space Telescope and Far
Ultraviolet Spectroscopic Explorer Observations of the Capella Line
of Sight
Authors: Wood, Brian E.; Redfield, Seth; Linsky, Jeffrey L.; Sahu,
M. S.
2002ApJ...581.1168W Altcode: 2002astro.ph..8214W
We use ultraviolet spectra of Capella from the Hubble Space Telescope
and Far Ultraviolet Spectroscopic Explorer satellites to study
interstellar absorption lines from the Local Interstellar Cloud
(LIC). Measurements of these lines are used to empirically determine
the ionization states of carbon, nitrogen, and silicon in the LIC,
for comparison with the predictions of theoretical photoionization
models. We find that the observed ionization states are consistent with
previously published photoionization predictions. Total abundances are
determined for the elements mentioned above, and others, for comparison
with solar abundances. Magnesium, aluminum, silicon, and iron are all
depleted by at least a factor of 10 toward Capella. The abundances of
carbon, nitrogen, and oxygen are essentially solar, although the error
bars are large enough to also allow depletions of about a factor of 2
for these elements. Based on observations made with the NASA-CNES-CSA
Far Ultraviolet Spectroscopic Explorer. FUSE is operated for NASA by the
Johns Hopkins University under NASA contract NAS5-32985. Also based on
observations with the NASA/ESA Hubble Space Telescope, obtained from
the Data Archive at the Space Telescope Science Institute, which is
operated by the Association of Universities for Research in Astronomy,
Inc., under NASA contract NAS5-26555.

---------------------------------------------------------
Title: A Far Ultraviolet Spectroscopic Explorer Survey of Late-Type
Dwarf Stars
Authors: Redfield, Seth; Linsky, Jeffrey L.; Ake, Thomas B.; Ayres,
Thomas R.; Dupree, A. K.; Robinson, Richard D.; Wood, Brian E.; Young,
Peter R.
2002ApJ...581..626R Altcode:
We describe the 910-1180 Å spectra of seven late-type dwarf stars
obtained with the Far Ultraviolet Spectroscopic Explorer (FUSE)
satellite. The stars include Altair (A7 IV), Procyon (F5 IV-V), α
Cen A (G2 V), AB Dor (K1 V), α Cen B (K2 V), ɛ Eri (K2 V), and AU
Mic (M0 V). We present line identifications, fluxes, Doppler shifts,
and widths. Doppler shifts are measured with respect to heliocentric
wavelength scales determined from interstellar absorption lines, and
are compared with transition region line shifts seen in Hubble Space
Telescope (HST) ultraviolet spectra. For the warmer stars the O VI lines
extend the trend of increasing redshift with line formation temperature,
but for the cooler stars the O VI line redshifts are essentially
zero. The C III and O VI lines of most stars in the sample are best
fit with two Gaussians, and we confirm the correlation of increasing
importance of the broad component with increasing stellar activity. The
nonthermal velocities of the narrow component are subsonic and exhibit
a trend toward larger velocities with decreasing surface gravity, while
the nonthermal velocities of the broad components show no obvious trend
with stellar gravity. The C III and O VI lines of Altair show unique
broad horned profiles. Two flares were observed on AU Mic. One shows
increasing continuum flux to shorter wavelengths, which we interpret as
free-free emission from hot plasma, and relatively narrow, redshifted
C III and O VI emission. The other shows very broad line profiles.

---------------------------------------------------------
Title: Radio and X-ray Emission Properties of Magnetic Chemically
Peculiar Stars
Authors: Drake, S. A.; Linsky, J. L.; Wade, G. A.
2002AAS...201.3306D Altcode: 2002BAAS...34.1156D
Magnetic Chemically Peculiar (MCP) stars have been known since
the mid 1980's to be radio emitters, with high radio luminosities,
moderate circular polarization, and fairly flat microwave spectra,
which are similar to the radio properties of active cool stars such
as RS CVns. The radio emission mechanism in both cases is believed
to be gyrosynchrotron emission from mildly relativistic nonthermal
electrons. By 2002, about 120 MCP stars have been observed in the
radio, and 25% detected as radio emitters. Radio sources have been
found among all types of MCP stars except the subclass of A-type
SrCrEu-type stars. The radio luminosities of MCP stars are correlated
with increasing effective temperature and magnetic field strength, and
(with less confidence) with decreasing rotational period. The status of
MCP star X-ray emission is much less clear. Although many MCP stars have
been associated with X-ray sources in the last two decades, there is
still uncertainty as to whether X-ray emission is an intrinsic property
of this class, since is not obviously correlated with any of the other
stellar and/or radio properties. In many cases, the X-ray emission may,
in fact, be due to a lower-mass stellar companion rather than to the
MCP star. This lack of correlation with the radio properties is in
stark contrast with active late-type stars where the X-ray and radio
emission levels are well-correlated. We discuss the implications of the
observed radio and X-ray properties of MCP stars on the various models
proposed to explain the high-energy emission from these stars, such as
the magnetospheric and the magnetically confined wind shock models,
and suggest some observational tests which may help to constrain or
refine them.

---------------------------------------------------------
Title: Historical Perspective - Lessons Learned and Lessons to
be Learned
Authors: Linsky, J. L.
2002ASPC..277....3L Altcode: 2002sccx.conf....3L
No abstract at ADS

---------------------------------------------------------
Title: Spectral Imaging of Herbig Ae Stars in Lyman Alpha: Jets,
Disk Winds, and Envelopes
Authors: Woodgate, B.; Grady, C.; Heap, S.; Danks, A.; Vieira, G.;
Gull, T.; Brown, A.; Wilkinson, E.; Harper, G.; Herzceg, G.; Linsky, J.
2002AAS...201.2019W Altcode: 2002BAAS...34.1136W
We present HST/STIS long slit, R=10,000 spectroscopy of 2 Herbig Ae
stars at Lyman alpha. HD 104237 is driving a jet which can be traced
1.05" (120 AU) from the star at PA=-28 degrees. The fainter counter
jet can be traced 2.8" (320 AU) at PA=152 degrees. As for HD 163296,
the wind terminal velocity in Lyman alpha is the velocity of the
innermost knot in the jet. This suggests that the high velocity
wind component originates in the jet at r&lt;0.025" (2.9 AU). Long
slit spectra of the t&gt;10 Myr HD 100546 system reveal extended
Lyman alpha, continuum and fluorescent molecular hydrogen emission
along both the disk major and minor axes. The emission is symmetric
along the system major axis, with Lyman alpha extending 2" (206 AU)
from the star. Along the minor axis, emission is seen along the NE
side of the star, where it can be traced 3.3" (312 AU) from the star,
but is not seen SW of the star. The spatial distribution of emission
in this system is consistent with material from the envelope rather
than the protoplanetary disk. Unlike the younger Herbig Ae stars, HD
100546 does not appear to be driving a bipolar jet, but instead shows
blue-shifted Si III emission, similar to the C III 1175. A emission in
beta Pictoris. Si III absorption can be seen in silhouette against the
reflection nebulosity and is preferentially observed to the NE of the
star along the minor axis where it can be traced 0.65" (68 AU). Over
this distance the absorption displaces by 80 km/s, providing the first
direct detection of a disk wind. Comparison of the STIS data from the
two epochs also reveals that the star is intermittently obscured in
Lyman alpha by an opaque cloud blocking the inner 0.3" (30 AU) in our
2002 June observation.

---------------------------------------------------------
Title: HST/STIS High Resolution Echelle Spectra of α Centauri A
(G2 V)
Authors: Linsky, J. L.; Pagano, I.; Valenti, J.; Gagne, M.; Duncan,
D. K.
2002AAS...201.1209L Altcode: 2002BAAS...34.1114L
We report on HST/STIS observations of the G2 V star α Centauri A (HD
128620), a near twin to the Sun. The high resolution echelle spectra
obtained with the E140H and E230H gratings cover the complete spectral
range 1133--3150 Å with a resolution of 2.6 km s-1. This
beautiful spectrum contains a very large number of emission and
absorption lines. We present our study of the E140H spectrum. Of
particular interest are the shapes of the transition region lines
(e.g., Si IV, C IV), the density sensitive intersystem lines, and
the He II 1640 Å line. Our purpose is to compare the α Cen A UV
spectrum with the solar spectrum to determine how the atmosphere and
heating processes in α Cen A differ from the Sun as a result of the
small differences in gravity, age, and chemical composition of the
two stars. The α Cen A spectral atlas can serve as a useful spectral
atlas for the Sun as a star because the STIS spectrum is a true full
disk average with limb darkening, covers a broad spectral range, has
very high spectral resolution, and has excellent wavelength precision
and absolute flux calibration. This work is supported by grant GO-07263
from the Space Telescope Science Institute, which is operated by AURA,
Inc. under NASA contract NAS 5-26555.

---------------------------------------------------------
Title: Physical Structure of the Local Interstellar Medium
Authors: Redfield, S.; Linsky, J. L.
2002AAS...201.4708R Altcode: 2002BAAS...34.1179R
The physical structure and morphology of the interstellar medium
(ISM) that surrounds our solar system directly effects the heliosphere
and the interplanetary environment. Due to its proximity, the local
interstellar medium (LISM) is the only interstellar environment that
allows for a detailed three-dimensional study of ISM phenomena. High
resolution ultraviolet absorption spectra of nearby stars and the
intervening interstellar material, observed by the Hubble Space
Telescope, provide important information about the chemical abundance,
ionization, temperature, kinematics, density, morphology, and turbulent
structures of the LISM. The number of useful observations is large
enough that we can start analyzing the LISM as a three-dimensional
object, as opposed to focusing on individual sightlines. We present
the results of high resolution observations of the LISM obtained by
the Hubble Space Telescope. Our focus will be on the temperature and
turbulent velocity structure of the Local Interstellar Cloud (LIC) and
other nearby clouds. Understanding the physical characteristics of these
structures is necessary if we are to discuss the morphology of the LISM,
its evolution, origin, impact on the heliosphere and our solar system,
and applicability to galactic and extragalactic ISM environments.

---------------------------------------------------------
Title: Chandra HETGS Observations of the Active Binary σ2
Coronae Borealis
Authors: Osten, R. A.; Brown, A.; Ayres, T. R.; Linsky, J. L.
2002ASPC..277..239O Altcode: 2002sccx.conf..239O
No abstract at ADS

---------------------------------------------------------
Title: Limits on Chromospheres and Convection among the Main-Sequence
A Stars
Authors: Simon, Theodore; Ayres, Thomas R.; Redfield, Seth; Linsky,
Jeffrey L.
2002ApJ...579..800S Altcode:
In deeply convective stars, the nonthermal energy required
to heat the chromosphere ultimately is supplied by turbulent
magnetoconvection. Because the early and middle A stars have very
shallow convective layers, they are not expected to produce enough
magnetoconvective power to sustain luminous chromospheres or hot
coronae. Here we describe a search for chromospheric emission in the
far-ultraviolet (905-1185 Å) spectra of seven main-sequence A stars,
based on observations from the Far Ultraviolet Spectroscopic Explorer
(FUSE) telescope. Our survey spans the interval in effective temperature
along the main sequence over which powerful subsurface convection zones
and hence chromospheric emission are expected to vanish. The presence
or absence of high-temperature emissions in our FUSE spectra therefore
can be used to identify the locus for the transition from convective to
radiative envelopes-a change in stellar structure that is difficult to
assess by other means. We present our observations and analysis of the
subcoronal emission lines of C III λλ977, 1175 and O VI λλ1032,
1037, which bracket a range in formation temperatures from 50,000
to 300,000 K. To supplement our FUSE observations, we also report
Goddard High Resolution Spectrograph measurements of Si III λ1206 and
H I Lyα λ1215, obtained from archival observations of the Hubble
Space Telescope, as well as X-ray measurements from previous ROSAT
survey and pointed observations. We detected C III and O VI emission
features in the FUSE spectra of the coolest stars of our sample,
at Teff&lt;~8200 K. When normalized to the bolometric
luminosities, the detected emission-line fluxes are comparable to
solar values. We detected none of the hotter stars in our survey at
Teff&gt;=8300 K. Upper limits on the normalized flux in some
instances approach 40 times less than solar. Within an uncertainty in
the effective temperature scale of up to several hundred kelvins, our
FUSE observations indicate that the transition between convective and
radiative stellar envelopes takes place at, or very near, the point
along the main sequence where stellar structure models predict and,
moreover, that the changeover occurs very abruptly, over a temperature
interval no greater than ~100 K in width. Our FUSE sample also includes
two binary stars. In both cases, the narrow UV line profiles we have
observed suggest that the high-temperature emission is most likely
associated with the late-type companions rather than the A stars
themselves. Based on observations made with the NASA-CNES-CSA Far
Ultraviolet Spectroscopic Explorer, operated for NASA by Johns Hopkins
University under NASA contract NAS5-32985.

---------------------------------------------------------
Title: The deuterium-to-oxygen ratio in the local interstellar medium
from FUSE observations
Authors: Hébrard, G.; Friedman, S. D.; Kruk, J. W.; Lehner, N.;
Lemoine, M.; Linsky, J. L.; Moos, H. W.; Oliveira, C. M.; Sembach,
K. R.; Sonneborn, G.; Vidal-Madjar, A.; Wood, B. E.
2002P&SS...50.1169H Altcode:
Since HI, OI, and DI have nearly the same ionization potential,
the deuterium-to-oxygen ratio (D/O) is an important tracer of the
D/H ratio and its putative spatial variations. D/O is indeed very
sensitive to astration, both because of deuterium destruction and
oxygen production. Here, we present DI, OI, and NI interstellar column
density measurements performed with the Far Ultraviolet Spectroscopic
Explorer (FUSE) on eight nearby lines of sight. The first results of
this survey show that D/O is a better D/H proxy than D/N, and that D/O
is constant in the local interstellar medium. The mean value is D/
O=3.81(±0.18)×10 -2 (1σ) . This result supports both
D/H and O/H stability in the LISM.

---------------------------------------------------------
Title: Chandra Observations of the Pleiades Open Cluster: X-Ray
Emission from Late B- to Early F-Type Binaries
Authors: Daniel, Kathryne J.; Linsky, Jeffrey L.; Gagné, Marc
2002ApJ...578..486D Altcode: 2002astro.ph..4131D
We present the analysis of a 38.4 and 23.6 ks observation of the core
of the Pleiades open cluster. The Advanced CCD Imaging Spectrometer
on board the Chandra X-Ray Observatory detected 99 X-ray sources in
a 17'×17' region, including 18 of 23 Pleiades
members. Five candidate Pleiades members have also been detected,
confirming their cluster membership. Fifty-seven sources have no
optical or near-infrared counterparts to limiting magnitudes V=22.5
and J=14.5. The unidentified X-ray sources are probably background
active galactic nuclei and not stars. The Chandra field of view
contains seven intermediate-mass cluster members. Five of these,
HII 980 (B6+G), HII 956 (A7+F6), HII 1284 (A9+K), HII 1338 (F3+F6),
and HII 1122 (F4+K), are detected in this study. All but HII 1284
have high X-ray luminosity and soft X-ray spectra. HII 1284 has X-ray
properties comparable to nonflaring K-type stars. Since all five stars
are visual or spectroscopic binaries with X-ray properties similar
to F-G stars, the late-type binary companions are probably producing
the observed coronal X-ray emission. Strengthening this conclusion
is the nondetection by Chandra of two A stars, HII 1362 (A7, no known
companion) and HII 1375 (A0+A SB) with X-ray luminosity upper limits
27-54 times smaller than HII 980 and HII 956, the B6-A7 stars with
cooler companions. Despite the low number statistics, the Chandra data
appear to confirm the expectation that late B and A stars are not strong
intrinsic X-ray sources. The ACIS spectra and hardness ratios suggest a
gradual increase in coronal temperature with decreasing mass from F4 to
K. M stars appear to have somewhat cooler coronae than active K stars.

---------------------------------------------------------
Title: Measured Mass-Loss Rates of Solar-like Stars as a Function
of Age and Activity
Authors: Wood, Brian E.; Müller, Hans-Reinhard; Zank, Gary P.;
Linsky, Jeffrey L.
2002ApJ...574..412W Altcode: 2002astro.ph..3437W
Collisions between the winds of solar-like stars and the local
interstellar medium result in a population of hot hydrogen gas
surrounding these stars. Absorption from this hot H I can be detected
in high-resolution Lyα spectra of these stars from the Hubble Space
Telescope. The amount of absorption can be used as a diagnostic
for the stellar mass-loss rate. We present new mass-loss rate
measurements derived in this fashion for four stars (ɛ Eri, 61 Cyg A,
36 Oph AB, and 40 Eri A). Combining these measurements with others,
we study how mass loss varies with stellar activity. We find that
for the solar-like GK dwarfs, the mass loss per unit surface area
is correlated with X-ray surface flux. Fitting a power law to this
relation yields M~F1.15+/-0.20X. The active M
dwarf Proxima Cen and the very active RS CVn system λ And appear to be
inconsistent with this relation. Since activity is known to decrease
with age, the above power-law relation for solar-like stars suggests
that mass loss decreases with time. We infer a power-law relation of
M~t-2.00+/-0.52. This suggests that the solar wind may have
been as much as 1000 times more massive in the distant past, which
may have had important ramifications for the history of planetary
atmospheres in our solar system, that of Mars in particular. Based
on observations with the NASA/ESA Hubble Space Telescope, obtained
at the Space Telescope Science Institute, which is operated by the
Association of Universities for Research in Astronomy, Inc., under
NASA contract NAS5-26555.

---------------------------------------------------------
Title: Comparison of the spectrum of a sunspot-like star with
a sunspot
Authors: Linsky, J. L.; Ayres, T. R.; Brown, A.; Osten, R. A.
2002AN....323..321L Altcode:
A typical sunspot umbra has an effective temperature, gravity,
and strong magnetic field strength similar to the dM1e star AU
Microscopii. We compare STIS, Chandra, EUVE, and FUSE spectra of AU Mic
with typical spectra of sunspots to characterize the major differences
and then compare models of AU Mic with sunspot models. We find that the
emission, heating rates, and differential emission measure distributions
are very different for AU Mic and sunspots, and conclude that the root
cause of the difference lies in the very different geometries of the
two magnetic fields.

---------------------------------------------------------
Title: Opacity in the upper atmosphere of AU Mic
Authors: Bloomfield, D. S.; Mathioudakis, M.; Christian, D. J.;
Keenan, F. P.; Linsky, J. L.
2002A&A...390..219B Altcode:
In this paper we investigate the validity of the optically thin
assumption in the transition region of the late-type star AU Mic. We use
Far-Ultraviolet Spectroscopic Explorer (FUSE) observations of the C Iii
multiplet and O Vi resonance lines, hence yielding information at two
different levels within the atmosphere. Significant deviations from the
optically thin fluxes are found for C Iii in both quiescent and flare
spectra, where only 60% of the flux is actually observed. This could
explain the apparent deviation of C Iii observed in emission measure
distributions. We utilize escape probabilities for both homogeneous and
inhomogeneous geometries and calculate optical depths as high as 10 for
the C Iii 1175.71 Åcomponent of the multiplet. Using a lower limit
to the electron density (1011 cm-3) we derive
an effective thickness of &lt;100 km for the scattering layer. The
emission originates from very small and compact regions, consistent
with a filling factor of 10-5 derived for the flare plasma.

---------------------------------------------------------
Title: Using the HST Archive to Compile a Comprehensive Inventory
of LISM Structure and Physical Properties
Authors: Linsky, Jeffrey
2002hst..prop.9525L Altcode: 2002hst..prop.5871L
Analysis of high resolution archive spectra for at least 24 lines of
sight to stars located within 100 pc, together with 41 lines of sight
previously analyzed, will allow us to develop a comprehensive model
for the local ISM describing the structure and physical properties of
the important warm clouds. As Stage I of this program, we have already
analyzed the STIS E230H and GHRS Echelle-B spectra of the Mg II and
Fe II lines for these 24 lines of sight to determine the kinematics
and morphological structure of these clouds. The requested archive
investigation is Stage II of our program in which we will analyze
the interstellar absorption lines of H I, D I, C II, N I, O I, Mg I,
Al II, Si II, and Mn II in high resolution spectra for these lines of
sight to determine the temperature, turbulent velocity, ionization,
chemical abundances, and depletions in these clouds. When available
we will include analyses of FUSE and optical spectra of additional
ions for these same lines of sight. Our objective is to determine the
physical properties {and their spatial variations} of the warm gas
in these clouds for comparison with theoretical models based on the
radiation field in the LISM. This comprehensive study of the warm gas
in the LISM will become the guide for understanding physical processes
in the ISM elsewhere in the disk of the Galaxy. This work will be a
major part of Seth Redfield's PhD thesis.

---------------------------------------------------------
Title: The Far-Ultraviolet Spectrum of TW Hydrae. I. Observations
of H2 Fluorescence
Authors: Herczeg, Gregory J.; Linsky, Jeffrey L.; Valenti, Jeff A.;
Johns-Krull, Christopher M.; Wood, Brian E.
2002ApJ...572..310H Altcode: 2002astro.ph..1319H
We observed the classical T Tauri star TW Hya with the Space Telescope
Imaging Spectrograph on board the Hubble Space Telescope (HST) using
the E140M grating, from 1150 to 1700 Å, with the E230M grating,
from 2200 to 2900 Å, and with the Far Ultraviolet Spectroscopic
Explorer from 900 to 1180 Å. Emission in 146 Lyman-band H2
lines, representing 19 progressions, dominates the spectral region
from 1250 to 1650 Å. The total H2 emission line flux
is 1.94×10-12 ergs cm-2 s-1,
which corresponds to 1.90×10-4 Lsolar at
TW Hya's distance of 56 pc. A broad stellar Lyα line photoexcites
the H2 from excited rovibrational levels of the ground
electronic state to excited electronic states. The C II λ1335 doublet,
C III λ1175 multiplet, and C IV λ1550 doublet also electronically
excite H2. The velocity shift of the H2 lines
is consistent with the photospheric radial velocity of TW Hya, and
the emission is not spatially extended beyond the 0.05" resolution of
HST. The H2 lines have an intrinsic FWHM of 11.91+/-0.16
km s-1. One H2 line is significantly weaker
than predicted by this model because of C II wind absorption. We also
do not observe any H2 absorption against the stellar Lyα
profile. From these results we conclude that the H2 emission
is more consistent with an origin in a disk rather than in an outflow
or circumstellar shell. We also analyze the hot accretion region lines
(e.g., C IV, Si IV, O VI) of TW Hya, which are formed at the accretion
shock, and discuss some reasons why Si lines appear significantly weaker
than other TR region lines. Based on observations with the NASA/ESA
Hubble Space Telescope, obtained at the Space Telescope Science
Institute, which is operated by the Association of Universities for
Research in Astronomy, Inc., under NASA contract NAS5-26555.

---------------------------------------------------------
Title: The Diagnostic Potential of Heliospheric and Astrospheric
H~I Lyα Absorption Detected by HST
Authors: Wood, B. E.; Mueller, H.; Zank, G. P.; Linsky, J. L.
2002AGUSMSH32C..03W Altcode:
The collision between the solar wind and the local interstellar medium
(LISM) creates a population of hot hydrogen gas that permeates the
heliosphere. Absorption from this heliospheric hydrogen has been
detected in Hubble Space Telescope (HST) observations of the H~I
Lyα lines of nearby stars. Not only that, but absorption from
“astrospheric” hydrogen surrounding the stars has also been
detected. The heliospheric H~I absorption provides contraints on
the properties of the LISM surrounding the Sun. The astrospheric
H~I absorption provides constraints on the stellar wind properties
of the observed stars, representing the first opportunity to study
solar-like winds around other stars. These stellar wind studies of
stars of varying ages and activity levels can also lead to estimates
of the mass loss history of the Sun.

---------------------------------------------------------
Title: Deuterium Abundance toward WD 2211-495: Results from the
FUSE Mission
Authors: Hébrard, G.; Lemoine, M.; Vidal-Madjar, A.; Désert, J. -M.;
Lecavelier des Étangs, A.; Ferlet, R.; Wood, B. E.; Linsky, J. L.;
Kruk, J. W.; Chayer, P.; Lacour, S.; Blair, W. P.; Friedman, S. D.;
Moos, H. W.; Sembach, K. R.; Sonneborn, G.; Oegerle, W. R.; Jenkins,
E. B.
2002ApJS..140..103H Altcode:
We present a deuterium abundance analysis of the line of
sight toward the white dwarf WD 2211-495 observed with the Far
Ultraviolet Spectroscopic Explorer (FUSE). Numerous interstellar
lines are detected on the continuum of the stellar spectrum. A
thorough analysis was performed through the simultaneous fit of
interstellar absorption lines detected in the four FUSE channels
of multiple observations with different slits. We excluded all
saturated lines in order to reduce possible systematic errors on
the column density measurements. We report the determination of the
average interstellar D/O and D/N ratios along this line of sight
at the 95% confidence level: D/O=(4.0+/-1.2)×10-2 and
D/N=(4.4+/-1.3)×10-1. In conjunction with FUSE observations
of other nearby sight lines, the results of this study will allow
a deeper understanding of the present-day abundance of deuterium in
the local interstellar medium and its evolution with time. Based on
observations made with the NASA-CNES-CSA Far Ultraviolet Spectroscopic
Explorer (FUSE), which is operated for NASA by Johns Hopkins University
under NASA contract NAS 5-32985.

---------------------------------------------------------
Title: Abundances of Deuterium, Nitrogen, and Oxygen toward HZ 43A:
Results from the FUSE Mission
Authors: Kruk, J. W.; Howk, J. C.; André, M.; Moos, H. W.; Oegerle,
W. R.; Oliveira, C.; Sembach, K. R.; Chayer, P.; Linsky, J. L.;
Wood, B. E.; Ferlet, R.; Hébrard, G.; Lemoine, M.; Vidal-Madjar,
A.; Sonneborn, G.
2002ApJS..140...19K Altcode: 2002astro.ph..1298K
We present an analysis of interstellar absorption along the line of
sight to the nearby white dwarf star HZ 43A. The distance to this
star is 68+/-13 pc, and the line of sight extends toward the north
Galactic pole. Column densities of O I, N I, and N II were derived from
spectra obtained by the Far Ultraviolet Spectroscopic Explorer (FUSE),
the column density of D I was derived from a combination of our FUSE
spectra and an archival Hubble Space Telescope (HST) GHRS spectrum, and
the column density of H I was derived from a combination of the GHRS
spectrum and values derived from Extreme Ultraviolet Explorer (EUVE)
data obtained from the literature. We find the following abundance
ratios (with 2 σ uncertainties): DI/HI=(1.66+/-0.28)×10-5,
OI/HI=(3.63+/-0.84)×10-4, and
NI/HI=(3.80+/-0.74)×10-5. The N II column density
was slightly greater than that of N I, indicating that ionization
corrections are important when deriving nitrogen abundances. Other
interstellar species detected along the line of sight were C II, C III,
O VI, Si II, Ar I, Mg II, and Fe II; an upper limit was determined
for N III. No elements other than H I were detected in the stellar
photosphere. Based on observations made with the NASA-CNES-CSA Far
Ultraviolet Spectroscopic Explorer, which is operated for NASA by
Johns Hopkins University under NASA contract NAS 5-32985.

---------------------------------------------------------
Title: A Search for Astrospheric Lyα Emission Around 40 Eri A
Authors: Wood, B. E.; Linsky, J. L.; Müller, H. -R.; Zank, G. P.
2002AAS...200.7405W Altcode: 2002BAAS...34..770W
Hydrodynamic models of our heliosphere predict that the heliosphere
should be filled with hot neutral hydrogen gas created by the collision
between the solar wind and the surrounding interstellar medium. In
UV spectra from the Hubble Space Telescope (HST), heliospheric H I
Lyα absorption from this hot H I has been detected. Absorption from
analogous “astrospheric” H I surrounding many other solar-like stars
has also been detected. In principle, this astrospheric H I previously
seen only in absorption might also be observable in emission, since
the H I will scatter stellar Lyα photons. We report on an attempt
using HST to detect astrospheric Lyα emission around the nearby K1
V star 40 Eri A, for which a tentative detection of astrospheric H
I absorption already exists. This work is supported by NASA grant
NAG5-9041, and through grant GO-08237.01-A from STScI.

---------------------------------------------------------
Title: Deuterium Abundance toward G191-B2B: Results from the FUSE
Mission
Authors: Lemoine, M.; Vidal-Madjar, A.; Hébrard, G.; Désert, J. -M.;
Ferlet, R.; Lecavelier des Étangs, A.; Howk, J. C.; André, M.;
Blair, W. P.; Friedman, S. D.; Kruk, J. W.; Lacour, S.; Moos, H. W.;
Sembach, K.; Chayer, P.; Jenkins, E. B.; Koester, D.; Linsky, J. L.;
Wood, B. E.; Oegerle, W. R.; Sonneborn, G.; York, D. G.
2002ApJS..140...67L Altcode:
High-resolution spectra of the hot white dwarf G191-B2B, covering the
wavelength region 905-1187 Å, were obtained with the Far Ultraviolet
Spectroscopic Explorer (FUSE). These data were used in conjunction
with existing high-resolution Hubble Space Telescope Space Telescope
Imaging Spectrograph (STIS) observations to evaluate the total H I,
D I, O I, and N I column densities along the line of sight. Previous
determinations of N(D I) based upon GHRS and STIS observations were
controversial as a result of the saturated strength of the D I Lyα
line. In the present analysis the column density of D I has been
measured using only the unsaturated Lyβ and Lyγ lines observed by
FUSE. A careful inspection of possible systematic uncertainties tied
to the modeling of the stellar continuum or to the uncertainties in
the FUSE instrumental characteristics has been performed. The column
densities derived are logN(DI)=13.40+/-0.07, logN(OI)=14.86+/-0.07, and
logN(NI)=13.87+/-0.07, quoted with 2 σ uncertainties. The measurement
of the H I column density by profile fitting of the Lyα line has
been found to be uncertain. If additional weak, hot interstellar
components are added to the three detected clouds along the line of
sight, the H I column density can be reduced quite significantly,
even though the signal-to-noise ratio and spectral resolution at
Lyα are excellent. The new estimate of N(H I) toward G191-B2B reads
logN(HI)=18.18+/-0.18 (2 σ), so that the average D/H ratio on the line
of sight is D/H=(1.66+0.9-0.6)×10-5
(2 σ). This work is based on data obtained for the Guaranteed Time Team
by the NASA-CNES-CSA FUSE mission operated by Johns Hopkins University.

---------------------------------------------------------
Title: Abundances of Deuterium, Nitrogen, and Oxygen in the Local
Interstellar Medium: Overview of First Results from the FUSE Mission
Authors: Moos, H. W.; Sembach, K. R.; Vidal-Madjar, A.; York, D. G.;
Friedman, S. D.; Hébrard, G.; Kruk, J. W.; Lehner, N.; Lemoine, M.;
Sonneborn, G.; Wood, B. E.; Ake, T. B.; André, M.; Blair, W. P.;
Chayer, P.; Gry, C.; Dupree, A. K.; Ferlet, R.; Feldman, P. D.; Green,
J. C.; Howk, J. C.; Hutchings, J. B.; Jenkins, E. B.; Linsky, J. L.;
Murphy, E. M.; Oegerle, W. R.; Oliveira, C.; Roth, K.; Sahnow, D. J.;
Savage, B. D.; Shull, J. M.; Tripp, T. M.; Weiler, E. J.; Welsh,
B. Y.; Wilkinson, E.; Woodgate, B. E.
2002ApJS..140....3M Altcode: 2001astro.ph.12519M
Observations obtained with the Far Ultraviolet Spectroscopic Explorer
(FUSE) have been used to determine the column densities of D I, N I,
and O I along seven sight lines that probe the local interstellar
medium (LISM) at distances from 37 to 179 pc. Five of the sight lines
are within the Local Bubble, and two penetrate the surrounding H
I wall. Reliable values of N(H I) were determined for five of the
sight lines from Hubble Space Telescope (HST) data, International
Ultraviolet Explorer (IUE) data, and published Extreme Ultraviolet
Explorer (EUVE) measurements. The weighted mean of D I/H I for these
five sight lines is (1.52+/-0.08)×10-5 (1 σ uncertainty
in the mean). It is likely that the D I/H I ratio in the Local Bubble
has a single value. The D I/O I ratio for the five sight lines within
the Local Bubble is (3.76+/-0.20)×10-2. It is likely
that O I column densities can serve as a proxy for H I in the Local
Bubble. The weighted mean for O I/H I for the seven FUSE sight lines
is (3.03+/-0.21)×10-4, comparable to the weighted mean
(3.43+/-0.15)×10-4 reported for 13 sight lines probing
larger distances and higher column densities. The FUSE weighted mean
of N I/H I for five sight lines is half that reported by Meyer and
colleagues for seven sight lines with larger distances and higher
column densities. This result combined with the variability of O I/N I
(six sight lines) indicates that at the low column densities found in
the LISM, nitrogen ionization balance is important. Thus, unlike O I,
N I cannot be used as a proxy for H I or as a metallicity indicator
in the LISM.

---------------------------------------------------------
Title: CHANDRA Observations of the Corona of AU Mic (dM1e)
Authors: Linsky, J. L.; Brown, A.; Osten, R. A.
2002AAS...200.7415L Altcode: 2002BAAS...34..772L
The dM1e flare star AU Mic (HD 197481, Gl 803) is the most luminous
flare star in X-rays within 10 pc of the Sun. We observed the star in
November 2000 for 60 ks using Chandra's High Energy Transmission Grating
Spectrometer and ACIS-S detector. Since the X-ray flux was remarkably
constant during this interval with only one small flare, the results
we present refer to the quiescent state of the stellar corona. We have
analyzed the Chandra spectra using the approach described by Osten
et al (2002) for the analysis of similar observations of the active
binary σ 2 CrB. We used CIAO2.0 "threads" and custom IDL
procedures applied to the reprocessed Level 2 file. For the spectral
line identification and atomic parameters, we used the APEC v1.10
line list. We derive the coronal emission measure distribution and
abundances from the emission lines and continuum in the Chandra data
set and the emission lines observed by EUVE during similar quiescent
periods. The coronal model is compared with the fluxes of Fe XXI 1354A
observed by STIS and Fe XVIII 975A observed by FUSE and with the lower
temperature emission measure distribution obtained by Pagano et al
(2000) from quiescent STIS observations. We acknowledge support by
NASA through grant H-04630D to NIST and the University of Colorado.

---------------------------------------------------------
Title: Chandra HETGS Observes Tortured Coronae in the Rapid Braking
Zone
Authors: Ayres, T. R.; Osten, R. A.; Brown, A.; Gagne, M.; Linsky,
J. L.
2002AAS...200.7419A Altcode: 2002BAAS...34..773A
We have obtained Chandra High Energy Transmission Grating Spectrometer
observations of five moderate mass (2--3 Msun) giants
straddling the portion of the Hertzsprung gap where early-G III
stars---evolving rapidly toward the red giant branch---suffer strong
rotational braking and dramatic changes in their X-ray emitting
coronae. G0 III giants prior to the braking epoch are fast rotators
(υ rot ~ 50-100 km s-1) and display very hot
(T&gt; 107 K) coronae, but nevertheless have curiously
depressed X-ray luminosities. The post-braking giants are slow rotators
(υ rot&lt; 10 km s-1) with cooler coronae (T ~
106.8 K), but nevertheless manage a healthy level of X-ray
emission. We believe the differences reflect the violent replacement
of a “fossil” magnetosphere---inherited from the late-B or early-A
MS progenitor---by a solar-like regenerative magnetic dynamo. The
latter becomes dominant when the initially shallow surface convection
in yellow giants at the blue edge of the Hertzsprung gap gives way to
deep convective layers as the stars evolve to the red edge. Three of
the targets were observed in Cycle 2: 31 Com (G0 III) on 2001-03-12
[132.0 ks]; HR 9024 (G1 III) on 2001-08-11 [96.9 ks]; and μ Vel (G5
III) on 2001-09-24 [19.9 ks], 2001-10-29 [58.1 ks], and 2001-12-18
[57.7 ks]. (The first μ Vel observation was scheduled for 80 ks,
but was cut short by a solar flare. The second pointing was intended
to complete the exposure, but was affected by “threshold crossing
plane” latchup in the ACIS CCDs, and was repeated two months later,
accounting for the third pointing.) The remaining two stars are: Cycle 3
target 24 UMa (G4 III; ~50 ks pointings on 2002-03-26 and 2002-03-29);
and GTO target β Ceti (K0 III) observed on 2001-06-29 [87.5 ks]. We
describe the HETGS spectra and our efforts to infer plasma conditions
(temperature/density models), chemical fractionation, gas dynamics
(through emission line Doppler shifts), and coronal variability. [-3mm]
This work was supported by Chandra grant GO1-2018X to the University
of Colorado.

---------------------------------------------------------
Title: Deuterium Abundance toward WD 1634-573: Results from the
FUSE Mission
Authors: Wood, B. E.; Linsky, J. L.; Hébrard, G.; Vidal-Madjar, A.;
Lemoine, M.; Moos, H. W.; Sembach, K. R.; Jenkins, E. B.
2002ApJS..140...91W Altcode: 2001astro.ph.12296W
We use Far Ultraviolet Spectroscopic Explorer (FUSE) observations
to study interstellar absorption along the line of sight
to the white dwarf WD 1634-573 (d=37.1+/-2.6 pc). Combining
our measurement of D I with a measurement of H I from Extreme
Ultraviolet Explorer data, we find a D/H ratio toward WD 1634-573
of D/H=(1.6+/-0.5)×10-5. In contrast, multiplying our
measurements of DI/OI=0.035+/-0.006 and DI/NI=0.27+/-0.05 with
published mean Galactic interstellar medium (ISM) gas-phase O/H and
N/H ratios yields D/HO=(1.2+/-0.2)×10-5 and
D/HN=(2.0+/-0.4)×10-5, respectively. Note that
all uncertainties quoted above are 2 σ. The inconsistency between
D/HO and D/HN suggests that either the O I/H
I or the N I/H I ratio toward WD 1634-573 must be different from the
previously measured average ISM O/H and N/H values. The computation
of D/HN from D I/N I is more suspect, since the relative N
and H ionization states could conceivably vary within the local ISM,
while the O and H ionization states will be more tightly coupled by
charge exchange. Based on observations made with the NASA-CNES-CSA Far
Ultraviolet Spectroscopic Explorer (FUSE), which is operated for NASA
by Johns Hopkins University under NASA contract NAS 5-32985.

---------------------------------------------------------
Title: What EUV Spectroscopy can tell us about the Local Interstellar
Medium
Authors: Linsky, J. L.
2002AAS...200.5210L Altcode: 2002BAAS...34..728L
Fundamental questions concerning the interstellar gas in our local
region of the Galactic disk include: (1) the degree of ionization
of hydrogen and helium and the source(s) of the ionization, (2)
the geometrical structure of the various components of the local
interstellar medium, and (3) the physical explanation for the existence
and properties of these structures in the dynamic environment of the
Galactic disk. The extreme ultraviolet spectrum from 912A to 100A
and below contains essential spectroscopic diagnostics for measuring
the ionization of hydrogen and helium along lines of sight through
the Local Bubble and beyond, out to several hundred parsecs in some
directions. Pioneer measurements of the column densities of neutral
hydrogen, neutral helium, and ionized helium by EUVE provide essential
data for addressing these three questions, but the sensitivity and
spectral resolution of EUVE limited its contributions to answering
these questions. Measurements of the hydrogen column densities from the
Lyman continuum absorption are insensitive to the presence of multiple
velocity components along the line of sight, and thus are valuable tests
of column densities inferred from analyses of Lyman line absorption by
STIS and FUSE. A future EUV spectrometer with greater sensitivity will
be able to measure accurate hydrogen column densities to 1020
cm-2. A future instrument with higher spectral resolution
should also be able to measure column densities from the resonance lines
of HeI and HeII. Also, accurate measurements of the relative strengths
of stellar coronal emission lines originating from common upper levels
should provide accurate measurements of the hydrogen and helium column
densities along the lines of sight to late-type stars. This work is
supported by NASA through grant S-56500-D to NIST and the University
of Colorado.

---------------------------------------------------------
Title: The Structure of the Local Interstellar
Medium. I. High-Resolution Observations of Fe II, Mg II, and Ca II
toward Stars within 100 Parsecs
Authors: Redfield, Seth; Linsky, Jeffrey L.
2002ApJS..139..439R Altcode:
High-resolution absorption measurements (λ/Δλ&gt;~100,000) of
the resonance lines of Fe II, Mg II, and Ca II are presented for all
available observed targets within 100 pc. The Fe II and Mg II spectra
were obtained with the Goddard High Resolution Spectrograph (GHRS)
and the Space Telescope Imaging Spectrograph (STIS) instruments
aboard the Hubble Space Telescope (HST). Of the 63 observations of
targets within 100 pc, we present new measurements for 24 lines of
sight. We also compiled all published absorption measurements based on
Ca II spectra obtained by various ground-based instruments. For each
observation we provide measurements of the central velocity, Doppler
parameter, and column density for each absorption component. These
three ions provide the best opportunity to measure the component
velocity structure. Because these are the heaviest ions observed in
absorption through the warm local interstellar medium (LISM), the narrow
line widths minimize significant blending of components and allow for
accurate measurements of the central velocity. We present a statistical
analysis of the LISM absorption measurements, which provides an overview
of some physical characteristics of warm clouds in the LISM, such as,
temperature, turbulent velocity, ionization degree, and depletion. The
complete collection and reduction of all LISM absorption measurements
provides an important database for studying the structure of nearby
warm clouds. Subsequent papers will present models for the morphology
and physical properties of individual structures (clouds) in the LISM.

---------------------------------------------------------
Title: Crazy Coronal Abundances
Authors: Linsky, J. L.
2002ASPC..262...45L Altcode: 2002heus.conf...45L
Chandra high resolution X-ray spectra of active late-type stars and
binary systems show a pattern of strange coronal abundances. Elements
with low first ionization potential (FIP &lt; 10 eV) like Fe are
underabundant, whereas elements with FIP &gt; 10 eV (in particular
Ne and Ar) are overabundance compared to solar photospheric
values. Preliminary evidence for this pattern was already seen in
the ROSAT and ASCA data, but the the Chandra and XMM-Newton data
greatly strengthen the case. The coronal abundances in active stars
are especially interesting because the solar corona shows the opposite
effect (FIP deficiency). I will summarize the new results, compare
with the solar abundance results, and comment on the reliability of the
stellar abundance anomalies. The solar FIP and stellar anti-FIP effects
can be understood (at least in part) in terms of fractionation effects
in the chromosphere and perhaps diffusion in the corona. I will compare
theoretical predictions with the observed crazy coronal abundances.

---------------------------------------------------------
Title: The heliospheric hydrogen wall and astrospheres
Authors: Wood, B.; Mueller, H.; Zank, G.; Izmodenov, V.; Linsky, J.
2002cosp...34E.836W Altcode: 2002cosp.meetE.836W
Charge exchange processes in the outer heliosphere produce a population
of hot hydrogen gas within the heliosphere, creating a "hydrogen wall"
in between the heliopause and bow shock. The heliospheric hydrogen
wall scatters Ly photons passing through it, producing a detectable
absorption signature in observations of Ly emission from nearby
stars. This heliospheric absorption has been observed using observations
from the Hubble Space Telescope (HST), and these observations have
also yielded detections of analogous "astrospheric" absorption from
material surrounding the observed stars. The astrospheric detections
dramatize the importance of understanding the heliospheric interaction,
since similar interactions exist around other stars and can now
be detected and studied with HST. We present comparisons between
the observed heliospheric absorption and the predictions of various
kinetic and multifluid models in order to explore the constraints that
the absorption can furnish for heliospheric models. The astrospheric
absorption provides a way to empirically estimate the mass loss rates
of solar-like stars, leading to the first empirical estimates of how
solar-like winds vary with stellar age and activity. These estimates
require the use of models, providing an important new application for
heliospheric/astrospheric modeling. Finally, astrospheres are also
potential sources of Ly emission as well as absorption. We present
model Ly images of astrospheres and our heliosphere, and we also
present HST's attempt to detect this emission around the star 40 Eri A.

---------------------------------------------------------
Title: Deuterium abundance in the local ISM
Authors: Linsky, Jeffrey L.; Wood, Brian E.
2002IAUS..187...75L Altcode:
Excellent HST/GHRS spectra of interstellar hydrogen and deuterium
Lyman-α absorption toward nearby stars allow us to identify systematic
errors that have plagued earlier work and to measure accurate values
of the D/H ratio in local interstellar gas. Analysis of 12 sightlines
through the Local Interstellar Cloud leads to a mean value of D/H =
(1.50 +/- 0.10) ×10-5 with all data points lying within
+/-1σ of the mean. Deciding whether or not the D/H ratio has different
values elsewhere in the Galaxy and beyond will be one of the major
objectives of the FUSE mission.

---------------------------------------------------------
Title: Four Years of Multi-Wavelength Observations of the RS CVn
System HR 1099 (V711 Tau)
Authors: Osten, R. A.; Brown, A.; Ayres, T. R.; Linsky, J. L.
2002ASPC..264..156O Altcode: 2002ccea.conf..156O
No abstract at ADS

---------------------------------------------------------
Title: Physical Structure of the Local Interstellar Cloud and Other
Nearby Clouds
Authors: Redfield, S.; Wood, B.; Linsky, J.
2002cosp...34E1522R Altcode: 2002cosp.meetE1522R
The physical structure and morphology of the interstellar medium that
surrounds our solar system directly effects the heliosphere and the
interplanetary environment. High resolution ultraviolet absorption
spectra of nearby stars and the intervening interstellar medium,
observed by the Hubble Space Telescope, provide important information
about the chemical abundance, ionization, temperature, kinematics,
density, morphology, and turbulent structures of the local interstellar
medium (LISM). Fortunately, nearly all observations of objects beyond
the solar system contain LISM absorption lines. The number of useful
observations is large enough that we can start analyzing the LISM
as a three-dimensional object, as opposed to focusing on individual
sightlines. We present the results of high resolution observations of
the LISM obtained by the Hubble Space Telescope. Our focus will be on
the ionization and kinematic structure of the Local Interstellar Cloud
(LIC) and other nearby clouds. Fundamental issues we hope to address
include: 1) a revised shape of the LIC; 2) a revised kinematic model
of the LIC; 3) application of above analysis to other nearby clouds to
produce a revised model of the structure of the LISM. Understanding
the physical characteristics of these structures is necessary if we
are to discuss the morphology of the LISM, its evolution, origin,
and impact on the heliosphere and our solar system.

---------------------------------------------------------
Title: X-ray coronae of stars: recent results from Chandra
Authors: Linsky, J.; Ayres, T.; Brown, A.; Osten, R.
2002cosp...34E1302L Altcode: 2002cosp.meetE1302L
The Chandra X-ray Observatory has opened up the new field of
astronomical X-ray spectroscopy and has also provided beautiful X-ray
images of young star clusters with unprecedented angular resolution. We
will summarize some of the important discoveries coming from the
HETG and LETG observations of many active stars and binary systems
as well as early-type stars. For the active late-type stars, we
will intercompare derived differential emission measures and coronal
electron densities of stars with different properties and consider
the main uncertainties that enter such analyses. We will also discuss
whether coronae are geometrically extended and how coronae change when
a star flares. Chandra has also provided important new information on
differences between coronal and photospheric abundances. For early-type
stars we will summarize the evidence for and against coronal vs wind
emission mechanisms. The final topic will be the question of how the
coronae of pre-main sequence stars differ from older but still active
stars as a result of the presence of magnetic disks and accretion
flows. Deep ACIS images of young star clusters like the Trapezium in
Orion and M16 are providing insights on this topic.

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Title: \it HST STIS Observations of Fluoresced Molecular Hydrogen
Emission in Diverse Stellar Environments
Authors: Ayres, T. R.; Wood, B. E.; Herczeg, G. J.; Linsky, J. L.
2001AAS...19915805A Altcode: 2002BAAS...34..567A
The broad coverage, high sensitivity, and precise wavelength calibration
of the Space Telescope Imaging Spectrograph's E140M medium-resolution
echelle mode make it ideal for studies of broadly dispersed spectral
features, such as molecular band systems, in the 1150--1700 Å far-UV
interval. The present work focuses on the B--X electronic rovibration
bands of H 2, which can be radiatively pumped by H I
λ 1215 Lyα resonance emission in stellar environments where cold
molecular gas (T&lt; 4000 K) is irradiated by hotter, chromospheric
(T ~ 104 K) material. We compare three very different
stellar objects whose only common feature appears to be extensive
fluoresced H 2 bands: The 10 Gyr old red giant Arcturus
(α Bootis; K2 III); the 10 Myr young T-Tauri star TW Hya; and
the enigmatic accretion/wind source Mira B, which apparently was
caught in a low state during the 1999 August STIS observations. We
discuss implications of spectral differences among these objects
concerning physical properties (temperatures and column densities)
in the different environments where the molecular hydrogen is pumped
(stellar “COmosphere,” PMS accretion disk, and wind-shock interaction
zone), as well as intrinsic profiles of the Lyα irradiation field,
which can be deduced free from the usual strong interstellar absorption
that affects the H I emission core. This work was supported by STScI
grant GO-08614.02-02A to the University of Colorado, and NASA grant
S-56500-D to NIST and CU. Observations were from the NASA/ESA HST,
collected at the STScI, operated by AURA, under contract NAS5-26555.

---------------------------------------------------------
Title: Deuterium abundance toward G191-B2B: Results from the Far
Ultraviolet Spectroscopic Explorer (FUSE) Mission
Authors: Lemoine, M.; Vidal-Madjar, A.; Hebrard, G.; Desert, J. -M.;
Ferlet, R.; Lecavelier des Etangs, A.; Howk, J. C.; Andre, M.; Blair,
W. P.; Friedman, S. D.; Kruk, J. W.; Lacour, S.; Moos, H. W.; Sembach,
K.; Chayer, P.; Jenkins, E. B.; Koester, D.; Linsky, J. L.; Wood,
B. E.; Oegerle, W. R.; Sonneborn, G.; York, D. G.
2001astro.ph.12180L Altcode:
High-resolution spectra of the hot white dwarf G191-B2B, covering the
wavelength region 905-1187A, were obtained with the Far Ultraviolet
Spectroscopic Explorer (FUSE). This data was used in conjunction with
existing high-resolution Hubble Space Telescope STIS observations
to evaluate the total HI, DI, OI and NI column densities along the
line of sight. Previous determinations of N(DI) based upon GHRS and
STIS observations were controversial due to the saturated strength of
the DI Lyman-alpha line. In the present analysis the column density
of DI has been measured using only the unsaturated Lyman-beta and
Lyman-gamma lines observed by FUSE. A careful inspection of possible
systematic uncertainties tied to the modeling of the stellar continuum
or to the uncertainties in the FUSE instrumental characteristics has
been performed. The column densities derived are: log N(DI) = 13.40
+/-0.07, log N(OI) = 14.86 +/-0.07, and log N(NI) = 13.87 +/-0.07
quoted with 2-sigma uncertainties. The measurement of the HI column
density by profile fitting of the Lyman-alpha line has been found to be
unsecure. If additional weak hot interstellar components are added to
the three detected clouds along the line of sight, the HI column density
can be reduced quite significantly, even though the signal-to-noise
ratio and spectral resolution at Lyman-alpha are excellent. The new
estimate of N(HI) toward G191-B2B reads: log N(HI) = 18.18 +/-0.18
(2-sigma uncertainty), so that the average (D/H) ratio on the line of
sight is: (D/H) = 1.66 (+0.9/-0.6) *10^-5 (2-sigma uncertainty).

---------------------------------------------------------
Title: The D/H Abundance Ratio in Local Interstellar Gas
Authors: Sahu, M. S.; Landsman, W.; Bruhweiler, F. C.; Holberg, J.;
Hubeny, I.; Barstow, M.; Linsky, J.; Gull, T.; Lindler, D.; Lanz,
T.; Feggans, K.
2001AAS...199.1101S Altcode: 2001BAAS...33.1323S
Variations of the D/H ratio on scales of 100 pc are important for two
reasons: (1) they complicate the use of deuterium as a cosmological
probe, and (2) they imply non-uniform deuterium production/destruction
and an inefficient mixing of interstellar gas. The Local Interstellar
Medium (LISM) is an ideal location to test whether the D/H abundance
ratio varies or not, because the heating sources and radiation
fields are well-studied and we have a detailed knowledge of the
three-dimensional (3D) structure of the diffuse clouds in the LISM. This
detailed knowledge of the number, structure and velocities of the
absorbing clouds greatly helps in reducing errors in the derived
D/H ratios. We are working on a project to obtain high-precision
D/H abundance ratios in the interstellar gas within 100 pc. For this
purpose, we primarily use HST-STIS data towards nearby hot, white dwarfs
(WDs). We have also begun an HST archival research project to study
about 20 WD sightlines. In this poster, we present new STIS observations
for GD 153 and HZ 43 and report the results of our HST Archival project.

---------------------------------------------------------
Title: FUSE Survey of Cool Luminous Stars
Authors: Dupree, A. K.; Young, P. R.; Lobel, A.; Ake, T. R.; Linsky,
J. L.; Redfield, S.; FUSE Cool Star Team
2001AAS...199.1310D Altcode: 2001BAAS...33.1328D
The FUSE telescope has been used to survey spectroscopically eight
cool luminous stars (β Cet, α Ori,α Tau, α Car, β Gem, 31 Com,
β Dra, α Aqr) in the spectral region λ λ 910--1180. Emission from
O VI has been detected in all stars with the exception of α Ori,
decreasing in surface flux across the giant branch. This demonstrates
the pervasive extent of high temperature plasma ( ~ 3x 105K)
to stars as late as K5 III (α Tau). Densities in the lower transition
region ( ~ 70000K), as determined from C III line ratios, are on the
order of 109 cm-3, with densities in the active
stars 31 Com and β Cet perhaps as much as an order of magnitude
higher. Emission from coronal plasma represented by Fe XVIII occurs
in β Cet. Line profiles of individual species can be used to infer
atmospheric heating and dynamics. Extended atmospheres are signaled by
the presence of narrow Fe II emission that is fluoresced by H-Lyman α
in the coolest stars including α Ori. These rich spectra document the
energetics and dynamics of giant and supergiant atmospheres. Based on
Guaranteed Team observations made with the NASA-CNES-CSA Far Ultraviolet
Explorer which is operated for NASA by The Johns Hopkins University
under NASA contract NAS5-32985.

---------------------------------------------------------
Title: Deuterium Abundance Toward WD2211-495: Results from the Far
Ultraviolet Spectroscopic Explorer (FUSE) Mission
Authors: Hebrard, G.; Lemoine, M.; Vidal-Madjar, A.; Desert, J. -M.;
Lecavelier des Etangs, A.; Ferlet, R.; Wood, B. E.; Linsky, J. L.;
Kruk, J. W.; Chayer, P.; Lacour, S.; Blair, W. P.; Friedman, S. D.;
Moos, H. W.; Sembach, K. R.; Sonneborn, G.; Oegerle, W. R.; Jenkins,
E. B.
2001astro.ph.12181H Altcode:
We present a deuterium abundance analysis of the line of sight
toward the white dwarf WD2211-495 observed with the Far Ultraviolet
Spectroscopic Explorer (FUSE). Numerous interstellar lines are detected
on the continuum of the stellar spectrum. A thorough analysis was
performed through the simultaneous fit of interstellar absorption
lines detected in the four FUSE channels of multiple observations with
different slits. We excluded all saturated lines in order to reduce
possible systematic errors on the column density measurements. We
report the determination of the average interstellar D/O and D/N
ratios along this line of sight at the 95% confidence level: D/O =
4.0 +/-1.2 *10^-2; D/N = 4.4 +/-1.3 *10^-1. In conjunction with FUSE
observations of other nearby sight lines, the results of this study
will allow a deeper understanding of the present-day abundance of
deuterium in the local interstellar medium and its evolution with time.

---------------------------------------------------------
Title: A Survey of Nearby Cool Dwarf Star Spectra Obtained by FUSE
Authors: Redfield, S.; Linsky, J. L.; Dupree, A. K.; Young, P. R.;
Lobel, A.; Ake, T. B.; FUSE Cool Star Team
2001AAS...199.1312R Altcode: 2001BAAS...33.1329R
We present the cool star dwarf spectra obtained by the FUSE Science Team
using the Far Ultraviolet Spectroscopic Explorer (FUSE). The survey
includes the stars α Aql, α Cen A, α Cen B, ɛ Eri, AU Mic, and AB
Dor. The spectral range extends from 900 to 1200 ~Å, at a spectral
resolution of λ /Δ λ ~ 20,000. Numerous emission lines are present
and identified. Lines of particular interest, such as C III (977 Å),
O VI (1032 and 1038 Å), and the Lyman series, are present in all stars
and studied in detail. The forbidden coronal Fe XVIII (975 Å) line is
present in some spectra and is useful in studying the dynamics of the
107 K coronal plasma. Absorption by warm Local Interstellar
Medium (LISM) gas is visible in several lines, such as C III (977 Å)
and C II (1037 Å). Combined with LISM absorption studies of the same
stars at longer wavelengths (ie. using spectrographs aboard the Hubble
Space Telescope (HST)), the FUSE LISM absorption can provide important
insights into the structure of the nearby warm ISM. This atlas of
nearby cool stars in the far-ultraviolet provides important information
pertaining to the atmospheres of dwarf stars and will be a useful tool
in planning future observations of cool stars. This work is based on
data obtained for the Guaranteed Time Team by the NASA-CNES-CSA FUSE
mission operated by the Johns Hopkins Observatory. Financial support
to U.S. participants has been provided by NASA contract NAS5-32985.

---------------------------------------------------------
Title: Chandra Observations of the Eagle Nebula: Seeing through the
“Pillars of Creation”
Authors: Mytyk, A. M.; Daniel, K. J.; Gagne, M.; Linsky, J. L.
2001AAS...199.0408M Altcode: 2001BAAS...33.1307M
The Chandra X-ray Observatory obtained a deep 78-ks image of the young
star cluster M 16, also known as NGC 6611 or the Eagle Nebula on 2001
July 30. Over 1,000 X-ray sources were detected in the 17‧x17 '
ACIS-I FOV, making this the densest concentration of X-ray sources
observed to date. Most of the X-ray sources are associated with the
optically visible, 6-Myr old stars in NGC 6611. Of great interest is
the percentage of X-ray luminous B- and A-type stars. In what is perhaps
the most famous image obtained by HST, the central portion of the Eagle
Nebula shows dark fingers of dust and cold gas (called the “Pillars
of Creation”) being photoionized and photoevaporated by nearby hot
stars. Several highly absorbed X-ray sources are spatially coincident
with evaporating gaseous globules at the tips of the fingers. This work
is supported in part by NASA grant H-04630D to NIST and the University
of Colorado.

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Title: The Disk and Environment of the Herbig Be Star HD 100546
Authors: Grady, C. A.; Polomski, E. F.; Henning, Th.; Stecklum, B.;
Woodgate, B. E.; Telesco, C. M.; Piña, R. K.; Gull, T. R.; Boggess,
A.; Bowers, C. W.; Bruhweiler, F. C.; Clampin, M.; Danks, A. C.;
Green, R. F.; Heap, S. R.; Hutchings, J. B.; Jenkins, E. B.; Joseph,
C.; Kaiser, M. E.; Kimble, R. A.; Kraemer, S.; Lindler, D.; Linsky,
J. L.; Maran, S. P.; Moos, H. W.; Plait, P.; Roesler, F.; Timothy,
J. G.; Weistrop, D.
2001AJ....122.3396G Altcode:
Coronagraphic imaging of the nearest Herbig Be star with the Space
Telescope Imaging Spectrograph (STIS) on board the Hubble Space
Telescope, Ks (2.15 μm) imaging with ADONIS at the 3.6 m telescope
at La Silla, and mid-infrared imaging with OSCIR using the 4 m Blanco
Telescope at Cerro Tololo Inter-American Observatory confirm the
detection of the disk reported by Pantin et al. and map the disk out to
5" (~515 AU) in the optical and at Ks. While the source is unresolved
at 10 and 18 μm, it can be traced to 1.5" at 11.7 μm. We confirm the
change in the radial dependence of the disk surface brightness near 2.7"
seen at 1.6 μm by Augereau et al. at Ks. No such break in the power law
is seen in the optical. The STIS data reveal spiral dark lane structure,
making HD 100546 the third near-zero-age main-sequence Herbig Ae/Be
star with structure more than 100 AU from the star. We also optically
detect a low surface brightness envelope extending 10" (1000 AU) from
the star, in addition to nebulosity, which is probably associated
with DC 292.6-7.9. The survival of the envelope through essentially
the entire pre-main-sequence lifetime of the star, coupled with the
absence of physical companions within 1500 AU of the star, suggests
that envelope lifetimes owe more to the star-forming environment than
to mass-loss activity from the Herbig Ae/Be star. Based on observations
made with the NASA/ESA Hubble Space Telescope, obtained at the Space
Telescope Science Institute, which is operated by the Association
of Universities for Research in Astronomy, Inc., under NASA contract
NAS 5-26555. This study is part of the STIS IDT protoplanetary disk
Key Project. This work is also based on observations collected at
the European Southern Observatory, La Silla, Chile, Proposal ID
63.I-0196. This work is also based on observations made at the Cerro
Tololo Inter-American Observatory. CTIO is operated by AURA, Inc.,
under cooperative agreement with the National Science Foundation.

---------------------------------------------------------
Title: Observations of O VI Emission from the Diffuse Interstellar
Medium
Authors: Shelton, R. L.; Kruk, J. W.; Murphy, E. M.; Andersson,
B. G.; Blair, W. P.; Dixon, W. V.; Edelstein, J.; Fullerton, A. W.;
Gry, C.; Howk, J. C.; Jenkins, E. B.; Linsky, J. L.; Moos, H. W.;
Oegerle, W. R.; Oey, M. S.; Roth, K. C.; Sahnow, D. J.; Sankrit,
R.; Savage, B. D.; Sembach, K. R.; Shull, J. M.; Siegmund, O. H. W.;
Vidal-Madjar, A.; Welsh, B. Y.; York, D. G.
2001ApJ...560..730S Altcode: 2001astro.ph..5278S
We report the first Far-Ultraviolet Spectroscopic Explorer measurements
of diffuse O VI (λλ1032, 1038) emission from the general diffuse
interstellar medium outside of supernova remnants or superbubbles. We
observed a 30”×30” region of the sky centered
at l=315.0d and b=-41.3d. From the observed intensities (2930+/-290
[random]+/-410 [systematic] and 1790+/-260 [random]+/-250 [systematic]
photons cm-2 s-1 sr-1 in λλ1032
and 1038, respectively), derived equations, and assumptions about
the source location, we calculate the intrinsic intensity, electron
density, thermal pressure, and emitting depth. The intensities
are too large for the emission to originate solely in the Local
Bubble. Thus, we conclude that the Galactic thick disk and lower
halo also contribute. High-velocity clouds are ruled out because
there are none near the pointing direction. The calculated emitting
depth is small, indicating that the O VI-bearing gas fills a small
volume. The observations can also be used to estimate the cooling
rate of the hot interstellar medium and to constrain models. The
data also yield the first intensity measurement of the C II 3s
2S1/2-2p 2P3/2 emission
line at 1037 Å and place upper limits on the intensities of ultraviolet
line emission from C I, C III, Si II, S III, S IV, S VI, and Fe III.

---------------------------------------------------------
Title: Chandra Observations of Coronal Variability on the RS CVn
Binary σ2 CrB
Authors: Osten, R. A.; Linsky, J. L.
2001tysc.confE.117O Altcode:
We report on a deep observation (86 ks) of the short period
(Porb=1.14 d) active binary system σ2 CrB
with Chandra ACIS-S+HETGS taken on 2000 June 18-20, embedded within
a much longer EUVE observation and accompanied by radio observations
with the VLA. During the Chandra observation, the system was in a
quiescent state for the first 78 ks. In the remaining 8 ks, a flare was
observed in which the MEG count rate increased to nearly four times
the quiescent count rate. The rise and initial decline of the flare
was recorded. We find no evidence for any line broadening or shifts
due to orbital velocities, nor any flare-associated mass motions,
in the bright lines Ne X λ12.13 Å and Mg XII λ 8.42 Å. The
former behavior is consistent with both stars being active X-ray
emitters. We describe our analysis techniques to determine the shape
of the differential emission measure (DEM), and establish abundances
relative to hydrogen. We use an iterative procedure to measure line
fluxes, estimate and remove the effect of the continuum flux, and
determine abundances. The strongest emission lines of iron present
in the spectrum (Fe XVII-XXIV) are used to constrain the DEM over the
temperature range log T =6.6-7.4. The shape of the continuum spectrum
at short wavelengths places a constraint on higher temperatures. We
are able to derive abundances of O, Ne, Mg, Al, Si, and S relative to
Fe in this way, although the O/Fe ratio is less constrained due to the
mismatch in formation temperature between the He- and H-like O lines and
most of the Fe lines. We then use the continuum flux to constrain the
ratio of Fe to H in the stellar corona. We repeat the process starting
from initial abundance estimates, to achieve consistency between the
continuum shape and measured emission line fluxes. We discuss our
attempts to quantify the sources of error involved in this approach,
and describe the resulting differences we find between the quiescent
and flaring state of the binary system.

---------------------------------------------------------
Title: Crazy Coronal Abundances
Authors: Linsky, Jeffrey; Osten, Rachel; Brown, Alec; Skinner, Steve
2001tysc.confE..20L Altcode:
Chandra high resolution spectra of active late-type stars show
a pattern of strange coronal abundances. Elements with low first
ionization potential (FIP &lt; 10 eV) like Fe are underabundant,
whereas elements with FIP &gt; 10 eV (in particular, Ne and Ar) are
overabundant compared to solar photospheric values. Preliminary evidence
for this pattern was already seen in the ROSAT and ASCA data, but the
Chandra and XMM-Newton data greatly strengthen the case. The coronal
abundances in active stars are especially interesting because the solar
corona shows the opposite effect (FIP deficiency). We will summarize
the new results and comment on their limitations. In particular, We
will present the coronal abundances of four active stars observed with
the HETG - AB Dor, AU Mic, 44 Boo, and σ2 CrB. The solar
FIP and stellar anti-FIP effects can be understood (at least in part)
in terms of fractionation effects in the chromosphere and perhaps
diffusion in the corona. We will present theoretical and heuristic
models that can explain the observed crazy coronal abundances.

---------------------------------------------------------
Title: Far Ultraviolet Spectroscopic Explorer Observations of Capella
Authors: Young, P. R.; Dupree, A. K.; Wood, B. E.; Redfield, S.;
Linsky, J. L.; Ake, T. B.; Moos, H. W.
2001ApJ...555L.121Y Altcode:
Far Ultraviolet Spectroscopic Explorer observations of the binary
system Capella reveal a rich emission-line spectrum containing neutral
and ionic species, among them H I, O I, C III, O VI, S VI, Ne V,
and Ne VI. In addition, Fe XVIII λ974.85, formed at temperatures
of ~6×106 K, is detected. Whereas the strong transition
region lines principally come from the G1 giant, consistent with results
from previous ultraviolet observations, Fe XVIII is formed largely in
the G8 giant atmosphere. Line ratios from C III suggest densities of
(2-8)×1010 cm-3, although anomalous line profiles
of the 1176 Å transition may signal optical depth effects. Based on
observations made with the NASA-CNES-CSA Far Ultraviolet Spectroscopic
Explorer, which is operated for NASA by Johns Hopkins University under
NASA contract NAS5-32985.

---------------------------------------------------------
Title: The 3D-structure of the LISM
Authors: Wood, Brian E.; Redfield, Seth; Linsky, Jeffrey L.
2001astro.ph..7033W Altcode:
We review what is currently known about the structure of interstellar
material in the solar neighborhood, emphasizing how observations from
the Hubble Space Telescope (HST) have improved our understanding of
how interstellar gas is distributed near the Sun. The nearby ISM is not
uniform but shows variations in both temperature and metal abundances on
distance scales of just a few parsecs. The observations also show that
nearby gas does not have a single uniform velocity vector. Instead,
different components are often seen in different directions for even
very short lines of sight. However, interpretation of these components
remains difficult. It is uncertain whether the components represent
physically distinct clouds or perhaps are just symptomatic of velocity
gradients within the cloud. Finally, since it is the local interstellar
medium's interaction with the solar wind that is the primary application
of ISM studies considered in these proceedings, we also review how the
same HST data used to study the local ISM structure has also been used
to study both the heliospheric interaction with the solar wind and also
"astrospheric" interactions with the winds of other stars.

---------------------------------------------------------
Title: Goddard High Resolution Spectrograph Observations of NGC 4151
Authors: Brandt, J. C.; Heap, S. R.; Beaver, E. A.; Boggess, A.;
Carpenter, K. G.; Ebbets, D. C.; Hutchings, J. B.; Jura, M.; Leckrone,
D. S.; Linsky, J. L.; Maran, S. P.; Savage, B. D.; Smith, A. M.;
Trafton, L. M.; Walter, F. M.; Weymann, R. J.; Snow, M.; Ake, T. B.
2001AJ....121.2999B Altcode:
Goddard High Resolution Spectrograph observations of the nucleus of
the bright, nearby Seyfert galaxy NGC 4151 are presented andbriefly
described.

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Title: Far-Ultraviolet Observations of Flares on the dM0e Star
AU Microscopii
Authors: Robinson, Richard D.; Linsky, Jeffrey L.; Woodgate, Bruce E.;
Timothy, John G.
2001ApJ...554..368R Altcode:
We report on far-ultraviolet (FUV) observations of flares on the
dM0e star AU Microscopii obtained on 1998 September 6 with the
Space Telescope Imaging Spectrograph onboard the Hubble Space
Telescope. The data consist of medium-resolution echelle spectra
covering the wavelength region from 1170 to 1730 Å with a spectral
resolution of λ/Δλ=45,800. The observations were obtained using
the TIME-TAG observing mode in which the time and position of each
detected photon is recorded. This allows a study of variability that
is constrained only by counting statistics. During a total on-source
time of 10,105 s, we observed numerous microflare bursts as well as
four well-defined flare events. These flares lasted between 10 s and
3 minutes and were most easily detected in the FUV continuum and the
Si IV and C IV resonance lines. Variations in both the cooler (e.g.,
Lyα, C II, O I) and hotter (O V, N V, Fe XXI) emission lines were
much less pronounced. We examined the physical characteristics of the
flare events, including the time history of the wavelength-integrated
fluxes in the continuum and the various emission lines. In particular,
we searched for, but did not find, evidence for increased emission in
the red wing of the Lyα line, which would indicate the presence of
moderately energetic proton beams. We integrated the emission over
the entire time of major flare activity to investigate the average
line and continuum properties of the time-averaged spectrum, including
flows and turbulence as a function of temperature. We also considered
the shape of the FUV continuum, which may actually be caused by the
enhancement of numerous weak emission lines. Unfortunately, none of
the events were strong enough to allow a detailed examination of line
profiles as a function of time.

---------------------------------------------------------
Title: HST STIS Coronal Iron Survey
Authors: Ayres, T. R.; Brown, A.; Linsky, J. L.
2001AAS...198.4404A Altcode: 2001BAAS...33..845A
The broad coverage, high sensitivity, and precise wavelength calibration
of the Space Telescope Imaging Spectrograph's medium-resolution echelle
mode, coupled with the growing collection of GO and GTO E140M exposures,
are ideal for surveys of specific spectral diagnostics across a
diversity of stellar types, luminosities, and activity levels. Of great
current interest are the weak coronal forbidden lines that appear in the
far-UV, which are well known from solar flare work. Measuring coronal
lines with STIS in the 1150--1700 Å band has significant advantages
over using, say, Chandra HETGS or XMM-Newton RGS in the 1 keV range,
because the STIS velocity resolution is 40x, or more, higher; STIS has
an absolute wavelength calibration established by an onboard emission
lamp; and the large effective area of the HST telescope compensates
for the faintness of the forbidden lines. Here, we report a survey of
Fe XXI λ 1354 in a sample of ~25 stars. The forbidden iron feature
forms at a temperature of about 107 K, characteristic of
very active or flaring coronal conditions. Clear detections of the
coronal iron line are made in active M dwarfs (AU Mic, AD Leo), active
giants (α Aur, β Cet, ι Cap, 24 UMa, HR 9024), short-period RS CVn
binaries (e.g., HR 1099), and possibly in active solar-type dwarfs
(ζ Dor, χ1 Ori). We describe our semi-empirical method
for removing the C I blend that partially corrupts the Fe XXI profile,
and our measurements of coronal line widths and Doppler shifts. Although
α Aur displays clear variability between Fe XXI profiles obtained at
the same orbital phase, but four years apart; the hyperactive HR 1099
system showed virtually no change in its coronal iron feature during
a sequence of 14 spectra taken over a 7 hr period in 1999 September,
despite the occurrence of two large flares in far-UV lines such as
Si IV and C IV. This work was supported by grant GO-08280.01-97A
from STScI. Observations were from the NASA/ESA HST, collected at the
STScI, operated by AURA, under contract NAS5-26555. We thank the other
collaborators in HST program 8280 for their help in carrying out the
STIS stellar survey upon which the present study is based.

---------------------------------------------------------
Title: Analysis of Chandra X-ray Spectra of the Young, Active Star
AB Dor
Authors: Linsky, J. L.; Gagne, M.
2001AAS...198.4405L Altcode: 2001BAAS...33Q.846L
The early-K dwarf AB Dor is a nearby (15 pc), young (20--30 Myr),
rapidly rotating (Prot = 0.514 day) star with saturated X-ray
emission (Lx/Lbol ~ 10-3) and cool
prominence-like gas extending several stellar radii into its corona. We
observed this extensively studied star on 1999 Oct 9 for 60 ks with the
high energy transmission grating (HETG/ACIS-S) on Chandra. The rich
X-ray spectra contain emission lines of N, O, Ne, Mg, Al, Si, S, Ar,
Ca, Fe, and Ni. As is seen in other active stars, the Ne abundance is
high and the Fe abundance low compared to solar photospheric abundances,
indicating the reverse of the enhanced first ionization potential (FIP)
effect seen in the solar corona. The emission measure distribution
shows peaks near log T = 6.8 and 7.3, and the helium-like triplets of
O VII, Ne IX, and Mg XI indicate electron densities log ne
~ 11.0. We will use these data to infer the size and properties of
coronal loops in the stellar corona. We find no noticeable line shifts
indicative of a wind or downflows. This GTO Chandra program is supported
by NASA through a grant to NIST and the University of Colorado.

---------------------------------------------------------
Title: The STIS Coronagraphic Imaging Survey of Herbig Ae/Be Stars
Authors: Grady, C. A.; Woodgate, B.; Gull, T.; Kimble, R.; Bowers,
C.; Heap, S.; Maran, S.; Boggess, A.; Danks, A.; Lindler, D.; Linsky,
J.; Moos, W.; Roesler, F.; Timothy, J. G.
2001AAS...198.7716G Altcode: 2001BAAS...33..904G
We present the results of a coronagraphic imaging survey of some of the
nearest and optically brightest Herbig Ae/Be (HAEBE) stars made with the
Hubble Space Telescope and the Space Telescope Imaging Spectrograph. Our
sample includes 9 nearby HAEBE stars with ages spanning 0.6 to more
than 10 Myr. One of our sample members was previously known to have
a nearby companion: we report the detection of stars offset 1.8 -
2.0" from their primaries in two additional cases : HD 36112 and CQ
Tau. Our sample contains two stars, AB Aur and HD 100546, with envelopes
extending more than 1000 AU from the stars. Both envelopes show band
structure in their outer regions, which is closest to the star in
the direction of the star's proper motion. One other system, CQ Tau,
shows nebulosity at comparable distances, but with insufficient S/N to
probe the detailed morphology. The morphology of the nebulosity around
CQ Tau is broadly similar to SU Aur. The STIS data indicate survival
of envelopes through much, if not all, of the star's pre-main sequence
lifetime, but with surface brightness decreasing with stellar age. Disks
are detected in two cases (HD 163296 and HD 100546). When compared with
β Pic, the STIS data provide evidence for increasing flattening of
the disk material with increasing stellar age. The disks of a number
of millimeter-bright Herbig Ae/Be stars are not detected by STIS:
these are stars with IR spectral energy distributions indicating the
presence of larger grains. The implications for optical and near-IR
imaging of protoplanetary disks will be discussed.

---------------------------------------------------------
Title: AB Dor in '94. I. Hubble Space Telescope Goddard High
Resolution Spectrogaph Observations of the Quiescent Chromosphere
of an Active Star
Authors: Brandt, J. C.; Heap, S. R.; Walter, F. M.; Beaver, E. A.;
Boggess, A.; Carpenter, K. G.; Ebbets, D. C.; Hutchings, J. B.; Jura,
M.; Leckrone, D. S.; Linsky, J. L.; Maran, S. P.; Savage, B. D.;
Smith, A. M.; Trafton, L. M.; Weymann, R. J.; Norman, D.; Redfield, S.
2001AJ....121.2173B Altcode:
We analyze Hubble Space Telescope/Goddard High Resolution Spectrograph
spectra of AB Doradus, the prototypical, ultrarapidly rotating K
dwarf. We observed chromospheric (Mg II) and transition-region (C
II, Si IV, C IV, and N V) lines periodically throughout the stellar
rotation period and provide a low-dispersion stellar atlas of 78
emission lines. The quiescent line profiles of the chromospheric
and transition-region lines show narrow cores superposed on very
broad wings. The broad wings of the Mg II k and h lines and of
the transition-region lines can be explained by emission from gas
corotating with the star and extending out to near the Keplerian
corotation radius (2.8 stellar radii). While this is not a unique
solution, it is consistent with previous studies of Hα emission,
which are naturally explained by large corotating prominences. We find
no evidence for rotational modulation of the emission-line fluxes. The
density diagnostics suggest that the transition region is formed at
constant pressure, with an electron density of 2-3×1012
cm-3 at a temperature of 3×104 K. The electron
pressure is about 100 times larger than that for the quiet Sun. The
emission-measure distribution shows a minimum between logT=5 and
5.5. The Mg II line exhibits three interstellar absorption components
along the 15 pc line of sight. We identify the lowest velocity component
with the G Cloud, but the other components are not identified with
any interstellar clouds previously detected from other lines of sight.

---------------------------------------------------------
Title: Identification of Fe II Emission Lines in FUSE Stellar Spectra
Authors: Harper, Graham M.; Wilkinson, Erik; Brown, Alexander; Jordan,
Carole; Linsky, Jeffrey L.
2001ApJ...551..486H Altcode:
We identify two complexes of Fe II emission lines in far-ultraviolet
spectra of the stars α TrA and HD 104237. Using spectra from both the
Far Ultraviolet Spectroscopic Explorer (FUSE) and the Space Telescope
Imaging Spectrograph (STIS) on board the Hubble Space Telescope (HST),
we show that these emission lines, which represent the majority of
previously unidentifed emission features in cool star spectra between
912 and 1180 Å, are fluorescent decays in Fe II following excitation
by H Lyα. Specifically, following photoexcitation from the third term
(4s a 4D) of Fe II, subsequent decays are observed to the
two lowest terms (4s a 6D and 3d7 a 4F)
which are observed near 1100 and 1135 Å, respectively. Decays to higher
terms, and hence longer wavelengths, also are clearly seen in the STIS
spectra. Differences in the fluorescent Fe II spectra of α TrA and HD
104237 are tentatively identified as resulting from differences in the
intrinsic width of the density-weighted H Lyα radiation fields. The
additional Fe II lines observed in α TrA result from a broadened H
Lyα profile. Two features near 1060 Å appear to be fluorescent lines
of Cr II, also excited by H Lyα.

---------------------------------------------------------
Title: Microstructure of the Local Interstellar Cloud and the
Identification of the Hyades Cloud
Authors: Redfield, Seth; Linsky, Jeffrey L.
2001ApJ...551..413R Altcode: 2001astro.ph..1090R
We analyze high-resolution UV spectra of the Mg II h and k lines
for 18 members of the Hyades to study inhomogeneity along these
proximate lines of sight. The observations were taken by the Space
Telescope Imaging Spectrograph (STIS) instrument on board the
Hubble Space Telescope (HST). Three distinct velocity components
are observed. All 18 lines of sight show absorption by the Local
Interstellar Cloud (LIC); 10 stars show absorption by an additional
cloud, which we name the Hyades Cloud; and one star exhibits a third
absorption component. The LIC absorption is observed at a lower
radial velocity than predicted by the LIC velocity vector derived
by Lallement &amp; Bertin in 1992 and Lallement et al. in 1995
[vpredicted(LIC)-vobserved(LIC)=2.9+/-0.7 km
s-1], which may indicate a compression or deceleration at
the leading edge of the LIC. We propose an extension of the Hyades
Cloud boundary based on previous HST observations of other stars in
the general vicinity of the Hyades, as well as ground-based Ca II
observations. We present our fits of the interstellar parameters for
each absorption component. The availability of 18 similar lines of
sight provides an excellent opportunity to study the inhomogeneity
of the warm, partially ionized local interstellar medium (LISM). We
find that these structures are roughly homogeneous. The measured Mg
II column densities do not vary by more than a factor of 2 for angular
separations of &lt;~8°, which at the outer edge of the LIC correspond
to physical separations of &lt;~0.6 pc.

---------------------------------------------------------
Title: Chandra, EUVE, HST, and VLA Multiwavelength Campaign on HR
1099: Instrumental Capabilities, Data Reduction, and Initial Results
Authors: Ayres, Thomas R.; Brown, Alexander; Osten, Rachel A.;
Huenemoerder, David P.; Drake, Jeremy J.; Brickhouse, Nancy S.;
Linsky, Jeffrey L.
2001ApJ...549..554A Altcode:
In mid-September of 1999, a multiwavelength campaign was carried out
on the coronally active RS Canum Venaticorum binary HR 1099 (K1 IV+G5
V P=2.84 days), during commissioning of the High Energy Transmission
Grating Spectrometer (HETGS) of the Chandra X-ray Observatory (CXO). The
coordinated program involved the Extreme Ultraviolet Explorer (EUVE),
the Hubble Space Telescope Imaging Spectrograph (STIS), and the Very
Large Array (VLA). The objective was to study the system in quiescence,
across as much of the electromagnetic spectrum as practical, and to
catch any flares that might occur. The EUVE 80-180 Å light curve of
HR 1099, covering the period September 13-22, showed only a single
impulsive outburst, which occurred at the very end of the 9 day
pointing. The 3-25 Å bremsstrahlung continuum displayed an overall
decay during the 1.5 day Chandra observation on September 14-16,
with a few superimposed mild enhancements. The VLA 3.5 cm and 20 cm
radio light curves, obtained during a 10 hr period on September 15
immediately before the HST pointing, similarly revealed normal quiescent
gyrosynchrotron emission and an absence of impulsive events. In
contrast, the 7 hr STIS time series later on September 15 contained
two distinct flares. The first was accompanied by intensification of
the preexisting broad wings of the medium excitation species (e.g.,
Si IV λ1393 and C IV λ1548), while the second involved primarily
the narrow cores of the lines, and even cooler temperatures. The
Fe XXI λ1354 forbidden line showed little response to either flare,
consistent with the contemporaneous soft X-ray and EUV light curves. The
lack of coronal counterparts to the ultraviolet flares is unusual and
suggests that they belong to a separate class of outbursts, sharing
some similarities with the “transition zone explosive events”
seen on the Sun. The density sensitive O IV λ1400 multiplet was
not affected by either flare. The density sensitive Si III λ1300
multiplet showed little response to the first flare, but a dramatic
brightening in the second, likely due to the lower peak temperature
of that event. The O IV line ratios were near their low-density
limits and suggest ne~1010 cm-3
for the duration of the HST observations. The Si III ratios during
the second flare rise indicate ne~7×1010
cm-3. The far-UV diagnostics jointly imply electron pressures
of neT~2×1015 K cm-3, if formed
close to their respective ionization equilibrium temperatures. The
helium-like triplets of O VII, Ne IX, and Mg XI in the HETGS spectra
have forbidden-to-intercombination line ratios consistent with average
coronal electron densities of &lt;~1011 cm-3
at T~0.3-1×107 K over the duration of the Chandra
pointing. Fe XXI λ102/λ128 and λ142/λ128 ratios from EUVE suggest
ne&lt;~1012-1013 cm-3,
near 107 K. Thus, the coronal electron pressures could be
as much as several orders of magnitude larger than those of the lower
atmosphere. We constructed time-resolved spectra from the HETGS event
lists and measured the centroids of the three brightest X-ray lines of
HR 1099 in 60 minute bins. In high-S/N Ne X λ12.1, we believe that we
can see the changing radial velocity of the K1 IV star over the half
an orbital cycle recorded by Chandra. The amplitude of the velocity
change is only ~100 km s-1 over the 1.5 day interval,
a small fraction of the 300-500 km s-1 resolution of the
HETGS at 12 Å. Ne X λ12.1 also displayed a transient blueshift
of ~60 km s-1 immediately prior to the first STIS flare,
during which the far-UV lines briefly exhibited blueshifts of similar
magnitude. The apparent displacement of Ne X appears independently in
the -1 and +1 orders of the medium energy band (MEG), but there was no
confirmation in the redundant high energy band (HEG), nor in other X-ray
lines. Fe XXI λ1354 showed a blueshift about 30 minutes later at the
beginning of the second HST orbit, but only at the 20 km s-1
level. Analogous HETGS time series of the brightest lines of comparison
star Capella (α Aurigae G8 III+G1 III) exhibited steady behavior,
consistent with measurement uncertainties, without the transient
Doppler “bursts” seen in HR 1099. Although the reality of the Ne
X Lyα blueshift is in doubt, there is no question that the Chandra
HETGS velocity scales are stable and free from large systematic errors.

---------------------------------------------------------
Title: FUSE Observations of Capella
Authors: Young, P. R.; Dupree, A. K.; Wood, B. E.; Redfield, S.;
Linsky, J. L.; Ake, T. B.; Moos, H. W.
2001astro.ph..3261Y Altcode:
Far Ultraviolet Spectroscopic Explorer FUSE observations of the bright
binary system Capella (Alpha Aurigae; G1 III + G8 III) reveal a rich
emission line spectrum containing neutral and ionic species, among
them H I, O I, C III, O VI, S VI, Ne V and Ne VI. In addition the Fe
XVIII 974.85 A line, formed at temperatures of approx. 6 x 10^6 K,
is detected. Whereas the chromospheric and transition region emission
is dominated by that from the G1 giant, consistent with results from
previous ultraviolet observations, Fe XVIII is formed largely in the
G8 giant atmosphere. Line ratios from C III suggest densities of 2-8
x 10^10 cm^-3, although anomalous line profiles of the 1176 transition
may signal optical depth effects. The hydrogen Lyman series, detected
for the first time, displays asymmetric emission consistent with an
expanding atmosphere.

---------------------------------------------------------
Title: Chandra Spectra of Three Very Active Stars: AB Dor, 44i Boo,
and σ2 CrB
Authors: Linsky, J. L.; Skinner, S.; Osten, R.; Gagné, M.
2001ASPC..234...65L Altcode: 2001xras.conf...65L
No abstract at ADS

---------------------------------------------------------
Title: Components of the Local Interstellar Medium
Authors: Linsky, J. L.; Redfield, S.; Wood, B.
2001IAUS..203..595L Altcode:
HST, EUVE, and optical Ca II spectra are providing the critical velocity
and column density data needed to identify individual structures
(clouds) of warm gas in the local ISM near the Sun. We determine the
shape and physical properties of the Local Interstellar Cloud (LIC)
from 43 lines of sight. The Sun is located very close to the edge of
and will soon leave the LIC. Analysis of UV and optical spectra for
another 20 lines of sight permit us to determine preliminary sizes and
properties of other clouds located within about 50 pc of the Sun. We
will show new results for the G, NGP, SGP, and other clouds. These
nearby clouds appear to have the same D/H ratio as the LIC, but they
have different velocity vectors, temperatures, and metal depletions. We
will also discuss their ionization equilibria and relation to the
Scorpio-Centaurus Association and the Local Bubble.

---------------------------------------------------------
Title: Stellar Coronae: New Insights into Fundamental Questions
(Invited)
Authors: Linsky, Jeffrey L.; Ayres, Tom; Brown, Alec; Osten, Rachel;
Skinner, Steve; Gagne, Marc
2001ASPC..251...22L Altcode: 2001ncxa.conf...22L
No abstract at ADS

---------------------------------------------------------
Title: Searches for Magnetic Activity at the Bottom of the Main
Sequence and Beyond (CD-ROM Directory: contribs/krishnam)
Authors: Krishnamurthi, A.; Terndrup, D. M.; Linsky, J. L.; Leto, G.
2001ASPC..223.1538K Altcode: 2001csss...11.1538K
No abstract at ADS

---------------------------------------------------------
Title: Chandra Spectra of Four Very Active Stars: AB Dor, 44i Boo,
σ2 CrB, and AU Mic
Authors: Linsky, J. L.; Skinner, S.; Osten, R.; Gagné, M.
2001ASPC..248..255L Altcode: 2001mfah.conf..255L
No abstract at ADS

---------------------------------------------------------
Title: HST/STIS Quiescent Spectrum of AU Microscopii (CD-ROM
Directory: contribs/pagano)
Authors: Pagano, I.; Linsky, J. L.; Carkner, L.; Robinson, R. D.;
Woodgate, B.; Timothy, G.
2001ASPC..223.1039P Altcode: 2001csss...11.1039P
No abstract at ADS

---------------------------------------------------------
Title: Spectral imaging maps of <ASTROBJ>AR Lacertae</ASTROBJ>
. I. Results from IUE observations in 1994 October
Authors: Pagano, I.; Rodonò, M.; Linsky, J. L.; Neff, J. E.; Walter,
F. M.; Kovári, Zs.; Matthews, L. D.
2001A&A...365..128P Altcode:
In October 1994 the RS CVn eclipsing binary <ASTROBJ>AR
Lacertae</ASTROBJ> was monitored by IUE during two orbital cycles. We
have used 59 low resolution spectra, acquired in the range 1150-1950
Å, to derive light curves for emission lines formed at different
temperatures between about 10 000 and 200 000 K and to study the
flare signatures versus temperature of line formation. We have
analyzed a sequence of 59 high resolution Mg Ii k line profiles
using multi-Gaussian fits (the spectral imaging technique) to derive
information of the spatial structure of the chromospheres of both
stars in the <ASTROBJ>AR Lac</ASTROBJ> system. We discuss the quiet
chromospheric emission from both stars, and we show that enhanced Mg
Ii emission is present in extended structures corotating with the
K0 IVar\ and close to the system center-of-mass. We also report on
evidence for absorbing structures toward both the stars. This study of
<ASTROBJ>AR Lac</ASTROBJ> used the new orbital elements of Marino et
al. (\cite{Marino}) and spectra reduced and calibrated with NEWSIPS. A
comparison between fluxes derived from the analyzed NEWSIPS spectra
and from IUESIPS spectra is provided.

---------------------------------------------------------
Title: Far-UV Echelle Spectroscopy of Arcturus with HST STIS (CD-ROM
Directory: contribs/ayres)
Authors: Ayres, T. R.; Brown, A.; Harper, G. M.; Bennett, P. D.;
Linsky, J. L.; Carpenter, K. G.; Robinson, R. D.
2001ASPC..223.1079A Altcode: 2001csss...11.1079A
No abstract at ADS

---------------------------------------------------------
Title: VLA Observations of dMe Stars (CD-ROM Directory: contribs/leto)
Authors: Leto, G.; Pagano, I.; Linsky, J. L.; Rodonò, M.; Umana, G.
2001ASPC..223.1003L Altcode: 2001csss...11.1003L
No abstract at ADS

---------------------------------------------------------
Title: The Radio Signature of Molecular Catastrophes in the Extended
Envelope of Betelgeuse (CD-ROM Directory: contribs/harper2)
Authors: Harper, G. M.; Linsky, J. L.
2001ASPC..223.1603H Altcode: 2001csss...11.1603H
No abstract at ADS

---------------------------------------------------------
Title: Summary of the Eleventh Cool Stars Workshop (CD-ROM Directory:
contribs/linsky1)
Authors: Linsky, J. L.
2001ASPC..223..449L Altcode: 2001csss...11..449L
No abstract at ADS

---------------------------------------------------------
Title: The Warm Local ISM: Structure, Properties, and Theory
Authors: Linsky, J. L.; Redfield, S.; Wood, B.
2001ASPC..231..337L Altcode: 2001gssi.conf..337L
No abstract at ADS

---------------------------------------------------------
Title: Observational Estimates for the Mass-Loss Rates of α Centauri
and Proxima Centauri Using Hubble Space Telescope Lyα Spectra
Authors: Wood, Brian E.; Linsky, Jeffrey L.; Müller, Hans-Reinhard;
Zank, Gary P.
2001ApJ...547L..49W Altcode: 2000astro.ph.11153W
We study H I Lyα absorption observed by the Hubble Space Telescope
toward the nearby binary system α Centauri (G2 V + K0 V) and
its distant companion star Proxima Centauri (M5.5 Ve). Absorption
from heliospheric H I heated by the solar wind/interstellar medium
interaction is observed toward both α Cen and Proxima Cen. Absorption
from analogous “astrospheric” material surrounding the stars is
detected toward α Cen but not Proxima Cen. The nondetection of
astrospheric absorption toward Proxima Cen suggests that the stellar
wind of Proxima Cen must be significantly weaker than that of the α
Cen system. We compute several hydrodynamic models of the astrospheres
assuming different mass-loss rates in order to predict astrospheric Lyα
absorption for comparison with the observations. The model that best
matches the α Cen data has a mass-loss rate of M=2 Msolar,
and the models suggest an upper limit of M&lt;=0.2 Msolar
for Proxima Cen. Finally, we note that the heliospheric absorption
observed toward Proxima Cen in 2000 May is identical to the heliospheric
absorption observed toward α Cen in 1995 May, implying that the
structure of the outer heliosphere does not change significantly during
the solar activity cycle. Based on observations with the NASA/ESA Hubble
Space Telescope, obtained at the Space Telescope Science Institute,
which is operated by the Association of Universities for Research in
Astronomy, Inc., under NASA contract NAS5-26555.

---------------------------------------------------------
Title: Cool Star Chromospheres and the Sun
Authors: Linsky, J.; Redfield, S.; Ayres, T.; Brown, A.; Harper, G.
2001ASPC..242..247L Altcode: 2001ecom.conf..247L
No abstract at ADS

---------------------------------------------------------
Title: Observations of the Core of the Pleiades with the Chandra
X-Ray Observatory
Authors: Krishnamurthi, Anita; Reynolds, Christopher S.; Linsky,
Jeffrey L.; Martín, Eduardo; Gagné, Marc
2001AJ....121..337K Altcode: 2000astro.ph..9216K
We present results from a 36 ks observation of the core of the Pleiades
open cluster using ACIS-I on the Chandra X-Ray Observatory. We have
detected 57 sources, most of which do not have previously known
optical counterparts. Follow-up photometry indicates that many of the
detections are likely to be active galactic nuclei, in accordance with
extragalactic source counts, but some of the sources may be previously
undiscovered low-mass members of the Pleiades. We discuss our data
set and our findings about X-ray emission from early-type stars, as
well as very late-type stars. In particular, the large X-ray fluxes,
lack of variability, and hardness ratios of the four Pleiades B6
IV-F4 V stars suggest a tentative conclusion that Pleiades stars in
this spectral type range are intrinsic X-ray sources rather than
previously unknown binaries in which the X-ray emission is from a
late-type companion. Also, the sensitivity of Chandra allowed us to
detect nonflare X-ray emission from late M stars.

---------------------------------------------------------
Title: HST Observations of Heliospheric and Astrospheric Lyα
Absorption Toward the α Cen System
Authors: Wood, B. E.; Linsky, J. L.; Valenti, J. A.
2001IAUS..203..599W Altcode:
Charge exchange processes create a population of heated neutral
hydrogen gas throughout the heliosphere. This material produces a
detectable absorption signature in the Lyα lines of nearby stars with
low interstellar column densities. Such spectra have therefore been used
to study the properties of neutral hydrogen in the outer heliosphere,
and also to detect analogous astrospheric hydrogen surrounding other
stars. The first detection of heliospheric Lyα absorption was from
observations of α Cen A and B made in 1995 with the GHRS instrument
on board the Hubble Space Telescope. The heliospheric material produces
excess absorption on the red side of the interstellar absorption. Excess
absorption also exists on the blue side, which is believed to be due
to astrospheric material around the two stars. On 1999 February 12,
α Cen A was observed again by the STIS instrument, which replaced GHRS
in 1997; and on 2000 May 8, α Cen's distant companion star Proxima Cen
was also observed by STIS. We compare the GHRS and STIS data in order to
search for variations in the heliospheric absorption that would indicate
structural changes in the heliosphere, possibly induced by solar wind
variability associated with the Sun's activity cycle. We also search
for analogous changes in α Cen's astrosphere, and we compare the
astrospheric absorption of α Cen with that of Proxima Cen as a way
of comparing the stellar wind properties of these very different stars.

---------------------------------------------------------
Title: Mapping the detailed structure of the local interstellar medium
Authors: Redfield, S.; Linsky, J. L.
2001ohnf.conf..325R Altcode:
No abstract at ADS

---------------------------------------------------------
Title: STIS Observations of the Transition Region of α Cen A (G2 V)
(CD-ROM Directory: contribs/linsky3)
Authors: Linsky, J. L.; Pagano, I.; Valenti, J.; Gagné, M.; Duncan, D.
2001ASPC..223..697L Altcode: 2001csss...11..697L
No abstract at ADS

---------------------------------------------------------
Title: STIS Observations of the Transition Region of ζ Doradus
(CD-ROM Directory: contribs/redfield)
Authors: Redfield, S.; Linsky, J. L.; Ayres, T. R.; STIS Cycle 8 Cool
Star Survey Team
2001ASPC..223.1045R Altcode: 2001csss...11.1045R
No abstract at ADS

---------------------------------------------------------
Title: STIS Observations of the Hybrid-Chromosphere Star alpha TrA
(CD-ROM Directory: contribs/linsky2)
Authors: Linsky, J. L.; Redfield, S.; Harper, G.; Ayres, T.; Brown, A.
2001ASPC..223.1626L Altcode: 2001csss...11.1626L
No abstract at ADS

---------------------------------------------------------
Title: Highly Excited UV H2 emission around TW Hya
Authors: Herczeg, G. J.; Linsky, J. L.; Johns-Krull, C. M.; Valenti, J.
2001ASPC..244..265H Altcode: 2001ysne.conf..265H
No abstract at ADS

---------------------------------------------------------
Title: "Coronal" vs. "Noncoronal" Giants: A Spectral Comparison of
α Boo and β Gem (CD-ROM Directory: contribs/osten)
Authors: Osten, R. A.; Ayres, T. R.; Brown, A.; Linsky, J. L.
2001ASPC..223.1102O Altcode: 2001csss...11.1102O
No abstract at ADS

---------------------------------------------------------
Title: D/O and D/N towards HZ 43: First FUSE Results
Authors: Kruk, J. W.; Howk, J. C.; Andre, M.; Moos, H. W.; Oegerle,
W. R.; Oliveira, C.; Sembach, K. R.; Chayer, P.; Linsky, J. L.;
Wood, B. E.; Ferlet, R.; Hebrard, G.; Lemoine, M.; Vidal-Madjar, A.;
Sonneborn, G.; FUSE Science Team
2000AAS...197.3606K Altcode: 2000BAAS...32Q1450K
High resolution spectra of the DA white dwarf HZ 43 covering the
wavelength range 905--1187Å were obtained with the Far Ultraviolet
Spectroscopic Explorer (FUSE) for the purpose of studying the deuterium
abundance of the local interstellar medium. These spectra exhibit
clean interstellar lines of O i and N i, permitting a determination
of the column densities for these species. Only an upper limit to
the D i absorption could be determined, because of contamination
by the H i geocoronal airglow admitted by the large aperture used
for this observation. Archival HST/GHRS spectra in the vicinity
of Lyman α were used instead to determine the D i and H i column
densities, the latter determined from a fit to the damping wings of
the Lyman α transition. Further FUSE observations of HZ 43 using the
smaller MDRS aperture will be obtained in order to better constrain
the D i column density using the Lyman-series lines in the FUSE
bandpass. We will present determinations of the column densities and
uncertainties of interstellar D i, H i, O i, and N i along this sight
line and discuss the potential sources of systematic error in these
measurements. This work is based on data obtained for the Guaranteed
Time Team by the NASA-CNES-CSA FUSE mission operated by the Johns
Hopkins University. Financial support to U. S. participants has been
provided by NASA contract NAS5-32985.

---------------------------------------------------------
Title: Using Astrospheric Lyα Absorption Observed by HST to Study
the Stellar Winds of α Cen AB and Proxima Cen
Authors: Wood, B. E.; Linsky, J. L.; Mueller, H. -R.; Zank, G. P.
2000AAS...197.0804W Altcode: 2000AAS...197..804W; 2000BAAS...32.1406W
Using HST observations of the nearby α Cen AB binary system (G2 V+K0 V)
and its distant companion star Proxima Cen (M5.5 Ve), we study H I Lyα
absorption produced by heated neutral hydrogen gas in the heliosphere,
and we also study absorption from analogous “astrospheric” material
surrounding the stars. We use these data to show how astrospheric Lyα
absorption allows us for the first time to estimate the properties of
solar-like stellar winds. Unlike α Cen AB, no astrospheric absorption
whatsoever is detected toward Proxima Cen, suggesting that Proxima
Cen's wind must be significantly weaker than that of the α Cen AB
system. Hydrodynamic models of the astrospheres are computed assuming
different mass-loss rates to determine which predict the correct amount
of H I absorption, and these studies suggest a mass-loss rate of ˙
{M} ≈ 2 ˙ {M}sun for α Cen AB and ˙ {M} &lt;= 0.2 ˙
{M}sun for Proxima Cen. Support for this work is provided
by NASA grants NAG5-9041 and S-56500-D to the University of Colorado.

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Title: The Disk and Environment of HD 100546
Authors: Grady, C. A.; Polomski, E.; Henning, Th.; Stecklum, B.;
Woodgate, B.; Telesco, C.; Pina, R.; Plait, P.; Gull, T.; Boggess, A.;
Bowers, C.; Bruhweiler, F. C.; Clampin, M.; Danks, A.; Green, R. F.;
Heap, S. R.; Hutchings, J. B.; Jenkins, E.; Kaiser, M.; Kimble, R.;
Kraemer, S.; Lindler, D.; Linsky, J. L.; Maran, S. P.; Moos, H. W.;
Roesler, F.; Timothy, J. G.; Weistrop, D.
2000AAS...197.4702G Altcode: 2000BAAS...32.1481G
We present coronagraphic imaging of the nearest Herbig Be star with the
Space Telescope Imaging Spectrograph on board HST, K-short imaging with
ADONIS from the 3.6m telescope at La Silla, and mid-IR imaging with
OSCIR using the 4m telescope at CTIO. We confirm the disk detection
reported by Pantin et al. (2000). The brightest material associated
with the disk is located within 3.5" (365 AU) of the star, but disk
material can be traced to 5" (515 AU) based on the surface brightness
distribution. Spiral dark lanes are seen beyond 200 AU. HD 100546
is accompanied by a diffuse envelope which is more highly flared
than the disk and which extends 10" (1000 AU) from the star. Far
from the star, a band of nebulosity running from NNW to SSE is seen,
compatible with the orientation of filaments in DC 292.6-7.9 (Vieira et
al. 1999). Closer to the star, the bands are bowed out to the W and WSW,
in the direction of HD 100546's proper motion. The OSCIR images show
that the source is slightly extended at 11.7 microns, but unresolved
at 10 and 18 microns. The mid-IR color temperatures are consistent
with central clearing of the disk, supporting the inference of Pantin
et al. (2000). This study is based on observations made with HST,
and at ESO and CTIO. Funding was provided by NASA GTO funding to the
STIS Science Team in response to NASA A/O OSSA -4-84 through the HST
Project at GSFC, and through interagency transfer of funds to NOAO.

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Title: On the Temperature Structure of α TrA's Wind
Authors: Harper, G. M.; Brown, A.; Ayres, T. R.; Osten, R. A. .;
Bennett, P. D.; Linsky, J. L.; Skinner, S. L.; Redfield, S.; Baade,
R.; Reimers, D.; Andersson, B. -G.
2000AAS...197.0803H Altcode: 2000BAAS...32.1406H; 2000AAS...197..803H
We present new constraints on the wind temperature structure of the
hybrid bright-giant α TrA (K2 II) based on multi-wavelength datasets
(ATCA, HST/GHRS &amp; STIS, FUSE, ASCA). A previous study by Dupree
&amp; Brickhouse (1998), based on an ORFEUS-SPAS II spectrum, suggested
that α TrA's wind temperature was 3 x 105 K but this appears
inconsistent with the line profile shapes of lower excitation species
observed in GHRS spectra. The GHRS profiles indicate an ionization
temperature at the base of the wind of Tion &lt;= 20,000 K
(Harper 2001). We present new high sensitivity and R ~ 20,000 spectral
resolution FUSE spectra which allow us to examine the C III 977Å and
O VI line profiles in detail. Contrary to the ORFEUS-SPAS II spectra,
the O VI lines show no evidence that they are physically associated
with the stellar wind. To within the inherent uncertainties in the FUSE
wavelength scale, the O VI 1031.9Å line is symmetric when centered on
the photospheric rest frame. This indicates that (i) O VI photons are
not created within a 3 x 105 K outflow, and (ii) there is
no significant material at this temperature to scatter photons within
the wind. We also investigate the suggestion by Ayres &amp; Kashyap
(1994) that the large asymmetry observed in the H Lyα line, which is
also observed in the FUSE Lyβ profile, is a result of trace neutral
hydrogen in a high velocity (400\&gt;km\&gt;s-1) coronal
wind. This research is funded by NASA grants NAG5-9010 &amp; NAG5-3226.

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Title: STIS Coronagraphic Imaging of the Herbig AE Star: HD 163296
Authors: Grady, C. A.; Devine, David; Woodgate, B.; Kimble, R.;
Bruhweiler, F. C.; Boggess, A.; Linsky, J. L.; Plait, Philip; Clampin,
M.; Kalas, P.
2000ApJ...544..895G Altcode:
Coronagraphic imaging with the Space Telescope Imaging Spectrograph on
board the Hubble Space Telescope reveals a ~450 AU radius circumstellar
disk around the Herbig Ae star HD 163296. A broadband (0.2-1.0 μm)
reflected light image shows the disk oriented at a position angle of
140deg+/-5deg and inclined to our line of sight
by ~60deg+/-5deg. The disk includes an annulus
of reduced scattering at 325 AU and exhibits a flat trend of surface
brightness in to 180-122 AU (1.5"-1"), consistent with a cleared
central zone. For r&gt;=370 AU the disk surface brightness drops as r
to the approximately -3.5 power. The disk cannot be traced beyond 450
AU in our data. The disk is accompanied by a chain of nebulosities at
P.A.=42.5d+/-3.5d, compatible with detection of a Herbig-Haro flow. The
HD 163296 disk most closely resembles the disk of HD 141569. As in the
HD 141569 system, the dynamical effects of a planet may be necessary
to explain the structure in the outer disk.

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Title: D/H Toward WD 1634-573: First FUSE Results
Authors: Linsky, J. L.; Wood, B. E.; Hébrard, G.; Lemoine, M.;
Vidal-Madjar, A.; Sembach, K.; FUSE Science Team
2000AAS...197.3603L Altcode: 2000BAAS...32R1449L
We present and analyze spectra of the white dwarf WD1634-573 observed
by the Far Ultraviolet Spectroscopic Explorer (FUSE) satellite. The
spectra, observed through the large (LWRS) and medium (MDRS) apertures,
contain absorption lines of many interstellar atoms and ions along the
line of sight to the star. We fit profiles to lines of HI, DI, CII,
CIII, NI, NII, OI, SiII, and ArI. When making these fits we solved
for the column densities under a variety of assumptions concerning
the interstellar medium including whether the local ISM has one or
two velocity components and whether the temperatures, bulk velocities,
and turbulent velocities are solved self-consistently or constrained
to be typical values for the local ISM. We are able to fit the DI,
NI, and OI column densities with relatively small uncertainties for
this broad range of models. However the derived HI column density
has large uncertainty due to the very saturated nature of the Lyman
lines. We present accurate values of the D/O and D/N ratios from
the FUSE data. At this time the HI column density is more accurately
determined from EUVE spectra (Napiwotski et al 1996). We therefore
use the HI column density obtained from EUVE data when determining
D/H for this line of sight. This work is based on data obtained for
the Guaranteed Time Team by the NASA-CNES-CSA FUSE mission operated by
the Johns Hopkins University. Financial support to U. S. participants
has been provided by NASA contract NAS5-32985.

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Title: Microstructure of the Local Interstellar Cloud (LIC) and
Identification of the Hyades Interstellar Cloud
Authors: Redfield, S.; Linsky, J. L.; Wood, B. E.
2000AAS...197.0706R Altcode: 2000BAAS...32.1402R; 2000AAS...197..706R
We present an analysis of the Local Interstellar Medium (LISM) towards
the Hyades star cluster. High resolution (E230H), HST/STIS spectra
taken from the HST Data Archive were used. The Mg II h and k lines of
18 targets were used to calculate relevant ISM parameters (velocity,
Doppler parameter, and column density). Three velocity components are
observed. Absorption due to the Local Interstellar Cloud (LIC) is seen
in all targets. A second cloud, the Hyades Cloud, is observed in ten
of the 18 targets. A third component is seen in one object. Deviations
from the LIC velocity vector (Lallement et al. 1995) are observed
and may have implications for the three-dimensional structure and
evolution of the LIC. We discuss the characteristics of all clouds,
and make comparisons with previously observed, nearby targets. Due
to the close proximity of the lines of sight, we use this sample to
investigate the microstructure of the LISM and LIC. Changes in column
density do not exceed a factor of two at angular distances of less
than 10o. We discuss the implications of the homogeneity
or inhomogeneity of the LISM. This research is funded by NASA grant
NGT5-50242.

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Title: AB Dor in '94: I. HST/GHRS Observations of the Quiescent
Chromosphere of an Active Star
Authors: Brandt, J. C.; Heap, S. R.; Walter, F. M.; Beaver, E. A.;
Boggess, A.; Carpenter, K. G.; Ebbets, D. C.; Hutchings, J. B.; Jura,
M.; Leckrone, D. S.; Linsky, J. L.; Maran, S. P.; Savage, B. D.;
Smith, A. M.; Trafton, L. M.; Weymann, R. J.; Norman, D.; Redfield, S.
2000astro.ph.12487B Altcode:
We analyze HST/GHRS spectra of AB Doradus, the prototypical
ultra-rapidly rotating K dwarf. We observed chromospheric (Mg II)
and transition region (C II, Si IV, C IV, and N V) lines periodically
throughout the stellar rotation period, and provide a low dispersion
stellar atlas of 78 emission lines. The quiescent line profiles of the
chromospheric and transition region lines show narrow cores superposed
on very broad wings. The broad wings of the Mg II k &amp; h lines and
of the transition region lines can be explained by emission from gas
co-rotating with the star and extending out to near the Keplerian
co-rotation radius (2.8 stellar radii). While this is not a unique
solution, it is consistent with previous studies of H-alpha emission
that are naturally explained by large co-rotating prominences. We
find no evidence for rotational modulation of the emission line
fluxes. The density diagnostics suggest that the transition region is
formed at constant pressure, with an electron density 2-3 E12 /cm^3
at a temperature of 30,000 K. The electron pressure is about 100 times
larger than that for the quiet Sun. The emission measure distribution
shows a minimum between log(T) = 5 and 5.5. The Mg II line exhibits
three interstellar absorption components along the 15 pc line of
sight. We identify the lowest velocity component with the G cloud,
but the other components are not identified with any interstellar
clouds previously detected from other lines of sight.

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Title: STIS observations of the Ly-α bright jet associated with
the Herbig Ae star HD163296
Authors: Devine, D.; Grady, C. A.; Kimble, R. A.; Woodgate, B.;
Palunas, P.; Linsky, J. L.
2000AAS...197.0809D Altcode: 2000AAS...197..809D; 2000BAAS...32Q1407D
We present follow-up HST/STIS observations of the Ly-α bright jet
associated with the near-ZAMS Herbig Ae star HD163296. The proper
motions and radial velocities of the knots in the flow are consistent
with a collimated outflow inclined by 40 degrees relative to the plane
of the sky with a flow velocity that varies from 350 to 500 km/s along
the jet. A new knot is visible in the jet at a projected distance of
0.33" (40 AU) from the central star. The knot has a dynamical age of
only seven months, making it the youngest HH knot ever observed. We
did not detect any emission from the counterjet within 2.5" of the
source, which is consistent with absorption due to a uniform 450 AU
radius disk tilted at 50 degrees relative to the line of sight. We also
present observations made with the Goddard Fabry-Perot Imager which
show additional, more distant knots along the blue and red shifted
outflow lobes, and discuss the collimation of the jet and implications
for a magnetosphere associated with HD 163296. Support for this study
was provided by HST STIS GTO funding through support to the NOAO, in
response to the NASA A/O OSSA -4-84 through the Hubble Space Telescope
Project at GSFC, as well as NASA grant NRA--98--03--UVG--011. NOAO is
operated by the Association of Universities for Research in Astronomy
(AURA), Inc., under cooperative agreement with the National Science
Foundation. Data analysis facilities were provided by the Laboratory
for Astronomy &amp; Solar Physics, NASA/GSFC.

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Title: Radio, X-Ray, and Extreme-Ultraviolet Coronal Variability
of the Short-Period RS Canum Venaticorum Binary σ2
Coronae Borealis
Authors: Osten, Rachel A.; Brown, Alexander; Ayres, Thomas R.; Linsky,
Jeffrey L.; Drake, Stephen A.; Gagné, Marc; Stern, Robert A.
2000ApJ...544..953O Altcode:
We present the results of a coordinated observing campaign on the
short-period (1.14 days) RS CVn binary σ2 Coronae Borealis
with the VLA, ASCA, and RXTE. We also discuss earlier observations
of the same system obtained by the Extreme Ultraviolet Explorer
(EUVE). Dramatic coronal variability is present in all of these
observations across the electromagnetic spectrum. σ2
CrB undergoes frequent large flares that occur close together in
time. Radio flares are unambiguously correlated with X-ray flares;
the X-ray flares peak as much as 1.4 hr before the corresponding
radio maxima. Response to flares is more rapid in higher energy
X-ray bandpasses, signaling an increase in temperature during the
course of the flare. Flares are seen more frequently in the harder
RXTE bandpass than in simultaneously taken ASCA observations. There
is greater contrast between flaring and nonflaring conditions in the
RXTE light curve. Complex flaring is seen in the radio at 3 and 6 cm,
consistent with optically thin nonthermal gyrosynchrotron emission for
most of the duration of the observation. Bursts of left-circularly
polarized emission at 20 cm lasting &lt;=15 minutes appear to be
due to a coherent emission process. EUVE spectra reveal coronal
material at ne&lt;=1012 cm-3, with
no discernible density differences between flaring and quiescent time
intervals. Quiescent ASCA spectra show lower than solar photospheric
abundances with iron depleted by a factor of 4 from the solar
photospheric value. The abundances increase during a large flare
observed with ASCA, with iron enhanced to the solar photospheric
value during the rise phase of the flare. Two-temperature fits to
extracted spectra show a low-temperature quiescent value of 8 MK and a
high-temperature component that varies from 22 MK during quiescence to
50 MK at the peak of the flare. Emission measure distributions measured
from the ASCA observations are consistent with the temperatures derived
from the discrete two-temperature fits and indicate the presence
of very hot (&gt;100 MK) plasma during the rise phase of the ASCA
flare. Many of the flares observed with EUVE, ASCA, and RXTE show a
double exponential decay phase, further highlighting the importance of
this phenomenon in diagnosing flaring conditions. We also find that
the observed second decay timescale cannot be explained by some of
the currently used flare parameterizations.

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Title: Origins, Structure, and Evolution of Magnetic Activity in
the Cool Half of the H--R Diagram: Progress Report on a Major HST
STIS Stellar Survey
Authors: Ayres, T. R.; Brown, A.; Drake, S. A.; Dupree, A. K.; Guedel,
M.; Guinan, E.; Harper, G. M.; Jordan, C.; Linsky, J. L.; Reimers,
D.; Schmitt, J. H. M. M.; Simon, T.
2000AAS...197.4407A Altcode: 2000BAAS...32.1472A
In early October 2000, HST completed a year and a half long ultraviolet
spectral survey of late-type stars with its Space Telescope Imaging
Spectrograph (STIS). Thirteen stars were observed, ranging over
spectral types F7--K0 on the main sequence, F8--G8 in the giant branch,
and G0--G8 in the supergiants. A total of 72 observation sequences
were executed, some consisting of several independent exposures
(up to 13: in the case of HR 1099, recorded during a long grating
observation by Chandra ). Spectra were taken in the medium resolution
echelle modes (E140M, E230M: R ~ 30--40,000) below about 2500 Å,
and in the high-resolution echelle mode (E230H: R ~ 105)
between 2500--3000 Å. For each target, about 70% of the exposure
time was devoted to the key E140M interval (1150--1700 Å). Although
the observations were collected primarily to study the magnetically
disturbed outer atmospheres of late-type stars, they also are valuable
for investigating the local interstellar medium through UV absorptions
in H 1, O 1, Fe 2, and Mg 2, and for measuring the cosmologically
significant D/H ratio. We present examples of the superb spectra
resulting from the program, and discuss some of the new insights we
have gained concerning plasma dynamics in the 105 K layers
of the stellar “transition zone;” the super-rotational broadening
of the Si 4, C 4, and N 5 emissions in Hertzsprung gap giants; and the
spectral peculiarities of the “hybrid chromosphere” supergiants. This
work was supported by grant GO-08280.01-97A from STScI. Observations
were from the NASA/ESA HST, collected at the STScI, operated by AURA,
under contract NAS5-26555.

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Title: FUSE Observations of K--M Stars
Authors: Ake, T. B.; Dupree, A. K.; Linsky, J. L.; Harper, G. M.;
Young, P. R.
2000AAS...19712903A Altcode: 2001BAAS...33Q.712A
As part of the FUSE PI program, a representative sample of cool stars
is being surveyed in the LWRS (30 x 30 arcsec) aperture. We report on
recent observations of three late-type stars, AU Mic (HD 197481, M0 Ve),
β Gem (HD 62509, K0 IIIb), and α Ori (HD 39801, M1-2 Ia--Iab). AU
Mic and β Gem show strong emission lines of O VI 1032/1037 and C III
977/1176 and weaker lines of C II, N II, N III, S IV, Si III, Si IV,
and perhaps Fe III. AU Mic has evidence of He II and S III emission,
and β Gem shows S I emission. Differences are seen in line ratios and
line profiles between these stars. In α Ori, these features are very
weak or non-existent, and Fe II fluorescent lines in the 1100-1150 Å
region, pumped by H I Lyman α , are present. Several emission lines
are still unidentified in all spectra. Prospects for future cool star
observations will be discussed. This work is based on data obtained for
the Guaranteed Time Team by the NASA-CNES-CSA FUSE mission operated by
the Johns Hopkins University. Financial support to U. S. participants
has been provided by NASA contract NAS5-32985.

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Title: The D/H Abundance Ratio in Local Interstellar Gas
Authors: Sahu, M. S.; Landsman, W.; Bruhweiler, F. C.; Linsky, J.;
Hubeny, I.; Barstow, M.; Holberg, J.; Gull, T.; Bowers, C.; Lindler,
D.; Lanz, T.; Feggans, K.
2000AAS...197.0703S Altcode: 2000AAS...197..703S; 2000BAAS...32.1401S
Does the D/H ratio vary within ~ 100 pc of the Sun? If it does, what
is the range of these variations? Are the D/H variations correlated to
any physical property of the absorbing cloud? To answer these questions
we have begun a project to obtain high-precision D/H abundance ratios
in the Local Interstellar Medium within ~ 100 pc (Sahu et al. 1999,
ApJ 523, L159). For this purpose, we primarily use HST-Space Telescope
Imaging Spectrograph (STIS) data towards nearby hot, white dwarfs
(WDs). The advantages of using STIS for this study are: (1) The high
velocity resolution of STIS in the UV ( ~ 2 km s-1 in the
E140H and E230H modes) allows the velocity structure in the sightline
to be resolved and reliable component-to-component variations can be
studied (2) WDs provide a strong, smooth UV continuum against which
other diagnostic interstellar absorption lines can be measured. The
wider wavelength coverage ( ~ 200Å per setting) of STIS in the
high-resolution E140H mode allows important interstellar lines such as N
i, Si ii, O i and S ii to be measured in addition to D i and H i, at no
extra cost in HST time (3) The superior echelle scatter and background
corrections possible with the 2-dimensional STIS-MAMA detectors allow
more accurate D/H determinations from WD spectra. In this poster, we
present a status report of our project along with some recent results.

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Title: Overview of Deuterium in the Local Interstellar Medium:
First FUSE Results
Authors: Moos, H. W.; Sembach, K. R.; Friedman, S. D.; Kruk, J. W.;
Sonneborn, G.; Vidal-Madjar, A.; Hebrard, G.; Linsky, J. L.; FUSE
Science Team
2000AAS...197.3601M Altcode: 2000BAAS...32.1449M
The abundance of deuterium relative to hydrogen is a sensitive measure
of the cosmological baryon density. The Far Ultraviolet Spectroscopic
Explorer Mission (FUSE) is performing a comprehensive set of abundance
measurements for sight lines in the local interstellar medium (LISM)
in order to determine definitive values of D/H and its variability
on different scales. These results will provide fundamental knowledge
about the chemical evolution of the gas, the mixing of the interstellar
medium, and other astrophysical processes relevant to understanding the
D/H ratio. The accompanying papers describe the first set of FUSE D/H
measurements for the LISM. Eventually, this study will increase the
number of high precision D/H measurements for the local interstellar
medium by an order of magnitude. It will serve as a benchmark for
other FUSE studies of D/H in the Milky Way Galaxy and also for studies
of D/H at high redshift where the main objective is to determine the
primordial value of D/H produced by Big Bang nucleosynthesis. This paper
will provide an overview of the accompanying papers and compare the
results for individual sight lines. This work is based on data obtained
for the FUSE Guaranteed Time Team by the NASA-CNES-CSA FUSE mission
operated for NASA by the Johns Hopkins University. Financial support
to U. S. participants has been provided by NASA contract NAS5-32985.

---------------------------------------------------------
Title: Deuterium Toward WD2211-495: First FUSE results
Authors: Hébrard, G.; Lemoine, M.; Désert, J. -M.; Lecavelier des
Etangs, A.; Vidal-Madjar, A.; Ferlet, R.; Linsky, J. L.; Wood, B. E.;
Chayer, P.; Blair, W. P.; Friedman, S. D.; Kruk, J. W.; Moos, H. W.;
Oegerle, W. R.; Sembach, K. R.; Sonneborn, G.; FUSE Science Team
2000AAS...197.3604H Altcode: 2000BAAS...32.1449H
We present a deuterium abundance analysis of the 905-1187 Å spectrum
of the line of sight toward the white dwarf WD2211-495 obtained by the
Far Ultraviolet Spectroscopic Explorer (FUSE). Numerous interstellar
lines are detected on the continuum of the stellar spectrum. A thorough
analysis was performed through the simultaneous fit of interstellar
absorption lines detected in the four channels (LiF1, SiC1, LiF2
and SiC2) and obtained through the three apertures (LWRS, MDRS and
HIRS). The fit includes the following species: D i, O i, N i, Fe ii,
Si ii and P ii. We excluded all saturated lines in order to reduce
possible systematic errors on the column density measurements. We report
an accurate determination of the average interstellar D/O and D/N ratios
along this line of sight. This work is based on data obtained for the
Guaranteed Time Team by the NASA-CNES-CSA FUSE mission operated by the
Johns Hopkins University. Financial support to U. S. participants has
been provided by NASA contract NAS5-32985.

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Title: The Mg II and Lyα Lines of Nearby K Dwarfs: Interstellar
Medium Components and Flux Measurements
Authors: Wood, Brian E.; Ambruster, Carol W.; Brown, Alexander;
Linsky, Jeffrey L.
2000ApJ...542..411W Altcode: 2000astro.ph..7172W
We analyze local interstellar medium (LISM) absorption observed in
the Lyα and Mg II h and k lines of six nearby K dwarf stars, using
UV spectra of these stars obtained with the Goddard High Resolution
Spectrograph on the Hubble Space Telescope. For four of the six stars,
we detect an absorption component with a velocity and column density
consistent with the Local Interstellar Cloud (LIC). For HD 197890,
there is no observed component at the expected LIC velocity or at
the projected velocity of the G cloud, which is a nearby cloud in the
general direction of the Galactic center. It also seems doubtful that
either of the two components seen toward HD 82558 are LIC or G cloud
absorption. The total H I column density toward HD 82558 (d=18.3 pc)
is extremely high (logNH=19.05+/-0.15), representing
the largest average H I density detected for any line of sight
through the nearby LISM (nH~0.2 cm-3). This is
particularly remarkable considering that this star is only 39° from the
“interstellar tunnel” toward ɛ CMa, where column densities are an
order of magnitude lower than this toward stars that are an order of
magnitude farther away. Based on observations with the NASA/ESA Hubble
Space Telescope, obtained at the Space Telescope Science Institute,
which is operated by the Association of Universities for Research in
Astronomy, Inc., under NASA contract NAS5-26555.

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Title: A Lyα Bright Jet from a Herbig AE Star
Authors: Devine, David; Grady, C. A.; Kimble, R. A.; Woodgate, B.;
Bruhweiler, F. C.; Boggess, A.; Linsky, J. L.; Clampin, M.
2000ApJ...542L.115D Altcode:
We report the detection in Lyα of a collimated, bipolar outflow
(HH 409) associated with the 1.5-10 Myr old Herbig Ae star HD
163296. A blueshifted jet is visible in Lyα and Si III extending
toward the southwest for at least 6" (725 AU). The combination of low
line-of-sight extinction and relative faintness of the central star
near Lyα enables us to trace the jet to within an unprecedented 0.06"
(7.3 AU) of HD 163296. The jet has a radial velocity of 335-380 km
s-1, which is common for protostellar outflows. We also
detected redshifted Lyα emission southwest of the star that may be
due to infall or a poorly collimated wind component. If the age of the
star is correct, then protostellar outflows may last up to 10 times
longer than previously believed.

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Title: Coordinated Observations of the Active Binary σ 2
CrB with Chandra, EUVE, and the VLA
Authors: Osten, R. A.; Brown, A.; Ayres, T. R.; Krishnamurthi, A.;
Linsky, J. L.
2000HEAD....5.4214O Altcode: 2000BAAS...32.1257O
We report on coordinated observations of the short-period active
binary σ 2 CrB (F6V + G0V, P orb=1.14 d) taken
with the Chandra X-ray Observatory, the Extreme Ultraviolet Explorer,
and the Very Large Array. EUVE observations span more than 7 orbital
periods of the system. Centered in the middle of the nine day EUVE
observation is a Chandra ACIS-S+HETGS grating observation lasting
85 ks and an overlapping 12 hour multifrequency VLA observation. We
discuss the coronal variability, present high-resolution X-ray spectra
and preliminary analysis including the search for flares, and tie the
thermal high temperature emission together with nonthermal coronal
emission. RAO acknowledges funding from a NASA GSRP fellowship, grant
NGT5-50241. AB and TRA acknowledge funding from NASA grant NAG5-3226,
and JLL acknowledges support from NASA through grants S-56500-D and
H-04630D.

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Title: HETG Observations of the K Giant Beta Ceti
Authors: Linsky, Jeffrey
2000cxo..prop..441L Altcode: 2000chan.prop..400L; 2000cxo..prop..400L
Beta Ceti (HD 4128) is the brightest K giant as seen in X-rays. This K0
III post helium flash star is unusually luminous in X-rays compared to
other clump giants. The high X-ray luminosity may be due to its age or
to a rejuvenated dynamo as a result of angular momentum redistribution
in its core. We propose a deep (88 ks) HETG observation to measure
the coronal temperature structure, coronal densities, and coronal
abundances of this unusual star.

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Title: The M 16 Star-Forming Region
Authors: Linsky, Jeffrey
2000cxo..prop..445L Altcode: 2000cxo..prop..409L; 2000chan.prop..409L
The Eagle Nebula (M 16, NGC 6611) is a giant H II region with an
optically visible cluster of very young MS OB stars and low-mass
pre-main sequence stars. The fingers of the Eagle Nebula also contain
some of the youngest known embedded mm and infrared protostars. We
will obtain an 80-ks ACIS-I image of the core of the Eagle Nebula to
look for X-ray emission and flares from the stars and protostars of
M 16. To our knowledge, this is the first pointed X-ray observation
of M 16. Given the distance to M 16 (2.1 kpc) and the high density of
stars (2200 catalogued stars within 20 arcmin of the cluster center),
a long-exposure Chandra image is needed to reliably detect and identify
the X-ray sources.

---------------------------------------------------------
Title: An IUE Atlas of Pre-Main-Sequence Stars. II. Far-Ultraviolet
Accretion Diagnostics in T Tauri Stars
Authors: Johns-Krull, Christopher M.; Valenti, Jeff A.; Linsky,
Jeffrey L.
2000ApJ...539..815J Altcode:
We use our ultraviolet (UV) atlas of pre-main-sequence stars constructed
from all useful, short-wavelength, low-resolution spectra in the
International Ultraviolet Explorer (IUE) satellite Final Archive
to analyze the short-wavelength UV properties of 49 T Tauri stars
(TTSs). We compare the line and continuum fluxes in these TTSs with
each other and with previously published parameters of these systems,
including rotation rate, infrared excess, and mass accretion rate. The
short-wavelength continuum in the classical TTSs (CTTSs) appears to
originate in a ~10,000 K optically thick plasma, while in the naked TTSs
(NTTSs-stars without dusty disks) the continuum appears to originate
in the stellar atmosphere. We show that all of the TTSs in our sample
lie in the regime of “saturated” magnetic activity due to their
small Rossby numbers. However, while some of the TTSs show emission
line surface fluxes consistent with this saturation level, many CTTSs
show significantly stronger emission than predicted by saturation. In
these stars, the emission line luminosity in the high ionization lines
present in the spectrum between 1200 and 2000 Å correlates well
with the mass accretion rate. Therefore, we conclude that the bulk
of the short-wavelength emission seen in CTTSs results from accretion
related processes and not from dynamo-driven magnetic activity. Using
CTTSs with known mass accretion rates, we calibrate the relationship
between M and LC IV to derive the mass accretion rate for
some CTTSs which for various reasons have never had their mass accretion
rates measured. Finally, several of the CTTSs show strong emission from
molecular hydrogen. While emission from H2 cannot form in gas
at a temperature of ~105 K, the strength of the molecular
hydrogen emission is nevertheless well correlated with all the other
emissions displayed in the IUE short-wavelength bandpass. This suggests
that the H2 emission is in fact fluorescent emission pumped
by the emission (likely Lyα) from hotter gas.

---------------------------------------------------------
Title: STIS Observations of a Brown Dwarf
Authors: Linsky, Jeffrey
2000hst..prop.8482L Altcode: 2000hst..prop.4885L
Brown dwarfs are degenerate stars with masses smaller than 0.08 M_sun
that do not burn hydrogen except when very young. There are now about
a dozen good candidates based on near infrared photometry and low
resolution spectroscopy, but a large number of brown dwarfs are being
discovered daily by the DENIS and 2MASS surveys. The nearest and so
far the coolest of the brown dwarfs is Gl 229B, which is about 6 pc
distant and located about 7" from the early M dwarf primary star. The
second closest brown dwarf is Kelu-1, located about 10-12 pc from the
Sun. Little is known about brown dwarfs except that they are fully
convective, they have about the same radius as Jupiter, and they
probably cannot explain missing mass in our Galaxy. They likely have
strong magnetic fields given that strong fields are measured in the
latest of the M dwarfs and on Jupiter. Indirect evidence for magnetic
fields on brown dwarfs is provided by the ROSAT X-ray detection of
one young brown dwarf in the Chamaeleon I Dark Cloud and five brown
dwarf candidates in Taurus of which the brightest in X-rays is MHO-4
{Neuhauser et al. A+A, 343, 883 [1999]} and the detection of an H-alpha
flare on the 2MASS object J0149090+295613 {spectral type M9.5V} by
Liebert et al {ApJ, 519, 345L [1999]}. We select MHO-4 as our target
because young brown dwarf candidates are the most X-ray luminous and
this target has low extinction.

---------------------------------------------------------
Title: The Ionization of the Local Interstellar Medium as Revealed
by Far Ultraviolet Spectroscopic Explorer Observations of N, O,
and AR toward White Dwarf Stars
Authors: Jenkins, E. B.; Oegerle, W. R.; Gry, C.; Vallerga, J.;
Sembach, K. R.; Shelton, R. L.; Ferlet, R.; Vidal-Madjar, A.; York,
D. G.; Linsky, J. L.; Roth, K. C.; Dupree, A. K.; Edelstein, J.
2000ApJ...538L..81J Altcode: 2000astro.ph..4409J
Far Ultraviolet Spectroscopic Explorer spectra of the white dwarf stars
G191-B2B, GD 394, WD 2211-495, and WD 2331-475 cover the absorption
features out of the ground electronic states of N I, N II, N III, O I,
and Ar I in the far-ultraviolet, providing new insights on the origin of
the partial ionization of the local interstellar medium (LISM) and, for
the case of G191-B2B, the interstellar cloud that immediately surrounds
the solar system. Toward these targets the interstellar abundances
of Ar I, and sometimes N I, are significantly below their cosmic
abundances relative to H I. In the diffuse interstellar medium, these
elements are not likely to be depleted onto dust grains. Generally,
we expect that Ar should be more strongly ionized than H (and also O
and N, whose ionizations are coupled to that of H via charge-exchange
reactions) because the cross section for the photoionization of Ar I
is very high. Our finding that Ar I/H I is low may help to explain
the surprisingly high ionization of He in the LISM found by other
investigators. Our result favors the interpretation that the ionization
of the local medium is maintained by a strong extreme-ultraviolet flux
from nearby stars and hot gases, rather than an incomplete recovery
from a past, more highly ionized condition. Based on data obtained for
the Guaranteed Time Team by the NASA-CNES-CSA FUSE mission operated
by Johns Hopkins University. Financial support to US participants has
been provided by NASA contract NAS5-32985.

---------------------------------------------------------
Title: Far Ultraviolet Spectroscopic Explorer Observations of the
Active Cool Star AB Doradus
Authors: Ake, T. B.; Dupree, A. K.; Young, P. R.; Linsky, J. L.;
Malina, R. F.; Griffiths, N. W.; Siegmund, O. H. W.; Woodgate, B. E.
2000ApJ...538L..87A Altcode:
Far-ultraviolet spectra were obtained of the active cool star AB
Doradus (HD 36705) during the calibration and checkout period of the
Far Ultraviolet Spectroscopic Explorer (FUSE) satellite. Observations
in this early phase of the mission were taken at a resolving
power of 12,000-15,000 (~20-25 km s-1) and covered the
spectral range 905-1187 Å. The integrated spectrum exhibits strong,
rotationally broadened stellar emission from C III (λλ977, 1175)
and O VI (λλ1032, 1037) and many weaker lines. Strong emission
lines of C III and O VI exhibit broad wings. The C III λ977 profile
shows blueshifted absorption at ~30 km s-1, and C II
λ1036 absorption appears superposed on emission in the wing of O
VI λ1037. Rotational modulation of C III and O VI is present, in
harmony with its photometric variability. Flares were detected in
the brightest lines, and subexposures were analyzed to examine flux
and profile variations. Downflows that extend to 600 km s-1
during a flare are found in the O VI profiles. These early observations
demonstrate that FUSE will be an exceptional instrument for studying
chromospheres in cool stars.

---------------------------------------------------------
Title: Overview of the Far Ultraviolet Spectroscopic Explorer Mission
Authors: Moos, H. W.; Cash, W. C.; Cowie, L. L.; Davidsen, A. F.;
Dupree, A. K.; Feldman, P. D.; Friedman, S. D.; Green, J. C.; Green,
R. F.; Gry, C.; Hutchings, J. B.; Jenkins, E. B.; Linsky, J. L.;
Malina, R. F.; Michalitsianos, A. G.; Savage, B. D.; Shull, J. M.;
Siegmund, O. H. W.; Snow, T. P.; Sonneborn, G.; Vidal-Madjar, A.;
Willis, A. J.; Woodgate, B. E.; York, D. G.; Ake, T. B.; Andersson,
B. -G.; Andrews, J. P.; Barkhouser, R. H.; Bianchi, L.; Blair,
W. P.; Brownsberger, K. R.; Cha, A. N.; Chayer, P.; Conard, S. J.;
Fullerton, A. W.; Gaines, G. A.; Grange, R.; Gummin, M. A.; Hebrard,
G.; Kriss, G. A.; Kruk, J. W.; Mark, D.; McCarthy, D. K.; Morbey,
C. L.; Murowinski, R.; Murphy, E. M.; Oegerle, W. R.; Ohl, R. G.;
Oliveira, C.; Osterman, S. N.; Sahnow, D. J.; Saisse, M.; Sembach,
K. R.; Weaver, H. A.; Welsh, B. Y.; Wilkinson, E.; Zheng, W.
2000ApJ...538L...1M Altcode: 2000astro.ph..5529M
The Far Ultraviolet Spectroscopic Explorer satellite observes light
in the far-ultraviolet spectral region, 905-1187 Å, with a high
spectral resolution. The instrument consists of four co-aligned
prime-focus telescopes and Rowland spectrographs with microchannel
plate detectors. Two of the telescope channels use Al:LiF coatings
for optimum reflectivity between approximately 1000 and 1187 Å,
and the other two channels use SiC coatings for optimized throughput
between 905 and 1105 Å. The gratings are holographically ruled to
correct largely for astigmatism and to minimize scattered light. The
microchannel plate detectors have KBr photocathodes and use photon
counting to achieve good quantum efficiency with low background
signal. The sensitivity is sufficient to examine reddened lines
of sight within the Milky Way and also sufficient to use as active
galactic nuclei and QSOs for absorption-line studies of both Milky
Way and extragalactic gas clouds. This spectral region contains a
number of key scientific diagnostics, including O VI, H I, D I, and
the strong electronic transitions of H2 and HD.

---------------------------------------------------------
Title: Heliospheric, Astrospheric, and Interstellar Lyα Absorption
toward 36 Ophiuchi
Authors: Wood, Brian E.; Linsky, Jeffrey L.; Zank, Gary P.
2000ApJ...537..304W Altcode: 2000astro.ph..2444W
We use high-resolution UV spectra taken by the Space Telescope
Imaging Spectrograph instrument on board the Hubble Space Telescope
to study the 5.5 pc line of sight to the K0 V star 36 Oph A. The one
interstellar component detected for this line of sight has a velocity
inconsistent with the local interstellar cloud (LIC) flow vector
but consistent with the flow vector of the so-called G cloud, a very
nearby warm cloud in the Galactic center direction. From our data,
we measure the following values for the interstellar temperature,
nonthermal velocity, H I column density, and D/H value: T=5900+/-500
K, ξ=2.2+/-0.2 km s-1, logNH=17.85+/-0.15,
and D/H=(1.5+/-0.5)×10-5. The temperature of the G cloud
is somewhat lower than that of the LIC, and Mg and Fe depletions are
also lower, but the D/H value appears to be the same. Based on upper
limits for the LIC absorption, we estimate the distance to the edge of
the LIC to be dedge&lt;0.19 pc, which the Sun will reach in
tedge&lt;7400 yr. The H I Lyα absorption line has properties
inconsistent with those of the other absorption lines, indicating the
presence of one or more absorption components not seen in the other
lines. We present evidence that hot neutral hydrogen local to both the
Sun and the star is responsible for the excess Lyα absorption. This
hot H I is created by the interaction between the ISM and the winds of
the Sun and 36 Oph A. The observed line of sight lies only 12° from
the upwind direction of the LIC flow vector, where hydrodynamic models
of the heliosphere suggest that heliospheric H I absorption should be
particularly prominent. The properties of the heliospheric absorption
(T=38,000+/-8000 K and logNH=14.6+/-0.3) are consistent
with previous measurements of this absorption for the α Cen line
of sight 52° from the upwind direction. Based on observations with
the NASA/ESA Hubble Space Telescope, obtained at the Space Telescope
Science Institute, which is operated by the Association of Universities
for Research in Astronomy, Inc., under NASA contract NAS5-26555.

---------------------------------------------------------
Title: VLA observation of dMe stars
Authors: Leto, G.; Pagano, I.; Linsky, J. L.; Rodonò, M.; Umana, G.
2000A&A...359.1035L Altcode:
We present new VLA radio observations of a sample of dMe stars in X,
U, K, and Q bands (from 8.4 to 43 GHz) obtained during an observing
campaign in 1996 April-June. The aim of the project was to determine
the spectral energy distributions of late-type dwarf flare stars to
investigate the possible existence of an inversion of the spectrum
slope at frequencies higher than 8 GHz. We also tried to constrain the
possible emission mechanism at radio frequencies. We have detections in
X band (8.4 GHz), for three sources (UV Cet, V 1054 Oph, and EV Lac),
while all of our other measurements are upper limits. We discuss how
the weak radio emission of some sources (e.g. AU Mic) and the coronal
plasma properties deduced from X-ray observations constrain the coronal
magnetic field properties.

---------------------------------------------------------
Title: An IUE Atlas of Pre-Main-Sequence Stars. I. Co-added Final
Archive Spectra from the SWP Camera
Authors: Valenti, Jeff A.; Johns-Krull, Christopher M.; Linsky,
Jeffrey L.
2000ApJS..129..399V Altcode:
We have identified 50 T Tauri stars (TTS) and 74 Herbig Ae/Be (HAEBE)
stars observed in the IUE short-wavelength bandpass (1150-1980 Å). Each
low-resolution (R~6 Å) spectrum was visually inspected for source
contamination and data quality, and then all good spectra were combined
to form a single time-averaged spectrum for each star. Use of IUE Final
Archive spectra processed with NEWSIPS reduces fixed pattern noise in
individual spectra, allowing significant signal-to-noise ratio gains in
our co-added spectra. For the TTS observed by IUE, we measured fluxes
and uncertainties for 17 spectral features, including two continuum
windows and four fluoresced H2 complexes. Thirteen of
the 32 accreting TTS observed by IUE have detectable H2
emission, which until now had been reported only for T Tau. Using
an empirical correlation between H2 and C IV line flux,
we show that lack of sensitivity can account for practically all
nondetections, suggesting that H2 fluorescence may be
intrinsically strong in all accreting TTS systems. Comparison of
IUE and GHRS spectra of T Tau show extended emission primarily, but
not exclusively, in lines of H2. We also fit reddened
main-sequence templates to 72 HAEBE stars, determining extinction
and checking spectral types. Several of the HAEBE stars could not be
fitted well or yielded implausibly low extinctions, suggesting the
presence of a minority emission component hotter than the stellar
photosphere, perhaps caused by white dwarf companions or heating in
accretion shocks. We identified broad wavelength intervals in the
far-UV that contain circumstellar absorption features ubiquitous in
B5-A4 HAEBE stars, declining in prominence for earlier spectral types,
perhaps caused by increasing ionization of metal resonance lines. For
61 HAEBE stars, we measured or set upper limits on a depth index that
characterizes the strength of circumstellar absorption and compared
this depth index with published IR properties.

---------------------------------------------------------
Title: Inferring Mass Loss Rates for Cool Luminous Stars from
High-Resolution GHRS Spectra
Authors: Linsky, J. L.; Harper, G. M.; Valenti, J.; Bennett, P. D.;
Brown, A.
2000IAUS..177..303L Altcode:
No abstract at ADS

---------------------------------------------------------
Title: Stellar flares: How common? How Important?
Authors: Linsky, Jeffrey L.
2000AIPC..522..389L Altcode: 2000coex.conf..389L
Flares are often observed from a wide variety of stars that are called
active by virtue of their rapid rotation, young age, and strong magnetic
fields. Although the total energies of these flares cover many orders
of magnitude in range, they typically follow a common pattern with
impulsive and gradual stages and the distribution of energy among
the different radiating channels is remarkably similar. The similar
phenomenology points to a common scenario of magnetic reconnection,
electron beam heating, and evaporation of the lower atmosphere followed
by gradual cooling of the hot coronal plasma. The solar two-ribbon flare
is often cited as the prototypical model. However, this conclusion must
be viewed as tentative because the radiative response of an atmosphere
to the impulsive input of energy could be the same for a variety of
different energy input mechanisms. .

---------------------------------------------------------
Title: FUSE Observations of the Active Cool Star AB Doradus
Authors: Ake, T. B.; Dupree, A. K.; Young, P. R.; Linsky, J. L.;
Malina, R. F.; Griffiths, N. W.; Siegmund, O. H. W.; Woodgate, B. E.
2000astro.ph..6117A Altcode:
Far ultraviolet spectra were obtained of the active cool star AB
Doradus (HD 36705) during the calibration and checkout period of the
FUSE satellite. Observations in this early phase of the mission were
taken at a resolving power of 12000-15000 (~20-25 km/s) and covered the
spectral range 905-1187 A. The integrated spectrum exhibits strong,
rotationally broadened stellar emission from C III (977, 1175) and O
VI (1032, 1037), and many weaker lines. Strong emission lines of C III
and O VI exhibit broad wings. The C III 977 profile shows blue-shifted
absorption at ~30 km/s and C II 1036 absorption appears superposed on
emission in the wing of O VI 1037. Rotational modulation of C III and
O VI is present, in harmony with its photometric variability. Flares
were detected in the brightest lines and subexposures were analyzed to
examine flux and profile variations. Downflows that extend to 600 km/s
during a flare are found in the O VI profiles. These early observations
demonstrate that FUSE will be an exceptional instrument for studying
chromospheres in cool stars.

---------------------------------------------------------
Title: Chandra Sees Its First Stellar Flares: Results from Coordinated
{Chandra, EUVE, HST} STIS, and VLA Observations of HR 1099
Authors: Osten, R. A.; Ayres, T. R.; Brown, A.; Huenemoerder, D.;
Drake, J. J.; Linsky, J. L.; Brickhouse, N.
2000AAS...19511214O Altcode: 1999BAAS...31.1541O; 2000BAAS...32..877O
On September 15, 1999, the Chandra X-ray Observatory began a 36 hour
pointing on the coronally active RS CVn binary system HR 1099 (V711
Tau; K1 IV {+} dG) as part of the Emission Line Project. The High
Energy Transmission Grating Spectrometer delivered time-tagged moderate
resolution (E/Δ {E} 500--1000) spectra between 2--18 Angstroms (HEG)
and 6--30 Angstroms (MEG). Other space-based and ground facilities
participated in the campaign -- the Extreme Ultraviolet Explorer
provided 10 days of 70--170 Angstroms Deep Survey photometry and
70--300 Angstroms spectroscopy beginning September 14; HST STIS
contributed five orbits of echelle-resolution spectroscopy in the
1150--1700 Angstroms region, beginning 16 UT September 15; and the
VLA recorded 9 1/2 hours of emission at 3, 6, and 20 cm just before
the HST window. The coordinated program represented an unprecedented
opportunity to study the energetics and kinematics of stellar flares,
a trademark of active binaries like HR 1099. Sporadic flaring activity
was recorded by all the observatories, from radio to X-ray. The Chandra
MEG light curves of hydrogenic Ne X λ 12.1 and O VIII λ 19.0, derived
from 15-minute-binned spectra, exhibit a number of impulsive rises and
decays. The bright Ne X feature follows an overall velocity pattern
consistent with the 50 km s-1 orbital motion of the active
primary star during the long Chandra observation, which covered half a
binary cycle. There are a few “bursts” of Ne X velocity, including
a sustained 45 minute period of apparent 150--200 km s-1
blueshifts; immediately prior to the detection by HST STIS of a
dramatic hypersonic event in Si IV λ 1393 and C IV λ 1548, with
Doppler broadening up to +/-500 km s-1. Chandra's ability
to measure directly plasma motions in stellar coronal flare events
is a key diagnostic advance. Highlights of our initial studies of
the campaign data sets will be presented. [2mm] {Supported by NASA
(NAG5-3226) and STScI (GO-08280.01-97A).}

---------------------------------------------------------
Title: Probing the Multi-Wavelength Nature of Stellar Flares
Authors: Osten, R. A.; Brown, A.; Ayres, T. R.; Linsky, J. L.
2000AAS...196.1304O Altcode: 2000BAAS...32..691O
The Extreme Ultraviolet Explorer has been instrumental in advancing
our understanding of flares on late-type stars. Its long observations
of coronal sources for &gt; 100 ks are perfectly matched for studying
flaring variability on active binary systems, whose flaring time
scales can last for tens of hours. This ability makes EUVE an ideal
companion for multi-wavelength observations of flares, as it can
place the shorter observations of other satellites and telescopes in
perspective of the coronal variability. For example, EUVE recently
participated in a campaign to observe the RS CVn binary HR 1099
(V711 Tau) during a calibration observation with the Chandra X-ray
Observatory, with accompanying high-resolution UV coverage from HST/STIS
and radio coverage from the VLA. I will discuss the results of this
campaign as well as earlier multi-wavelength observations involving
EUVE and other satellites such as ASCA, RXTE, and BeppoSAX of flaring
variability on active binary systems. RAO acknowledges funding from a
NASA GSRP fellowship, grant number NGT5-50241. AB and TRA acknowledge
funding from NASA grant NAG5-3226 and JLL acknowledges support from
NASA through grants S-56500-D and H-04630D.

---------------------------------------------------------
Title: UV Spectroscopy with Hubble Space Telescope- A Success Story
of Pro/Am Collaboration
Authors: Alexander, W. R.; Linsky, J. L.; Wood, B. E.
2000AAS...196.1202A Altcode: 2000BAAS...32..690A
The Hubble Space Telescope amateur program has provided a unique
opportunity for amateur astronomers to not only perform research
on HST, but to also to interact with many professional astronomers
during their research. In particular, a very successful partnership
was established between William Alexander (amateur) and Jeff Linsky
and Brian Wood (professionals). At the heart of this project was the
use of the Goddard High Resolution Spectrograph (GHRS) aboard HST
to provide high-resolution UV spectra in the Lyman-alpha region at
1216 angstroms. These spectra were needed to study the Deuterium to
Hydrogen (D/H) ratio along the line of sight toward lambda-Andromedae
and epsilon-Indi. These measurements were important to more fully
understand big bang nucleosynthesis. The amateur, Alexander, was
fully involved at each stage of the project, from obtaining all of
the raw data to collaborating with Linsky and Wood in the writing of
the article that appeared in The Astrophysical Journal (APJ, 470:
1157-1171). This collaboration has shown that amateurs can provide
significant `academic' contributions to astronomy. This contribution
can be added to the numerous observational contributions that amateurs
have made to astronomy through out the centuries. Funding support
was provided by NASA grant GO-0100.01-92A from the Space Telescope
Science Institute.

---------------------------------------------------------
Title: The D/H Abundance Ratio in Local Interstellar Gas
Authors: Sahu, M. S.; Landsman, W.; Bruhweiler, F. C.; Linsky, J. L.;
Hubeny, I.; Barstow, M.; Holberg, J.; Gull, T.; Bowers, C.; Lindler,
D.; Lanz, T.; Feggans, K.
2000AAS...196.2620S Altcode: 2000BAAS...32..713S
Does the D/H ratio vary within ~ 100 pc of the Sun? If it does, what
is the range of these variations? Are the D/H variations correlated to
any physical property of the absorbing cloud? To answer these questions
we have begun a project to obtain high-precision D/H abundance ratios
in the Local Interstellar Medium within ~ 100 pc (Sahu et al. 1999,
ApJ 523, L159). For this purpose, we primarily use HST-Space Telescope
Imaging Spectrograph (STIS) data towards nearby hot, white dwarfs
(WDs). The advantages of using STIS for this study are: (1) The high
velocity resolution of STIS in the UV ( ~ 2 km s-1 in the
E140H and E230H modes) allows the velocity structure in the sightline
to be resolved and reliable component-to-component variations can be
studied (2) WDs provide a strong, smooth UV continuum against which
other diagnostic interstellar absorption lines can be measured. The
wider wavelength coverage ( ~ 200 Angstroms per setting) of STIS in the
high-resolution E140H mode allows important interstellar lines such as N
i, Si ii, O i and S ii to be measured in addition to D i and H i, at no
extra cost in HST time (3) The superior echelle scatter and background
corrections possible with the 2-dimensional STIS-MAMA detectors allow
more accurate D/H determinations from WD spectra. In this poster, we
present a status report of our project along with some recent results.

---------------------------------------------------------
Title: Stellar Activity and Outer Atmospheric Structure of Yellow
Supergiants from HST STIS and GHRS Spectroscopy
Authors: Brown, A.; Ayres, T. R.; Harper, G. M.; Osten, R. A.; Linsky,
J. L.; Dupree, A. K.; Jordan, C.
2000AAS...196.4013B Altcode: 2000BAAS...32..739B
Yellow supergiants with spectral types F-G show a complex pattern of
outer atmospheric structure with stellar wind and activity indicators
varying significantly for stars with similar positions in the H-R
diagram. The efficiency of the processes driving their stellar winds and
heating their atmospheres is critically dependent on the evolutionary
position and surface gravity of each star. We present high-resolution
ultraviolet HST/STIS and HST/GHRS spectra for a range of intermediate
mass F and G supergiants, including Alpha Car (F0 Ib), Beta Cam (G0 Ib),
Beta Dra (G2 Ib), and Epsilon Gem (G8 Ib), and compare the atmospheric
properties of these stars with lower luminosity giants and bright
giants. We provide a systematic overview of the supergiant atmospheric
properties dealing particularly with activity levels, the presence
of hot “transition region” plasma, signatures of wind outflow, and
the role of overlying cool absorbing plasma that becomes increasingly
prominent for the cooler stars like Epsilon Gem. This work is supported
by HST grants for program GO-08280 and by NASA grant NAG5-3226.

---------------------------------------------------------
Title: Chandra Observations of the Pleiades and Other Young Clusters
Authors: Linsky, J. L.; Krishnamurthi, A.
2000AAS...196.3406L Altcode: 2000BAAS...32..724L
The high sensitivity, exquisite angular resolution, 16 by 16 arcmin
field of view, low background, and modest energy resolution of the
ACIS-I detector make Chandra a powerful new resource for the study
of young stellar clusters and associations. In the first 8 months of
operation, Chandra has observed a number of young clusters ranging in
age from 1x 106 to 1x 108 years, including the
Pleiades, NGC 2516, Trapezium, and ρ Ophiucus. These rich images
containing hundreds of detected sources provide the information
needed to address a number of important questions in star formation and
evolution including the shape of the initial mass function, the presence
or absence of hot X-ray emitting coronae in brown dwarfs and hot stars
with shallow convective zones, coronal variability and flaring as a
function of stellar mass, the dependence of X-ray luminosity on age and
rotation and the presence of disks, and The 60 ks ACIS-I image of the
Pleiades, for example, provides 3.5σ detections down to Lx
= 5x 1027 ergs, about a factor of 10 deeper than the ROSAT
surveys. This low threshold permits the detection of coronae down to
the end of the M dwarf sequence and beyond into the brown dwarfs. This
work is supported by NASA through grant H-04630D to the University of
Colorado and NIST.

---------------------------------------------------------
Title: Comparing solar and stellar activity: New results from HST,
Chandra, and XMM
Authors: Linsky, J. L.
2000SPD....31.1003L Altcode: 2000BAAS...32R.842L
Beautiful spectra and precise photometry from space instruments on
HST, Chandra, XMM, and ASCA, together with ground-based observations,
provide new insights and form the basis for detailed models of active
phenomena on late-type dwarf stars. I would like to summarize some
of the important new results concerning stellar activity and compare
them with active phenomena observed on the Sun. Is the Sun a basal
flux star? What are we learning about stellar magnetic fields and
starspots? What evidence is there for cool structures (prominences)
and hot loops in stellar coronae? Are stellar flares qualitatively
different from solar flares? Are the outer atmospheres of active stars
heated by microflares? Are relativistic electrons present in stellar
coronae? Does the thermal structure of active star coronae differ from
the solar corona? Do stars have astrospheres with structures analogous
to the outer heliosphere? This work is supported by NASA through grants
S-56500-D and H-04630D.

---------------------------------------------------------
Title: The Three-dimensional Structure of the Warm Local Interstellar
Medium. II. The Colorado Model of the Local Interstellar Cloud
Authors: Redfield, Seth; Linsky, Jeffrey L.
2000ApJ...534..825R Altcode:
In this second paper in a series on the structure of the local
interstellar medium (LISM), we construct a three-dimensional model of
the local interstellar cloud (LIC) based on Hubble Space Telescope
(HST), Extreme Ultraviolet Explorer (EUVE), and ground-based Ca II
spectra. Starting with hydrogen column densities derived from deuterium
column densities measured with the Goddard High Resolution Spectrograph
instrument on HST for 16 lines of sight to nearby stars, we derive a
model consisting of the sum of nine spherical harmonics that best fit
the data. We then rederive the model by including the lines of sight
to three hot white dwarfs observed by EUVE and 13 lines of sight with
Ca II column densities at the projected LIC velocity. The LIC model is
clearly not a long thin filamentary structure like optical images of
some interstellar clouds (e.g., reflection nebulae in the Pleiades),
but neither is it spherical in shape. As seen from the north Galactic
pole, the LIC is egg-shaped with an axis of symmetry that points
in the direction l~315deg. Since the direction of the
center of the Scorpius-Centaurus association is l=320deg,
the shape of the LIC could be determined by the flow of hot gas from
Sco-Cen. The model shows that the Sun is located just inside the LIC
in the direction of the Galactic center and toward the north Galactic
pole. The absence of Mg II absorption at the LIC velocity toward α Cen
indicates that the distance to the edge of the LIC in this direction
is &lt;=0.05 pc and the Sun should cross the boundary between the LIC
and the Galactic (G) cloud in less than 3000 yr. We estimate that the
volume of the LIC is about 93 pc3 and its mass is about
0.32 Msolar. The physical parameters and hydrogen column
density of the LIC are roughly consistent with theoretical models
of the warm interstellar medium that assume pressure and ionization
equilibrium. However, the empirical hydrogen ionization of the LIC is
much higher and the gas temperature lower than the theoretical models
predict. Therefore, the ionization is likely due to shock activity from
a nearby supernova that has not yet reached equilibrium. The higher
ionization increases the gas cooling, which can explain why the gas is
2400 K cooler than the ionization equilibrium models predict. Computed
and observed temperatures are in agreement for a model with the observed
LIC electron density. Based on observations with the NASA/ESA Hubble
Space Telescope, obtained at the Space Telescope Science Institute,
which is operated by the Association of Universities for Research in
Astronomy, Inc., under NASA contract NAS 5-26555.

---------------------------------------------------------
Title: HST/STIS Echelle Spectra of the dM1e Star AU Microscopii
Outside of Flares
Authors: Pagano, Isabella; Linsky, Jeffrey L.; Carkner, Lee; Robinson,
Richard D.; Woodgate, Bruce; Timothy, Gethyn
2000ApJ...532..497P Altcode:
We report on observations of the dM1e flare star AU Microscopii
obtained with the Space Telescope Imaging Spectrograph (STIS) on 1998
September 6. A total of 10,105 s of observations were obtained with
the medium-resolution E140M grating. We report here on the 9200 s of
“quiescent” data when the star did not obviously flare. In this
data set, we identify 142 emission lines from 28 species, including
low-temperature chromospheric lines (e.g., C I, O I), transition-region
lines (e.g., C II-IV, N IV, O III-V, Si II-IV), and the coronal line Fe
XXI 1354 Å. There are a number of intersystem lines that are useful for
measuring electron densities. We discuss line redshifts and the broad
wings of transition-region lines that provide evidence of microflare
heating. We derive the emission-measure distribution and compare it
with the solar one. We also discuss the shape and formation mechanisms
of the He II 1640 Å lines. The analysis of the flare data and of the
interstellar absorption features seen in the H I, D I, C II, and O
I resonance lines will be published elsewhere. Based on observations
made with the NASA/ESA Hubble Space Telescope, obtained at the Space
Telescope Science Institute, which is operated by the Association of
Universities for Research in Astronomy, Inc., under NASA contract NAS
5-26555. These observations are associated with proposal ID 7556.

---------------------------------------------------------
Title: Are the shapes of coronal emission measure distributions
controlled by rotation and convection zone parameters?
Authors: Linsky, J. L.; Krishnamurthi, A.; Gagné, M.; Güdel, M.
2000ASPC..198..467L Altcode: 2000scac.conf..467L
No abstract at ADS

---------------------------------------------------------
Title: Spectroscopic Survey of Cool Stars
Authors: Linsky, J.
2000fuse.prop.P118L Altcode:
This program will obtain far-UV spectra of cool stars that span a broad
range of spectral type and luminosity class. It is our intention to
obtain these spectra early in the FUSE program and to provide the
spectra quickly to the user community in order to guide potential
guest investigators in designing their observing programs. The
specific science objectives include: (1) studying transition region
dynamics (winds and downflows), (2) modeling the thermal structure
of transition regions, (3) measuring electron densities, (4) search
for low temperature coronae, (5) studying molecular excitation and
fluorescence processes, and (6) inferring how the transition regions
of spectroscopic binary systems differ from those of single stars.

---------------------------------------------------------
Title: Deuterium Observations in our Galaxy - View A (Invited Paper)
Authors: Linsky, J. L.; Wood, B. E.
2000IAUS..198..141L Altcode:
No abstract at ADS

---------------------------------------------------------
Title: What have we learned? Where are we going? And some lessons
from the past
Authors: Linsky, J. L.
2000ASPC..198..563L Altcode: 2000scac.conf..563L
No abstract at ADS

---------------------------------------------------------
Title: Working Group on Future Large Scale Facilities in Astronomy:
(Groupe de Travail Pour les Futures Grandes Infrastructures)
Authors: Ekers, R. D.; Appenzeller, I.; Butcher, H. R.; Kardashev,
N. S.; Lequeux, J.; Linsky, J. L.; Pacini, F.; Praderie, F.; Swarup,
G.; Tarenghi, M.; Okuda, H.
2000IAUTA..24..444E Altcode:
No abstract at ADS

---------------------------------------------------------
Title: The Three-dimensional Structure of the Warm Local Interstellar
Medium. I. Methodology
Authors: Linsky, Jeffrey L.; Redfield, Seth; Wood, Brian E.; Piskunov,
Nikolai
2000ApJ...528..756L Altcode:
In this first in a series of papers, we develop a methodology for
constructing three-dimensional models of the local interstellar
cloud (LIC) and adjacent warm clouds in the local interstellar medium
(LISM). Our models are based on the column density of neutral hydrogen
gas (NHI) inferred primarily from measurements of the
deuterium column density toward nearby stars obtained from the analysis
of Hubble Space Telescope ultraviolet spectra. We also use values of
NHI inferred from spectra of hot white dwarfs and B-type
stars obtained by the Extreme Ultraviolet Explorer satellite. These
very different methods give consistent results for the three white
dwarf stars in common. We assume that along each line of sight all
interstellar gas moving with a speed consistent with the LIC velocity
vector has a constant density, NHI=0.10 cm-3,
and extends from the heliosphere to an edge determined by the value of
NHI moving at this speed. A number of stars have velocities
and/or depletions that indicate absorption by other warm clouds in
their lines of sight. On this basis α Cen A and B and probably also
ɛ Ind lie inside the Galactic center (G) cloud, HZ 43 and 31 Com
lie inside what we call the north Galactic pole cloud, and β Cet is
located inside what we call the south Galactic pole cloud. We show the
locations of these clouds in Galactic coordinates. The Sun is located
very close to the edge of the LIC toward the Galactic center and the
north Galactic pole. The absence of Mg II absorption at the LIC velocity
toward α Cen indicates that the distance to the edge of the LIC in
this direction is &lt;=0.05 pc and the Sun should leave the LIC and
perhaps enter the G cloud in less than 3000 yr. Comparison of LIC and
total values of NHI toward pairs of stars with separations
between 0.9d and 20° reveals a pattern of good agreement so long as
both stars lie within 60 pc of the Sun. Thus the LIC and perhaps also
other nearby warm clouds have shapes that are smooth on these angular
scales. In our second paper we will therefore fit the shape of the
LIC with a set of smooth basis functions (spherical harmonics). Based on observations with the NASA/ESA Hubble Space Telescope,
obtained at the Space Telescope Science Institute, which is operated
by the Association of Universities for Research in Astronomy, Inc.,
under NASA contract NAS5-26555.

---------------------------------------------------------
Title: Origins, Structure, and Evolution of Magnetic Activity in
the Cool Half of the H--R Diagram: an HST STIS Survey
Authors: Ayres, T. R.; Brown, A.; Drake, S. A.; Dupree, A. K.; Guedel,
M.; Guinan, E.; Harper, G. M.; Jordan, C.; Linsky, J. L.; Reimers,
D.; Schmitt, J. H. M. M.; Simon, T.
1999AAS...195.5013A Altcode: 1999BAAS...31Q1449A
In HST's cycle 8, we are carrying out a major ultraviolet spectral
survey of late-type stars using the powerful capabilities of the
Space Telescope Imaging Spectrograph (STIS). The origin of the hot
UV emissions of otherwise cool stars is a fundamental puzzle in
astrophysics. Magnetic phenomena---at the heart of chromospheric and
coronal activity, and perhaps wind driving as well---play a central
role in many cosmic settings. Our objective is to obtain high-quality
ultraviolet spectra of a diverse collection of F--K stars, of all
luminosity classes. Such a major project was unthinkable before
STIS, but now is practical given the high resolution, broad spectral
coverage, and sensitivity of the second generation spectrograph. Here,
we discuss our choice of the thirteen targets; the observing strategy
(which captures the entire UV spectrum between 1150--3000 Angstroms
at resolutions λ /δ λ 30--100*E3 with good S/N); and
preliminary results for the several targets observed to date (ζ Dor, F7
V, 1 May 1999, 2 CVZ orbits; V711 Tau, K1 IV+G5 IV, 15 September 1999, 5
orbits; β Cam, G0 I, 19 September 1999, 4 CVZ orbits). The observation
of V711 Tau (HR 1099) was carried out during a long transmission grating
pointing by the Chandra X-ray Observatory, in support of its “Emission
Line Project.” This work was supported by grant GO-08280.01-97A from
STScI. Observations were from the NASA/ESA HST, collected at the STScI,
operated by AURA, under contract NAS5-26555.

---------------------------------------------------------
Title: Chandra images of the Pleiades
Authors: Krishnamurthi, A.; Linsky, J. L.; Gagne, M.
1999AAS...19511210K Altcode: 1999BAAS...31.1541K
We present first results from a 60-ks image of the core of the
Pleiades cluster with ACIS-I on the Chandra X-ray observatory. The
observations were obtained as part of the Cycle-1 GTO observations. The
ACIS data will be used with recently derived rotational periods to
test rotation-activity relations at the low end of the zero-age main
sequence. The ACIS spectra and light curves will also allow modelling
of X-ray flares and coronal heating for these young, active stars.

---------------------------------------------------------
Title: FUSE Observations of the Active Cool Star: AB Dor
Authors: Ake, T. B.; Dupree, A. K.; Linsky, J. L.; Malina, R. F.;
FUSE Science Team
1999AAS...195.0622A Altcode: 1999BAAS...31.1377A
FUSE spectra were obtained of the active cool star AB Dor (HD 36705)
on 20 and 22 October 1999 during the calibration and checkout period of
the satellite. Observations in this early phase of the FUSE mission were
taken at a resolution of 15000 ( 20 km s-1) and covered the
spectral range 980 -- 1180 Angstroms. Exposures of 20000 s and 30000
s, separated by two days, enabled coverage of different phases of the
12.4 hour rotation period of this K0 dwarf. The integrated spectrum
exhibits strong broadened stellar emission from C III (1176 Angstroms)
and O VI (1032, 1037 Angstroms) corresponding to the v sin i of 90
km s-1. High temperature plasma (3 x 105 K) is
clearly present. Other weaker lines are apparent, including Si III,
Si IV, C I, and Fe III, demonstrating that FUSE will be an effective
instrument for study of emission from cool stars. This work is supported
in part by NASA contract NAS5-32985.

---------------------------------------------------------
Title: The Circumstellar Disk of HD 163296: A Young Planetary System
Authors: Grady, C. A.; Devine, D.; Woodgate, B.; Kimble, R.;
Bruhweiler, F. C.; Boggess, A.; Linsky, J. L.; Plait, P.; Clampin,
M.; Kalas, P.
1999AAS...195.0208G Altcode: 1999BAAS...31.1367G
Coronagraphic imaging with STIS on the HST reveals an 450 AU
circumstellar disk around the 4-10 Myr old Herbig Ae star HD
163296. A broad-band (0.2-1.1 micron) reflected light image shows
the disk oriented with its semi-major axis at PA=140+/-5 degrees,
and inclination of 60+/-5 degrees. The disk includes an annulus of
depleted material at 325 AU, and a flat trend of surface brightness in
to 1-1.5", consistent with a partially cleared zone extending from 300
to 180-122 AU. For radii r &gt; 370 AU the disk surface brightness
distribution drops as r-3.5. The disk cannot be traced
beyond 450 AU in our data. The disk is accompanied by a chain of HH
knots at PA=42.5+/-3.5 degrees. The dynamical effects of more than
one planet appear necessary to explain the outer disk morphology and
the apparent central clearing. HD 163296 is the third A star under
t &lt; 10 Myr with disk structure indicating that planet formation
has occurred, and is present at larger radii than expected based on
theoretical modelling of gas giant planet formation. The STIS data
favor early formation of massive planets. Support for this study
was provided by HST STIS GTO funding through support to the NOAO,
in response to NASA A/O OSSA -4-84 through the Hubble Space Telescope
Project at GSFC. NOAO is operated by the Association of Universities
for Research in Astronomy (AURA), Inc., under cooperative agreement
with the National Science Foundation. Data analysis facilities were
provided by the Laboratory for Astronomy &amp; Solar Physics, NASA/GSFC.

---------------------------------------------------------
Title: STIS observations of Ly alpha jet associated with the Near-ZAMS
star HD163296
Authors: Devine, D.; Grady, C.; Kimble, R.; Plait, P.; Linsky, J.;
Woodgate, B.; Boggess, A.; Bruhweiler, F. C.
1999AAS...195.0207D Altcode: 1999BAAS...31.1367D
STIS long slit spectroscopy of the 4-10 Myr old near-ZAMS Herbig Ae
star HD163296 reveals the presence of a jet associated with the bipolar
Herbig-Haro flow driven by HD163296. This is somewhat surprising since
HD163296 is roughly a factor of ten older than most protostars that
drive outflows. The jet is visible in Ly alpha and Si III and can be
traced to within 0.1" (12 AU) of HD163296. The counterjet is appreciably
fainter within 4" of the star in Ly alpha and is not detected in Si
III. We also obtained optical long slit spectroscopy of HD163296 that
shows faint [SII] emission associated with the counterjet that can be
traced to within 1" of the star. This suggests that the counterjet
is obscured at FUV wavelengths by the circumstellar disk associated
with HD163296. STIS coronographic imaging of this disk shows evidence
for clearing that may be due to planet formation. We will discuss
mechanisms for driving the outflow under these circumstances. Support
for this study was provided by HST STIS GTO funding through support
to the NOAO, in response to the NOAO A/O OSSA -4-84 through the
Hubble Space Telescope Project at GSFC. NOAO is operated by the
Association of Universities for Research in Astronomy (AURA), Inc.,
under cooperative agreement with the National Science Foundation. Data
analysis facilities were provided by the Laboratory for Astronomy&amp;
Solar Physics, NASA/GSFC.

---------------------------------------------------------
Title: Discovery space for stellar astrophysics by small missions
Authors: Linsky, Jeffrey L.
1999AIPC..499..127L Altcode: 1999smea.conf..127L
The last 20 years has been a time of major advances in our ability to
observe stars at a variety of wavelengths across the electromagnetic
spectrum. Many questions concerning the existence of phenomena (e.g.,
coronae, winds, accretion disks, nonthermal particles, shocks, magnetic
fields) are now answered, but important details about the phenomena
and questions concerning the physical processes responsible for the
observed phenomena remain unanswered. Well-conceived small space
missions can answer many of these questions. I describe one small
mission-Wide Angle Stellar Coronal Explorer-that could answer many of
these questions at modest cost.

---------------------------------------------------------
Title: The amazing high resolution ultraviolet spectrum of DF Tauri
Authors: Linsky, J. L.; Valenti, J.; Johns-Krull, C. M.
1999AAS...195.0214L Altcode: 1999BAAS...31.1369L
DF Tau (HD 283654, M0V) is a classical T Tauri star (CTTS), with strong
utraviolet emission lines that provide fascinating clues about flows
near an actively forming star. On 1999 September 18, we observed DF
Tau with HST/STIS, using the medium resolution echelle modes (E140M
and E230M). The spectrum includes many emission lines from both low
temperature plasma (e.g. O I, Fe II, H2) and high temperature plasma
(e.g. He II, C IV, Si IV?). The combination of good resolution and
complete FUV wavelength coverage makes it possible to explore the
physical conditions giving rise to the observed fluorescence. The
high temperature lines show strikingly sharp absorption edges in
the blue wing, likely due to a wind with temperatures up to at least
105 K. The 2300--2900 Angstroms region contains many Fe II
lines with P-Cygni shaped profiles, which constrain lower temperature
regions of the outflow. We will report on the line of sight flows seen
in both the low and high temperature lines and relate these flows to
models of CTTS. This work is supported by a NASA grant to the University
of Colorado.

---------------------------------------------------------
Title: HST/STIS Observations of the 36 Oph Line of Sight
Authors: Wood, B. E.; Linsky, J. L.
1999AAS...195.7202W Altcode: 1999BAAS...31R1474W
We present new HST/STIS observations of absorption lines seen in
the UV spectrum of the nearby (d=5.5 pc) K0 V star 36 Oph A. These
data were taken to study both the local interstellar medium (LISM)
along the line of sight, and to study H I Lyman-α absorption from hot
neutral hydrogen in the outer heliosphere. This heliospheric absorption
has previously been detected towards both α Cen and Sirius, which
are 52o and 139o from the upwind direction,
respectively (Linsky &amp; Wood, 1996, ApJ, 463, 254; Izmodenov et
al. 1999, A&amp;A, 342, L13). Our target, 36 Oph A, was chosen for
its location only 12o from the upwind direction, where
the velocity separation between the LISM and heliospheric absorption
should be at its largest, making detection and measurement of the
heliospheric component easier. Analogous to what was seen in the α
Cen analysis, the H I Lyman-α absorption is redshifted relative to
the Mg II, Fe II, and D I absorption lines, demonstrating that an
absorption component exists on the red side of the highly optically
thick H I line which is not present in the other lines. As in the
α Cen analysis, we interpret this extra component to be due to H
I in the outer heliosphere that is heated and decelerated by charge
exchange processes. This detection provides additional information for
mapping the distribution of heliospheric hydrogen and constraining
heliospheric models. In addition to the heliospheric absorption, we
also find evidence that absorption from analogous “astrospheric”
material around the star may be present on the blue side of the line.

---------------------------------------------------------
Title: The Wilson-Bappu Relation Between Ca II Emisison and Stellar
Luminosities
Authors: Linsky, Jeffrey L.
1999ApJ...525C.776L Altcode: 1999ApJC..525..776L
No abstract at ADS

---------------------------------------------------------
Title: VLA observation of NVSS J191656+051126
Authors: Leto, G.; Pagano, I.; Linsky, J. L.; Krishnamurthi, A.
1999A&A...350..753L Altcode:
We present new Very Large Array (VLA) radio observations in X, U, K,
and Q bands (from 8.4 to 43 GHz) of a serendipitously detected radio
source observed during a campaign on dMe stars in April 1996. Cross
correlating the coordinates, we found an entry in the NRAO NVSS survey
catalog at 1.4 GHz. According to the rules of this survey, we named
this serendipitous source “NVSS J191656+051126”. No optical or
X-ray counterpart could be identified, while we find that the IRAS
point source IRAS 19145+0505 could be the IR counterpart. Using the
radio data, we determined that the source spectral index is compatible
with synchrotron emission mechanism. We have also investigated the
structure of the source that is resolved into two components and their
time variability.

---------------------------------------------------------
Title: Coordinated AXAF and HST Spectroscopy of Flares on Proxima
Centauri
Authors: Linsky, Jeffrey
1999cxo..prop..198L Altcode:
AXAF provides the first opportunity to study the dynamics of flaring
plasma using the powerful tools of X-ray spectroscopy. We request AXAF
observations of the nearest flare star, Proxima Centauri (M6 Ve),
as part of a UNIQUE OPPORTUNITY for simultaneous X-ray and UV flare
spectroscopy. We have 8 orbits (about 46 ks) of HST Cycle 8 GTO time
(June 1999-May 2000) for high resolution UV spectra of Prox Cen in the
continuous viewing zone. Simultaneous AXAF grating spectra will permit
us to study the plasma motions and EM(T) with high time resolution to
characterize the flare energetics at all layers in the atmosphere and
to determine whether the 2-ribbon flare model as appropriate.

---------------------------------------------------------
Title: AXAF Grating Spectroscopy of Active Binaries
Authors: Linsky, Jeffrey
1999cxo..prop..215L Altcode:
We propose to observe two active binaries with the AXAF HETGS and
LETGS. TZ CrB is a G0 V + G0 V RS CVn binary. The HETGS observation
will span an entire 1.14-d orbital period and will probably include one
large flare. The HETGS line profiles may reveal high-velocity material
ejected at the onset of a flare. Density and temperature-sensitive
line ratios obtained at different orbital phases will be used to map
the coronal geometry of TZ CrB. 44 Boo is an eclipsing, W UMa-type
contact binary. The LETGS observation of 44 Boo will span no less
than two 0.27-d orbital periods and will be used to perform coronal
eclipse mapping and to investigate flares. Moreover, 44 Boo's maximum
radial velocity separation of 230 km/s should be resolved in the longer
wavelength LETG line profiles.

---------------------------------------------------------
Title: A Search for Radio Emission at the Bottom of the Main Sequence
and Beyond
Authors: Krishnamurthi, Anita; Leto, Giuseppe; Linsky, Jeffrey L.
1999AJ....118.1369K Altcode: 1999astro.ph..6116K
We have used the VLA to conduct a deep search for 3.6 cm radio emission
from nearby very low mass stars and brown dwarfs. The Güdel-Benz
relation is used to predict radio luminosities for some very low mass
stars and candidate brown dwarfs with measured X-ray fluxes. The
predicted radio fluxes are quite small, whereas the measured radio
flux from the brown dwarf candidate GY 31 in the rho Oph cloud is
relatively strong. In light of our new observations, this object
remains an anomaly. We present upper limits for our measured radio
fluxes at 3.6 cm for our targets.

---------------------------------------------------------
Title: a Comprehensive Investigation of X-Ray Emission from
Intermediate Mass Stars
Authors: Linsky, Jeffrey
1999cxo..prop..101L Altcode:
Although X-rays have been detected from essentially all types of stars,
one portion of the X-ray H-R Diagram remains an enigma. Despite large
surveys using Einstein and ROSAT, it is still not clear whether or
not main sequence stars of intermediate mass (spectral types B3--A7)
are intrinsic X-ray sources. Stars cooler than spectral type F0 are
coronal X-ray sources and O3--B3 stars are wind X-ray sources, but are
the intermediate mass stars intrinsic X-ray sources and how are they
heated? We will exploit AXAF's three unique properties (high resolution
imaging, high energy resolution, and high sensitivity detectors with
very low background) to determine whether or not the intermediate mass
stars are intrinsic X-ray sources and to study the nature of the X-ray
emitting plasma.

---------------------------------------------------------
Title: Deep ACIS Imaging of the Core of the Pleaides Cluster
Authors: Linsky, Jeffrey
1999cxo..prop..214L Altcode:
We propose to obtain a single, 60 ksec, ACIS-I exposure of the core
of the 100 million year-old Pleiades open cluster. The 16x16 arcmin
ACIS-I field of view will contain at least 20 known ROSAT PSPC sources
for which ACIS-I will provide simultaneous, high signal-to-noise 0.5-7
keV light curves and low-resolution spectra. The ACIS-I image will
also reveal 100-200 previously unknown X-ray sources. Most will be
associated with low-mass cluster members including a few candidate brown
dwarfs. The ACIS data will be used with recently derived rotational
periods to test rotation-activity at the low end of the zero-age main
sequence. The ACIS spectra and light curves will allow modeling of
X-ray flares and coronal heating for these young, active stars.

---------------------------------------------------------
Title: AXAF Grating Spectroscopy of Active Single Stars
Authors: Linsky, Jeffrey
1999cxo..prop..216L Altcode:
We propose to observe two active late-type single dwarfs with
the AXAF HETGS. AB Dor is a Pleiades-age K2 V rapid rotator at a
distance of 15 pc. AB Dor exhibits large-amplitude long-duration
flares and rotationally modulated activity at many wavelengths. The
HETGS observation of AB Dor will span an entire 0.51-d rotational
period. AU Mic is a very active M1 V flare star at a distance of 10
pc. AB Dor and AU Mic are prototypes for extreme main-sequence magnetic
activity. The principal objectives of the HETGS observations are (i)
to obtain time-resolved X-ray spectra of flares and (ii) to obtain
high signal-to-noise, high-resolution spectra of very hot coronal
sources to test optically thin collisional ionization equilibrium
plasma codes. Supporting ground-based observations are planned.

---------------------------------------------------------
Title: Atmospheric Structure of Hybrid Giants
Authors: Linsky, Jeffrey
1999hst..prop.8035L Altcode: 1999hst..prop.4413L
Modes E140M, E230M, and E230H will be used to construct a complete
UV spectral atlas of Alpha TrA, which is one of the brightest
hybrid-chromosphere stars. The atlas will be used to study both
the wind and the high temperature lines. Line fluxes will be used
to construct a detailed emission measure model and to determine the
electron density. The line profiles will be studied for evidence o
f bulk motions, turbulent motions, and heating mechanisms. Analysis
of the Mg II, Fe II, and other lines will provide information on the
wind acceleration.

---------------------------------------------------------
Title: Dynamics and Energetics of Stellar Flares
Authors: Linsky, Jeffrey
1999hst..prop.8040L Altcode: 1999hst..prop.4418L
Mode 1.3 echelle spectra will be used to explore the dynamics and
energetics of flares on M dwarfs. We will use line fluxes to determine
emission measure distributions {10^4 to 10^7 K} and electron densities
as a function of time during the flare. Line shapes and Doppler shifts
will be used to characterize plasma dynamics {flows, turbulence}
throughout the flare. We will search for cooling via UV continuum
emission in the early phases of the flare. Nonflare spectra will be
used to model the quiescent atmosphere.

---------------------------------------------------------
Title: Spectral Imaging of Stellar Winds
Authors: Linsky, Jeffrey
1999hst..prop.8039L Altcode: 1999hst..prop.4417L
We propose to obtain a deep E140M spectrum of the clump giant Beta Ceti,
to search for signatures of mass loss in emission lines formed over
the wide range of excitation temperatures present in the 1150-1700
A interval.

---------------------------------------------------------
Title: Accretion and Winds in T Tauri Systems
Authors: Linsky, Jeffrey
1999hst..prop.8041L Altcode: 1999hst..prop.4419L
We will obtain echelle spectra {modes 1.3 and 2.3} of a classical
T Tauri star to study the geometry, dynamics and energetics of
accretion and winds in pre- main-sequence stars. Line fluxes will be
used to construct an emission measure distribution and to determine
electron densities. Line shapes will help to constrain the geometry
and kinematics of the wind and the accreting material. Many Fe II
lines, spanning a range in optical depth, will provide new insight
into the radial variations in wind properties. We will also use the
spectra to study the mechanisms responsible for exciting flourescence
of molecular hydrogen.

---------------------------------------------------------
Title: STIS UV Atlas of the Red Giant Arcturus(1)
Authors: Ayres, T. R.; Brown, A.; Harper, G. M.; Bennett, P. D.;
Linsky, J. L.; Carpenter, K. G.; Robinson, R. D.
1999AAS...194.6701A Altcode: 1999BAAS...31..930A
The Space Telescope Imaging Spectrograph (STIS) conducted a series
of observations of the archetype “noncoronal” red giant Arcturus
(HD 124897; alpha Boo; K1 III) on 24 August 1998, 17--23 UT. The STIS
program was the result of a failed cycle 5 pointing, which could not
be rescheduled during the abbreviated cycle 6, and was carried over
to cycle 7. Three grating settings---E230H (t_exp= 1340 s), E230M
(2493 s), and E140M (5208 s)---covered the ultraviolet spectrum
from 1150--2850 Angstroms, at resolutions between R ~ 4*E(4) -
1*E(5) , with essentially no gaps. The resulting spectrograms are
stunning. The resolution is very high, as is the S/N; the spectral
coverage is broad and comprehensive. The far-UV interval (1150--1700
Angstroms) is a rich emission line spectrum, dominated by the broad
resonance transitions of atomic hydrogen (lambda 1215) and oxygen
(lambda 1305 triplet). There are numerous narrow emissions, mostly
from low-excitation species such as Si I, Fe II, and fluoresced bands
of carbon monoxide. Surprisingly, high-excitation species---Si IV
(lambda 1393: 6*E(4) K) and C IV (lambda 1548: 1*E(5) K)---are present
as well (as seen in the earlier “failed” GHRS spectra). The mid-UV
(1700--2600 Angstroms) shows additional emission lines, particularly [C
II] and [Si II] in the 2325 Angstroms region; the photospheric continuum
rises strongly toward the longer wavelengths. The 2600--2850 Angstroms
interval is mostly a photospheric absorption spectrum, although the
bright chromospheric emission doublet of Mg II lords over the 2800
Angstroms region. We present a comprehensive spectral atlas based on
our reductions of the STIS echellograms. We discuss the processing
strategies, line identifications, and some of the preliminary results
from our analysis of this windy, noncoronal giant. (1) This work was
supported by grants GO-06066.01-94A from STScI, and NAG5-3226 from
NASA. Observations were from the NASA/ESA HST, collected at the STScI,
operated by AURA, under contract NAS5-26555.

---------------------------------------------------------
Title: The Three-Dimensional Structure of the Warm Local Interstellar
Medium II: The Colorado Model of the Local Interstellar Cloud (LIC)
Authors: Linsky, J. L.; Redfield, S.
1999AAS...194.4715L Altcode: 1999BAAS...31..890L
We have constructed a three-dimensional model of the LIC based on
GHRS, EUVE, and ground-based Ca II spectra. Our model is based on
(1) hydrogen column densities derived from GHRS deuterium column
densities for 16 lines of sight to nearby stars, (2) EUVE spectra
of three hot white dwarfs, and (3) Ca II spectra for 13 lines of
sight with absorption at the projected LIC velocity. The model is a
sum of nine spherical harmonics that best fit the data for these 32
lines of sight. The model can be viewed at the Colorado Model of the
Local Interstellar Medium website. The input data, prescription for
computing the model, and a tool for calculating the hydrogen column
density through the LIC along any line of sight are also available at
this website. As new data appear the website will include new versions
of the Colorado LIC model and models for nearby warm clouds in the
LISM. The LIC model is neither a long thin filamentary structure like
optical images of some interstellar clouds, nor is it spherical in
shape. As seen from the North Galactic Pole, the LIC is egg-shaped with
an axis of symmetry that points in the direction l~ 315(deg) . Since
the direction of the center of the Scorpius-Centaurus Association is
l=320(deg) , the shape of the LIC could be determined by the flow of
hot gas from Sco-Cen. The model shows that the Sun is located just
inside the LIC in the direction of the Galactic Center and toward
the North Galactic Pole. The absence of Mg II absorption at the LIC
velocity toward alpha Cen indicates that the distance to the edge of
the LIC in this direction is &lt;= 0.05 pc and the Sun should cross
the boundary between the LIC and the G cloud in less than 3,000 yr. We
estimate that the volume of the LIC is about 115 pc(3) and its mass is
about 0.79 Msun. The physical parameters and hydrogen column
density of the LIC are roughly consistent with theoretical models of
the warm ISM that assume pressure and ionization equilibrium. However,
the empirical hydrogen ionization of the LIC is much higher (~ 50%)
and the gas temperature lower (7000 K) than the theoretical models
predict. The high ionization can be explained by the recombination of
the LIC gas following shock ionization from a nearby supernova. The
high ionization increases the gas cooling which can explain why the
gas is about 2400 K cooler than the ionization equilibrium models
predict. Computed and observed temperatures are in agreement for a
theoretical model with the observed LIC electron density. This work
is supported by NASA grants to the University of Colorado.

---------------------------------------------------------
Title: ASCA Spectra of the Central Star of the Orion Nebula: a
Magnetic O star
Authors: Gagne, M.; Caillault, J. P.; Song, I.; Tsuboi, Y.; Linsky,
J. L.; Stauffer, J. R.
1999HEAD....4.0903G Altcode: 1999BAAS...31..705G
The discovery of 15-day periodic H-alpha and He II emission on the
central star of the Orion Nebula, theta 1 Orionis C (O7 V), suggests
that this O star is an oblique magnetic rotator. The subsequent
detection of large-amplitude, periodic X-ray variations led Babel and
Montmerle to propose that the O star's magnetically confined wind is
shocked near the magnetic equator, producing an X-ray cooling disk. In
this poster, we present ASCA SIS spectra of the Trapezium obtained
at rotational phases 0.01, 0.45, and 0.77. Because many unresolved T
Tauri stars and OB stars produce about half the ASCA SIS flux, ROSAT
HRI images obtained at similar phases and an ASCA raytrace code have
been used to help reconstruct the SIS spectra. By all indications,
theta 1 Ori C is a very hot source (kT &gt; 3.0 keV). Suprisingly,
we see little or no evidence of variable wind attenuation.

---------------------------------------------------------
Title: The Active Corona of HD 35850 (F8 V)
Authors: Gagné, Marc; Valenti, Jeff A.; Linsky, Jeffrey L.;
Tagliaferri, Gianpiero; Covino, Stefano; Güdel, Manuel
1999ApJ...515..423G Altcode: 1998astro.ph.12270G
We present Extreme Ultraviolet Explorer (EUVE) spectroscopy and
photometry of the nearby F8 V star HD 35850 (HR 1817). The EUVE
short-wavelength 75-175 Å and medium-wavelength 160-365 Å spectra
reveal 28 emission lines from Fe IX and Fe XV to Fe XXIV. The
Fe XXI λλ102, 129 ratio yields an upper limit for the coronal
electron density, logne&lt;11.6 cm-3. The EUVE
short-wavelength spectrum shows a small but clearly detectable
continuum. The 75-150 Å line-to-continuum ratio indicates
approximately solar Fe abundances, with 0.8&lt;Z&lt;1.6 (90% confidence
interval). Upper limits have been derived for a dozen high-emissivity
Fe X through Fe XIV lines. The resulting emission measure distribution
is characterized by two broad temperature components at logT of 6.8
and 7.4. Over the course of the 1 week observation, large-amplitude,
long-duration flares were not seen in the EUVE Deep Survey light curve,
although the light curve does show signs of persistent, low-level
flaring and possible rotational modulation. The EUVE spectra have been
compared with nonsimultaneous ASCA SIS spectra of HD 35850 obtained
in 1995. The SPEX DEM analysis of the SIS spectrum indicates the same
temperature distribution as the EUVE DEM analysis. However, the SIS
spectra suggest subsolar abundances, 0.34&lt;Z&lt;0.81. Although some
of the discrepancy may be the result of incomplete X-ray line lists,
we cannot explain the disagreement between the EUVE line-to-continuum
ratio and the ASCA-derived Fe abundance. The X-ray surface flux on HD
35850 is comparable to that of cooler dwarfs of comparable age and
rotation like EK Draconis (G0 V) and AB Doradus (K1 V). Given its
youth (t~100 Myr), its rapid rotation (vsini~50 km s-1),
and its high X-ray activity (LX~1.5×1030
ergs s-1), HD 35850 may represent an activity extremum
for single, main-sequence F-type stars. The variability and emission
measure distribution can be reconstructed using the continuous flaring
model of Güdel provided that the flare distribution has a power-law
index α~1.8. Similar results obtained for other young solar analogs
suggest that continuous flaring is a viable coronal heating mechanism
on rapidly rotating, late-type, main-sequence stars.

---------------------------------------------------------
Title: A Goddard High Resolution Spectrograph Atlas of Echelle
Observations of the HGMN Star chi LUPI
Authors: Brandt, J. C.; Heap, S. R.; Beaver, E. A.; Boggess,
A.; Carpenter, K. G.; Ebbets, D. C.; Hutchings, J. B.; Jura, M.;
Leckrone, D. S.; Linsky, J. L.; Maran, S. P.; Savage, B. D.; Smith,
A. M.; Trafton, L. M.; Walter, F. M.; Weymann, R. J.; Proffitt, C. R.;
Wahlgren, G. M.; Johansson, S. G.; Nilsson, H.; Brage, T.; Snow, M.;
Ake, T. B.
1999AJ....117.1505B Altcode:
Observations of the ultra-sharp-lined, chemically peculiar star chi
Lupi taken by the Goddard High Resolution Spectrograph in echelle mode
are presented. Thirty-six intervals of the spectral region between
1249 and 2688 Å are covered with resolving powers in the range
75,000-93,000. Line identifications are provided, and the observed
spectra are compared with synthetic spectra calculated using the
SYNTHE program and associated line lists with changes to the line
lists. The significance of these spectra for the chi Lupi Pathfinder
Project and the closely related atomic physics effort is discussed in
a companion paper.

---------------------------------------------------------
Title: Galactic Science Panel Discussion
Authors: Linsky, J. L.
1999ASPC..164...26L Altcode: 1999uosa.conf...26L
No abstract at ADS

---------------------------------------------------------
Title: Magnetic Fields in the Hertzsprung-Russell Diagram
Authors: Linsky, J. L.
1999ASPC..158....3L Altcode: 1999ssa..conf....3L
No abstract at ADS

---------------------------------------------------------
Title: Wolf-Rayet star spectra from 1150 Å to 1200 Å
Authors: Nichols, J. S.; Linsky, J. L.
1999IAUS..193...80N Altcode:
No abstract at ADS

---------------------------------------------------------
Title: Echelle Spectroscopy of Interstellar Absorption toward MU
Columbae with the Goddard High Resolution Spectrograph
Authors: Brandt, J. C.; Heap, S. R.; Beaver, E. A.; Boggess, A.;
Carpenter, K. G.; Ebbets, D. C.; Hutchings, J. B.; Jura, M.; Leckrone,
D. S.; Linsky, J. L.; Maran, S. P.; Savage, B. D.; Smith, A. M.;
Trafton, L. M.; Walter, F. M.; Weymann, R. J.; Howk, J. C.; Snow,
M.; Ake, T. B.; Sembach, K. R.
1999AJ....117..400B Altcode:
Goddard High Resolution Spectrograph echelle-mode observations of
the interstellar absorption lines of Mg II, Si IV, C IV, and N V
toward mu Columbae (HD 38666) are presented. The observations have a
spectral resolution of 3.5 km s^-1 and signal-to-noise ratios (S/Ns)
of 20-200. The mu Col sight line (l=237.3d, b=-27.1d, d=0.40 kpc,
z=-0.18 kpc) extends though the Local Bubble and the warm neutral,
warm ionized, and hot ionized phases of the interstellar medium
(ISM). The high-ionization column densities toward mu Col are
log N(Si IV)=12.16+/-0.05, log N(C IV)=12.88+/-0.02, and logN(N
V)=11.8-12.3. Profile fits to Copernicus satellite measures of O VI
absorption toward mu Col yield log N(O VI)=13.82+/-0.01 and b=38.7
km s^-1. This implies N(C IV)/N(O VI)=0.11+/-0.01, which is typical
of the values found for the hot ISM of the Galactic disk. The O VI
profile is twice as broad as the C IV and N V profiles, even though
these species have roughly similar average velocities. Some of the C
IV, N V, and O VI absorption toward mu Col may occur at the interface
of the Local Cloud and Local Bubble, although additional contributions
to these ions probably also occur in more distant gas along the sight
line. A substantial part of the Si IV absorption likely arises in warm
photoionized gas in an H II region surrounding mu Col. The profile
width differences among the high-ionization lines of C IV, N V, and
O VI could be produced if the line of sight passes through a highly
evolved supernova remnant. The observations for mu Col and for other
stars observed at high resolution with the GHRS reveal that multiple
gas types (warm and hot) contribute to the absorption by the highly
ionized atoms along both nearby and distant sight lines. Disentangling
the relative contributions from the different gas types requires
high-resolution and high-S/N observations. The Mg II observations,
combined with a solar Mg reference abundance, imply that the Mg
depletion toward mu Col is -0.31 dex. As observed for other sight
lines through the warm neutral medium, the gas-phase observations of
Mg, when combined with results for Fe and Si, suggest that Mg and Fe
are more deficient from the gas phase than one would expect if these
elements are only contained in silicate dust grains.

---------------------------------------------------------
Title: Nonprimordial Deuterium in the Interstellar Medium
Authors: Mullan, D. J.; Linsky, J. L.
1999ApJ...511..502M Altcode:
Contrary to a widespread assumption, deuterium is not simply destroyed
in stars: deuterium is also synthesized in the atmospheres of active
stars. This nonprimordial synthesis of D arises when protons accelerated
in flares interact with the atmosphere, create a flux of free neutrons,
and these neutrons then undergo radiative capture on atmospheric
protons. Radiative capture does not result in excess production of
Li, Be, or B. Ejection of flare-processed material contaminates the
interstellar medium (ISM), as was originally suggested by Coleman
&amp; Worden. Estimates of the amount of flare-created D are subject
to considerable uncertainties, but we find, using stellar parameters
within permitted ranges, that flares may contribute significantly to
the current ISM D content. Observational data indicate that different
clouds of gas in the ISM exhibit variations in the value of D/H. We
suggest that contamination of the ISM by D-enriched material ejected
from stellar flares contributes to the observed D/H inhomogeneity. More
precise estimates of the efficiency of D ejection from flares into
the solar wind are required to evaluate this suggestion.

---------------------------------------------------------
Title: ERO Observation of Altair
Authors: Linsky, Jeffrey
1999fuse.prop.X025L Altcode:
The A7 V star Altair (= HD 187642) occupies a unique position in the HR
Diagram as the hottest star with late-type star characteristics. IUE,
Einstein, and ROSAT observations show that Altair has ultraviolet
emission lines and X-ray emission indicative of chromospheric and
coronal plasma heated either by shock waves or magnetic reconnection
events similar to the active late-type stars. Stars slightly hotter
than Altair do not show these phenomena, apparently due to shallower
convective zones. FUSE can obtain a rich FUV emission line spectrum
that will likely contain C III, O VI, and the hydrogen Lyman emission
lines. A FUSE spectrum of Altair will enable us to determine whether or
not the relative heating rates for the 104, 105,
and &gt;106 K plasma follow the trends seen in the cooler
stars, whether the heating is acoustic or magnetic in character, and
whether the emission line shapes and Doppler shifts indicate a wind or
interesting dynamics. A 5 ks exposure should obtain S/N in the range 16
to 33 per 0.032 A resolution element for the important emission lines.

---------------------------------------------------------
Title: Activity in the Sun and Late-type Stars - What have we Learned
so Far?
Authors: Linsky, J. L.
1999ASPC..158..401L Altcode: 1999ssa..conf..401L
No abstract at ADS

---------------------------------------------------------
Title: Transition Regions of PMS and Pleiades-Age Stars
Authors: Linsky, J.
1999fuse.prop.P186L Altcode:
The objectives of this program are to study the dynamics, thermal
structure, and energy balance in the transition regions of young stars,
including pre-main sequence and Pleiades age stars. The observations
will address these questions by measuring the far-UV fluxes, line
widths, and Doppler shifts of the O VI and other far-UV transition
region lines. We will be studying some young A-type stars to determine
whether their transition regions differ from those of cooler stars, and
will analyze any flares observed in these young stars and a reference
late-M star.

---------------------------------------------------------
Title: Flaring and Quiescent Coronae of UX Arietis: Results from
ASCA and EUVE Campaigns
Authors: Güdel, Manuel; Linsky, Jeffrey L.; Brown, Alexander;
Nagase, Fumiaki
1999ApJ...511..405G Altcode:
The RS CVn binary star UX Ari was observed for 14 hr with all
four detectors onboard the Advanced Satellite for Cosmology and
Astrophysics (ASCA), and for 135 ks with the spectrometers onboard the
Extreme-Ultraviolet Explorer (EUVE). During the ASCA observations,
the X-ray emission was at a constant, quiescent level during the
first 12 hr, after which time a powerful flare with a peak luminosity
of 1.4×1032 ergs s-1 started. The flare was
observed until shortly after its peak. The EUVE observations were
obtained on two different days when the star was in a quiescent
phase. We present a spectral and temporal analysis of the UX Ari
observations and interpret the ASCA flare data with a two-ribbon flare
model including estimates for cooling losses. The quiescent emission
measure (EM) distributions derived independently from ASCA and EUVE
data agree remarkably. The distribution increases up to a peak around
25 MK. We find elemental abundances that are significantly subsolar,
in particular for Fe (~17%). A time-dependent reconstruction of the
flare EM distribution shows that two separate plasma components
evolve during the flare (one being identified with the quiescent
EM). Most of the flare EM reaches temperatures between 50 and 100
MK or more. Magnetic confinement requires the loop arcade to be
geometrically large, with length scales on the order of one stellar
radius. The electron densities inferred from the model decrease
from initial values around 1012 cm-3 early
in the flare to about 1011 cm-3 at the flare
peak. The best-fit models require surface magnetic field strengths
of a few hundred G, compatible with the maximum photospheric fields
expected from equipartition. The flare parameters imply a (conductive
and radiative) cooling loss time of less than 1 hr at flare peak. The
elemental abundances increase significantly during the flare rise, with
the abundances of the low first ionization potential (FIP) elements Fe,
Mg, Si, and Ni typically increasing to higher levels than the high-FIP
elements, such as S or Ne. The Fe abundance increases from 17%+/-4%
of the solar photospheric value during quiescence up to 89%+/-18% at
flare peak. A fractionation process that occurs during the chromospheric
evaporation phase may selectively enrich low-FIP elements as in the
solar corona; alternatively, the chromospheric evaporation may itself
bring metal-rich chromospheric plasma into the metal-poor corona.

---------------------------------------------------------
Title: Far Ultraviolet Imaging of HH-1 and HH-2 with the Space
Telescope Imaging Spectrograph
Authors: Kimble, R. A.; Devine, D.; Linsky, J. L.; Valenti, J. A.
1998AAS...193.1707K Altcode: 1998BAAS...30.1279K
In 1998 April, we observed the bright Herbig-Haro objects HH-1
and HH-2 in the far ultraviolet using the Space Telescope Imaging
Spectrograph on board the Hubble Space Telescope. The observations were
made in imaging mode with the photon-counting, solar-blind FUV-MAMA
detector and a crystalline quartz filter that combined to provide
a bandpass from 145-190 nm, with a FWHM spatial resolution of 60-70
milliarcseconds. Each object was observed for 2538 seconds. We report
here on the morphology and brightness of the UV emissions observed,
compare with previous FUV spectroscopic observations and with previous
HST imaging in the visible, and discuss the prospects for followup
spectroscopy of the brighter features.

---------------------------------------------------------
Title: FUV Observations of Flares on the dM0e star AU MIC
Authors: Robinson, R. D.; Linsky, J. L.; Woodgate, B.; Carkner, L.;
Timothy, G.
1998AAS...193.9906R Altcode: 1998BAAS...30R1396R
We report on FUV observations of stellar flares on the dM0e star AU
Microscopii obtained on 1998 Sept 06 with the Space Telescope Imaging
Spectrograph (STIS) aboard the Hubble Space Telescope. The data consist
of medium resolution echelle observations covering the wavelength region
from 1170-1730 Angstroms with a resolution of 45,800. The observations
were obtained using the TIME-TAG observing mode in which the time and
position of each detected photon is recorded. This allows an analysis
of variability which is limited only by the counting statistics of the
data. During a total on-source time of 10,000 s we observed numerous
microflare bursts as well as 4 well defined flare events. These flares
lasted between 1 and 3 minutes and and were most easily observed in
the FUV continuum and the Si IV and C IV resonance lines. Variations
in both the cooler (e.g. Lyalpha , C II, O I) and hotter (O V, N V, Fe
XXI) emission lines were much less pronounced. In this paper we will
examine the physical characteristics of the main flare events. This
discussion will include the time history of the wavelength integrated
fluxes in the continuum and various emission lines. In particular, we
search for increased emission in the red wing of the Lyalpha line which
would indicate the presence of moderately energetic proton beams. We
also integrate the time sequences over the entire flare duration and
investigate the average line and continuum properties during each of
the events, including flows and turbulence as a function of temperature
as well as the shape of the FUV continuum. Unfortunately, none of
the events was strong enough to allow a detailed examination of line
profiles as a function of time. This work is supported by NASA grants
to the Catholic University of America and the University of Colorado.

---------------------------------------------------------
Title: HST/STIS Echelle Spectra of the dM0e Star AU MIC Outside
of Flares
Authors: Linsky, J. L.; Robinson, R. D.; Carkner, L.; Woodgate, B.;
Timothy, G.
1998AAS...193.4510L Altcode: 1998BAAS...30.1318L
We report on observations of the dM0e flare star AU Microscopii
(HD197481) obtained with the Space Telescope Imaging Spectrograph
(STIS) on 1998 Sept 6. We analyze 10105 seconds of observations
obtained with the medium resolution E140M grating, which covers the
complete 1170--1730 Angstroms spectral range with a resolution of
45,800 (corresponding to 6.6 km/s). The data were obtained in the
TIME-TAG mode to isolate time intervals of flaring. We report here
on the 9200 seconds of data for which the star did not have a large
flare. In this beautiful data set we identify more than 70 emission
lines including low temperature chromospheric lines (e.g., C I, O I),
transition region lines (e.g., C II--IV, N IV, O III-V, Si II-IV),
and the coronal line Fe XXI 1354 Angstroms. There are a number of
intersystem lines that are useful for measuring electron densities. We
discuss line redshifts and the broad wings of transition region lines
that provide evidence of microflare heating. We also discuss the shapes
of the Lyman-alpha and He II 1640 Angstroms lines, and the interstellar
absorption features seen in the H I, D I, C II, and Mg II resonance
lines. This work is supported by NASA grants to the University of
Colorado and the Catholic University of America.

---------------------------------------------------------
Title: The Space Telescope Imaging Spectrograph Design
Authors: Woodgate, B. E.; Kimble, R. A.; Bowers, C. W.; Kraemer, S.;
Kaiser, M. E.; Danks, A. C.; Grady, J. F.; Loiacono, J. J.; Brumfield,
M.; Feinberg, L.; Gull, T. R.; Heap, S. R.; Maran, S. P.; Lindler,
D.; Hood, D.; Meyer, W.; Vanhouten, C.; Argabright, V.; Franka, S.;
Bybee, R.; Dorn, D.; Bottema, M.; Woodruff, R.; Michika, D.; Sullivan,
J.; Hetlinger, J.; Ludtke, C.; Stocker, R.; Delamere, A.; Rose, D.;
Becker, I.; Garner, H.; Timothy, J. G.; Blouke, M.; Joseph, C. L.;
Hartig, G.; Green, R. F.; Jenkins, E. B.; Linsky, J. L.; Hutchings,
J. B.; Moos, H. W.; Boggess, A.; Roesler, F.; Weistrop, D.
1998PASP..110.1183W Altcode:
The Space Telescope Imaging Spectrograph (STIS) instrument was installed
on the Hubble Space Telescope (HST) during the second servicing mission,
in 1997 February. Four bands cover the wavelength range of 115-1000 nm,
with spectral resolving powers between 26 and 200,000. Camera modes
are used for target acquisition and deep imaging. Correction for HST's
spherical aberration and astigmatism is included. The 115-170 nm range
is covered by a CsI MAMA (Multianode Microchannel Array) detector
and the 165-310 nm range by a Cs_2Te MAMA, each with a format of
2048x2048 pixels, while the 305-555 and 550-1000 nm ranges are covered
by a single CCD with a format of 1024x1024 pixels. The multiplexing
advantage of using these two-dimensional detectors compared with the
1x512 pixel detectors of the first-generation spectrographs is 1 or
2 orders of magnitude, depending on the mode used. The relationship
between the scientific goals and the instrument specifications and
design is discussed.

---------------------------------------------------------
Title: Performance overview and science goals of the Cosmic Origins
Spectrograph for the Hubble Space Telescope
Authors: Morse, Jon A.; Green, James C.; Ebbets, Dennis C.; Andrews,
John P.; Heap, Sara R.; Leitherer, Claus; Linsky, J. L.; Savage,
Blair D.; Shull, J. M.; Snow, Theodore P.; Stern, S. Alan; Stocke,
John T.; Wilkinson, Erik
1998SPIE.3356..361M Altcode:
We present an overview of the expected performance and science
goals of the cosmic origins spectrograph (COS), a fourth generation
instrument to be installed aborad the Hubble Space Telescope (HST)
during the fourth HST servicing mission scheduled for late 2002. COS
is a UV spectrograph optimized for observing faint point sources with
moderate spectral resolution. The instrument has two channels: a far-
UV channel that is sensitive in the 1150-1775 angstrom wavelength range
and a near-UV channel that operates between 1750-3200 angstrom. The
COS science team program concentrates on QSO absorption line systems
and the IGM, dynamics of the ISM in galaxies and galaxy halos, UV
extinction in the Milky Way, horizontal-branch stars in globular
clusters, and volatile gases in the atmospheres of solar system bodies.

---------------------------------------------------------
Title: An Ultraviolet Spectral Atlas of 10 Lacertae Obtained with
the Goddard High Resolution Spectrograph on the Hubble Space Telescope
Authors: Brandt, J. C.; Heap, S. R.; Beaver, E. A.; Boggess,
A.; Carpenter, K. G.; Ebbets, D. C.; Hutchings, J. B.; Jura, M.;
Leckrone, D. S.; Linsky, J. L.; Maran, S. P.; Savage, B. D.; Smith,
A. M.; Trafton, L. M.; Walter, F. M.; Weymann, R. J.; Snow, M.; Ake,
T. B.; Hogen, R. H.
1998AJ....116..941B Altcode:
Observations of the narrow-lined O-type star 10 Lacertae taken with the
Goddard High Resolution Spectrograph in 1992 November are presented. The
spectra cover the wavelength range 1181-1777 Å with a resolution of
15 km s^-1 and signal-to-noise ratio greater than 100:1. Absorption
lines arising in the interstellar medium, the photosphere, and the
stellar wind are identified and discussed.

---------------------------------------------------------
Title: On-orbit performance of the space telescope imaging
spectrograph
Authors: Kimble, Randy A.; Woodgate, Bruce E.; Bowers, Charles W.;
Kraemer, Steven B.; Kaiser, M. E.; Gull, Theodore R.; Heap, Sara R.;
Danks, Anthony C.; Boggess, A.; Green, Richard F.; Hutchings, J. B.;
Jenkins, Edward B.; Joseph, Charles L.; Linsky, J. L.; Maran, S. P.
1998SPIE.3356..188K Altcode:
The Space Telescope Imaging Spectrograph (STIS) is a second- generation
instrument for the Hubble Space Telescope (HST), designed to cover the
115-1000 nm wavelength range in a versatile array of spectroscopic
and imaging modes that take advantage of the angular resolution,
unobstructed wavelength coverage, and dark sky offered by the HST. STIS
was successfully installed into HST in 1997 February and has since
completed a year of orbital checkout, capabilities that it brings
to HST, illustrate those capabilities with examples drawn from the
first year of STIS observing, and describe at a top level the on-orbit
performance of the STIS hardware. We also point the reader to related
papers that describe particular aspects of the STIS design, performance,
or scientific usage in more detail.

---------------------------------------------------------
Title: The Fascination of Far-UV Astrophysics
Authors: Linsky, J. L.
1998AAS...192.4902L Altcode: 1998BAAS...30..884L
A one-day topical session will review the observational and theoretical
status of astrophysical problems where data in the 900 to 1200 Angstroms
range are essential for future advances. The session will include
the study of FUV rest wavelengths at high redshifts. For example,
the deuterium-to-hydrogen abundance ratio will address the Milky Way
and QSO absorption line systems. The FUV spectral region is well known
for its unique spectral features and important scientific problems they
address. The Lyman series of atomic hydrogen provides the only means to
determine the production of deuterium in the Big Bang and its subsequent
processing during galactic chemical evolution. The resonance doublet
of the O VI ion is the highest temperature resonance line available
to study the abundance and kinematics of diffuse hot gas in the disk
and halo of the Galaxy and hot gas in accretion disks. The Lyman and
Werner bands, the only electronic transitions of molecular hydrogen,
probe cold gas in the diffuse ISM as well as the outer regions of
dense molecular clouds. Strong transitions of several ionization states
of carbon, nitrogen, oxygen, neon, sulphur, and argon provide unique
diagnostics for studying interstellar gas and emission plasmas. This
special session focuses on recent observational material and how the
data limit the range of acceptable pictures. This session will highlight
key puzzles and describe anticipated progress from new instrumentation,
in particular the Far Ultraviolet Spectroscopic Explorer (FUSE) mission,
due to be launched in early 1999. The first talk of the session will
summarize the critically important spectral diagnostics that reside
in the FUV spectral region and show how they allow FUSE to address the
main scientific objectives of FUV astrophysics. FUSE spectra will also
enhance the value of longer wavelength spectra provided by HST and IUE,
shorter wavelength spectra of EUVE and soon AXAF, lower sensitivity
FUV spectra of Copernicus, and lower resolution FUV spectra of ORFEUS.

---------------------------------------------------------
Title: Goddard High-Resolution Spectrograph Observations of beta
Geminorum
Authors: Osten, R. A.; Wood, B. E.; Linsky, J. L.; Brown, A.
1998AAS...192.6714O Altcode: 1998BAAS...30..919O
We report on a rich set of observations of the K0 III star beta
Geminorum (Pollux) with the Goddard High-Resolution Spectrograph
(GHRS). The dataset consists of low-dispersion spectra (lambda /Delta
lambda = 2,000) of the 1169 - 1671 Angstroms region, moderate dispersion
spectra (lambda /Delta lambda = 20,000) of selected spectral intervals,
and echelle observations (lambda /Delta lambda = 90,000) of the O I
resonance lines and Mg II h and k lines. We perform an analysis of
intersystem lines and determine the emission measure distribution,
from which we infer properties of the stellar transition region. The
line profile shapes do not reveal evidence of broad components, similar
to what is observed in the atmosphere of the inactive star Procyon and
unlike what is observed in active stars. We find a trend of increasing
redshift with line formation temperature up to a maximum log T of 5.2,
and a decrease for temperatures greater than log T of 5.2, similar to
what is seen on the Sun and dissimilar to what is seen on Procyon. We
interpret these findings in light of differences in activity and
atmospheric structure.

---------------------------------------------------------
Title: Simulations of FUSE spectra of A-type and cooler stars:
D/H and warm plasma emission
Authors: O'Neal, D.; Linsky, J. L.
1998AAS...192.5602O Altcode: 1998BAAS...30..902O
The Far Ultraviolet Spectroscopic Explorer (FUSE) will observe many
stars in the 905--1187 Angstroms spectral region with a resolving
power of 24,000--30,000. FUSE will explore this critically important
spectral region, which is mostly inaccessible to HST (and previously
to IUE), observing sources much fainter than Copernicus and with much
better spectral resolution than HUT or ORFEUS. We present simulations
of stellar spectra that will be observed with FUSE. The FUSE bandpass
includes the Ly beta (1025 Angstroms)\ and Ly gamma (972 Angstroms)\
lines. Extrapolating from GHRS Ly alpha spectra, we simulate FUSE
spectra of the Ly beta and Ly gamma lines of Capella and some other
late-type stars. These simulations will address the accuracy with
which the interstellar D/H ratio can be measured using these lines. In
addition, one of our FUSE observing programs will measure for the
first time the amount of warm (60,000--300,000 K) plasma present in
the outer atmospheres of A and early-F stars, using the C III 977
Angstroms and O VI 1032 Angstroms lines. This program will explore
whether the outer atmospheric layers of these stars are heated to
these temperatures and whether the heating process is magnetic or
acoustic. Our simulations indicate that FUSE will be sensitive enough
to measure very low luminosities in these lines. This work is supported
by NASA grants to the University of Colorado.

---------------------------------------------------------
Title: Astronephography: the 3-D shape of the Local Interstellar Cloud
Authors: Linsky, J. L.; Piskunov, N.; Wood, B. E.
1998AAS...192.1018L Altcode: 1998BAAS...30..830L
GHRS spectra of 19 mostly late-type stars provide interstellar hydrogen
and metal column densities along these lines of sight with sufficient
resolution to resolve individual clouds. For 16 of these lines of sight
we can infer the hydrogen column density at the projected velocity
of the Local Interstellar Cloud (LIC). We construct a 3 dimensional
representation of the LIC by assuming that the neutral hydrogen density
in the cloud is the same as the highest mean density observed, about
0.1 cm(-3) , and that the LIC extends continuously along each line of
sight to a distance determined by the hydrogen column density and the
assumed density. We will present our model of the LIC as an animated
video that shows its shape from different directions. We find that
the hydrogen column densities obtained from EUVE spectra of white
dwarfs are in excellent agreement with the GHRS column densities for
the stars. Also, some other nearby white dwarfs fit our LIC model
well and are included in the model. As viewed from the North Galactic
Pole, the LIC has an irregular shape with the Sun very near the edge
toward the Galactic Center and very little column density in the first
and fourth Galactic quadrants. As viewed from in the Galactic plane,
there is more material to the south and the cloud has narrow extensions
toward the Galactic Center and toward Galactic longitude 270 Degrees. We
propose that the study of the structure of interstellar clouds be called
"astronephography" based on the Greek word for cloud, "nephos". This
work is supported by NASA grants to the University of Colorado.

---------------------------------------------------------
Title: An IUE Far Ultraviolet Spectral Atlas
Authors: Nichols, J. S.; Linsky, J. L.
1998AAS...192.5605N Altcode: 1998BAAS...30..903N
The NEWSIPS reprocessing of IUE data accurately follows and extracts
the echelle spectral orders and properly subtracts the interorder
background even at the shortest wavelengths. NEWSIPS therefore permits
the extraction of spectra to wavelengths as short as 1150 A. We present
representative well-exposed IUE spectra covering the 1150 - 1220 A
region with a resolution of 0.1 A which will be included in an IUE
FUV Spectral Atlas. These spectra consist primarily of O, B, and WR
stars, but also include a few of the brighter late-type stars as well
as other types of objects. Stellar features include the CIII 1175 A,
SiIII 1206 A, SiII 1190, 1193 A lines and an unidentified feature near
1154 A. Many of the WR stars also show a broad emission feature at 1173
- 1185 A which may be due to CIII or NIII. The CIII 1175 A line in OB
giants and supergiants typically shows a P-Cygni shape. Superimposed
on the stellar spectra are many strong interstellar absorption lines
of NI, SiII, and other species. The IUE FUV Spectral Atlas provides a
useful bridge between the HST GHRS/STIS spectra and the FUV spectra
to be obtained by FUSE in the 900-1180 A spectral region. Since IUE
observed several hundred targets with well-exposed SWP-HI spectra in
the range 1150-1200 A, the Atlas can be an important tool for selecting
targets to be observed by FUSE.

---------------------------------------------------------
Title: Local Interstellar Medium Summary of Working Group VI
Authors: Linsky, Jeffrey L.; Wilson, T. L.; Rood, R. T.
1998SSRv...84..309L Altcode:
This report summarizes the issues discussed in Working Group VI
concerning the accuracy of measurements of D/H and 3He/H in the local
interstellar medium, possible systematic errors, and emerging trends
in the results.

---------------------------------------------------------
Title: Deuterium Abundance in the Local ISM and Possible Spatial
Variations
Authors: Linsky, Jeffrey L.
1998SSRv...84..285L Altcode:
Excellent HST/GHRS spectra of interstellar hydrogen and deuterium
Lyman-alpha absorption toward nearby stars allow us to identify
systematic errors that have plagued earlier work and to measure accurate
values of the D/H ratio in local interstellar gas. Analysis of 12
sightlines through the Local Interstellar Cloud leads to a mean value
of D/H = (1.50 +/- 0.10) x 10-5 with all data points lying within +/-
1sigma of the mean. Whether or not the D/H ratio has different values
elsewhere in the Galaxy and beyond is a very important open question
that will be one of the major objectives of the Far Ultraviolet
Spectroscopic Explorer (FUSE) mission.

---------------------------------------------------------
Title: The Goddard High Resolution Spectrograph: Post-COSTAR
Characteristics
Authors: Robinson, R. D.; Ake, T. B.; Lindler, D. J.; Heap, S. R.;
Carpenter, K. G.; Leckrone, D. S.; Maran, S. P.; Smith, A. M.; Brandt,
J. C.; Beaver, E. A.; Boggess, A.; Ebbets, D. C.; Hutchings, J. B.;
Jura, M.; Linsky, J. L.; Savage, B. D.; Trafton, L. M.; Walter, F. M.;
Weymann, R. J.
1998PASP..110...68R Altcode:
We review changes to the characteristics of the Goddard High Resolution
Spectrograph (GHRS) which resulted from the installation of the
Corrective Optics Space Telescope Axial Replacement (COSTAR) on the
Hubble Space Telescope. The introduction of two new optical elements
into the light path altered the spectral distribution of the light,
decreasing the amount of light striking the instrument by about 30%
at wavelengths greater than 1200 Å and effectively eliminated all
radiation at wavelengths less than 1130 Å. However, at the longer
wavelengths the improved focus offset this loss when the Large Science
Aperture (LSA) was used and increased the overall throughput of the
Small Science Aperture (SSA) by a factor of 2. The improved focus also
enhanced the spectral resolution of LSA observations and improved the
ability of the instrument to observe in crowded fields.

---------------------------------------------------------
Title: An Atlas of IUE Far Ulraviolet Spectra of T Tauri and Herbig
Ae/be Stars
Authors: Linsky, J. L.; Valenti, J.; Johns-Krull, C.
1998ESASP.413..125L Altcode: 1998uabi.conf..125L
No abstract at ADS

---------------------------------------------------------
Title: The On-Orbit Performance of the Space Telescope Imaging
Spectrograph
Authors: Kimble, R. A.; Woodgate, B. E.; Bowers, C. W.; Kraemer,
S. B.; Kaiser, M. E.; Gull, T. R.; Heap, S. R.; Danks, A. C.; Boggess,
A.; Green, R. F.; Hutchings, J. B.; Jenkins, E. B.; Joseph, C. L.;
Linsky, J. L.; Maran, S. P.; Moos, H. W.; Roesler, F.; Timothy,
J. G.; Weistrop, D. E.; Grady, J. F.; Loiacono, J. J.; Brown, L. W.;
Brumfield, M. D.; Content, D. A.; Feinberg, L. D.; Isaacs, M. N.;
Krebs, C. A.; Krueger, V. L.; Melcher, R. W.; Rebar, F. J.; Vitagliano,
H. D.; Yagelowich, J. J.; Meyer, W. W.; Hood, D. F.; Argabright,
V. S.; Becker, S. I.; Bottema, M.; Breyer, R. R.; Bybee, R. L.;
Christon, P. R.; Delamere, A. W.; Dorn, D. A.; Downey, S.; Driggers,
P. A.; Ebbets, D. C.; Gallegos, J. S.; Garner, H.; Hetlinger, J. C.;
Lettieri, R. L.; Ludtke, C. W.; Michika, D.; Nyquist, R.; Rose, D. M.;
Stocker, R. B.; Sullivan, J. F.; Van Houten, C. N.; Woodruff, R. A.;
Baum, S. A.; Hartig, G. F.; Balzano, V.; Biagetti, C.; Blades, J. C.;
Bohlin, R. C.; Clampin, M.; Doxsey, R.; Ferguson, H. C.; Goudfrooij,
P.; Hulbert, S. J.; Kutina, R.; McGrath, M.; Lindler, D. J.; Beck,
T. L.; Feggans, J. K.; Plait, P. C.; Sandoval, J. L.; Hill, R. S.;
Collins, N. R.; Cornett, R. H.; Fowler, W. B.; Hill, R. J.; Landsman,
W. B.; Malumuth, E. M.; Standley, C.; Blouke, M.; Grusczak, A.; Reed,
R.; Robinson, R. D.; Valenti, J. A.; Wolfe, T.
1998ApJ...492L..83K Altcode:
The Space Telescope Imaging Spectrograph (STIS) was successfully
installed into the Hubble Space Telescope (HST) in 1997 February,
during the second HST servicing mission, STS-82. STIS is a versatile
spectrograph, covering the 115-1000 nm wavelength range in a variety
of spectroscopic and imaging modes that take advantage of the angular
resolution, unobstructed wavelength coverage, and dark sky offered by
the HST. In the months since launch, a number of performance tests and
calibrations have been carried out and are continuing. These tests
demonstrate that the instrument is performing very well. We present
here a synopsis of the results to date.

---------------------------------------------------------
Title: Coordinated VLA, Optical, EUVE, and RXTE Monitoring of Flares
on EQ Pegasi and AU Microscopii
Authors: Gagne, Marc; Valenti, Jeff; Johns-Krull, Christopher; Linsky,
Jeffrey; Brown, Alex; Gudel, Manuel
1998ASPC..154.1484G Altcode: 1998csss...10.1484G
We present initial results from coordinated, multi-wavelength monitoring
of two nearby dMe flare stars: EQ Pegasi and AU Microscopii. Our
primary goal was to observe the impulsive and cooling phases of stellar
flares. AU Mic was observed 1996 June 12-15 with the RXTE and EUVE
satellites. EQ Peg was observed 1996 October 2-6 with RXTE, EUVE, the
ubvr photometer on the McDonald Observatory 0.9-m telescope, and the VLA
at 3.5 and 20 cm. We present light curves in most observed wavebands
and X-ray spectra obtained during flares and quiescence. Although a
number of moderately polarized VLA radio flares are seen, there is
no compelling evidence in the RXTE data for hard, non-thermal X-ray
emission. We also discuss an extreme ultraviolet transient event
detected by ALEXIS on 1996 June 15 in the direction of AU Mic.

---------------------------------------------------------
Title: Deuterium Abundance in the Local ISM and Possible Spatial
Variations
Authors: Linsky, J. L.
1998pnge.conf..285L Altcode:
No abstract at ADS

---------------------------------------------------------
Title: Dynamics, Winds and Structure in Cool Stars
Authors: Linsky, J. L.
1998ESASP.413...83L Altcode: 1998uabi.conf...83L
No abstract at ADS

---------------------------------------------------------
Title: From Top to Bottom --- the Multiwavelength Campaign of V824
ARA (HD 155555)
Authors: Dempsey, Robert; Neff, James; Strassmeier, Klaus; Linsky,
Jeffrey; Lim, Jeremy; Donati, J. -F.; Walter, Fred; Budding, Edwin;
Marang, Fred; Jordan, Ian; Walker, Stan; Downing, David G.; Inwood,
Doug; Petterson, Orlon
1998ASPC..154.1402D Altcode: 1998csss...10.1402D
In the spring of 1996, we conducted a multiwavelength campaign on V824
Ara (HD 155555, P=1.68d, G5 IV + K0 IV-V) covering one continuous,
complete rotation cycle. At the core of this campaign were observations
using the GHRS on HST. In all, ~46,000 spectra, many in rapid
readout mode, were obtained with the GHRS covering the C IV, Mg II,
and Fe XXI wavelength regions at 11-15 separate phases. Simultaneous
observations were made with the EUVE. Radio observations (3.5 &amp;
6 cm) were conducted at the Australian Telescope while ground based
optical spectroscopic and photometric observations were made at ESO,
CTIO, AAT and SAAO. Additional amateur photometry were obtained
from New Zealand before, during, and after the campaign. Our primary
intent is to obtain a 3-D model of the atmosphere, extending from the
photosphere to the corona. Variability was clearly detected including
several flares observed in the HST, EUVE and radio data. We present
preliminary results from modeling the UV Transition region (TR)
lines using an anisotropic macroturbulence model proposed by Gray
(1976, The Observation and Analysis of Stellar Photospheres, Cambridge
Astrophysics Series). Previous studies of TR lines in late-type active
stars have used multiple gaussians to fit the observed line profiles,
adding additional, broad components to account for the extended wings
observed in several active systems including V711 Tau (HR 1099). This
broad component has been interpreted as arising from the continuous
presence of microflaring (Wood et al., 1995, ApJ, 458, 761). We discuss
how anisotropic macroturbulence can also fit the Mg II profiles and,
in some cases, with smaller residuals than is possible using only
gaussians.

---------------------------------------------------------
Title: From Top to Bottom: The Multiwavelength Campaign of V824 ARA
(HD 155555)
Authors: Dempsey, Robert; Neff, James; Strassmeier, Klaus; Linsky,
Jeffrey; Lim, Jeremy; Donati, J. -F.; Walter, Fred; Budding, Edwin;
Marang, Fred; Jordan, Ian; Walker, Stan; Downing, David G.; Inwood,
Doug; Petterson, Orlon
1998fmml.conf.....D Altcode:
A great deal of progress has been made in recent years in decomposing
the 2-D structure in the atmospheres of late-type stars. Doppler
images of many photospheres - single stars, T Tauri stars, Algols,
RS CVn binaries to name a few are regularly published. Ultraviolet
spectral images of chromospheres appear in the literature but are
less common owing to the difficult nature of obtaining complete
phase coverage. Zeeman doppler images of magnetic fields are now
feasible. Performing Doppler imaging of the same targets over
many seasons has also been accomplished. Even when a true image
reconstruction is not possible due to poor spectral resolution, we can
still infer a great deal about spatial structure if enough phases are
observed. However, it is increasingly apparent that to make sense of
recent results, many different spectral features spanning a range of
formation temperature and density must be observed simultaneously for
a coherent picture to emerge. Here we report on one such campaign. In
1996, we observed the southern hemisphere RS CVn binary V824 Ara
(P=1d.68, G51V+K0V-IV) over one complete stellar rotation with the
Hubble Space Telescope and EUVE. In conjunction, radio and optical
photometry and spectroscopy were obtained from the ground. Unique to
this campaign is the complete phase coverage of a number of activity
proxy indicators that cover source temperatures ranging from the
photosphere to the corona.

---------------------------------------------------------
Title: The Scientific Impact of the GHRS on our Understanding of
the Local Interstellar Medium
Authors: Linsky, J. L.; Wood, B. E.
1998ASPC..143..197L Altcode: 1998sigh.conf..197L
No abstract at ADS

---------------------------------------------------------
Title: Dissecting Capella's Corona: GHRS Spectra of the Fe XXI λ1354
and He II λ1640 Lines from Each of the Capella Stars
Authors: Linsky, Jeffrey L.; Wood, Brian E.; Brown, Alexander; Osten,
Rachel A.
1998ApJ...492..767L Altcode:
We report on moderate (λ/Δλ = 20,000) and high (λ/Δλ = 90,000)
resolution spectra of the 104-day period Capella binary system (HD
34029) obtained with Hubble Space Telescope's Goddard High-Resolution
Spectrometer (GHRS) on 1995 September 9 and 1996 April 9. The
observations include a long-duration, moderate-resolution spectrum of
the coronal Fe XXI λ1354 line and both moderate- and high-resolution
spectra of the He II λ1640 multiplet. Our objective in observing
the Fe XXI line formed at T = 1 × 107 K is to determine
for the first time the line shape parameters and the contribution of
each star's corona. This is feasible because the GHRS can resolve the
53 km s-1 radial velocity separation of the stars. Our
analysis led to four surprising results: (1) The contribution of
the slowly rotating G8 III star to the total Fe XXI λ1354 flux is
similar to that of the more active rapidly rotating G1 III star,
in contrast to other UV lines formed at lower temperatures. (2) The
centroid velocities of the Fe XXI lines from both stars are near their
respective photospheric radial velocities. Thus, there is no evidence
for downflows or winds, and the hot coronal plasma must be confined,
presumably by strong, closed magnetic fields. This is the first direct
kinematic evidence for magnetic confinement in the corona of a giant
star. (3) The line widths are thermal, indicating very low turbulence
(ξ &lt; 23 km s-1) compared with the 54 km s-1
thermal speed. (4) Our analysis of Extreme-Ultraviolet Explorer (EUVE)
spectra that include four Fe XXI lines shows that the volume emission
measures of these lines are about a factor of 3 smaller than for the
λ1354 line, which was observed several months after the closest EUVE
observation. We consider possible explanations for this discrepancy and
conclude that variability of the high-temperature coronal emission is
the most likely explanation. We observed the He II λ1640 line
twice with a time separation of 7 months, corresponding to about
2 orbital periods. The profiles are nearly identical, except for a
large difference in flux near the expected radial velocity of the G8
III star. We believe that the broad He II emission produced by the
G1 star is formed mostly by collisional excitation in its transition
region, while the emission from the G8 star is produced predominantly
by a photoionization/recombination process driven by EUV radiation from
the G8 star's corona. The He II λ1640 flux that we measure from the G8
star is consistent with predictions based on EUVE flux measurements. The
decrease in the λ1640 emission from the G8 star between the phase 0.73
and 0.78 measurements indicates that its EUV radiation is variable, as
is observed by EUVE. Based on observations with the NASA/ESA Hubble
Space Telescope, obtained at the Space Telescope Science Institute,
which is operated by the Association of Universities for Research in
Astronomy, Inc., under NASA contract NAS5-26555.

---------------------------------------------------------
Title: Space Telescope Imaging Spectrograph Observations of the
Interstellar Velocity Structure and Chemical Composition toward the
Carina Nebula
Authors: Walborn, Nolan R.; Danks, Anthony C.; Sembach, Kenneth R.;
Bohlin, Ralph C.; Jenkins, Edward B.; Gull, Theodore R.; Lindler,
Don J.; Feggans, J. Keith; Hulbert, Stephen J.; Linsky, Jeffrey;
Hutchings, John B.; Joseph, Charles L.
1998ApJ...492L.169W Altcode:
We have observed the O-type star CPD -59°2603 in the Carina Nebula
with the Space Telescope Imaging Spectrograph near-UV and far-UV
high-resolution echelles, at a resolving power of ~110,000 (FWHM)
and S/N ~ 30. This sight line has complex velocity and excitation
structure in the interstellar absorption lines, corresponding to
three distinct regions: very high velocity components formed within
the nebula; a warm, expanding H II region; and cool, low-velocity
gas near the Sun. The Mg I and Mg II profiles show many components,
with velocities extending from -235 to +123 km s-1. We
have derived physical conditions in the expanding H II region from
the Si IV doublet and the excited fine-structure lines of C I. Heavy
elements (O, Ni, Cu, Ga) are present in the low-velocity gas, and
their abundances indicate depletions consistent with nearby, cool
diffuse clouds. 12CO is detected in just one low-velocity
component, suggesting different amounts of processing among the clouds
near the Sun. Based on observations with the NASA/ESA Hubble
Space Telescope, obtained at the Space Telescope Science Institute,
which is operated by the Association of Universities for Research in
Astronomy, Inc., under NASA contract NAS5-26555.

---------------------------------------------------------
Title: Ultraviolet Spectral Dating of Stars and Galaxies
Authors: Heap, S. R.; Brown, T. M.; Hubeny, I.; Landsman, W.; Yi,
S.; Fanelli, M.; Gardner, J. P.; Lanz, T.; Maran, S. P.; Sweigart,
A.; Kaiser, M. E.; Linsky, J.; Timothy, J. G.; Lindler, D.; Beck,
T.; Bohlin, R. C.; Clampin, M.; Grady, J.; Loiacono, J.; Krebs, C.
1998ApJ...492L.131H Altcode:
An echelle spectrogram (R = 30,000) of the 2300-3100 Å region in
the ultraviolet spectrum of the F8 V star 9 Comae is presented. The
observation is used to calibrate features in the mid-ultraviolet spectra
of similar stars according to age and metal content. In particular, the
spectral break at 2640 Å is interpreted using the spectral synthesis
code SYNSPEC. We use this feature to estimate the time since the last
major star formation episode in the early-type galaxy LBDS 53W091 at
redshift z=1.55, whose rest-frame mid-ultraviolet spectrum, observed
with the Keck Telescope, is dominated by the flux from similar stars
that are at or near the main-sequence turnoff in that system (Spinrad
et al.). Our result, 1 Gyr if the flux-dominating stellar population
has a metallicity twice solar, or 2 Gyr for a more plausible solar
metallicity, is significantly lower than the previous estimate and
thereby relaxes constraints on cosmological parameters that were implied
by the earlier work. Based on observations with the NASA/ESA Hubble
Space Telescope, obtained at the Space Telescope Science Institute,
which is operated by the Association of Universities for Research in
Astronomy, Inc., under NASA contract NAS5-2655.

---------------------------------------------------------
Title: Local Interstellar Medium
Authors: Linsky, J. L.; Wilson, T. L.; Rood, R. T.
1998pnge.conf..309L Altcode:
No abstract at ADS

---------------------------------------------------------
Title: Studying new problems in Stellar Coronal Physics with AXAF
and XMM
Authors: Linsky, J. L. Gagné, M.
1998PhST...77..127L Altcode:
No abstract at ADS

---------------------------------------------------------
Title: A Critical Evaluation of Mass-Loss Rates and Wind Properties
of Evolved Late-Type Stars
Authors: Linsky, J. L.; Harper, G. M.; Bennett, P. D.; et al.
1998cvsw.conf...30L Altcode:
No abstract at ADS

---------------------------------------------------------
Title: The Local ISM and Its Interaction with the Winds of Nearby
Late-Type Stars
Authors: Wood, Brian E.; Linsky, Jeffrey L.
1998ApJ...492..788W Altcode:
We present new Goddard High-Resolution Spectrograph (GHRS) observations
of the Lyα and Mg II absorption lines seen toward the nearby stars
61 Cyg A and 40 Eri A. We use these data to measure interstellar
properties along these lines of sight and to search for evidence of
circumstellar hydrogen walls, which are produced by collisions between
the stellar winds and the local interstellar medium (LISM). We were
able to model the Lyα lines of both stars without hydrogen-wall
absorption components, but for 61 Cyg A the fit required a stellar
Lyα line profile with an improbably deep self-reversal, and for 40
Eri A the fit required a very low deuterium-to-hydrogen ratio that
is inconsistent with previous GHRS measurements. Since these problems
could be rectified simply by including stellar hydrogen-wall components
with reasonable attributes, our preferred fits to the data include
these components. We have explored several ways in which the
hydrogen-wall properties measured here and in previous work can be
used to study stellar winds and the LISM. We argue that the existence
of a hydrogen wall around 40 Eri A and a low H I column density along
that line of sight imply that either the interstellar density must
decrease toward 40 Eri A or the hydrogen ionization fraction (x)
must increase. We find that hydrogen-wall temperatures are larger
for stars with faster velocities through the LISM. The observed
temperature-velocity relation is consistent with the predictions of
hydromagnetic shock jump conditions. More precise comparison of the
data and the jump conditions suggests crude upper limits for both
x and the ratio of magnetic to thermal pressure in the LISM (α):
x &lt; 0.6 and α &lt; 2. The latter upper limit corresponds to
a limit on the LISM magnetic field of B &lt; 5 μG. These results
imply that the plasma Mach number of the interstellar wind flowing
into the heliosphere is MA &gt; 1.3, which indicates that
the collision is supersonic and that there should therefore be a bow
shock outside the heliopause in the upwind direction. Finally, we
estimate stellar wind pressures (Pwind) from the measured
hydrogen-wall column densities. These estimates represent the first
empirical measurements of wind properties for late-type main-sequence
stars. The wind pressures appear to be correlated with stellar X-ray
surface fluxes, FX, in a manner consistent with the relation
Pwind~F-1/2X, a relation that is also
consistent with the variations of Pwind and FX
observed during the solar activity cycle. If this relation can in
fact be generalized to solar-like stars, as is suggested by our data,
then it is possible to estimate stellar wind properties simply by
measuring stellar X-rays. One implication of this is that stellar wind
pressures and mass-loss rates are then predicted to increase with
time, since FX is known to decrease with stellar age. Based on observations with the NASA/ESA Hubble Space Telescope,
obtained at the Space Telescope Science Institute, which is operated
by the Association of Universities for Research in Astronomy Inc.,
under NASA Contract NAS5-26555.

---------------------------------------------------------
Title: Deuterium Abundance in the Local ISM and Possible Spatial
Variations
Authors: Linsky, J. L.
1998tsra.conf..236L Altcode:
No abstract at ADS

---------------------------------------------------------
Title: The Winds of Solar-like Stars and Their Interactions with
the ISM
Authors: Wood, Brian E.; Linsky, Jeffrey L.
1998ASPC..154.1652W Altcode: 1998csss...10.1652W
Models of the solar wind's interaction with the local interstellar
medium predict the existence of hot, decelerated neutral hydrogen
gas just outside the heliopause. Lyman-alpha absorption from this
“hydrogen wall” has been detected in HST GHRS spectra. The recent
detection of Lyman-alpha absorption from stellar hydrogen walls allows
us for the first time to study the solar-like winds of other stars. In
this article, we summarize the hydrogen walls detected to date (some
only tentatively). We then try to determine if the measured properties
of the walls are consistent with theoretical expectations, and we
assess the usefulness of the hydrogen wall properties for inferring
properties of the stellar winds. Stellar wind pressures estimated from
the hydrogen wall column densities appear to be correlated with stellar
X-ray surface fluxes, F_X, in a manner consistent with the relation
P_wind propto F_X^{-1/2}, a relation that is also consistent with
the variations of P_wind and F_X observed during the solar activity
cycle. If this relation does in fact apply to solar-like stars in
general, stellar wind pressures and mass loss rates are then predicted
to increase with time, since F_X is known to decrease with stellar age.

---------------------------------------------------------
Title: Studying New Problems in Stellar Coronal Physics with AXAF
and XMM
Authors: Linsky, Jeffrey L.; Gagne, Marc
1998ASPC..154..527L Altcode: 1998csss...10..527L
AXAF and XMM have instruments with far higher angular and spectral
resolution than ASCA, ROSAT, or Einstein. In particular, we look forward
to the first generation of moderate resolution coronal spectroscopy
of cool stars. We will summarize here the capabilities of the AXAF
and XMM instruments and identify some of the new coronal physics that
these instruments will soon allow us to study.

---------------------------------------------------------
Title: A Critical Evaluation of Mass Loss Rates and Wind Properties
of Evolved Late-type Stars
Authors: Linsky, Jeffrey L.; Harper, Graham M.; Bennett, Philip D.;
Brown, Alex; Valenti, Jeffrey
1998IAUS..191P.217L Altcode:
We evaluate the accuracy with which the wind properties of late-type
giants and supergiants can be estimated by fitting ultraviolet line
profiles obtained with the echelle gratings on the GHRS and STIS
intruments on HST and the radio continuum emission obtained with the VLA
and AT. Our test cases include the stars alpha TrA (K4 II), lambda Vel
(K4 Ib-II), and zeta Aur (K4 IB + B5 V). Of particular interest is the
sensitivity of the line profiles to the wind parameters (mass loss rate,
terminal velocity, turbulent velocity, velocity law parameter beta, and
the wind temperature). While the wind inversion problem is difficult,
we are now obtaining accurate and reliable values of the mass loss
rates with the application of two or more independent techniques.

---------------------------------------------------------
Title: A Short Wavelength IUE Atlas of Pre-Main-Sequence Stars
Authors: Johns-Krull, Christopher M.; Valenti, Jeff A.; Linsky,
Jeffrey L.
1998ASPC..154.1724J Altcode: 1998csss...10.1724J
We present an atlas of IUE low-dispersion short-wavelength spectra of
pre-main-sequence (PMS) stars. These spectra are coadditions from all
useful images which have been reprocessed with NEWSIPS and placed in the
IUE final archive. Compared to the earlier processing of the spectra
with IUESIPS, each spectrum has significantly higher signal/noise and
most blemishes and cosmic ray hits are now removed. Since most of the
fixed pattern noise is removed by NEWSIPS, the spectra can be coadded
with considerable increase in signal/noise. Using the available lists of
PMS stars we have identified 128 objects observed by IUE, including 50 T
Tauri stars and 78 Herbig Ae/Be stars. 663 usable spectra are available
from the IUE Final Archive for these targets, and our atlas consists
of coadded spectra for each star based on up to 94 individual spectra
(AB Aur). The stars cover the spectral type range B0 to M3. This atlas
includes most, if not all PMS stars that were observed by IUE in the
far-UV (1175 - 2000 AA). Our objective is to obtain the highest quality
spectra of these stars and to extract time-averaged fluxes for the
broad range of emission features produced in the atmospheres, disks,
and winds of different kinds of PMS stars. These spectral features
consist of emission lines formed at temperatures as high as 150,000 K
(N 5), molecular features (H_2), and absorption lines formed in the
hotter stars. We tabulate line and continuum fluxes and compare these
UV properties with stellar, accretion, and wind properties.

---------------------------------------------------------
Title: Digging Deeper in the Coronal Graveyard
Authors: Ayres, Thomas R.; Brown, Alexander; Harper, G. M.; Bennett,
P. D.; Linsky, J. L.; Carpenter, K. G.; Robinson, R. D.
1997ApJ...491..876A Altcode:
Soft X-ray detections of stellar coronae (T ~ 106 K) are
rare in the giant branch redward of ~K1 III. We have conducted a less
direct--but more sensitive--search using the Hubble Space Telescope
Goddard High-Resolution Spectrograph to probe for far-ultraviolet
proxies of the hot coronal gas in representative “noncoronal”
red giants. In every target so far examined, we find weak but
statistically significant Si IV emission, as well as, commonly,
C IV and, in some cases, N V. Si IV is not affected by the CNO
anomalies produced by the first dredge-up, which can deplete the
carbon abundance and weaken C IV. In the low-activity giants,
the λ1393 component of the Si IV doublet must be corrected
for sharp absorptions, which we believe are caused by carbon
monoxide in overlying cool material. The normalized flux ratios
(\Rscr≡f/fbol) of Si IV and X-rays among the “coronal”
yellow giants (lying just blueward of the “noncoronal” zone) fall on a
uniform track, \RscrX~\Rscr2SiIV. In
the noncoronal zone, however, the Si IV index is nearly constant
(\RscrSiIV~10-8), independent of \RscrX
(which ranges from ~10-8 to &lt;~10-10). The
mechanism that diminishes X-ray activity in the red giants is highly
sensitive to an as yet unidentified stellar property. Photoelectric
absorption by cool gas might play a more important role than previously
suspected, particularly if hot magnetic loops are partly or completely
buried in the chromosphere.

---------------------------------------------------------
Title: Flaring and Quiescent Coronae of UX Arietis: The ASCA View
Authors: Linsky, J. L.; Gudel, M.; Nagase, F.
1997AAS...191.4412L Altcode: 1997BAAS...29.1279L
The RS CVn-type binary UX Ari was observed for 14 hours with all four
detectors onboard the ASCA satellite. After 12 hours of constant,
quiescent X-ray emission, ASCA observed a powerful flare with a
peak luminosity of 1.4x 10(32) ergs s(-1) . We present a spectral
and temporal analysis of the observations using a two-ribbon flare
model. A time-dependent reconstruction of the emission measure
(EM) distribution shows that two separate plasma components evolve
initially. One is identified as the quiescent EM, and the other
(flare) EM reaches temperatures between 50 MK and more than 100
MK. The maximum arcade length is estimated to be about 2R_⋆, with
a width and height about 1R_⋆. Lower limits to the flare density
obtained with the maximum flux model drop from about 8.5x 10(10)
cm(-3) at flare start to 3x 10(10) cm(-3) at flare peak. The flare
parameters imply a (conductive and radiative) cooling loss time of
about one hour at flare peak for the maximum volume model, or less for
more compact flares. The elemental abundances increase significantly
during the flare rise, with the abundances of the low-FIP elements Fe,
Mg, Si, and Ni typically increasing to higher levels than the high-FIP
elements such as S or Ne. The Fe abundance increases from (17+/-4)%
of the solar photospheric value during quiescence up to (89+/-18)%
at flare peak. Either fractionation occurs during the chromospheric
evaporation phase to selectively enrich low-FIP elements in the corona,
or the evaporation itself brings metal-rich plasma into the metal-poor
corona. This work is supported by NASA grant NAG5-2750.

---------------------------------------------------------
Title: Space Telescope Imaging Spectrograph (STIS) Observations of
the ISM towards the Carina Nebula.
Authors: Danks, A. C.; Walborn, N. R.; Sembach, K. R.; Bohlin, R. C.;
Jenkins, E. B.; Gull, T. R.; Lindler, D.; Feggans, K.; Hulbert, S. J.;
Linsky, J.; Hutchings, J. B.; Joseph, C. L.
1997AAS...191.5104D Altcode: 1997BAAS...29R1296D
Spectroscopic observations of the star CPD -59 2603 in the Carina Nebula
have been obtained with STIS using the near and far UV high-resolution
echelle modes. The resolving power is approximately 110,000 with a
signal to noise of 30. The interstellar absorption lines along this
sightline exhibit complex velocity and excitation structure, from which
three distinct regions can be identified: multiple, very-high-velocity
components formed within the nebula: the warm, globally expanding HII
region; and cool, low-velocity gas probably associated with clouds
near the Sun. The behavior of the atomic species Mg I, MgII, SiIV,
and CI are discussed. Similarly, the heavy element species OI, NiII,
CuII and GaII are detected and discussed.

---------------------------------------------------------
Title: D.M. Rabin, J.T. Jefferies, and C. Lindsey (eds.), Infrared
Solar Physics, IAU Symposium 154
Authors: Linsky, J. L.; Linsky, J. L.
1997SoPh..176..217L Altcode:
No abstract at ADS

---------------------------------------------------------
Title: Lyman-Alpha Absorption and the D/H Ratio in the Local
Interstellar Medium
Authors: Dring, Andrew R.; Linsky, J.; Murthy, Jayant; Henry, R. C.;
Moos, W.; Vidal-Madjar, A.; Audouze, J.; Landsman, W.
1997ApJ...488..760D Altcode:
Using the Goddard High Resolution Spectrograph onboard the Hubble
Space Telescope, we have observed Lyα absorption against stellar
chromospheres along six lines of sight, with additional observations
of the Mg II H and K lines along five of the lines of sight and Fe II
absorption along four of the lines of sight. We found absorption near
the projected velocity of the local interstellar cloud (LIC) along three
lines of sight. The velocity toward the stars β Gem and σ Gem was only
marginally consistent with the LIC. The single interstellar component
toward 31 Com had a velocity that was inconsistent with the projected
LIC velocity. Three of the lines of sight showed a multicomponent
velocity structure. For the star ɛ Eri we required an additional hot,
low-density component which we have interpreted as a stellar hydrogen
wall. The LIC temperatures derived from our data range from 7800 to
9700 K with values of the microturbulence parameter less than 2.0 km
s-1. The measured D/H ratio for the LIC along every sight
line is consistent with a value of 1.6 × 10-5, the best
determined value being the β Cas line of sight with D/H = 1.7 +/- 0.3
× 10-5. Based on observations with the NASA/ESA Hubble
Space Telescope, obtained at the Space Telescope Science Institute,
which is operated by the Association of Universities for Research in
Astronomy, Inc., under NASA contract NAS 5-26555.

---------------------------------------------------------
Title: STIS Observations of the Nucleus of M84
Authors: Green, R.; Bower, G.; Boggess, A.; Bowers, C.; Danks, A.;
Gull, T.; Heap, S.; Hutchings, J.; Jenkins, E.; Joseph, C.; Kaiser,
M. B.; Kimble, R.; Kraemer, S.; Linsky, J.; Maran, S.; Moos, H. W.;
Roesler, F.; Timothy, J. G.; Weistrop, D.; Woodgate, B.; Lindler,
D.; Hill, R. S.; Malumuth, E.; Sarajedini, V.; Baum, S.; Clampin,
M.; Hartig, G.; Hulbert, S.
1997AAS...190.4214G Altcode: 1997BAAS...29Q1112G
No abstract at ADS

---------------------------------------------------------
Title: Science Observations with the Space Telescope Imaging
Spectrograph (STIS) aboard HST: Spectroscopy of the Brown Dwarf
Gl 229B
Authors: Schultz, A. B.; Clampin, M.; McGrath, M.; Hulbert, S.;
Baum, S.; Allard, F.; Woodgate, B.; Kimble, R.; Maran, S.; Valenti,
J.; Bruhweiler, F.; Bowers, C.; Gull, T.; Heap, S.; Boggess, A.;
Crenshaw, M.; Kraemer, S.; Danks, A.; Green, R.; Hill, G.; Hutchings,
J. B.; Jenkins, E.; Joseph, C.; Kaiser, M. E.; Moos, H. W.; Linsky,
J.; Roesler, F.; Timothy, G.; Weistrop, D.
1997AAS...190.4213S Altcode: 1997BAAS...29.1112S
No abstract at ADS

---------------------------------------------------------
Title: STIS Slitless Spectroscopy of SN 1987A
Authors: Pun, C. S. J.; Sonneborn, G.; Gull, T. R.; Bowers, C.;
Heap, S. R.; Kimble, R.; Maran, S. P.; Woodgate, B. E.; Boggess, A.;
Kraemer, S.; Danks, A.; Green, R.; Hutchings, J. B.; Jenkins, E. B.;
Joseph, C. L.; Kaiser, M. E.; Moos, W.; Linsky, J. L.; Roesler, F.;
Timothy, G.; Weistrop, D.; Plait, P.; Lindler, D.
1997AAS...190.4211P Altcode: 1997BAAS...29.1111P
No abstract at ADS

---------------------------------------------------------
Title: Science Observations with the Space Telescope Imaging
Spectrograph (STIS) aboard HST: Dynamics of NGC4151
Authors: Hutchings, J. B.; Kraemer, S.; Kaiser, M. E.; Woodgate, B.;
Boggess, A.; Bowers, C.; Danks, A.; Green, R.; Gull, T.; Heap, S.;
Jenkins, E.; Joseph, C.; Kimble, R.; Linsky, J.; Maran, S.; Moos,
H. W.; Roesler, F.; Timothy, G.; Weistrop, D.; Hill, G.; Crenshaw,
M.; Baum, S.; Clampin, M.; Hartig, G.; Hulbert, S.
1997AAS...190.5702H Altcode: 1997BAAS...29.1109H
No abstract at ADS

---------------------------------------------------------
Title: Observations of 3C273 with the Goddard High Resolution
Spectrograph on the Hubble Space Telescope. II.
Authors: Brandt, J. C.; Heap, S. R.; Beaver, E. A.; Boggess, A.;
Carpenter, K. G.; Ebbets, D. C.; Hutchings, J. B.; Jura, M.; Leckrone,
D. S.; Linsky, J. L.; Maran, S. P.; Savage, B. D.; Smith, A. M.;
Trafton, L. M.; Walter, F. M.; Weymann, R. J.; Snow, M.; Randall,
C. E.; Tripp, T. M.; Ake, T. B.; Crenshaw, D. M.; Bruhweiler, F. C.
1997AJ....114..554B Altcode:
Observations of the quasar 3C 273 taken with the Goddard High Resolution
Spectrograph in November and December 1993 are presented here. We have
included both the fully-reduced spectra, and spectra combined with
our earlier (1991) observations. There are a total of 10 new medium
resolution exposures covering four wavelength regions: 1164-1201
Angstroms, 1214-1251 Angstroms, 1537-1573 Angstroms, and 1633-1670
Angstroms. We confirm the suggestion of Morris et al. (1991) that the
galactic Si IV lambda 1393 line is blended with an extragalactic lya
line by observing the lyb counterpart to this extragalactic line. We
obtain an improved upper limit on the C IV/H I ratio in these weak
low redshift lya absorption systems by coadding the corresponding C IV
spectral regions. Improved line profiles for the galactic C IV and N V
absorption are also presented and discussed. The improved measurements
lead to a downward revision of the galactic C IV column density, log N
(C IV) = 14.46+/- 0.04.

---------------------------------------------------------
Title: Dynamics And Energetics of Stellar Flares
Authors: Linsky, Jeffrey
1997hst..prop.7556L Altcode:
Mode 1.3 echelle spectra will be used to explore the dynamics and
energetics of flares on M dwarfs. We will use line fluxes to determine
emission measure distributions {10^4 to 10^7 K} and electron densities
as a function of time during the flare. Line shapes and Doppler shifts
will be used to characterize plasma dynamics {flows, turbulence}
throughout the flare. We will search for cooling via UV continuum
emission in the early phases of the flare. Nonflare spectra will be
used to model the quiescent atmosphere.

---------------------------------------------------------
Title: Exploring the Outer Heliosphere with STIS
Authors: Linsky, Jeffrey
1997hst..prop.7262L Altcode:
Recent models of the heliosphere predict that charge exchange processes
should produce a region of hot H I just outside the heliopause. This
“hydrogen wall” was detected serendipitously in GHRS observations of
the nearby stars Alpha Cen A and B. In addition to the interstellar
H I absorption line seen in the Lyman-Alpha lines of these stars,
a second H I absorption component was detected with a temperature and
column density consistent with the properties predicted for the solar
hydrogen wall. Lyman-Alpha absorption in the hydrogen wall provides
us with a new way to observationally study the outer heliosphere,
and could provide theorists with important observational constraints
for their models. We propose to study the hydrogen wall further using
STIS observations of 36 Oph A, a K1 V star only 12 degrees from the
direction of the incoming interstellar wind. If the models are correct,
the hydrogen wall absorption should be particularly conspicuous for
this line of sight, because the temperature and column density of the
hydrogen wall should be at their highest in the upwind direction, and
because there should be a large velocity separation between the H I
absorption lines of the hydrogen wall and the interstellar medium. We
also hope to detect interstellar C II 1335, 1336 absorption lines in
our planned observations. Detection of these lines would allow us to
estimate the interstellar electron density, which is a very important
quantity for studies of the heliosphere.

---------------------------------------------------------
Title: Physical Processes in Stellar Atmospheres: Comparative Analysis
of the Sun and Alpha Cen A
Authors: Linsky, Jeffrey
1997hst..prop.7263L Altcode:
The quantity and quality of solar data far exceeds what is available
for all other stars combined. Nonetheless, solar data alone does not
discriminate between competing theories for certain fundamental plasma
processes, e.g. magnetic dynamos or heating of the outer atmosphere. By
studying stars of different mass, age, composition, and rotation,
we can test models of solar phenomena in a broader context. STIS
now makes it practical to obtain a high resolution NUV/FUV atlas
sufficient to quantitatively understand in detail the photospheres,
chromospheres, and transition regions of late-type dwarfs. We propose
a detailed study of Alpha Cen A {G2V}, which has small temperature,
metallicity, and activity differences, relative to the Sun, allowing
a simplified perturbative analysis of atmospheric structure, heating
mechanisms, and dynamical processes. We will compare our Alpha Cen A
spectrum with existing full-disk atlases of the Sun, using anomalies to
guide subsequent analysis. We will then fit the Alpha Cen A spectrum
in detail by combining intensity spectra for quiet, network, plage,
spot, and flare components. Intensity spectra will be determined using
perturbed solar models {e.g. the VAL series} and the NLTE radiative
transfer code MULTI, adapted to include line blanketing. The complete
inventory of constraints provided by STIS will yield the first model
chromosphere approaching solar quality. Using this atmosphere along
with observed velocity fields, we will reassess competing theories
for various phenomena observed in solar-type stars.

---------------------------------------------------------
Title: Accretion and Winds in T Tauri Systems
Authors: Linsky, Jeffrey
1997hst..prop.7718L Altcode: 1997hst..prop.4056L
We will obtain echelle spectra {modes 1.3 and 2.3} of a classical
T Tauri star to study the geometry, dynamics and energetics of
accretion and winds in pre- main-sequence stars. Line fluxes will be
used to construct an emission measure distribution and to determine
electron densities. Line shapes will help to constrain the geometry
and kinematics of the wind and the accreting material. Many Fe II
lines, spanning a range in optical depth, will provide new insight
into the radial variations in wind properties. We will also use the
spectra to study the mechanisms responsible for exciting flourescence
of molecular hydrogen.

---------------------------------------------------------
Title: Overview of the Space Telescope Imaging Spectrograph (STIS)
Authors: Woodgate, B.; Kimble, R.; Bowers, C.; Kraemer, S.; Kaiser,
M. B.; Gull, T.; Danks, A.; Grady, J.; Loiacono, J.; Brumfield,
M.; Feinberg, L.; Hood, D.; Meyer, W.; Vanhouten, C.; Argabright,
V.; Bybee, R.; Timothy, J. G.; Blouke, M.; Dorn, D.; Bottema, M.;
Woodruff, R.; Michika, D.; Sullivan, J.; Hetlinger, J.; Stocker, R.;
Ludtke, C.; Ebbets, D.; Delamere, A.; Rose, D.; Gardner, H.; Breyer,
R.; Lindler, D.; Content, D.; Standley, C.; Hartig, G.; Heap, S.;
Joseph, C.; Green, R.; Jenkins, E.; Linsky, J.; Hutchings, J.; Moos,
H. W.; Boggess, A.; Maran, S.; Roesler, F.; Weistrop, D.
1997AAS...190.4205W Altcode: 1997BAAS...29..836W
The STIS instrument was installed on the HST in February 97 and is
currently being commissioned. It covers the wavelength range 115-1000
nm, with spectral resolving powers between 20 and 200,000. The
two-dimensional detector formats, 2048x2048 pixels for the MAMA
detectors covering the range 115-310 nm and 1024x1024 pixels for the
CCD detector covering the range 165-1000 nm, allow echelle spectroscopy
with high resolution and broad wavelength coverage in the UV, and
long slit and slitless spectroscopy and imaging throughout the entire
spectral range.

---------------------------------------------------------
Title: An Atlas of IUE Far Ultraviolet Spectra of T Tauri and Herbig
Ae/Be Stars
Authors: Linsky, J. L.; Valenti, J.; Johns-Krull, C.
1997AAS...190.4103L Altcode: 1997BAAS...29..832L
We present an atlas of IUE low-dispersion short-wavelength spectra
of pre-main sequence stars. These spectra are co-additions from all
useful images which have been reprocessed with NEWSIPS. Compared to
the earlier processing of these spectra with IUESIPS, each spectrum
has significantly higher signal/noise and most blemishes and cosmic ray
hits are now removed. Since most of the fixed pattern noise is removed
by NEWSIPS, the spectra can be coadded with considerable increase in
signal/noise. Using the available lists of pre-main sequence stars
(e.g., SIMBAD, Herbig and Bell catalog, The et al. catalog, Walter
Sco-Cen catalog, and Jones and Walker catalog), we have identified
128 objects observed by IUE, including 50 T Tauri stars and 78 Herbig
Ae/Be stars. 663 usable spectra are available from the IUE Final Archive
for these targets, and our atlas consists of coadded spectra for each
star based on up to 94 individual spectra (AB Aur). The stars cover the
spectral type range from B0 to M3. This atlas is essentially a complete
sample of all PMS stars that were observed by IUE in the far-UV (1175 --
2000 Angstroms). Our objective is to obtain the highest quality spectra
of these stars and to extract fluxes of the broad range of emission
features produced in the atmospheres and disks of different kinds of
PMS stars. These spectral features consist of emission lines formed at
temperatures as high as 150,000 K (N V), molecular features (e.g., H_2),
and absorption lines formed in the hotter stars. Our identification of
emission lines and blends is aided by comparison with an archival GHRS
spectrum of T Tauri. We tabulate line and continuum fluxes and compare
these UV properties (in particular, H_2) with stellar, accretion,
and wind properties. These mean spectra will also serve as fiducials
for future studies of time variability. This work is supported by NASA
grants to the University of Colorado.

---------------------------------------------------------
Title: Periodic X-Ray Emission from the O7 V Star θ1
Orionis C
Authors: Gagné, Marc; Caillault, Jean-Pierre; Stauffer, John R.;
Linsky, Jeffrey L.
1997ApJ...478L..87G Altcode: 1997astro.ph..1145G
We report the discovery of large-amplitude, periodic X-ray emission
from the O7 V star θ1 Orionis C, the central star of the
Orion Nebula. Ten ROSAT HRI snapshots of the Trapezium cluster taken
over the course of 21 days show that the count rate of θ1
Ori C varies from 0.26 to 0.41 counts s-1 with a clear 15
day period. The soft X-ray variations have the same phase and period
as Hα and He II λ4686 variations reported by Stahl et al. and are in
antiphase with the C IV and Si IV ultraviolet absorption features. We
consider five mechanisms which might explain the amplitude, phase,
and periodicity of the X-ray variations: (1) colliding-wind emission
with an unseen binary companion, (2) coronal emission from an unseen
late-type pre-main-sequence star, (3) periodic density fluctuations,
(4) absorption of magnetospheric X-rays in a corotating wind, and
(5) magnetosphere eclipses. The ROSAT data rule out the first three
scenarios but cannot rule out either of the latter two which require the
presence of an extended magnetosphere, consistent with the suggestion
of Stahl et al. that θ1 Ori C is an oblique magnetic
rotator. As such, θ1 Ori C may be the best example of a
high-mass analog to the chemically peculiar, magnetic Bp stars.

---------------------------------------------------------
Title: The ROSAT All-Sky Survey of Active Binary
Coronae. III. Quiescent Coronal Properties for the BY Draconis-Type
Binaries
Authors: Dempsey, Robert C.; Linsky, Jeffrey L.; Fleming, Thomas A.;
Schmitt, J. H. M. M.
1997ApJ...478..358D Altcode:
We present X-ray observations of 35 active late-type BY Draconis
dwarf binary systems and 28 evolved binary systems, similar in
nature to the RS Canum Venaticorum systems, obtained with the
Position Sensitive Proportional Counter (PSPC) during the ROSAT
All-Sky Survey phase of the mission. Of this sample, 52 targets were
detected in exposures of roughly 600 s or less. When these new data
are combined with the earlier results from Dempsey et al. (1993b),
this survey represents the largest sample of active binary systems
observed to date at any wavelength, including X-rays. We expand our
investigation of how coronal properties (e.g., surface flux, luminosity,
etc.) correlate with stellar parameters (e.g., rotation period, color,
etc.) and confirm the conclusions of Dempsey et al. (1993b). Rotation
period provides the best correlation with X-ray surface flux with
FX~P-0.59+/-0.10rot for the entire
sample. We find no evidence for a “basal” or nonmagnetic X-ray flux
component. We model the low-resolution pulse-height spectra for 12
systems with two-temperature thermal plasmas. The derived temperatures
for the BY Dra systems are identical to those previously derived
for active evolved giants and subgiants in close binaries (Dempsey
et al. 1993c). We also show that the dependence of temperature and
emission measures on rotation period is the same for the dwarf,
subgiant, and giant binaries.

---------------------------------------------------------
Title: Evaluating Possible Heating Mechanisms Using the Transition
Region Line Profiles of Late-Type Stars
Authors: Wood, Brian E.; Linsky, Jeffrey L.; Ayres, Thomas R.
1997ApJ...478..745W Altcode:
Our analysis of high-resolution Goddard High-Resolution Spectrograph
(GHRS) spectra of late-type stars shows that the Si IV and C IV lines
formed near 105 K can be decomposed into the sum of two
Gaussians, a broad component and a narrow component. We find that
the flux contribution of the broad components is correlated with
both the C IV and X-ray surface fluxes. For main-sequence stars,
the widths of the narrow components suggest subsonic nonthermal
velocities, and there appears to be a tight correlation between these
nonthermal velocities and stellar surface gravity (ξNC
~ g-0.68+/-0.07). For evolved stars with lower surface
gravities, the nonthermal velocities suggested by the narrow components
are at or just above the sound speed. Nonthermal velocities computed
from the widths of the broad components are always highly supersonic. We
propose that the broad components are diagnostics for microflare
heating. Turbulent dissipation and Alfvén waves are both viable
candidates for the narrow component heating mechanism. A solar
analog for the broad components might be the “explosive events”
detected by the High-Resolution Telescope and Spectrograph (HRTS)
experiment. The broad component we observe for the Si IV λ1394
line of α Cen A, a star that is nearly identical to the Sun, has
a FWHM of 109 +/- 10 km s-1 and is blueshifted by 9 +/-
3 km s-1 relative to the narrow component. Both of these
properties are consistent with the properties of the solar explosive
events. However, the α Cen A broad component accounts for 25% +/-
4% of the total Si IV line flux, while solar explosive events are
currently thought to account for no more than 5% of the Sun's total
transition region emission. This discrepancy must be resolved before
the connection between broad components and explosive events can be
positively established. In addition to our analysis of the Si IV
and C IV lines of many stars, we also provide a more thorough analysis
of all of the available GHRS data for α Cen A (G2 V) and α Cen B
(K1 V). We find that the transition region lines of both stars have
redshifts almost identical to those observed on the Sun: showing an
increase with line formation temperature up to about log T = 5.2 and
then a rapid decrease. Using the O IV] lines as density diagnostics,
we compute electron densities of log ne = 9.65 +/- 0.20
and log ne = 9.50 +/- 0.30 for α Cen A and α Cen B,
respectively. Based on observations with the NASA/ESA Hubble
Space Telescope, obtained at the Space Telescope Science Institute,
which is operated by the Association of Universities for Research in
Astronomy Inc., under NASA Contract NAS5-26555.

---------------------------------------------------------
Title: The alpha Centauri Line of Sight: D/H Ratio, Physical
Properties of Local Interstellar Gas, and Measurement of Heated
Hydrogen (the "Hydrogen Wall") near the Heliopause
Authors: Linsky, Jeffrey L.; Wood, Brian E.
1997ldpf.book..321L Altcode:
No abstract at ADS

---------------------------------------------------------
Title: Local Interstellar Medium Properties and Deuterium Abundances
for the Lines of Sight toward HR 1099, 31 Comae, β Ceti, and β
Cassiopeiae
Authors: Piskunov, Nikolai; Wood, Brian E.; Linsky, Jeffrey L.;
Dempsey, Robert C.; Ayres, R.
1997ApJ...474..315P Altcode:
We analyze Goddard High-Resolution Spectrograph data to infer the
properties of local interstellar gas and the deuterium/hydrogen (D/H)
ratio for lines of sight toward four nearby late-type stars--HR 1099,
31 Comae, β Ceti, and β Cassiopeiae. The data consist of spectra
of the hydrogen and deuterium Lyα lines, and echelle spectra of the
Mg II h and k lines toward all stars except β Cas. Spectra of the RS
CVn-type spectroscopic binary system HR 1099 were obtained near opposite
quadratures to determine the intrinsic stellar emission line profile and
the interstellar absorption separately. Multiple-velocity components
were found toward HR 1099 and β Cet. The spectra of 31 Com and β
Cet are particularly interesting because they sample lines of sight
toward the north and south Galactic poles, respectively, for which H I
and D I column densities were not previously available. The north
Galactic pole appears to be a region of low hydrogen density like the
“interstellar tunnel” toward ɛ CMa. The temperature and turbulent
velocities of the local interstellar medium (LISM) that we measure
for the lines of sight toward HR 1099, 31 Com, β Cet, and β Cas are
similar to previously measured values (T ~ 7000 K and ξ = 1.0-1.6 km
s-1). The deuterium/hydrogen ratios found for these lines
of sight are also consistent with previous measurements of other short
lines of sight, which suggest D/H ~ 1.6 × 10-5. In contrast,
the Mg abundance measured for the β Cet line of sight [implying a
logarithmic depletion of D(Mg) = +0.30 +/- 0.15] is about 5 times larger
than the Mg abundance previously observed toward α Cen, and about 20
times larger than all other previous measurements for the LISM. These
results demonstrate that metal abundances in the LISM vary greatly
over distances of only a few parsecs. Based on observations with
the NASA/ESA Hubble Space Telescope, obtained at the Space Telescope
Science Institute, which is operated by the Association of Universities
for Research in Astronomy, Inc., under NASA contract NAS5-26555.

---------------------------------------------------------
Title: A New Measurement of the Electron Density in the Local
Interstellar Medium
Authors: Wood, Brian E.; Linsky, Jeffrey L.
1997ApJ...474L..39W Altcode:
Using the echelle-A grating of the Goddard High-Resolution Spectrograph,
we have observed the C II λλ1335, 1336 emission lines of the nearby
(d = 13.3 pc) star system Capella (G8 III + G1 III). Interstellar
C II absorption features are detected within both stellar emission
lines. The ground-state and excited-state C II column densities derived
from these absorption lines imply an electron density of ne
= 0.11+0.12-0.06 cm-3 in the local
interstellar medium (LISM). Unlike previous derivations of ne
from Mg II/Mg I ratios, the density suggested by the C II lines is
independent of assumptions about ionization equilibrium. Current
estimates of the H I density in the LISM are in the range 0.1-0.2
cm-3. The He I/H I ratio toward the white dwarf G191-B2B,
which is only 7° from Capella, has been measured to be He I/H I =
0.068-0.082 from the Extreme-Ultraviolet Explorer data. These results
indicate hydrogen and helium ionization fractions toward Capella of X(H)
= 0.45 +/- 0.25 and X(He) = 0.57 +/- 0.23, respectively, confirming
that hydrogen and helium are substantially ionized in the LISM. Based on observations with the NASA/ESA Hubble Space Telescope,
obtained at the Space Telescope Science Institute, which is operated
by the Association of Universities for Research in Astronomy Inc.,
under NASA contract NAS5-26555.

---------------------------------------------------------
Title: From Top to Bottom - the Multiwavelength Campaign of V824 ARA
(HD 155555)
Authors: Dempsey, Robert; Neff, James; Strassmeier, Klaus; Linsky,
Jeffrey; Lim, Jeremy; Donati, J. -F.; Walter, Fred; Marang, Fred;
Budding, Edwin; Jordan, Ian; Walker, Stan; Downing, David G.; Inwood,
Doug; Petterson, Orlon; Petterson, Orlon
1997stsc.rept.....D Altcode:
A great deal of progress has been made in recent years in decomposing
the 2-D structure in the atmospheres of late-type stars. Doppler
images of many photospheres single stars, T Tauri stars, Algols,
RS CVn binaries to name a few - are regularly published
(Strassmeier 1996; Richards and Albright 1996; Rice and Strassmeier
1996; Kuerster et al. 1994). Ultraviolet spectral images of
chromospheres appear in the literature (e.g., Walter et al. 1987;
Neff et al. 1989) but are less common owing to the difficult nature of
obtaining complete phase coverage. Zeeman doppler images of magnetic
fields are now feasible (e.g., Donati et al. 1992). Performing Doppler
imaging of the same targets over many seasons has also been accomplished
(e.g, Vogt et al. 1997). Even when a true image reconstruction is not
possible due to poor spectral resolution, we can still infer a great
deal about spatial structure if enough phases are observed. However,
it is increasingly apparent that to make sense of recent results,
many different spectral features spanning a range of formation
temperature and density must be observed simultaneously for a coherent
picture to emerge. Here we report on one such campaign. In 1996,
we observed the southern hemisphere RS CVn binary V824
Ara (P=1d.68, G5IV+K0V-IV-IV) over one complete stellar
rotation with the Hubble Space Telescope and EUVE. In conjunction,
radio and optical photometry and spectroscopy were obtained from the
ground. Unique to this campaign is the complete phase coverage of a
number of activity proxy indicators that cover source temperatures
ranging from the photosphere to the corona.

---------------------------------------------------------
Title: Periodic X-ray Emission from the O7 V star theta (1) Orionis C
Authors: Gagne, M.; Linsky, J. L.; Caillault, J. -P.; Stauffer, J. R.
1996AAS...18911902G Altcode: 1996BAAS...28.1431G
Ten ROSAT HRI snapshots of the Trapezium cluster taken over the
course of 21 days show that the count rate of the O7 V star theta
(1) Orionis C varies from 0.26 to 0.41 counts s(-1) with a clear
15-day period. The soft X-ray variations have the same phase and
period as Hα and He II lambda 4686 variations reported by Stahl
et al., and are in anti-phase with the C IV and Si IV ultraviolet
absorption features. We consider five mechanisms which might explain
the amplitude, phase, and periodicity of the X-ray variations: (1)
colliding-wind emission with the wind of an unseen binary companion,
(2) coronal emission from an unseen late-type pre-main--sequence star,
(3) periodic density fluctuations, (4) absorption of magnetospheric
X-rays in a corotating wind, and (5) magnetosphere eclipses. The ROSAT
data rule out the first three scenarios, but cannot rule out either of
the latter two which require the presence of an extended magnetosphere,
consistent with the suggestion of Stahl et al. that theta (1) Ori C is
an oblique magnetic rotator. We present preliminary models of X-ray
emission and absorption from the magnetosphere and wind of an O-type
oblique magnetic rotator.

---------------------------------------------------------
Title: HST/GHRS Observations of 61 CYG A and 40 ERI A
Authors: Wood, B. E.; Linsky, J. L.
1996AAS...189.1712W Altcode: 1996BAAS...28W1296W
We present new HST/GHRS observations of interstellar absorption lines
seen in UV spectra of 61 Cyg A (K5 V) and 40 Eri A (K1 V). These include
the Lyman-alpha lines of H I and D I, and the Mg II h and k lines. We
use these data to measure the properties of the local interstellar
medium (LISM) and to search for absorption from “hydrogen walls”
surrounding the stars created by the interactions between the stellar
winds and the LISM. The two target stars were chosen on the basis of
their close proximity (d=3.5 pc and d=4.8 pc) and their large radial
velocities (Vrad=-64 km s(-1) and Vrad=-42 km
s(-1) ). For each star, the large negative radial velocity creates a
large velocity separation between the stellar Lyman-alpha emission line
and the LISM absorption, which means that the wings of the interstellar
H I absorption feature preferentially absorb the red wing of the line,
thereby creating an apparent blueshift of the wings of the Lyman-alpha
emission line with respect to the star. We expect the intrinsic
stellar emission to be centered on the radial velocity of the star. By
trial and error, we can determine the H I column density necessary to
recenter the emission line wings on the star and thereby measure the H
I column density without estimating the full stellar Lyman-alpha line
profile, which is generally the largest source of systematic error in
measurements of the H I column density toward cool stars. High radial
velocity stars are also excellent targets for studies of stellar
hydrogen walls. The large velocity through the LISM creates a very
hot hydrogen wall and a large velocity separation between the LISM
and hydrogen wall absorption components, thereby producing a broad,
easily detectable absorption feature. This work is supported by grant
GO-06617.01.95A to the University of Colorado.

---------------------------------------------------------
Title: HST/GHRS observations of 61 Cyg A and 40 Eri A.
Authors: Wood, B. E.; Linsky, J. L.
1996BAAS...28.1296W Altcode:
No abstract at ADS

---------------------------------------------------------
Title: Fishing in the Coronal Graveyard
Authors: Ayres, T. R.; Brown, A.; Harper, G. M.; Bennett, P. D.;
Linsky, J. L.; Carpenter, K. G.; Robinson, R. D.
1996AAS...189.7815A Altcode: 1996BAAS...28.1379A
Hot coronae (T ~ 10(6) K) are thought to be rare among single giant
stars to the right of the “Linsky--Haisch dividing line” near K0 in
the H--R diagram. K and M giants are such slow rotators that absence of
dynamo generated magnetic activity would be natural. Nevertheless,
gamma Dra (K5 III) unexpectedly was detected in FUV coronal
proxies---hot lines Si IV lambda 1393 and C IV lambda 1548---by HST
/GHRS during Science Verification, and subsequently was discovered
as a faint X-ray source in a deep ROSAT /PSPC pointing. Is gamma Dra
anomalous, or is the lack of coronal detections among the K giants
simply a matter of insufficient sensitivity? We have used the GHRS
low resolution mode to search for additional examples of hot lines
among inactive single red giants. Si IV provides a clean diagnostic
of subcoronal material because it falls near the peak sensitivity
of the G140L mode and does not suffer from abundance depletions that
can affect C IV in red giants. X-ray/Si IV ratios are such that HST
can reach to much fainter limiting “coronal” magnitudes than even
very deep ROSAT pointings. In every target so far examined, we find
weak---but statistically significant---Si IV emission. These include:
the ancient red giant Arcturus (alpha Boo: K1 III), recorded at the
end of Cycle 5; and epsilon Crv (K2.5 III) and epsilon Sco (K2 III)
observed in Cycle 6. X-ray/Si IV ratios of red giants (for which
measurements, or upper limits, of both diagnostics are available)
fall on a uniform track, extending downward from active K0 “Clump”
giants like beta Ceti all the way to Arcturus itself, in the depths of
the “coronal graveyard.” The systematic behavior argues that magnetic
dynamo action continues even when long term angular momentum loss has
slowed the stellar spin to a crawl. This work was supported by grant
GO-06066.01-94A from STScI.

---------------------------------------------------------
Title: GHRS Spectra of the Fe XXI 1354 Angstroms and He II 1640
Angstroms Lines from each of the Capella Stars
Authors: Linsky, J. L.; Wood, B. E.
1996AAS...189.7814L Altcode: 1996BAAS...28.1379L
We report on moderate (lambda /Delta lambda = 20,000) and high
(lambda /Delta lambda = 90,000) resolution spectra of the 104 day
period Capella binary system (HD 34029). These spectra were obtained
with the HST Goddard High Resolution Spectrometer on 1995 September
9 and 1996 April 9. The observations include a long duration moderate
resolution spectrum of the coronal Fe XXI 1354 Angstroms line and one
moderate resolution and one high resolution echelle spectrum of the
He II 1640 Angstroms line. Our data set also includes lines of C II,
O III, N IV, and O V. Our objective in observing the Fe XXI line, which
is formed at T=10(7) K, was to infer the contribution of each star's
corona. This is feasible because the GHRS can easily resolve the 50
km s(-1) radial velocity separation of the stars. Present day X-ray
instruments and even the upcoming XMM and AXAF spectrometers cannot
resolve the emission from each star. We will report on the relative
contribution of each star and the Doppler shift and line width for
each star. With these data we can estimate the X-ray luminosities of
the G1 III and G8 III stars individually. We observed the He II 1640
Angstroms line twice with a time separation of 7 months corresponding
to almost exactly 2 orbital periods. The profiles are nearly identical,
except for a large difference in flux at the expected velocty of the
G8 III star. We will discuss the relative emission from each star and
the roles of collisional excitation and photoionization/recombination
in producing the 1640 Angstroms emission from each star. This work is
supported by grant GO-05886.01.94A to the University of Colorado.

---------------------------------------------------------
Title: Goddard High Resolution Spectrograph Observations of
Variability in the RS Canum Venaticorum System V711 Tauri (HR 1099)
Authors: Dempsey, Robert C.; Neff, James E.; Thorpe, Marjorie J.;
Linsky, Jeffrey L.; Brown, Alexander; Cutispoto, Giuseppe; Rodono,
Marcello
1996ApJ...470.1172D Altcode:
Goddard High Resolution Spectrograph (GHRS) observations of the RS
CVn-type binary V711 Tau (K1 IV + G5 IV) were obtained at several
phases over two consecutive stellar orbital cycles in order to study
ultraviolet emission-line profile and flux variability. Spectra cover
the Mg II h and k lines, C IV doublet, and Si IV region, as well as the
density-sensitive lines of C III] (1909 A) and Si III] (1892 A). lUE
spectra, EUV data, and UBV photometry were obtained contemporaneously
with the GHRS data. Variable extended wings were detected in the Mg
II lines. We discuss the Mg II line profile variability using various
Gaussian emission profile models. No rotational modulation of the line
profiles was observed, but there were several large flares. These flares
produced enhanced emission in the extended line wings, radial velocity
shifts, and asymmetries in some line profiles. Nearly continuous flaring
for more than 24 hr, as indicated in the lUE data, represents the most
energetic and long-lived chromospheric and transition region flare
ever observed with a total energy much greater than 5 x 1035
ergs. The C III] to Si III] line ratio is used to estimate the plasma
density during the flares.

---------------------------------------------------------
Title: The Properties of the Local Interstellar Medium and the
Interaction of the Stellar Winds of epsilon INDI and lambda Andromedae
with the Interstellar Environment
Authors: Wood, Brian E.; Alexander, William R.; Linsky, Jeffrey L.
1996ApJ...470.1157W Altcode:
We present new observations of the Lyα lines of ɛ Indi (KS V)
and λ Andromedae (G8 IV-III + ?). These data were obtained by the
Goddard High Resolution Spectrograph (GHRS) on the Hubble Space
Telescope. Analysis of the interstellar H I and D I absorption lines
reveals that the velocities and temperatures inferred from the H
I lines are inconsistent with the parameters inferred from the D I
lines, unless the H I absorption is assumed to be produced by two
absorption components. One absorption component is produced by
interstellar material. For both lines of sight observed, the velocity
of this component is consistent with the velocity predicted by the
local flow vector. For the E Ind data, the large velocity separation
between the stellar emission and the interstellar absorption allows
us to measure the H I column density independent of the shape of the
intrinsic stellar Lyα profile. This approach permits us to quote
an accurate column density and to assess its uncertainty with far
more confidence than in previous analyses, for which the errors were
dominated by uncertainties in the assumed stellar profiles. For the
short (d = 3.46 pc) line of sight to ɛ Ind, the H I column density is
found to be log NHI = 18.0±0.1, which implies an average
density for the local interstellar medium (LISM) of nHI =
0.094±0.022 cm-3. For the much longer (d = 23 pc) line
of sight to λ And, we estimate the H I column density to be log
NHi = 18.45±0.15 which corresponds to an average density
of nHI = 0.041±0.014 cm-3. The D/H ratios we
measure from the data are (1.6±0.4) x 10-5 and (1.7±0.5)
x 1O-5 for ɛ Ind and λ And, respectively. These values are
consistent with those measured from observations of Capella, Procyon,
and α Cen. We measure LISM temperatures of T = 8500±500 K and T =
11,500±500 K from the ɛ Ind and λ And data, respectively. The λ
And temperature is significantly higher than temperatures previously
measured from GHRS data, which leads us to speculate that the H I and
D I absorption lines may be broadened by multiple ISM components with
different velocities. The results of our λ And analysis should be
considered as tentative, until GHRS observations of the much narrower
Mg II and/or Fe II absorption lines can be obtained. We believe
that hot hydrogen surrounding ɛ Ind and λ And is responsible for the
second H I absorption component, although we consider this conclusion
to be tentative in the case of λ And. These "hydrogen walls" are
produced by the interaction of the winds of these stars with the
surrounding interstellar material. An anologous solar hydrogen wall has
been predicted by recent models of the heliospheric interface region
and confirmed by GHRS observations of α Cen. The column densities we
measure for the second components are log NHI = 14.2±0.2
and log NHI = 14.8±0.2 for ɛ Ind and λ And, respectively,
and the temperatures are 100,000±20000 K and 62,000±18 000 K. These
temperatures are too hot for the solar hydrogen wall, and for ɛ Ind
the velocity of the second component is clearly inconsistent with the
solar hydrogen wall. Thus, for these components we assume a stellar
origin, in which the higher temperatures are a consequence of higher
interstellar wind velocities in the stellar rest frames. Because the
heliospheric models demonstrate the importance of the solar wind in
the formation of the solar hydrogen wall, our detection of anologous
structure around ɛ Ind and perhaps λ And may constitute a first
detection of solar-like winds around dwarf and subgiant stars.

---------------------------------------------------------
Title: Physical and Chemical Characteristics of the ISM Inside and
Outside the Heliosphere
Authors: Lallement, R.; Linsky, J. L.; Lequeux, J.; Baranov, V. B.
1996SSRv...78..299L Altcode:
This paper summarizes some of the discussions of working group 8
9 during the ISSI Conference on “The Heliosphere in the Local
Interstellar Medium”. Because the subject of these working groups
has become significantly broader during the last ten years, we have
selected three topics for which recent observations have modified
and improved our knowledge of the heliosphere and the surrounding
interstellar medium. These topics are the number densities and ISM
ionization states of hydrogen and helium, the newly discovered hot gas
from the “H wall” seen in absorption, and the comparison between ISM
and heliospheric minor element abundances. Papers from this volume in
which more details on these topics can be found are quoted throughout
the report.

---------------------------------------------------------
Title: GHRS Observations of the LISM
Authors: Linsky, Jeffrey L.
1996SSRv...78..157L Altcode:
The GHRS has obtained high-resolution spectra of interstellar gas
toward 19 nearby stars. These excellent data show that the Sun is
located inside the Local Interstellar Cloud (LIC) with other warm clouds
nearby. I will summarize the physical properties of these clouds and the
three-dimensional structure of this warm interstellar gas. There is now
clear evidence that the Sun and other late-type stars are surrounded
by hydrogen walls in the upwind direction. The D/H ratio probably
has a constant value in the LIC, (1.6 ± 0.2) × 10-5,
consistent with the measured values for all LIC lines of sight.

---------------------------------------------------------
Title: Lyman Alpha Absorption in the Interstellar Medium
Authors: Dring, A. R.; Murthy, J.; Henry, R. C.; Moos, H. W.; Landsman,
W.; Audouze, J.; Vidal-Madjar, A.; Linsky, J.; Brown, A.
1996AAS...189.1701D Altcode: 1996BAAS...28R1295D
We have observed the chromospheric Lyman alpha emission line of
the stars beta Cas, alpha Tri, epsilon Eri, sigma Gem, beta Gem,
and 31 Com, using the GHRS on the Hubble Space Telescope. Very high
signal-to-noise data allow us to accurately model the interstellar
absorption by hydrogen and deuterium, in a study to both determine
the Deuterium-to-Hydrogen ratio, and study the structure of the local
interstellar medium.

---------------------------------------------------------
Title: High Signal-to-Noise Ratio Observations of Weak Interstellar
Absorption Lines Towards XI Ophiuchi With the Goddard High-Resolution
Spectrograph Aboard the Hubble Space Telescope
Authors: Brandt, J. C.; Heap, S. R.; Beaver, E. A.; Boggess, A.;
Carpenter, K. G.; Ebbets, D. C.; Hutchings, J. B.; Jura, M.; Leckrone,
D. S.; Linsky, J. L.; Maran, S. P.; Savage, B. D.; Smith, A. M.;
Trafton, L. M.; Walter, F. M.; Weymann, R. J.; Hogen, R.; Snow, M.;
Cardelli, J. A.; Ake, T. B.; Bruhweiler, F.
1996AJ....112.1128B Altcode:
We present an atlas and tabulation of weak interstellar absorption lines
in the ultraviolet spectrum of ζ Ophiuchi in four selected wavelength
regions observed with the Goddard High Resolution Spectrograph aboard
the Hubble Space Telescope. The signal-to-noise ratio ranges from 150 to
nearly 400, and the spectral resolving power exceeds 20 000, allowing
2σ detections of features as weak as Wλ=0.8 mÅ. We report positive
measurements of two lines of OH, and weak detections of P I, Tl II,
and N V. Upper limits of Wλ&lt;1 mÅ are found for the molecules
H2O, HCl, SiO, NO+, and CH2. Similar limits
are found for heavy elements Te II, Co II, and Sb II. Three lines are
present in our spectrum for which we have no identifications. They are
found at wavelengths of λ=1229.84, 1313.98, and 1314.23 Å. However,
none of the features reported by previous authors as unidentified
absorption lines in the wavelength regions we have observed are present
in our data.

---------------------------------------------------------
Title: The ISM Toward Nearby High-Velocity Stars: Accurate H Columns,
D/h, and H Walls
Authors: Linsky, Jeffrey
1996hst..prop.6617L Altcode: 1996hst..prop.3028L
Accurate measurements of the deuterium/hydrogen (D/H) ratio inlocal
interstellar gas can provide a critical benchmark forestimates
of the primordial D/H ratio, one of the majorconstraints on Big
Bang cosmology, and credible measurementsof spatial variations in
D/H can constrain Galactic chemicalevolution models. Our extensive
modelling of H I and D Iabsorption in the Ly-alpha line toward nearby
stars andcomparison with GHRS echelle spectra has shown that the D
Icolumn density can be measured accurately, but that the H Icolumn
is uncertain because the opacity is high and theintrinsic stellar
emission line is not well known. An elegantsolution to this problem
is to study the interstellarabsorption for lines of sight to NEARBY
HIGH-VELOCITY stars.Large stellar radial velocities shift half of the
stellaremission line away from the interstellar absorption. One canthen
determine what H I column density produces an intrinsicstellar line
profile centered on the stellar radial velocity.We propose to study 2
high radial velocity stars locatedwithin 6 pc to measure accurately:
(1) the H I columndensities, (2) the mean value and possible variations
in D/H,(3) trace the size, temperature, density, and turbulentvelocity
of the local interstellar cloud (LIC) and the Gcloud, and (4) search
for hot H I that theoretical modelspredict should be located at the
interfaces between the ISMand solar/stellar winds. GHRS spectra of
Alpha Cen and EpsilonIndi provide the first evidence for this hot H I.

---------------------------------------------------------
Title: Flare energetics: analysis of a large flare on YZ Canis
Minoris observed simultaneously in the ultraviolet, optical and radio.
Authors: van den Oord, G. H. J.; Doyle, J. G.; Rodono, M.; Gary,
D. E.; Henry, G. W.; Byrne, P. B.; Linsky, J. L.; Haisch, B. M.;
Pagano, I.; Leto, G.
1996A&A...310..908V Altcode:
The results of coordinated observations of the dMe star YZ CMi
at optical, UV and radio wavelengths during 3-7 February 1983 are
presented. YZ CMi showed repeated optical flaring with the largest
flare having a magnitude of 3.8 in the U-band. This flare coincided
with an IUE exposure which permits a comparison of the emission measure
curves of YZ CMi in its flaring and quiescent state. During the flare a
downward shift of the transition zone is observed while the radiative
losses in the range 10^4^-10^7^K strongly increase. The optical flare
is accompanied with a radio flare at 6cm, while at 20cm no emission
is detected. The flare is interpreted in terms of optically thick
synchrotron emission. We present a combined interpretation of the
optical/radio flare and show that the flare can be interpreted within
the context of solar two-ribbon/white-light flares. Special attention
is paid to the bombardment of dMe atmospheres by particle beams. We
show that the characteristic temperature of the heated atmosphere is
almost independent of the beam flux and lies within the range of solar
white-light flare temperatures. We also show that it is unlikely that
stellar flares emit black-body spectra. The fraction of accelerated
particles, as follows from our combined optical/radio interpretation
is in good agreement with the fraction determined by two-ribbon flare
reconnection models.

---------------------------------------------------------
Title: Rotational modulation and flares on RS Canum Venaticorum and
BY Draconis stars. XIX. Simultaneous IUE, ROSAT, VLA, and visual
observations of TY Pyxidis.
Authors: Neff, J. E.; Pagano, I.; Rodono, M.; Brown, A.; Dempsey,
R. C.; Fox, D. C.; Linsky, J. L.
1996A&A...310..173N Altcode:
In November 1990, we observed the eclipsing binary system TY Pyxidis
with the IUE satellite simultaneously with the ROSAT All-Sky Survey. The
IUE and ROSAT/WFC observations covered the 3.2-day period of this
system continuously, while the ROSAT/PSPC coverage was limited to
2.26days. We also observed TY Pyx with the VLA for a total of 22 hours
throughout this period, and we obtained simultaneous visual photometry
and spectroscopy. We compare the rotational and eclipse modulation
of the ultraviolet line fluxes and line profiles with the x-ray,
extreme-ultraviolet, radio, and visual-light variability. We present the
multi-wavelength light curves, and we compare the high-resolution Mgiik
profiles with the simultaneously obtained CaiiK profiles. Although the
visual light curve suggests the presence of large photospheric spots,
no rotational modulation is evident in the ultraviolet, x-ray, and
radio flux. This suggests that the outer atmosphere is more uniformly
covered with magnetic activity than the photosphere. The rare absence
of large flux variations permits us to study an RS CVn system with
large intrinsic ultraviolet, x-ray, and radio fluxes but without
complications introduced by large active regions or flares. Until now,
among the extensively monitored RS CVn systems, only the long-period
Capella has shown such a constant radiative output.

---------------------------------------------------------
Title: The Three-Dimensional Structure of the Local Interstellar
Medium
Authors: Linsky, J. L.; Piskunov, N.; Wood, B. E.
1996AAS...188.4407L Altcode: 1996BAAS...28..892L
We construct the first detailed three-dimensional models of the Local
Interstellar Cloud (LIC) and the total amount of warm gas in the
local interstellar medium (LISM) within 10 parsecs of the Sun. These
models are based on the amount of neutral hydrogen gas deduced (a) from
measurements of the deuterium column density toward nearby late-type
stars, obtained from the analysis of Hubble Space Telescope spectra,
and (b) from the spectra of hot white dwarf stars measured with the
Extreme Ultraviolet Explorer satellite. The two methods give consistent
results. We find that the LIC is flattened in the Galactic plane and
that the hydrogen column densities are very similar for stars located
in the sky within 12(deg) , indicating the angular scale of the gas
close to the Sun. The direction of minimum hydrogen absorption through
the LISM is near Galactic longitude l=262(deg) and latitude b=+22(deg)
. This work is supported by NASA Grant S-56460-D.

---------------------------------------------------------
Title: The α Centauri line of sight: D/H ratio, physical properties
of local interstellar gas, and measurement of heated hydrogen (the
"hydrogen wall") near the heliopause.
Authors: Linsky, Jeffrey L.; Wood, Brian E.
1996ApJ...463..254L Altcode:
The authors analyze high resolution spectra of the nearby (1.34 pc)
stars α Cen A (G2 V) and α Cen B (K1 V), which were obtained with
the GHRS on the HST. The observations consist of echelle spectra of
the Mg II 2800 Å and Fe II 2599 Å resonance lines and the Lyman-α
lines of hydrogen and deuterium. The interstellar gas has a velocity
of v = -18.0±0.2 km s-1. The temperature and nonthermal
velocity inferred from the Fe II, Mg II, and D I line profiles are T =
5400±500K and ξ = 1.20±0.25 km s-1, respectively. However,
single component fits to the H I Lyman-α lines yield a Doppler
parameter (bHI = 11.80 km s-1) that implies a
significantly higher temperature of 8350K, and the velocity of the
H I absorption is redshifted by about 2.2 km s-1 with
respect to the Fe II, Mg II, and D I lines. The one component model
of the interstellar gas suggests log NHI = 18.03±0.01
and D/H = (5.7±0.2)×10-6. The most sensible way to
resolve the discrepancy between H I and the other lines is to add
a second absorption component to the H I lines. This component is
hotter, is redshifted relative to the primary component by 2 - 4
km s-1, and has a column density too low to be detected
in the Fe II, Mg II, and D I lines. The authors propose that the
gas responsible for this component is located near the heliopause,
consisting of the heated H I gas from the interstellar medium that
is compressed by the solar wind (the solar "hydrogen wall"). After
considering the effects of a possible similar hydrogen wall around α
Cen on the analysis, the authors derive for the solar hydrogen wall
the parameters: log NHI = 14.74±0.24, bHI =
21.9±1.7 km s-1 (corresponding to T = 29,000±5000K) and
vHI &gt; -16 km s-1. Taking the solar hydrogen
wall into account, the H I column density along the line of sight to α
Cen is log NHI = 17.80±0.30, corresponding to nHI
= 0.15 cm-3 (± a factor of 2), and D/H is in the range
(0.5 - 1.9)×10-5.

---------------------------------------------------------
Title: VizieR Online Data Catalog: TY Pyx IUE FES observations
(Neff+, 1996)
Authors: Neff, J. E.; Pagano, I.; Rodono, M.; Brown, A.; Dempsey,
R. C.; Fox, D. C.; Linsky, J. L.
1996yCat..33100173N Altcode:
This is a 3-part table presenting a log of the IUE Fine-Error Sensor
Observations of TY Pyxidis in November 1990. In order to determine
accurate magnitudes from FES measurements, a focus and a reference-point
offset corrections must be applied. The data presented in the paper
(Figure 1) have these corrections applied and are averages of two or
more measures taken close in time. (2 data files).

---------------------------------------------------------
Title: The hot corona of YY Mensae.
Authors: Güdel, M.; Guinan, E. F.; Skinner, S. L.; Linsky, J. L.
1996rftu.proc...33G Altcode:
The authors report on results of a long time series of ROSAT PSPC
pointings together with the first ASCA observation of the FK Comae-type
star YY Men. YY Men reveals a rather hot (up to 3 keV) dominant coronal
plasma, with less material at 0.7 keV.

---------------------------------------------------------
Title: Goddard High-Resolution Spectrograph Observations of Procyon
and HR 1099
Authors: Wood, Brian E.; Harper, Graham M.; Linsky, Jeffrey L.;
Dempsey, Robert C.
1996ApJ...458..761W Altcode:
Goddard High Resolution Spectrograph (GHRS) observations have revealed
the presence of broad wings in the transition-region lines of AU Mic
and Capella. It has been proposed that these wings are signatures of
microflares in the transition regions of these stars and that the solar
analog for this phenomenon might be the "transition region explosive
events" discussed by Dere, Bartoe, &amp; Brueckner. We have analyzed
GHRS observations of Procyon (F5 IV-V) and HR 1099 (K1 IV + G5 IV) to
search for broad wings in the UV emission lines of these stars. We find
that the transition-region lines of HR 1099, which are emitted almost
entirely by the K1 star, do indeed have broad wings that are even more
prominent than those of AU Mic and Capella. This is consistent with
the association of the broad wings with microflaring since HR 1099 is
a very active binary system. In contrast, the transition-region lines
of Procyon, a relatively inactive star, do not show evidence for broad
wings, with the possible exception of N V λ21239. However, Procyon's
lines do appear to have excess emission in their blue wings. Linsky
et al. found no evidence for broad wings in Capella's chromospheric
lines, but we find that the Mg II resonance lines of HR 1099 do have
broad wings. The striking resemblance between HR 1099's Mg II and
C IV lines suggests that the Mg II line profiles may be regulated by
turbulent processes similar to those that control the transition-region
line profiles. If this is the case, microflaring may be occurring in the
K1 star's chromosphere as well as in its transition region. However,
radiative transfer calculations suggest that the broad wings of the
Mg II lines can also result from normal chromospheric opacity effects
rather than pure turbulence. The prominence of broad wings in the
transition region and perhaps even chromospheric lines of active stars
suggests that microflaring is very prevalent in the outer atmospheres
of active stars.

---------------------------------------------------------
Title: GHRS studies of stellar chromospheres, transition regions,
and coronae
Authors: Linsky, J. L.; Wood, B. E.
1996ASPC..109..497L Altcode: 1996csss....9..497L
No abstract at ADS

---------------------------------------------------------
Title: Accurate Measurements of the Local Deuterium Abundance from
HST Spectra
Authors: Linsky, Jeffrey
1996IAUS..168..529L Altcode:
No abstract at ADS

---------------------------------------------------------
Title: Summary of IAU Symposium 176
Authors: Linsky, J. L.
1996IAUS..176..567L Altcode:
No abstract at ADS

---------------------------------------------------------
Title: Modeling resonance lines in winds from cool stars
Authors: Valenti, J. A.; Harper, G. M.; Bennett, P. D.; Linsky, J. L.
1996ASPC..109..577V Altcode: 1996csss....9..577V
No abstract at ADS

---------------------------------------------------------
Title: Goddard-HRS observations of variability in the RS CVn system
V711 Tau (HR 1099)
Authors: Dempsey, H. C.; Neff, J. F.; Linsky, J. L.; Brown, A.
1996IAUS..176..411D Altcode:
No abstract at ADS

---------------------------------------------------------
Title: Steady Radio Emission from Stars: Observations and Emission
Processes
Authors: Linsky, J. L.
1996ASPC...93..439L Altcode: 1996ress.conf..439L
No abstract at ADS

---------------------------------------------------------
Title: Rotational Modulation of Radio Emission from the Magnetic BP
Star HR 5624
Authors: Lim, J.; Drake, S. A.; Linsky, J. L.
1996ASPC...93..324L Altcode: 1996ress.conf..324L
No abstract at ADS

---------------------------------------------------------
Title: Summary of Cool Stars 9
Authors: Linsky, J. L.
1996ASPC..109..739L Altcode: 1996csss....9..739L
No abstract at ADS

---------------------------------------------------------
Title: Lyman Alpha absorption in the interstellar medium.
Authors: Dring, A. R.; Murthy, J.; Henry, R. C.; Moos, H. W.; Landsman,
W.; Audouze, J.; Vidal-Madjar, A.; Linsky, J. L.; Brown, A.
1996BAAS...28Q1295D Altcode:
No abstract at ADS

---------------------------------------------------------
Title: Stellar surface structure: proceedings of the 176th Symposium
of the International Astronomical Union, held in Vienna, Austria,
October 9-13, 1995.
Authors: Strassmeier, Klaus G.; Linsky, Jeffrey L.
1996IAUS..176.....S Altcode:
No abstract at ADS

---------------------------------------------------------
Title: Chromospheres of Coronal Stars
Authors: Linsky, J. L.; Wood, B. E.
1996mpsa.conf...55L Altcode: 1996IAUCo.153...55L
No abstract at ADS

---------------------------------------------------------
Title: Probing Coronal Flare Energetics: XTE Observations of Nearby
Flare Stars
Authors: Linsky, Jeffrey
1996rxte.prop10007L Altcode:
We propose to use XTE to probe the energetics of coronal flares on
late-type dwarfs. 50 ks exposures of AU Mic and EQ Peg will each
likely provide time-resolved PCA spectroscopy of at least one strong
flare. We also expect that non-thermal hard (15-50 keV) X-ray bursts
will be detectable for tens to hundreds of seconds with both the PCA
and HEXTE detectors. To date, the hard X-ray bursts which accompany
microwave bursts in strong solar flares have never been observed on
a star other than the sun. Together with simultaneous monitoring of
the microwave, balmer-line, and ultraviolet-continuum emission, these
XTE observations will allow us, for the first time, to trace the time
evolution of thermal and non-thermal processes in the flaring plasma.

---------------------------------------------------------
Title: The Final Archive and Recalibration of the International
Ultraviolet Explorer (IUE) Satellite
Authors: Nichols, Joy S.; Linsky, Jeffrey L.
1996AJ....111..517N Altcode:
Since 1978 the International Ultraviolet Explorer (lUE) satellite
has been acquiring the largest collection of astronomical ultraviolet
spectra that will likely be obtained in the foreseeable future. The
more than 100 000 spectral images, from which low and high dispersion
spectra are extracted, include a very broad range of sources from solar
system objects, stars of all types, interstellar and Galactic halo gas,
normal galaxies, and active galactic nuclei. The Final Archive of lUE
data will contain all of these spectral images and extracted spectra,
reprocessed with uniform software and calibrations that enhance the
quality of the data products. This paper summarizes the rationale
for and content of the new processing algorithms, together with the
calibration chronology of the lUE scientific instrument. Examples
of spectra processed for the Final Archive demonstrate an increased
signal-to-noise ratio of 10%-50% for low dispersion data and ∼100%
or more for high dispersion data compared to the old processing scheme,
the extension of the usable spectral range down to 1150 and up to 3400
Å, and the emergence of new spectral features from the fixed pattern
noise that is now largely eliminated.

---------------------------------------------------------
Title: Stellar Activity at the End of the Main Sequence: GHRS
Observations of the M8 Ve Star VB 10
Authors: Linsky, Jeffrey L.; Wood, Brian E.; Brown, Alexander;
Giampapa, Mark S.; Ambruster, Carol
1995ApJ...455..670L Altcode:
We present Goddard High Resolution Spectrograph observations of the M8
Ve star VB 10 (= Gl 752B), located very near the end of the stellar
main sequence, and its dM3.5 binary companion Gl 752A. These coeval
stars provide a test bed for studying whether the outer atmospheres of
stars respond to changes in internal structure as stars become fully
convective near mass 0.3 Msun (about spectral type MS), where
the nature of the stellar magnetic dynamo presumably changes, and near
the transition from red to brown dwarfs near mass 0.08 Msun
(about spectral type M9), when hydrogen burning ceases at the end of
the main sequence. We obtain upper limits for the quiescent emission
of VB 10 but observe a transition region spectrum during a large flare,
which indicates that some type of magnetic dynamo must be present. Two
indirect lines of evidence scaling from the observed X-ray emission and
scaling from a time-resolved flare on AD Le suggest that the fraction of
the stellar bolometric luminosity that heats the transition region of
VB 10 outside of obvious flares is comparable to, or larger than, that
for Gl 752A. This suggests an increase in the magnetic heating rates,
as measured by Lline/Lbol ratios, across the
radiative/convective core boundary and as stars approach the red/brown
dwarf boundary. These results provide new constraints for dynamo models
and models of coronal and transition-region heating in late-type stars.

---------------------------------------------------------
Title: First Measurement of the Hydrogen Wall around the Heliosphere
and the Interstellar Medium toward Alpha Centauri
Authors: Linsky, J. L.; Wood, B.
1995AAS...187.4503L Altcode: 1995BAAS...27.1347L
We analyze high-resolution GHRS spectra of the nearby (1.34 pc)
stars alpha Cen A (G2 V) and alpha Cen B (K1 V). The observations
consist of echelle spectra of the Mg II 2800 Angstroms and Fe II 2599
Angstroms resonance lines and the Lyman-alpha lines of hydrogen and
deuterium. The centroid velocity of the interstellar absorption of
all lines except hydrogen is consistent with the local flow vector
proposed for this line of sight by Lallement &amp; Bertin (1992). The
temperature and nonthermal velocity inferred from the Fe II, Mg II,
and D I line profiles are T=5400+/- 500 K and xi =1.20+/- 0.25 km s(-1)
, respectively. However, single-component fits to the H I Lyman-alpha
lines yield a Doppler parameter (b_H I=11.80 km s(-1) ) that implies a
significantly warmer temperature of 8350 K. Furthermore, the velocity
of the H I absorption (v=-15.8+/- 0.2 km s(-1) ) is redshifted by about
2.2 km s(-1) with respect to the velocity of the Fe II, Mg II, and D
I lines. The most sensible way to resolve the discrepancy between H I
and the other lines is to include a second absorption component when
fitting the H I lines. Compared to the main absorption component,
this second component is hotter (T~ 30,000 K), redshifted relative
to the primary component by 2--4 km s(-1) , and has a column density
too low to be detected in the Fe II, Mg II, and D I lines. We propose
that the gas responsible for this second component is located near
the heliopause, consisting of the heated H I gas from the interstellar
medium that is compressed by the solar wind. This so-called “hydrogen
wall” is predicted by recent multifluid gasdynamical models of the
interstellar gas and solar wind interaction. Our data provide the first
measurements of the temperature, velocity, and column density of H I
in the hydrogen wall. We estimate that the parameters of hydrogen wall
gas are log N_H I((2)) =14.74+/- 0.24, b_H I((2)) =21.9+/- 1.7 km s(-1)
(corresponding to a temperature of T=29,000+/- 5,000 K), and v_H I((2))
&gt; -16 km s(-1) . This work was sponsored by NASA Interagency Transfer
S-56460-D to the National Institute of Standards and Technology.

---------------------------------------------------------
Title: A Non-LTE Analysis of the zeta Aurigae B-Type
Secondary. I. Determination of the Fundamental Stellar Parameters
Authors: Bennett, Philip D.; Brown, Alexander; Linsky, Jeffrey L.
1995ApJ...455..317B Altcode:
We present a non-LTE model atmosphere analysis of the B star secondary
of ζ Aurigae (B5 V+K4 Ib) and determine its stellar parameters. A grid
of model atmospheres and synthetic spectra were computed for stellar
parameters typical of mid-B stars, using the TLUSTY and SYNSPEC codes of
Hubeny with the lines and continua of H and He calculated in non-LTE. We
observed ζ Aur with the Goddard High Resolution Spectrograph (GHRS)
of the Hubble Space Telescope (HST) at several epochs near the 1993
eclipse. By carefully removing the circumstellar wind features at
the two epochs furthest from eclipse, we recovered the intrinsic
photospheric spectrum of the B star. The photospheric spectrum of ζAur
B is compared to the grid of synthetic spectra, and the best fit is
determined using a least-squares technique. We find Teff =
15,400±300 K, log g = 3.9±0.1, and V sin i = 200±15 km s-1
The corresponding spectral type, using the effective temperature scale
of Underhill et al., is B5 V. The C I UV 5, 6, 7, and 9 resonance
multiplets (1277-1281 Å) and the Si II UV 4 (1260-1265 Å) and UV 5
(1190-1197 A) resonance multiplets are observed to be much weaker than
our models predict. We empirically determine departure coefficients of
C I and Si II by varying the oscillator strengths of transitions of each
of these ions until a good match with the GHRS spectra is obtained. For
C I, we provide theoretical confirmation of these empirically determined
departure coefficients by computing a more detailed model atmosphere
including levels and transitions of C I, C II, and C III treated
in non-LTE. The synthetic spectra computed from this model are in
good agreement with the GHRS observations, and the C I ground-state
departure coefficient is consistent with the empirically determined
value. We examine several possible causes of the weakness of the
Si II lines and conclude that an underabundance due to non-LTE effects
is the probable explanation. Previous model atmospheres including Si
II computed in non-LTE show that the Si II resonance lines are formed
essentially in LTE. We suggest that autoionization of Si II (neglected
in previous modeling) may shift the silicon ionization balance enough
to account for the weakness of the Si II lines.

---------------------------------------------------------
Title: A Semiempirical Determination of the Wind Velocity Structure
for the Hybrid-Chromosphere Star alpha Trianguli Australis
Authors: Harper, Graham M.; Wood, Brian E.; Linsky, Jeffrey L.;
Bennett, Philip D.; Ayres, Thomas R.; Brown, Alexander
1995ApJ...452..407H Altcode:
We have used the Goddard High-Resolution Spectrograph (GHRS) on the
Hubble Space Telescope to study the wind of the hybrid-chromosphere
star α TrA (K4 II). The stellar wind produces significant
absorption at negative radial velocities in the chromospheric Mg II
resonance lines (h and k). Spectra obtained with the GHRS echelle
high-resolution grating (4A 85,000) on 1993 February 10 and 1994
May 1 reveal complex interstellar absorption in the Mg II emission
lines and a high-velocity wind absorption feature centered near -95
km s-1. The 1993 February observation shows an asymmetry
of the Mg II emission cores, corresponding to an apparent redshift
of 6.0±1.5 km s-1. We construct a simple wind model that
explains several of the key observational features. The scattering of
the Mg II h and k photons in a geometrically extended region dominates
the observed flux near line center, which supports the assignment
of the low-velocity absorption components to interstellar absorption
rather than to a chromospheric self-reversal. For the 1993 February
observation, the parameters for our simple wind model are as follows:
terminal velocity V(∞) = 100 km s-1, turbulent velocity
Vturb = 24 km s-1, Mṡ ∼ 1.8 ×
1010 Msun yr-1, for a fixed value
of the velocity-law parameter β = 1 and fixed stellar radius of
R* = 97 Rsun, assuming Mg II is the dominant
ionization state in the flow. Our analysis of the 1994 May observation
resulted in similar values for these parameters, and the mass-loss
rate could be as small as Mṡ ∼ 1.6 × 10-10
Msun yr-1. The value of β is uncertain (≥
0.3) and if β ∼ 3.5 as found from the recent analysis of the ζ
Aurigae systems, Mṡ could be larger by a factor of 3-4. A
comparison of our result with numerical solutions to the momentum and
conservation equations reveals that the derived velocity distribution
lies within a limited region of parameter space where there is a
large nonthermal pressure on the plasma close to the base of the wind
consistent with previous wind models for α TrA. Our best model fit to
the two interstellar absorption components indicates a total hydrogen
column density toward α TrA of NHI = 2 × 1019
cm-2.

---------------------------------------------------------
Title: Deuterium and the Local Interstellar Medium Properties for
the Procyon and Capella Lines of Sight
Authors: Linsky, Jeffrey L.; Diplas, Athanassios; Wood, Brian E.;
Brown, Alexander; Ayres, Thomas R.; Savage, Blair D.
1995ApJ...451..335L Altcode:
We present Goddard High-Resolution Spectrograph observations of the
interstellar H I and D I Lyα lines and the Mg II and Fe II resonance
lines formed along the lines of sight toward the nearby stars Procyon
(3.5 pc, l = 214°, b = 13°) and Capella (12.5 pc, l = 163°, b =
5°). New observations of Capella were obtained at orbital phase 0.80,
when the radial velocities of the intrinsic Lyα emission lines of each
star were nearly reversed from those of the previous observations at
phase 0.26 (analyzed by Linsky et al.). Since the intrinsic Lyα line
of the Capella system the "continuum" against which the interstellar
absorption is measured has different shapes at phases 0.26 and 0.80,
we can derive both the intrinsic stellar profiles and the interstellar
absorption lines more precisely by jointly analyzing the two data
sets. We derive interstellar parameters from the simultaneous analysis
of the two data sets as follows: (D/H)LISM = (1.60±0.09
[+0.05, - 0.10 systematic error]) × 10-5, temperature T =
7000±500 [±400 systematic error] K, and microturbulence ξ = 1.6±0.4
[and ±0.2 systematic error] km s-1. (All random errors
determined in this paper are ±2 σ.) For the analysis of the
Procyon line of sight, we first assumed that the intrinsic Lyα line
profile is a broadened solar profile, but this assumption does not
lead to a good fit to the observed D I line profile for any value of
D/H. We then assumed that (D/H)LISM = 1.6 × 10-5,
the same value as for the Capella line of sight, and we modified the
broadened solar profile to achieve agreement between the simulated and
observed line profiles. The resulting asymmetric intrinsic stellar
line profile is consistent with the shapes of the scaled Mg II line
profiles. We believe therefore that the Procyon data are consistent with
(D/H)LISM = 1.6 × 10-5, but the uncertainty
in the intrinsic Lyα emission-line profile does not permit us to
conclude that the D/H ratio is constant in the local interstellar medium
(LISM). The temperature and turbulence in the Procyon line of sight
are T = 6900±80 (±300 systematic error) K and ξ = 1.21±0.27 km
s-1. These properties are similar to those of Capella, except
that the gas toward Procyon is divided into two velocity components
separated by 2.6 km s-1 and the Procyon line of sight has a
mean neutral hydrogen density that is a factor of 2.4 larger than that
of the Capella line of sight. This suggests that the first 5.3 pc along
the Capella line of sight lies within the local cloud and the remaining
7.2 pc lies in the hot gas surrounding the local cloud. We propose
that nHI = 0.1065±0.0028 cm-2 be adopted for
the neutral hydrogen density within the local cloud and that ξ =
1.21±0.27 km s-1 be adopted for the nonthermal motions. The
existence of different second velocity components toward the nearby
stars Procyon and Sirius provides the first glimpse of a turbulent
cloudlet boundary layer between the local cloud and the surrounding hot
interstellar gas. We speculate that what is often called "turbulence"
may instead be velocity shear within the local cloud that is not a rigid
comoving structure. We also derive gas phase abundances of iron and
magnesium in the Procyon line of sight and the abundance of oxygen in
the Capella line of sight. Within the context of standard big bang
nucleosynthesis, our observed value of (D/H)LISM leads to
0.042 ≤ ΩBh250 ≤ 0.09, depending
on the assumed model for Galactic chemical evolution of deuterium. Our
lower limit (D/H)LISM &gt; 1.41 × 10-5 provides
a hard lower limit to the primordial D abundance and thus a hard upper
limit on ΩBh250 ≤ 0.125. These
limits are independent of Galactic chemical evolution models and only
assume that D is destroyed with time.

---------------------------------------------------------
Title: The Goddard High Resolution Spectrograph: In-Orbit Performance
Authors: Heap, S. R.; Brandt, J. C.; Randall, C. E.; Carpenter, K. G.;
Leckrone, D. S.; Maran, S. P.; Smith, A. M.; Beaver, E. A.; Boggess,
A.; Ebbets, D. C.; Garner, H. W.; Hutchings, J. B.; Jura, M.; Linsky,
J. L.; Savage, B. D.; Cardelli, J. A.; Trafton, L. M.; Walter, F. M.;
Weymann, R. J.; Ake, T. B.; Crenshaw, D. M.; Malumuth, E. M.; Robinson,
R. D.; Sandoval, J. L.; Shore, S. N.; Wahlgren, G. M.; Bruhweiler,
F.; Lindler, D. J.; Gilliland, R. L.; Hulbert, S. J.; Soderblom, D. R.
1995PASP..107..871H Altcode:
The in-orbit performance of the Goddard High Resolution Spectrograph
onboard the Hubble Space Telescope (HST) is presented. This report
covers the pre-COSTAR period, when instrument performance was
limited by the effects of spherical aberration of the telescope's
primary mirror. The digicon detectors provide a linear response
to count rates spanning over six orders of magnitude, ranging from
the normal background flux of 0.01 counts diode ^-1 s^-1 to values
larger than 10^4 counts diode^-1 s^-1. Scattered light from the
first-order gratings is small and can be removed by standard background
subtraction techniques. Scattered light in the echelle mode is more
complex in origin, but it also can be accurately removed. Data
have been obtained over a wavelength range from below 1100 A to
3300 A, at spectral resolutions as high as R = lambda/delta-lambda =
90,000. The wavelength scale is influenced by spectrograph temperature,
outgassing of the optical bench, and interaction of the magnetic field
within the detector with the earth's magnetic field. Models of these
effects lead to a default wavelength scale with an accuracy better
than 1 diode, corresponding to 3 km s^-1 in the echelle mode. With
care, the wavelength scale can be determined to an accuracy of 0.2
diodes. Calibration of the instrument sensitivity functions is tied into
the HST flux calibration through observations of spectrophotometric
standard stars. The measurements of vignetting and the echelle
blaze function provide relative photometric precision to about 5% or
better. The effects of fixed-pattern noise have been investigated,
and techniques have been devised for recognizing and removing it
from the data. The ultimate signal-to-noise ratio achievable with the
spectrograph is essentially limited only by counting statistics, and
values approaching 1000:1 have been obtained. (SECTION: Astronomical
Instrumentation)

---------------------------------------------------------
Title: New Insights into Nonradiative Heating in Late A Star
Chromospheres
Authors: Walter, Frederick M.; Matthews, Lynn D.; Linsky, Jeffrey L.
1995ApJ...447..353W Altcode: 1995astro.ph..1069W
Using new and archival spectra from the Goddard High Resolution
Spectrograph, we have searched for evidence of chromospheric and
transition region emission in six stars of mid to late A spectral
type. Two of the stars, α Aql (A7 IV-V) and alpha Cep (A7 IV-V),
show emission in the C II 1335 Å doublet, confirming the presence of
hot plasma with temperatures comparable to that of the solar transition
region. Using radiative equilibrium photospheric models, we estimate the
net surface fluxes in the C II emission line to be 9.4 × 104
ergs cm-2s-1 for α Aql and 6.5 × 104
ergs cm-2 s-1 for α Cep. These are comparable
to fluxes observed in early to mid F-type dwarfs, indicating that
significant upper atmospheric heating is present in at least some
stars as hot as ∼8000 K (B - V = 0.22). We find no evidence for
the blueshifted emission reported by Simon et al. (1994). We estimate
the basal flux level to be about 30% of that seen in early F stars,
and that the bulk of the emission is not basal in origin. We conclude
that the basal flux level drops rapidly for B - V ≲ 0.3, but that
magnetic activity may persist to B - V as small as 0.22.

---------------------------------------------------------
Title: An In-Depth Study of Transition Region Physics: Capella
Authors: Linsky, Jeffrey
1995hst..prop.5886L Altcode: 1995hst..prop.2359L
With the brightest UV emission line spectrum of any late-type star,
Capella provides an excellent target for detailed studies of physical
processes occuring in magnetically heated plasmas, commonly called
transition regions, at temperatures of 10^4 - 10^5 K. In our recently
completed analysis of GHRS spectra of Capella (Linsky et al. 1994),
we find three distinct transition regions in the Capella system -- the
plasma on the hotter star (G1 III) that emits moderately broad lines,
the plasma on the cooler star (G8 III) that emits narrow lines, and
microflaring plasma on the hotter star that emits very broad lines. We
now propose a follow-up study to answer the critical new questions
raised in the previous work that require analysis of a very different
data set. Our objectives are (1) to determine the relative roles of
recombination and collisional excition in the formation of the He II
1640 Angstrom line in both stars, (2) to obtain accurate values of
the electron density in both the moderately broad and very broad line
regions on the hotter star, (3) to obtain an accurate measurement of
the differential emission measure distribution of the microflaring
component, and (4) to measure the coronal Fe XXI 1354 Angstrom and
Fe XII 1349 Angstrom lines for comparison with models based on x-ray
data and to determine their Doppler shift and coronal turbulence. The
analysis of the requested data will form a portion of Brian Wood's
Ph.D thesis.

---------------------------------------------------------
Title: An Atlas of Alpha Orionis Obtained with the Goddard High
Resolution Spectrograph on the Hubble Space Telescope
Authors: Brandt, J. C.; Heap, S. R.; Beaver, E. A.; Boggess,
A.; Carpenter, K. G.; Ebbets, D. C.; Hutchings, J. B.; Jura, M.;
Leckrone, D. S.; Linsky, J. L.; Maran, S. P.; Savage, B. D.; Smith,
A. M.; Trafton, L. M.; Walter, F. M.; Weymann, R.; Snow, M.; Randall,
C. E.; Ake, T. B.; Robinson, R. D.; Wahlgren, G.
1995AJ....109.2706B Altcode:
An atlas of observations of the late-type supergiant a Orionis taken
with the Goddard High Resolution Spectrograph in 1992 September is
presented. We have included identifications of the major features along
with the fully reduced spectrum. The 33 exposures consist of 3 high
resolution (R∼80,000) and 30 medium resolution (R ∼20,000∼35,000)
observations. The latter provide complete wavelength coverage from
1980 to 3300 Å.

---------------------------------------------------------
Title: Outer Layers of a Carbon Star: The View from the Hubble
Space Telescope
Authors: Johnson, Hollis R.; Ensman, Lisa M.; Alexander, David R.;
Avrett, Eugene H.; Brown, Alexander; Carpenter, Kenneth G.; Eriksson,
Kjell; Gustafsson, Bengt; Jorgensen, Uffe G.; Judge, Philip D.; Linsky,
Jeffrey L.; Luttermoser, Donald G.; Querci, Francois; Querci, Monique;
Robinson, Richard D.; Wing, Robert F.
1995ApJ...443..281J Altcode:
To advance our understanding of the relationship between stellar
chromospheres and mass loss, which is a common property of carbon stars
and other asymptotic giant branch stars, we have obtained ultraviolet
spectra of the nearby N-type carbon star UU Aur using the Hubble
Space Telescope (HST). In this paper we describe the HST observations,
identify spectral features in both absorption and emission, and attempt
to infer the velocity field in the chromosphere, upper troposphere,
and circumstellar envelope from spectral line shifts. A mechanism
for producing fluoresced emission to explain a previously unobserved
emission line is proposed. Some related ground-based observations are
also described.

---------------------------------------------------------
Title: The Transition Regions of Capella
Authors: Linsky, Jeffrey L.; Wood, Brian E.; Judge, Philip; Brown,
Alexander; Andrulis, Catherine; Ayres, Thomas R.
1995ApJ...442..381L Altcode:
We have used the Goddard High Resolution Spectrometer (GHRS) to observe
the spectoscopic binary system Capella (G8 III + G1 III). Exposures
with the G140L, G140M, G160M, G200M, and echelle gratings provide
emission line profiles with unprecedented signal-to-noise and spectral
resolving power (lambda/Delta-lambda) up to 92,000. Multi-Gaussin fits
to the line profiles show that the hotter star contributes 60%-70% of
the total flux in the chromospheric O I and Mg II resonance lines, but
about 90% of the flux in the Si III, Si IV, and C IV lines formed in the
transition region at T less than or = 105 K. We find clear
evidence that the emission lines from the hotter star are systemtically
redshifted relative to the photosphere with Doppler shifts of 5 +/-
1 km/s for the +9 +/- 3 km/s in the chromospheric Mg II and O I lines,
respectively, increasing to +24 +/- 5 km/s for the transition region Si
IV 1393.8A line. The multi-Gaussian fits to permitted transition region
lines of SI III, Si IV, C IV, and N V indicate the presence of three
components: moderately broad lines formed in the transition region of
the hotter star (component H), narrow lines formed in the transition
region of the cooler star (component C), and very broad lines that we
think are formed in microflares on the hotter star (component B). The
He II 1640.4 A feature has an broad profile, which indicates that it
is formed by collisional excitation primarily from the hotter star,
and a weak narrow component that we interpret as due to radiative
recombination on the cooler star. We observed spin-forbidden emission
lines of C III), O III), Si III), O IV), O V), and S IV) that are
sensitive to electron density. Fainter members of the O IV) multiplet
and all of the S IV) lines have never before been seen in any star than
the Sun. We determine electron densities in the transition regions
of the Capella stars using lines ratios of O IV) lines and emission
measure analysis. The emission measures are self-consistent only when
the fluxes from each emitting component are considered separately. In
particular, the transition region abundance distributions appear to
be different on the two stars, and the spin-forbidden lines were not
detected in the B component. The emission measures for component
H (the G1 star) are consistent with a constant electron pressure
(or hydrostatic equilibrium) transition region with Pe =
1015 + 0.1/cu cm K and possibly solar 'coronal' abundances.

---------------------------------------------------------
Title: The Hydrogen Hole at the North Galactic Pole
Authors: Ayres, T. R.; Linsky, J. L.; Diplas, A.
1995AAS...186.3508A Altcode: 1995BAAS...27..860A
The yellow giant 31 Comae (HD111812: G0 III) lies near the North Galatic
Pole (b(II) = +89{fdg }6; l(II) = 114{fdg }9). Although 80 pc distant in
the Coma Berenices open cluster, 31 Com is a strong EUV source. Recent
HST/GHRS spectra of the star show surprisingly weak Mg II lambda2800 and
H I lambda1215 interstellar absorptions. The neutral hydrogen column
in that direction must be quite low, reminiscent of the interstellar
“void” toward epsilon CMa discovered by the EUVE. Indeed, previous
EUVE observations have shown that the lines of sight to the hot white
dwarfs HZ 43 (b(II) = +84deg ; l(II) = 54deg ) and GD 153 (b(II) =
+85deg ; l(II) = 317deg ) have very low columns, NH &lt;
1*E(18) cm(-2) , suggesting another “tunnel” near the NGP. We modeled
the GHRS spectra of 31 Com to determine whether there is a further
northward extension of the HZ 43/GD 153 void. [-3mm] The interstellar
Mg II h and k absorptions in the 31 Com spectrum are quite sharp,
suggesting only a single velocity component along the line of sight
(compared with several distinct clouds in the direction of epsilon
CMa). Our preliminary modeling of the Mg II, H I, and D I ISM features
indicates that xi_t , T, and [D/H] are similar to the values measured
previously for the lines of sight toward the nearby stars Capella and
Procyon. Furthermore, the bulk velocity (-2 km s(-1) , heliocentric) is
the same as predicted for the local cloud. The inferred neutral hydrogen
column, NH ~ 8*E(17) cm(-2) , is one of the smallest ever
measured directly from the Lyalpha absorption. We speculate that the
majority of the neutral gas in the direction of 31 Com lies very close
to the Sun in a few pc extension of the local “fluff”, and that the
remainder of the sightline is quite rarified and probably hot. In all
likelihood the HZ 43/GD 153 void is considerably larger than suspected
previously. [-2mm] This work was supported by NASA grants GO-5323.01-93A
(HST), S-56460-D (HST), and NAG5-2274 (EUVE).

---------------------------------------------------------
Title: Determination of Plasma Temperatures and Luminosities Using
Multiple Extreme-Ultraviolet and X-Ray Filters
Authors: Wood, Brian E.; Brown, Alexander; Linsky, Jeffrey L.
1995ApJ...438..350W Altcode:
We carefully examine the techniques used to infer temperatures of
stellar coronal plasmas from the count rates of several broadband
instruments in the X-ray and extreme-ultraviolet spectral ranges. In
particular, we determine to what extent temperatures can be constrained
and the corresponding uncertainties in the luminosities and emission
measures lowered by fitting simultaneously count rates from the Einstein
imaging proportional counter (IPC), the ROSAT Position Sensitive
Proportional Counter (PSPC), the ROSAT Wide Field Camera (WFC) (both
filters), and the EXOSAT Low Energy Telescope (LET) with the 3-Lex
filter. We use published plasma emissivities with solar photospheric
abundances. Since it has been found that single-temperature plasmas do
not fit IPC data well, we assume a two-temperature plasma model. We
find that, even with count rates from all of the above filters
and overly optimistic error estimates, it is still not possible
to determine a unique two-temperature solution. However, since the
use of count rates from many filters can reduce substantially the
number of possible solutions, temperature solutions determined by
other means can be tested. We carry out such an analysis on a set
of 18 nearby late-type stars to determine possible two-temperature
solutions using multifilter photometry, and we compare these results
with the temperature solutions derived by Schmitt et al. (1990) using
IPC spectral data. In general, the two-temperature fits derived from
the IPC spectral data are inconsistent with our results, with our data
implying that, for many stars, the two temperatures derived by the IPC
may be too low by about a factor of 2. The EXOSAT transmission grating
Spectrometer (TGS) spectra of capella and sigma2 CrB support
this conclusion. For Procyon and 70 Oph, though, the presence of a
temperature component cooler than a million degress (not detected by the
IPC) is deduced. While our analysis suggests the existence of more than
one temperature in the coronae of late-type stars, in many instances
our WFC data appear to be inconsistent with the presence of significant
emission measure over a broad temperature distribution. This, together
with the success of two-temperature plasmas in fitting IPC and TGS data,
implies that for many stars, the coronal emission measure distribution
may in fact be dominated by two distinct temperature regimes.

---------------------------------------------------------
Title: Probing Coronal Flare Energetics: Coordinated EUVE, XTE,
and IUE Observations of Nearby Flare Stars
Authors: Linsky, Jeffrey L.
1995euve.prop...25L Altcode:
We request EUVE observations of EQ Peg and AU Mic as a central component
of a coordinated campaign to monitor flaring on very active nearby
dMe stars. Approved observations so far include 6 days of monitoring
with XTE to probe the very hottest coronal plasma and to search for
impulsive hard X-rays. Simultaneous rapid U-band photometry, IUE,
and 3.6 cm radio observations are also planned. Time-resolved EUVE SW
and MW spectra will trace the tempertaure distribution of the flaring
coronal plasma in the temperature range 1-16 MK. We will compare the
time scales for flare cooling (as seen with EUVE) and heating (as seen
with XTE) and look for a stellar Neupert effect. To date the hard X-ray
bursts which accompany microwave bursts in strong coronal flares have
never been observed on a star other than the sun. The EUVE data will
allow us to examine the overall energy budget in large stellar flares
and to further test the validity of the solar analogy when extended
to very active low-mass stars.

---------------------------------------------------------
Title: Hubble Observations of D/H in the Local ISM and Consequences
for
Authors: Linsky, J. L.; Diplas, A.; Ayres, T. R.; Wood, B.; Brown, A.
1995lea..conf..215L Altcode:
No abstract at ADS

---------------------------------------------------------
Title: The RIASS Coronathon: Joint X-Ray and Ultraviolet Observations
of Normal F--K Stars
Authors: Ayres, Thomas R.; Fleming, T. A.; Simon, T.; Haisch, B. M.;
Brown, A.; Lenz, D.; Wamsteker, W.; de Martino, D.; Gonzalez, C.;
Bonnell, J.; Mas-Hesse, J. M.; Rosso, C.; Schmitt, J. H. M. M.;
Truemper, J.; Voges, W.; Pye, J.; Dempsey, R. C.; Linsky, J. L.;
Guinan, E. F.; Harper, G. M.; Jordan, C.; Montesinos, B. M.; Pagano,
I.; Rodono, M.
1995ApJS...96..223A Altcode:
Between 1990 August and 1991 January the ROSAT/IUE All Sky Survey
(RIASS) coordinated pointings by the International Ultraviolet Explorer
(IUE) with the continuous X-ray/EUV mapping by the Roentgensatellit
(ROSAT). The campaign provided an unprecedented multiwavelength
view of a wide variety of cosmic sources. We report findings for
F-K stars, a large proportion of the RIASS targets. Forty-eight of
our 91 'Coronathon' candidates were observed by the IUE during the
campaign. For stars missed by the IUE, we supplemented the ROSAT survey
fluxes with archival UV spectra and/or follow-on observations.

---------------------------------------------------------
Title: A Search for Radio Emission From the "Nonmagnetic" Chemically
Peculiar Stars
Authors: Drake, S. A.; Linsky, J. L.; Bookbinder, J. A.
1994AJ....108.2203D Altcode:
We have observed 23 members of the Am and HgMn subclasses of
chemically peculiar (CP) stars with the Very Large Array (VLA) to
search for nonthermal radio emission at levels comparable to those
found for the Si and He peculiar subclasses of the CP stars by Linsky
et al. (1992). This study was motivated by recent claims that magnetic
fields of kilogauss strength are present in at least some of the Am
and HgMn stars, contrary to previous beliefs, which would indicate
that radio-emitting magnetospheres could be present in these stars. We
detected none of the Am and HgMn stars as radio emitters with upper
limits typically less than 0.20 mJy. Applying a correlation between
radio luminosity, surface magnetic field, and effective temperature
derived from previous radio studies of the Si and He peculiar CP stars,
we find that the predicted radio luminosities of alpha And (an HgMn
star) and Sirius (a hot Am star) are more than an order of magnitude
larger than the observed upper limits, indicating that these stars
lack magnetospheres, and, by inference, surface magnetic fields.

---------------------------------------------------------
Title: GHRS Spectra of the Very Low Mass Star VB 10 (M8 Ve)
Authors: Linsky, J. L.; Wood, B.; Brown, A.
1994AAS...185.4504L Altcode: 1994BAAS...26.1380L
We report on ultraviolet spectra of the M8 Ve star VB10 = Gl 752B,
probably the coolest and lowest mass star observed so far in the
ultraviolet. This star is of great interest because it lies almost
at the end of the main sequence where stars are thought to be fully
convective and solar-type dynamo processes should not be present. On
1994 October 12 we observed the brighter companion Gl 752A (M3 Ve)
and then offset to VB10. Both stars were observed with the G140L
grating on the HST Goddard High Resolution Spectrograph. The spectrum
of Gl 752A shows the expected transition region lines of solar-type
stars consisting of C III 1175 Angstroms, H I Lyman-alpha , N V
1240 Angstroms, O I 1304 Angstroms, C II 1335 Angstroms, Si IV 1400
Angstroms, C IV 1550 Angstroms, He II 1640 Angstroms, and others. The
spectrum of VB10, on the other hand, provided a surprise. Our spectra
of this star consists of 11 integrations, each of about 5 minutes
duration. The first 10 integrations show no emission features with
very small upper limits to the surface fluxes in the transition region
lines. The last integration, however, shows strong emission in the C II,
Si IV, and C IV lines, which we interpret as a flare. The VB10 spectra
imply that there is little if any continuous heating of the transition
regions of the very coolest M dwarf stars. Instead, there is only
transient emission during major realignments of the magnetic field. By
contrast, hotter stars show continuous emission in the transition region
lines, indicating a continuous heating process or a large number of
small flares (microflaring). This change in behavior may be due to the
absence of radiative cores in the coolest M dwarfs and the inability
of the solar-type alpha -omega dynamo to operate in stars without
an interface between a radiative core and a convective envelope. Our
data indicate that the coolest M dwarfs nevertheless do have magnetic
fields. This work is supported by NASA Interagency Transfer S-56460-D
to the National Institute of Standards and Technology.

---------------------------------------------------------
Title: GHRS Observations of Procyon and HR 1099
Authors: Wood, B. E.; Linsky, J. L.
1994AAS...185.4501W Altcode: 1994BAAS...26.1379W
Linsky &amp; Wood (1994, ApJ, 430, 342) discovered broad wings
in the transition region lines of AU Mic, and proposed that these
wings are signatures of microflares in the transition region of this
active M0 Ve star. The solar analog for this phenomenon might be the
“transition region explosive events” discussed by Dere, Bartoe, &amp;
Brueckner (1989, Sol. Phys., 123, 41). Broad wings have been found in
Capella's transition region lines as well, and these have also been
interpreted as being caused by microflaring (Linsky et al., ApJ, to
appear 20 March 1995). We have used Goddard High Resolution Spectrograph
(GHRS) observations of Procyon (F5 IV-V) and HR 1099 (K1 IV + G5 IV)
to search for broad wings in the UV emission lines of these stars. We
find that the transition region lines of HR 1099, which are emitted
almost entirely by the K1 star, do indeed have broad wings which are
even stronger than those of AU Mic and Capella. This is consistent with
the association of the broad wings with microflaring since HR 1099 is
a very active binary system. In contrast, the transition region lines
of Procyon, an inactive star, do not show evidence for any broad wings,
with the possible exception of N V lambda 1239. However, these lines do
seem to have a slight blue wing excess. Linsky et al. (1995) found no
evidence for broad wings in Capella's chromospheric lines. However, we
find that the Mg II lines of HR 1099 and AU Mic do have broad wings. The
striking resemblance between the Mg II and C IV lines seen for both
these stars suggests that the Mg II line profiles may be regulated
by turbulent processes similar to those that control the transition
region line profiles. For HR 1099 and AU Mic, microflaring may be
a common occurence in the chromosphere as well as in the transition
region. This work is supported by NASA Interagency Transfer S-56500-D
to the National Institute of Standards and Technology.

---------------------------------------------------------
Title: The Goddard High Resolution Spectrograph: Instrument, Goals,
and Science Results
Authors: Brandt, J. C.; Heap, S. R.; Beaver, E. A.; Boggess, A.;
Carpenter, K. G.; Ebbets, D. C.; Hutchings, J. B.; Jura, M.; Leckrone,
D. S.; Linsky, J. L.; Maran, S. P.; Savage, B. D.; Smith, A. M.;
Trafton, L. M.; Walter, F. M.; Weymann, R. J.; Ake, T. B.; Bruhweiler,
F.; Cardelli, J. A.; Lindler, D. J.; Malumuth, E.; Randall, C. E.;
Robinson, R.; Shore, S. N.; Wahlgren, G.
1994PASP..106..890B Altcode:
The Goddard High Resolution Spectrograph (GHRS), currently in Earth
orbit on the Hubble Space Telescope (HST), operates in the wavelength
range of 1150-3200A with spectral resolutions (lambda/delta-lambda)
of approximately 2 X 10^3, 2 X 10^4, and 1 X 10^5. This paper describes
the instrument and its development from inception, its current status,
the approach to operations, representative results in the major areas
of the scientific goals, and prospects for the future. (SECTION:
Instrumentation and Data Analysis)

---------------------------------------------------------
Title: High-Velocity Plasma in the Transition Region of AU
Microscopii: Evidence for Magnetic Reconnection and Saturated Heating
during Quiescent and Flaring Conditions
Authors: Linsky, Jeffrey L.; Wood, Brian E.
1994ApJ...430..342L Altcode:
We analyze high-resolution HST spectra of the dMOe flare star AU
Mic, including the profiles of the C IV 1548.2 A, 1550.8 A and Si IV
1393.8 A, 1402.8 A lines obtained with the G160M grating of the Goddard
High-Resolution Spectrograph. The quiescent profiles of the C IV and Si
IV lines are broad, and not simple Gaussians in shape. Flux in the C IV
and Si IV lines, for example, can be measured reliably out to about +/-
200 km/s from line center. Each of the C IV and Si IV profiles can be
fitted accurately by two Gaussians (one narrow and the other broad)
centered on nearly the same wavelength, with the narrower component
accounting for roughly 60% ofthe total integrated flux. The narrow
components have similar line widths to those observed in solar active
and quiet regions. The broad Gaussian components of the AU Mic line
profiles are reminiscent of the broad C IV profiles observed in solar
transition region explosive events, which are thought to be associated
with emerging magnetic flux regions where field reconnection occurs.

---------------------------------------------------------
Title: A Volume-limited ROSAT Survey of Extreme Ultraviolet Emission
from All Nondegenerate Stars within 10 Parsecs
Authors: Wood, Brian E.; Brown, Alexander; Linsky, Jeffrey L.; Kellett,
Barry J.; Bromage, Gordon E.; Hodgkin, Simon T.; Pye, John P.
1994ApJS...93..287W Altcode:
We report the results of a volume-limited ROSAT Wide Field Camera
(WFC) survey of all nondegenerate stars within 10 pc. Of the 220 known
star systems within 10 pc, we find that 41 are positive detections
in at least one of the two WFC filter bandpasses (S1 and S2),
while we consider another 14 to be marginal detections. We compute
X-ray luminosities for the WFC detections using Einstein Imaging
Proportional Counter (IPC) data, and these IPC luminosities are
discussed along with the WFC luminosities throughout the paper for
purposes of comparison. Extreme ultraviolet (EUV) luminosity functions
are computed for single stars of different spectral types using both
S1 and S2 luminosities, and these luminosity functions are compared
with X-ray luminosity functions derived by previous authors using
IPC data. We also analyze the S1 and S2 luminosity functions of the
binary stars within 10 pc. We find that most stars in binary systems
do not emit EUV radiation at levels different from those of single
stars, but there may be a few EUV-luminous multiple-star systems
which emit excess EUV radiation due to some effect of binarity. In
general, the ratio of X-ray luminosity to EUV luminosity increases
with increasing coronal emission, suggesting that coronally active
stars have higher coronal temperatures. We find that our S1, S2,
and IPC luminosities are well correlated with rotational velocity,
and we compare activity-rotation relations determined using these
different luminosities. Late M stars are found to be significantly
less luminous in the EUV than other late-type stars. The most natural
explanation for this results is the concept of coronal saturation --
the idea that late-type stars can emit only a limited fraction of their
total luminosity in X-ray and EUV radiation, which means stars with
very low bolometric luminosities must have relatively low X-ray and
EUV luminosities as well. The maximum level of coronal emission from
stars with earlier spectral types is studied also. To understand the
saturation levels for these stars, we have compiled a large number
of IPC luminosities for stars with a wide variety of spectral types
and luminosity classes. We show quantitatively that if the Sun were
completely covered with X-ray-emitting coronal loops, it would be near
the saturation limit implied by this compilation, supporting the idea
that stars near upper limits in coronal activity are completely covered
with active regions.

---------------------------------------------------------
Title: GHRS Observations of Cool, Low-Gravity Stars. I. The
Far-Ultraviolet Spectrum of alpha Orionis (M2 Iab)
Authors: Carpenter, Kenneth G.; Robinson, Richard D.; Wahlgren,
Glenn M.; Linsky, Jeffrey L.; Brown, Alexander
1994ApJ...428..329C Altcode:
We present far-UV (1200-1930 A) observations of the prototypical red
supergiant star alpha Ori, obtained with the Goddard High Resolution
Spectrograph (GHRS) on the Hubble Space Telescope (HST). The
observations, obtained in both low- (G140L) and medium- (G160/200M)
resolution modes, unambiguously confirm that the UV 'continuum'
tentatively seen with (IUE) is in fact a true continuum and is not due
to a blend of numerous faint emission features or scattering inside
the IUE spectrograph. This continuum appears to originate in the
chromospheric of the star at temperatures ranging from 3000-5000 K,
and we argue that it is not related to previously reported putative
companions or to bright spots on the stellar disk. Its stellar origin
is further confirmed by overlying atomic and molecular absorptions from
the chromosphere and circumstellar shell. The dominant structure in
this spectral region is due to nine strong, broad absorption bands of
the fourth-positive A-X system of CO, superposed on this continuum in
the 1300-1600 A region. Modeling of this CO absorption indicates that it
originates in the circumstellar shell in material characterized by T =
500 K, N(CO) = 1.0 x 1018 per sq cm, and Vturb
= 5.0 km per sec. The numerous chromospheric emission features are
attributed mostly to fluorescent lines of Fe II and Cr II (both
pumped by Lyman Alpha) and S I lines, plus a few lines of O I, C I,
and Si II. The O I and C I UV 2 multiplets are very deficient in flux,
compared to both the flux observed in lines originating from common
upper levels but with markedly weaker intrinsic strength (i.e., O I
UV 146 and C I UV 32) and to the UV 2 line fluxes seen in other cool,
less luminous stars. This deficiency appears to be caused by strong
self-absorption of these resonance lines in the circumstellar shell
and/or upper chromosphere of alpha Ori. Atomic absorption features,
primarily due to C I and Fe II are clearly seen in the G160M spectrum
centered near 1655 A. These Fe II features are formed at temperatures
that can occur only in the chromosphere of the star and are clearly
not photospheric or circumstellar in origin.

---------------------------------------------------------
Title: EUVE Coronal Spectroscopy of the RS CVn Binaries sigma (2)
CrB and II Peg
Authors: Brown, A.; Linsky, J. L.; Dempsey, R.
1994AAS...184.0517B Altcode: 1994BAAS...26Q.865B
We have used the Extreme Ultraviolet Explorer satellite to study
the coronal emission from the EUV-bright RS CVn binaries sigma (2)
CrB, observed 1994 Feb 16-21, and II Peg, observed 1993 Oct 1-5. We
present time-resolved and integrated EUV short, medium and long
wavelength spectra for these binaries. sigma (2) CrB shows significant
first-order emission features in the long wavelength region. The coronal
emission measure distributions and electron densities are estimated
for these active coronae dominated by high temperature (&gt;= 10(7)
K) plasma. This work is supported by NASA Grants NAG5-2259 &amp;
NAGW-2904 to the University of Colorado.

---------------------------------------------------------
Title: Examining the Corona of HR 1099 with the Hubble Space Telescope
Authors: Robinson, R. D.; Maran, S. P.; Carpenter, K. G.; Brandt,
J. C.; Linsky, J. L.
1994AAS...184.0515R Altcode: 1994BAAS...26Q.865R
A pilot program for the study of stellar coronae through ultraviolet
diagnostic lines is in progress with the Goddard High Resolution
Spectrograph on the Hubble Space Telescope. An initial result of this
program was the detection of the coronal emission line of Fe XXI at 1354
Angstroms in the quiescent spectrum of the dMe star AU Mic (ApJ 421,
800, 1994). The line appeared to be symmetrical, had no measurable
radial velocity with respect to the stellar rest frame, and had a
width which was consistent with a thermal gas of temperature 10(7) K,
suggesting very small turbulence within the formation region. In March
1994, we observed the RS CVn binary HR 1099 = HD 22468 (K1 IV + G5 IV )
using instrumental settings identical to those employed with AU Mic,
but with the added benefit of the recently-installed HST corrective
optics (COSTAR). Each exposure was bracketed by observations of an
on-board wavelength calibration lamp. The results of the series of
eight 27-minute integrations, obtained at one-orbit intervals, will
be presented and compared with the AU Mic spectrum.

---------------------------------------------------------
Title: GHRS Spectra of the Active Chromosphere Binary V711 Tau
(HR 1099)
Authors: Dempsey, Robert C.; Neff, James E.; Linsky, Jeffrey L.
1994AAS...184.0514D Altcode: 1994BAAS...26..865D
During a multiwavelength campaign in September of 1993 a unique
array of telescopes was directed at the chromospherically-active
binary system V711 Tau (HR 1099) in an effort to determine fundamental
properties of a late-type stellar atmosphere from the photosphere to the
corona. Observations of the RS CVn system V711 Tau were obtained with
the HST, IUE, VLA, and EUVE observatories. In addition, ground-based
optical spectroscopy and photometry were obtained with the APT in
Phoenix and at Penn State's Black Moshannon Observatory. We present
preliminary results from GHRS observations obtained at 5 phases
over 2.5 stellar rotations. GHRS spectra of Mg II h &amp; k (2796,
2830 Angstroms)\ and the C IV doublet (1548,1550 Angstroms)\ are used
to probe the chromosphere and transition regions of the K1 IV star,
while electron density diagnostics are extracted from the Si III] (1892
Angstroms)\ and C III] (1909 Angstroms)\ intersystem lines. Additional
spectra of the 2600 Angstroms region and H I Lyman-alpha spectral
regions were obtained at one quadrature phase. Although phase coverage
is poor, we are able to extract limited information on temporal
and/or spatial variability of the system. Changes in line flux and
profile shape are observed in several lines including a variation of
approximately 60% in the Si III]/C III] ratio. Finally, since V711 Tau
has been observed extensively by IUE over the past 16 years, the HST
data provide a high resolution benchmark for this larger body of data.

---------------------------------------------------------
Title: Wind Velocity and Density Laws for the Hybrid-Chromosphere
Star alpha TrA obtained from GHRS Spectra
Authors: Linsky, J. L.; Harper, G. M.; Wood, B.; Brown, A.
1994AAS...184.0504L Altcode: 1994BAAS...26..863L
We have used the Goddard High Resolution Spectrometer on HST
to study the wind of the hybrid-chromosphere star alpha TrA (K2
IIb-IIIa). The stellar wind is detected by the absorption seen
against the chromospheric Mg II resonance lines (h and k) centered
at 2795.53 Angstroms and 2802.70 Angstroms. Spectra obtained with
the high spectral resolution (lambda /Delta lambda =84,750) and low
scattered light properties of the GHRS echelle grating reveal stellar
Mg II emission lines with complex interstellar absorption and a broad
wind absorption feature centered at --90 km s(-1) . We infer the Mg
II opacity as a function of velocity and derive velocity laws for the
stellar wind by comparing the observed line profiles with synthetic
profiles computed for a range of wind parameters. We also discuss the
origin of the observed broad lines of Si III], C III], and C IV. This
work is supported by NASA Interagency Transfer S-56460-D to the National
Institute of Standards and Technology.

---------------------------------------------------------
Title: Examining the corona of HR 1099 with the Hubble Space
Telescope.
Authors: Robinson, R. D.; Maran, S. P.; Carpenter, K. G.; Brandt,
J. C.; Linsky, J. L.
1994BAAS...26..865R Altcode:
No abstract at ADS

---------------------------------------------------------
Title: Rotational modulation and flares on RS Canum Venaticorum and
BY Draconis stars. XVIII. Coordinated VLA, ROSAT, and IUE observations
of RS CVn binaries .
Authors: Fox, D. C.; Linsky, J. L.; Veale, A.; Dempsey, R. C.; Brown,
A.; Neff, J. E.; Pagano, I.; Rodono, M.; Bromage, G. E.; Kuerster,
M.; Schmitt, J. H. M. M.
1994A&A...284...91F Altcode:
As part of a coordinated program of multi-wavelength observations of
RS CVn close binary systems, we observed 15 systems with the VLA and
10 systems with IUE, simultaneously or nearly simultaneously with the
ROSAT All Sky Survey observations of these stars. Of the 22 systems
observed with ROSAT, three were observed both by IUE and the VLA. The
principal aim of this program was to check the validity of the existing
empirical correlations between the radio and soft X-ray emissions of
their coronae, and between the chromospheric/transition region and
coronal emissions. Previous studies of these correlations were usually
based on nonsimultaneous observations and thus might be biased by source
variability. Radio observations were made at 3.6, 6 and 20 cm. Of the
15 observed RS CVn systems, we detected 11 with &gt;= 4 σ confidence at
one or more wavelengths. The IUE observations were made within the RIASS
(ROSAT-IUE All Sky Survey) program. We present the results of the VLA
observations, along with the corresponding subsets of the ROSAT PSPC
X-ray and WFC XUV survey, and RIASS IUE observations. We obtained an
extended VLA/IUE/ROSAT simultaneous coverage of one system, TY Pyx,
covering more than one orbital period. These observations reveal that
the quiescent radio flux of TY Pyx is relatively constant over time
scales of up to 7 hours, but that it did change by a factor of 3 over
24 hours, probably due to a flare on 1990 Nov 12. The UV, XUV and X-ray
fluxes do not show large day-to-day or phase-related variability. The
observation of the decay phase of a radio flare on EI Eri, with no
accompanying X-ray or XUV flare, suggests that the lack of a strong
correlation between X-ray and radio flares previously noted for dMe
flare stars holds for RS CVn systems as well. We suggest that the
radio flare may have been due to a coherent emission process such as
electron cyclotron emission. The simultaneous measurements presented
here provide a unique test of the general correlation between radio
and soft X-ray luminosities, L_radio_~L^m^_x_ (Drake et al. 1989)
with a power-law slope close to unity, which was previously derived
using data obtained years apart. Our derived slopes are consistent
with and thus support the general correlations between coronal and
chromospheric/transition region emissions previously derived from
nonsimultaneous measurements of a much larger sample of these variable
sources. However, the importance of simultaneous measurements for
accurate energy balance calculations is stressed.

---------------------------------------------------------
Title: Observing Stellar Coronae with the Goddard High Resolution
Spectrograph. I. The dMe Star AU Microscopii
Authors: Maran, S. P.; Robinson, R. D.; Shore, S. N.; Brosius, J. W.;
Carpenter, K. G.; Woodgate, B. E.; Linsky, J. L.; Brown, A.; Byrne,
P. B.; Kundu, M. R.; White, S.; Brandt, J. C.; Shine, R. A.; Walter,
F. M.
1994ApJ...421..800M Altcode:
We report on an observation of AU Mic taken with the Goddard High
Resolution Spectrograph (GHRS) aboard the Hubble Space Telescope. The
data consist of a rapid sequence of spectra covering the wavelength
range 1345-1375 A with a spectral resolution of 10,000. The observations
were originally intended to search for spectral variations during
flares. No flares were detected during the 3.5 hr of monitoring. A
method of reducing the noise while combining the individual spectra
in the time series is described which resulted in the elimination of
half of the noise while rejecting only a small fraction of the stellar
signal. The resultant spectrum was of sufficient quality to allow the
detection of emission lines with an integrated flux of 10-15
ergs/sq cm(sec) or greater. Lines of C I, O I, O V, Cl I, and Fe XXI
were detected. This is the first indisputable detection of the 1354
A Fe XXI line, formed at T approximately = 107 K, on a
star other than the Sun. The line was well resolved and displayed
no significant bulk motions or profile asymmetry. From the upper
limit on the observed line width, we derive an upper limit of 38 km/s
for the turbulent velocity in the 107 K plasma. An upper
limit is derived for the flux of the 1349 A Fe XII line, formed at T
approximately = 1.3 x 106 K. These data are combined with
contemporaneous GHRS and International Ultraviolet Explorer (IUE) data
to derive the volume emission measure distribution of AU Mic over the
temperature range 104-107 K. Models of coronal
loops in hydrostatic equilibrium are consistent with the observed
volume emission measures of the coronal lines. The fraction of the
stellar surface covered by the footprints of the loops depends upon the
loop length and is less than 14% for lengths smaller than the stellar
radius. From the upper limit to the estimated width of the Fe XXI line
profile we find that the we cannot rule out Alfven wave dissipation
as a possible contributor to the required quiescent loop heating rate.

---------------------------------------------------------
Title: Sleuthing the Dynamo: HST/FOS Observations of UV Emissions
of Solar-Type Stars in Young Clusters
Authors: Ayres, T.; Basri, G.; Simon, T.; Stauffer, J.; Stern, R.;
Antiochos, S.; Bookbinder, J.; Brown, A.; Doschek, G.; Linsky, J.;
Ramsey, L.; Walter, F.
1994ASPC...64...53A Altcode: 1994csss....8...53A
No abstract at ADS

---------------------------------------------------------
Title: The Corona of the K5 Giant γ Dra, and its Relation to the
HybridChromosphere Stars
Authors: Brown, A.; Linsky, J. L.; Ayres, T. R.
1994AIPC..313...36B Altcode: 1994sxrc.conf...36B
Gamma Draconis is the first, normal, single late K giant located on
the red side of the coronal “dividing line” known to show conclusive
evidence for hot (∼105 K) transition region (TR) and
coronal plasma. We present ROSAT PSPC data and HST GHRS spectra of
γ Dra and describe the coronal and TR properties of this K5 III
star. The high temperature emissions of γ Dra are compared to those
of a sample of hybrid-chromosphere bright giants and supergiants. New
PSPC detections of the K3 giant α Hya and the G supergiant β Aqr are
presented. Upper limits are found for the hybrid-chromosphere stars
θ Her and α Aqr. These new measurements extend the X-ray to C IV
flux-flux relations to significantly lower activity levels.

---------------------------------------------------------
Title: A Far-Ultraviolet Flare on a Pleiades G Dwarf
Authors: Ayres, T. R.; Stauffer, J. R.; Simon, Theodore; Stern, R. A.;
Antiochos, S. K.; Basri, G. S.; Bookbinder, J. A.; Brown, A.; Doschek,
G. A.; Linsky, J. L.; Ramsey, L. W.; Walter, F. M.
1994ApJ...420L..33A Altcode:
The Hubble Space Telescope/Faint Object Spectrograph (HST/FOS) recorded
a remarkable transient brightening in the C IV lambda lambda 1548,50
emissions of the rapidly rotating Pleiades G dwarf H II 314. On the one
hand the 'flare' might be a rare event luckily observed; on the other
hand it might be a bellwether of the coronal heating in very young
solar-mass stars. If the latter, flaring provides a natural spin-down
mechanism through associated sporadic magnetospheric mass loss.

---------------------------------------------------------
Title: EUVE coronal spectroscopy of the RS CVn binaries σ2
CrB and II Peg.
Authors: Brown, A.; Linsky, J. L.; Dempsey, R.
1994BAAS...26R.865B Altcode:
No abstract at ADS

---------------------------------------------------------
Title: The Transition Regions of Capella
Authors: Linsky, J. L.; Wood, B. E.; Brown, A.; Andrulis, C.; Judge,
P.; Ayres, T. R.
1994ASPC...64...62L Altcode: 1994csss....8...62L
No abstract at ADS

---------------------------------------------------------
Title: X-Ray Emission from Chemically Peculiar Stars
Authors: Drake, S. A.; Linsky, J. L.; Schmitt, J. H. M. M.; Rosso, C.
1994ApJ...420..387D Altcode:
We have searched the Roentgen Satellite (ROSAT) All-Sky Survey
(RASS) database at the positions of about 100 magnetic Bp-Ap stars
of the helium-strong, helium-weak, silicon, and strontium-chromium
subclasses. We detect X-ray sources at the positions of 10 of these
stars; in four cases the X-ray emission presumably arises from an
early-type companion with a radiatively driven wind, while we believe
that the magnetic chemically peculiar (CP) star is the most likely
X-ray source (as opposed to a binary companion) in at least three and
at most five of the six remaining cases. The helium-strong stars have
X-ray emission levels that are characteristic of the luminous OB stars
with massive winds (log Lx/Lbol is about -7),
whereas the He-weak and Si stars (which generally show no evidence
for significant mass loss) have log Lx/Lbol
values that can reach as high as about -6. In contrast, we find no
convincing evidence that the cooler SrCrEu-type CP stars are intrinsic
X-ray sources. We discuss the X-ray and radio emission properties
of our sample of CP stars, and argue that both types of emission may
be magnetospheric in origin; however, there is clearly not a simple
one-to-one correspondence between them, since many of the magnetic stars
that are detected radio sources were not detected as X-ray sources in
the present survey.

---------------------------------------------------------
Title: Redshifts in Stellar Transition Regions
Authors: Linsky, J. L.; Wood, B. E.; Andrulis, C.
1994ASPC...64...59L Altcode: 1994csss....8...59L
No abstract at ADS

---------------------------------------------------------
Title: Dynamics and Energy Balance in Stellar Transition Regions
Cycle 3 Augmentation - Missing Exposure
Authors: Linsky, Jeffrey
1994hst..prop.5733L Altcode: 1994hst..prop.2174L
We will observe with 80,000 spectral resolution the stellar Lyman
alpha emission line and interstellar hydrogen and deuterium absorption
towards local late-type stars to derive the H and D column densities
and D/H ratios along different lines of sight. High resolution (90,000)
spectra of the MgII and FeII lines will help determine the interstellar
line broadening and whether material along each line of sight has more
than one velocity component. This is critical for accurate measurements
of D/H, because both the D and H lines are on or near the flat part of
the curve of growth. Previous IUE and Copernicus observations, which
had low signal/noise and inadequate spectral resolution, provided
very crude D/H values and suggested that the D/H ratio may vary
within a few parsecs of the Sun. We will measure D/H with at least
one order of magnitude improved precision and determine whether the
proposed local variations are real. The local value(s) of D/H may be
extrapolated to zero metal abundance to estimate the primordial value,
which is valuable for constraining cosmological models. THIS PHASE II
IS FOR OBSERVATION OF AN UNSCHEDULED CYCLE3 LYMAN ALPHA OBSERVATION
OF HR1099 AT ORBITAL PHASE 0.75.

---------------------------------------------------------
Title: Dynamics and Energy Balance in Stellar Transition Regions -
Repeat for HOPR#120
Authors: Linsky, Jeffrey
1994hst..prop.6153L Altcode: 1994hst..prop.2238L
We propose to study the dynamics of stellar transition regions by
measuring the redshifts, indicative of downflows, in lines of C III,
C IV, Si IV, and O IV.The energy balance and heating rates in stellar
chromospheres and transition regions will be derived from an emission
measure analysis of emission line fluxes and densities inferred
from density sensitive line ratios. This proposal is a repeat of a
failed repeat of a Cycle 1 observation of the C IV and Si IV of the
G supergiant Beta Draconis (HOPR 66 and 120).

---------------------------------------------------------
Title: The Relationship Between Radiative and Magnetic Fluxes on
Three Active Solar-type Dwarfs
Authors: Linsky, J. L.; Andrulis, C.; Saar, S. H.; Ayres, T. R.;
Giampapa, M. S.
1994ASPC...64..438L Altcode: 1994csss....8..438L
We present some preliminary results from our coordinated campaign of
IUE and McMath Telescope magnetic field measurements of three active
solar-type dwarf stars: 59 Vir, xi Boo A, and HD 131511. We observed
the three stars nearly every day from May 9 to May 25, 1993, covering
between 1 and 3 rotations. We explore the functional and spatial
relationship between magnetic and radiative fluxes.

---------------------------------------------------------
Title: The ROSAT All-Sky Survey of BY Draconis Coronae
Authors: Dempsey, Robert C.; Linsky, Jeffrey L.; Fleming, Thomas A.;
Schmitt, J. H. M. M.
1994ASPC...64...74D Altcode: 1994csss....8...74D
No abstract at ADS

---------------------------------------------------------
Title: Deuterium in the Local Interstellar Medium: its Cosmological
Significance
Authors: Linsky, J. L.; Diplas, A.; Savage, B.; Andrulis, C.; Brown, A.
1994ASSL..187..301L Altcode: 1994fsgb.book..301L
No abstract at ADS

---------------------------------------------------------
Title: Coronal Temperature Distributions and Convection-Zone Depth:
The F and G-type Dwarfs
Authors: Linsky, Jeffrey L.
1994euve.prop...82L Altcode:
We propose to obtain coronal temperature distributions for a
carefully selected sample of mid-F to mid-G type dwarfs using the EUVE
spectrometers to probe the mechanisms which give rise to hot and cool
coronal plasma in late-type, main-sequence stars. The five program
stars chosen meet five basic criteria. They a) are single stars, b)
are normal, main-sequence F5-G5 dwarfs, c) have measured rotational
velocities, d) have measured parallaxes, and e) have EUVE 100A survey
count rates in excess of 50 counts per kilosecond. These stars span
a critical spectral range where the depth of the outer convection
zone and, presumably, the level of magnetic heating increases with
decreasing effective temperature. EUVE spectra provide Fe lines covering
a broad range of ionization states to determine the emission measure
distribution independent of coronal abundance uncertainties. While
low-resolution Einstein IPC and ROSAT PSPC spectra hint at increasing
coronal temperatures from mid-F to mid-G, only with high-resolution
EUVE spectra can we derive the true emission measure distribution
across the full range of coronal plasma temperatures.

---------------------------------------------------------
Title: Local Interstellar Medium and D/h Ratio -- Repeat Alpha CEN
a and B -- Hopr 145
Authors: Linsky, Jeffrey
1994hst..prop.5712L Altcode: 1994hst..prop.2153L
We will observe with 80,000 spectral resolution the stellar Lyman
alpha emission line and interstellar hydrogen and deuterium absorption
towards local late-type stars to derive the H and D column densities
and D/H ratios along different lines of sight. High resolution (90,000)
spectra of the MgII and FeII lines will help determine the interstellar
line broadening and whether material along each line of sight has more
than one velocity component. This is critical for accurate measurements
of D/H, because both the D and H lines are on or near the flat part of
the curve of growth. Previous IUE and Copernicus observations, which
had low signal/noise and inadequate spectral resolution, provided very
crude D/H values and suggested that the D/H ratio may vary within a
few parsecs of the Sun. We will measure D/H with at least one order of
magnitude improved precision and determine whether the proposed local
variations are real. The local value(s) of D/H may be extrapolated
to zero metal abundance to estimate the primordial value, which is
valuable for constraining cosmological models. THIS IS A REPEAT OF
FAILED CYCLE 2 OBSERVATIONS (HOPR 145).

---------------------------------------------------------
Title: High Velocity Plasma in the Transition Region of AU Mic:
A Stellar Analog of Solar Explosive Events
Authors: Linsky, J. L.; Wood, B. E.
1994ASPC...64..441L Altcode: 1994csss....8..441L
No abstract at ADS

---------------------------------------------------------
Title: Search for Hot Plasmas in the Outer Atmospheres of K Giants -
Repeat of GTO1177 for HOPR#132 and 144
Authors: Linsky, Jeffrey
1994hst..prop.5647L Altcode: 1994hst..prop.2088L
We will measure the amount of plasma hotter than 10,000 K (or establish
small upper limits) in the outer atmospheres of K giant stars thought
to have little hot material. A second goal is to derive models of
the hot plasma in the transition regions of early K giants with
very low heating rates due to slow rotation and very weak magnetic
field generation. We will measure emission lines of C III, Si III,
C IV, Si IV, and N V in deep specta. Upper limits to the strength
of these emission lines will place stringent constraints on possible
nonradiative heating processes. Observations of weak intersystem lines
will provide estimates of the electron density needed for atmospheric
modeling. We will attempt to determine whether the hot plasma (and
the required heating) are global or isolated to small regions on the
star due to magnetic fields or stochastic heating processes. Echelle
resolution Mg II and O I emission profiles will be used for stellar
wind modeling. G140L exposures are returned to the proposal to detect
weak high temperature lines. THIS IS AN AMMENDED VERSION OF GTO 1177
WHICH FAILED IN CYCLE 2.

---------------------------------------------------------
Title: Transition Regions in Very Late M Dwarfs Cycle Later
Observations
Authors: Linsky, Jeffrey
1994hst..prop.5163L Altcode: 1994hst..prop.1667L
We propose to search for transition region emission lines indicative
of 1.0E+5 K plasma in the ultraviolet spectra of the coolest M dwarf
stars of both the dM and dMe types. With such data we will study the
heating rates and energy balance in the transition regions of these
stars and compare such data with stars of earlier spectral type. An
important question is whether transition regions disappear or have
significantly smaller heating rates in the late M dwarfs as is suggested
by the X-ray data.

---------------------------------------------------------
Title: An Efficient Way of Identifying New Active Stars: A VLA Survey
of X-Ray-Selected Active Stellar Candidates
Authors: Drake, S. A.; Simon, T.; Linsky, J. L.; White, N. E.
1994ASPC...64..690D Altcode: 1994csss....8..690D
No abstract at ADS

---------------------------------------------------------
Title: Stellar Coronal Structures (Concluding Review)
Authors: Linsky, J. L.
1994scs..conf..641L Altcode: 1994IAUCo.144..641L
Large magnetic structures in the coronae of stars containing gas at
a wide variety of temperatures are now being studied in X-rays, radio
wavelengths, and Hα. The author summarizes what we are learning about
coronal structures in three types of stellar systems: the magnetic
chemically peculiar stars, the RS CVn binary systems containing G-
and K-type subgiants, and active solar-type dwarfs like V471 Tauri
and AB Doradus.

---------------------------------------------------------
Title: The IUE Final Archive: Conception to Completion
Authors: Nichols-Bohlin, J.; de La Peña, M.; Linsky, J.; Kondo, Y.;
Michalitsianos, A.; Ponz, D.; Talavera, A.; González-Riestra, R.;
Wamsteker, W.
1994ASSL..187..715N Altcode: 1994fsgb.book..715N
No abstract at ADS

---------------------------------------------------------
Title: HST/GHRS studies of ζ Aurigae. I. GHRS observations of the
1993 eclipse.
Authors: Brown, A.; Linsky, J. L.; Bennett, P. D.; Harper, G. M.;
Baade, R.; Kirsch, T.; Reimers, D.
1993BAAS...25Q1321B Altcode:
No abstract at ADS

---------------------------------------------------------
Title: HST/GHRS Study of zeta Aurigae III. The Ionization Structure
of the Wind of zeta AUR A (K4 Ib)
Authors: Harper, Graham M.; Bennett, Philip D.; Brown, Alexander;
Linsky, Jeffrey L.
1993AAS...183.1810H Altcode: 1993BAAS...25.1322H
We present models of the ionization structure of the K4 Ib star wind
in the binary system zeta Aurigae for the epochs corresponding to
the Hubble Space Telescope (HST) observations of the 1993 eclipse. We
have modeled the atmospheric density structure using a description of
the winds from both components of the binary system. New models of
the K star chromosphere and wind are used to constrain the electron
temperatures and electron densities. Thermodynamic properties from
these atmospheric models combined with the radiation fields from
both stellar components have then been used to model the ionization
balance of H I/H II, Fe I/Fe II/Fe III and Si I/Si II/Si III. These
ionization models represent the first stage in interpreting the new HST
observations. The column densities deduced from selected absorption
features can then be used to derive new estimates of the density and
temperature structure in the K star wind. This work is supported by
HST Grant GO-3626.01-91A to the University of Colorado.

---------------------------------------------------------
Title: A Reanalysis of the Interstellar Medium along the Capella
Line of Sight
Authors: Linsky, J. L.; Diplas, A.; Ayres, T.; Wood, B.; Brown, A.
1993AAS...18311413L Altcode: 1993BAAS...25.1464L
We report on new GHRS/HST observations of the interstellar HI and DI
Lyman-alpha lines and the FeII and MgII resonance lines along the line
of sight toward the nearby (12.5 pc) star Capella. These observations
were obtained at orbital phase 0.80 when the combined stellar emission
lines had different shapes compared to those obtained in earlier
observations at phase 0.26 and analyzed by Linsky et al. (ApJ 402,
694 (1993)). By reversing the radial velocities of the two stars we
are better able to derive the intrinsic stellar profiles, especially
for the Lyman alpha line, and therefore to determine the interstellar
absorption lines more precisely. We compare the derived properties
of the local interstellar medium (D/H ratio, temperature, turbulent
velocity, hydrogen column density, and gas phase abundances) for Capella
at the two phases with the properties derived for the line of sight to
another nearby (3.5 pc) star Procyon. This work is supported by NASA
grant S-56460-D to the National Institute of Standards and Technology.

---------------------------------------------------------
Title: HST/GHRS Studies of zeta Aurigae II. A Non-LTE Model Atmosphere
Analysis of the B-Type Secondary
Authors: Bennett, Philip D.; Brown, Alexander; Linsky, Jeffrey L.
1993AAS...183.1809B Altcode: 1993BAAS...25R1321B
The TLUSTY model code of Hubeny &amp; Lanz are used to compute the B
star photospheric spectrum in the ultraviolet and optical regions. These
models treated H and He continua in NLTE, but the lines were assumed
to be in detailed balance. A few models were computed with 5 levels
of H and 14 levels of He I, plus continua, in NLTE. There were no
significant differences between the models with the lines treated in
detailed balance and in explicit NLTE. Solar abundances were assumed
throughout this study. Effective temperatures are derived by fitting
line profiles observed by the Hubble Space Telescope GHRS to the
computed synthetic spectra. We find T_eff= 15300 K, and a rotational
velocity of about 150 km s(-1) . The strengths of the Si II resonance
lines in the ultraviolet are shown to be anomalously weak in the
observed spectra, consistent with an overionization of Si II by 1.1
dex. Additional model atmospheres were computed treating the bound
levels of Si II and Si III and the corresponding continua explicitly in
NLTE. We will report on the results of these ongoing model studies of
zeta Aur B and present the latest estimates of the stellar parameters
(T_eff, log g, and vrot). This work is supported by HST
Grant GO-3626.01-91A to the University of Colorado.

---------------------------------------------------------
Title: HST/GHRS Studies of zeta Aurigae. I. GHRS Observations of
the 1993 Eclipse
Authors: Brown, Alexander; Linsky, Jeffrey L.; Bennett, Philip D.;
Harper, Graham M.; Baade, Robert; Kirsch, Thomas; Reimers, Dieter
1993AAS...183.1808B Altcode: 1993BAAS...25.1321B
The eclipsing binary zeta Aurigae (K4 Ib + B5 V) was observed
using the Goddard High Resolution Spectrograph (GHRS) on Hubble
Space Telescope (HST) at five epochs immediately preceeding and one
following the April 1993 eclipse of the the hot B-type secondary
by the K supergiant primary. A combination of Echelle-B and medium
resolution G160M spectra were obtained at phases 0.78, 0.948, 0.957,
0.972, 0.978 and 1.13. These observations sample the absorption of
the hot star's photospheric spectrum by the extended intervening cool
star atmosphere. The GHRS spectra are presented and the circumstances
of the individual observations are described. Fundamental parameters
of the binary system derived from these data are discussed. This work
is supported by HST grant GO-3626.01-91A to the University of Colorado.

---------------------------------------------------------
Title: The ROSAT All-Sky Survey of Active Binary Coronae. II. Coronal
Temperatures of the RS Canum Venaticorum Systems
Authors: Dempsey, Robert C.; Linsky, Jeffrey L.; Schmitt, J. H. M. M.;
Fleming, T. A.
1993ApJ...413..333D Altcode:
We present the results from an analysis of X-ray spectra of 44 RS CVn
systems obtained during the ROSAT All-Sky Survey with the Position
Sensitive Proportional Counter (PSPC). Thermal plasma models with
two temperature components are found to reproduce the observations
better than single or continuous temperature models. We typically
find that a bimodal distribution of temperatures centered near 2 x
10 exp 6 and 1.6 x 10 exp 7 K fit the data best. We show that the
PSPC temperatures agree well with those from similar low-resolution
measurements, although differences exist, primarily due to differing
detector bandpasses. After comparing coronal (either temperature
or emission measure) characteristics with stellar parameters
including rotation period and dynamo number, we find no compelling
relationship. The height-integrated emission measures of the components
in the two-temperature models, including a gravity term, are found to
be well correlated with temperature.

---------------------------------------------------------
Title: Hubble Telescope Research
Authors: Villard, Ray; Linsky, Jeffrey L.
1993Sci...261..665V Altcode:
No abstract at ADS

---------------------------------------------------------
Title: The ROSAT All-Sky Survey of Active Binary Coronae. I. Quiescent
Fluxes for the RS Canum Venaticorum Systems
Authors: Dempsey, Robert C.; Linsky, Jeffrey L.; Fleming, Thomas A.;
Schmitt, J. H. M. M.
1993ApJS...86..599D Altcode:
One hundred and thirty-six RS CV(n) active binary systems were observed
with the ROSAT Position Sensitive Proportional Counter (PSPC) during the
All-Sky Survey component of the mission. The entire sky was surveyed,
which represents the largest sample of RS CV(n) systems observed to
date at any wavelength, including X-rays. X-ray surface fluxes for
the RS CV(n) systems are found to lie in the range 10 exp 4 to 10 exp
8 ergs/sq cm seconds. Surface flux as a function of (B - V) color is
reported. A decrease in surface flux with increasing rotation period
for the entire sample is observed. The rotation period provides the
best stellar or orbital parameter to predict the X-ray surface flux
level. The absence of correlation of F(x) or L(x) with Gamma is noted
due to the fact that the coronal heating mechanism for these active
stars must be magnetic in character, and the magnetic field depends on
the interaction between convection and differential rotation inside
the star. X-ray properties of the RS CV(n) systems with 6 cm radio
and C IV UV emission systems is compared.

---------------------------------------------------------
Title: A ROSAT Wide Field Camera Survey of All Nondegenerate Stars
Within 10 PC
Authors: Wood, B. E.; Brown, A.; Linsky, J. L.; Bromage, G. E.;
Kellett, B. J.
1993AAS...182.4123W Altcode: 1993BAAS...25..864W
We will report on our ROSAT Wide Field Camera (WFC) survey of all
nondegenerate stars within 10 pc. Extreme ultraviolet (EUV) luminosity
functions will be constructed for each stellar spectral type represented
in this survey (F, G, K, and M) for comparison with each other and with
X-ray luminosity functions previously derived from Einstein Imaging
Proportional Counter (IPC) data. We will also study the effects of
binarity and stellar rotation rate on EUV luminosity. Since count
rates from different EUV and X-ray spectral ranges can be used to
determine possible coronal plasmas temperatures, the WFC count rates
(for both the S1 and S2 filters) have been analyzed together with
those of the Einstein IPC, the ROSAT Position Sensitive Proportional
Counter, and the EXOSAT Low Energy Telescope with the 3000 Angstroms
Lexan filter. We analyze in depth the advantages and limitations
of using count rates from these different bandpasses together to
constrain coronal temperatures. For a set of 18 stars in our survey,
we have compared temperature solutions computed using multi-filter
photometry with the IPC-derived temperature solutions of Schmitt et
al. (1990 ApJ 365, 704). In general, the two temperature fits derived
by the IPC are inconsistent with our results; our data imply that in
many cases, the two temperatures derived by the IPC may be too low by
about a factor of 2. While our analysis does suggest the existence
of more than one temperature in the coronae of late-type stars,
in many instances our data are inconsistent with the presence of a
broad temperature distribution. This, together with the success of two
temperature plasmas in fitting IPC data, implies that for many stars,
the coronal emission measure distribution is in fact dominated by two
distinct temperatures. This work is supported by NASA grants NAGW-2904
and NAG5-1792 to the University of Colorado.

---------------------------------------------------------
Title: A Remarkable FUV Flare on the Pleiades G Dwarf HZ 314
Authors: Ayers, T.; Basri, G.; Simon, T.; Stauffer, J.; Stern, R.;
Antiochon, S.; Bookbinger, J.; Brown, A.; Doschek, G.; Linsky, J.;
Ramsey, L.; Walter, F.
1993AAS...182.4611A Altcode: 1993BAAS...25..875A
No abstract at ADS

---------------------------------------------------------
Title: Coronal Spectroscopy and Structure of the RS CVn Binary HR1099
Using EUVE
Authors: Brown, A.; Linsky, J. L.; Wood, B.; Vedder, P. W.; Drake,
J. J.; Guinan, E. F.
1993AAS...182.3805B Altcode: 1993BAAS...25..856B
The RS CVn binary system HR1099 (V711 Tau) was observed by the Extreme
Ultraviolet Explorer (EUVE) satellite as a calibration target on
1992 October 22-24. Emission from the system is detected in both the
short (75-175 Angstroms) and medium (150-370 Angstroms) wavelength
EUVE spectrometers. No stellar signal is seen in the long wavelength
spectrum. Over 20 coronal and transition region emission lines are
present, along with continuum emission from hot (~ 107
K) coronal plasma at the shorter wavelengths. The short wavelength
spectrum is dominated by coronal lines from the hot 107
K coronal component; the highest excitation line definitely present is
Fe XXIII 132.8 Anstroms. The medium wavelength spectrum is dominated by
He II 304 Anstroms from transition region (105 K) plasma. The
volume emission measure (VEM) distribution of HR1099 is determined over
the temperature range 105 to over 107 K. This
distribution is compared with previous broadband X-ray estimates
of the coronal temperature and VEM for HR1099. The implications of
these data for the likely coronal structure of active binaries like
HR1099 are discussed. This work is supported by NASA grant NAGW-2904
to the University of Colorado. We thank the EGO Center staff at CEA
for their assistance.

---------------------------------------------------------
Title: Deuterium in the Line of Sight Towards Procyon and its
Cosmological Significance
Authors: Linsky, J. L.; Diplas, A.; Andrulis, C.; Brown, A.; Savage,
B.; Ebbets, D.
1993AAS...182.0806L Altcode: 1993BAAS...25..804L
We will report here on our ongoing program to measure the
deuterium/hydrogen (D/H) ratio and interstellar gas properties along
many lines-of-sight through the local interstellar medium using the
HST Goddard High Resolution Spectrograph. We have previously reported
(ApJ 402, 694 (1993)) that for the line-of-sight towards Capella (12.5
pc, l=163(deg) , b=+5(deg) ) that D/H = 1.65 (+0.07, -0.18) *E(-5) ,
T = 7,000+/-200 K and the turbulent velocity is 1.66+/-0.03 km s(-1)
. These quantities were determined by modeling the interstellar hydrogen
and deuterium Lyman-alpha lines and the resonance lines of FeII and
MgII against the background stellar emission line profiles. We now
report on the analysis of these spectral lines for the line-of-sight
towards Procyon (3.5 pc, l=214(deg) , b=+13(deg) ). Our new data set
consists of very high signal-to-noise G160M spectra of the Lyman-alpha
lines and Echelle spectra of the FeII 2599 Angstroms and MgII 2796,
2803 Angstroms lines. Comparison of these new data with those for the
Capella line-of-sight will provide information on the nonuniformity
of the local interstellar medium and begin to tell us whether the D/H
ratio is constant or varies with line-of-sight in the local interstellar
medium. We infer the primordial value of D/H from Galactic evolution
models and comment on the inferred baryon density of the Universe. This
work is supported by NASA grants, including Interagency Transfer
No. S-56460-D to the NIST.

---------------------------------------------------------
Title: Observations of 3C 273 With the Goddard High Resolution
Spectrograph on the Hubble Space Telescope
Authors: Brandt, J. C.; Heap, S. R.; Beaver, E. A.; Boggess, E. A.;
Carpenter, K. G.; Ebbets, D. C.; Hutchings, J. B.; Jura, M.; Leckrone,
D. S.; Linsky, J. L.; Maran, S. P.; Savage, B. D.; Smith, A. M.;
Trafton, L. M.; Walter, F. M.; Weymann, R. J.; Snow, M.; Randall,
C. E.; Lindler, D. J.; Shore, S. N.; Morris, S. L.; Gilliland, R. L.;
Lu, L.; Robinson, R. D.
1993AJ....105..831B Altcode:
The observations of the quasar 3C 273 taken with the Goddard High
Resolution Spectrograph in 1991 February are presented here. We have
included both the reduced raw data, and smoothed and deconvolved
spectra. Also, a list of observed absorption lines is presented. The
data comprise 11 spectra, including 1 low resolution observation and 10
medium resolution observations. The wavelength region covered ranged
from about 1150 to 2820 A, but was not all inclusive. The procedures
used to obtain and reduce the data, including corrections for fixed
pattern noise, compensation for the effects of spherical aberration
in the HST primary mirror, and objective detection of weak absorption
lines, are described. We also have included a short discussion on the
detection of galactic Ni II and Virgo cluster metal lines.

---------------------------------------------------------
Title: Scientific rationale and present implementation strategy for
the Far Ultraviolet Spectrograph Explorer (FUSE).
Authors: Linsky, J. L.
1993MmSAI..64..323L Altcode:
No abstract at ADS

---------------------------------------------------------
Title: Radio and X-Ray Emissions from Chemically Peculiar B-Stars
and A-Type Stars - Observations and a Model
Authors: Linsky, J. L.
1993ASPC...44..507L Altcode: 1993IAUCo.138..507L; 1993pvnp.conf..507L
No abstract at ADS

---------------------------------------------------------
Title: Radiative and Magnetic Properties of Plages on Solar-Type
Dwarfs
Authors: Linsky, Jeffrey L.
1993iue..prop.4549L Altcode:
Our objective is to determine the functional and spatial relationship
between magnetic and radiative fluxes on the surfaces of solar-like
stars. While these relationships are known for the Sun and are
consistent with a very limited set, of observations of one star, xi
Boo A, we believe that a major accomplishment of IUE in its remaining
years would be to establish these functional relationships definitively
for solar-like stars. We will obtain a sequence of spectra for three
active solar-type dwarfs: 59 Vir (GO V), Xi Boo A (G8 V), and HD
131511 (K1 V), because they are among the brightest solartype dwarfs
that show large rotational modulation, have rotational periods of
5-10 days, do not rotate too fast for magnetic field observations,
and he dose enough together in the sky. Crude surface brightness
maps in the CII, CIV and Mg II will be compared with simultaneous
ground-based observations of the magnetic field strength, the magnetic
filling factor, and the net, transverse magnetic field (as measured by
broadband linear polarization). These maps will provide estimates of
plage areas and surface brightnesses. Our IUE data will serve as a basis
for realistic two-component models (quiet+plage) for the chromospheres
and transition-regions of active solar-like dwarfs. The new observations
of Xi Boo A can be compared with those made in June 1986 to study the
evolution of magnetic features on magnetic cycle timescales. We propose
this ambitious observing program while IUE is still operating. One
of IUE's great, strengths is that it can monitor stars daily to study
variations in their ultraviolet spectra. No other satellite, existing or
under construction, can accomplish this important task. The observations
are deliberately planned to extend over 2 rotational periods in order
to separate secular flux variations from the rotational modulation of
an inhomogeneous spatial distribution of brightness across the stellar
surface, which is our indicator of the presence and sizes of plages.

---------------------------------------------------------
Title: Physics of Solar and Stellar Coronae
Authors: Linsky, Jeffrey L.; Serio, Salvatore
1993ASSL..183.....L Altcode: 1993pssc.symp.....L
No abstract at ADS

---------------------------------------------------------
Title: The ROSAT All-Sky Survey of Active Binary Coronae: The RS
CVn Systems
Authors: Dempsey, R. C.; Linsky, J. L.; Fleming, T. A.; Schmitt,
J. H. M. M.; Kürster, M.
1993ASSL..183..361D Altcode: 1993pssc.symp..361D
No abstract at ADS

---------------------------------------------------------
Title: The Hydrogen Lyman-Alpha Emission of Capella
Authors: Ayres, Thomas R.; Brown, A.; Gayley, K. G.; Linsky, Jeffrey L.
1993ApJ...402..710A Altcode:
We describe the hydrogen Ly-alpha emission of the spectroscopic
binary Capella (G8 III + GO III) recorded at 0.1 A resolution by the
International Ultraviolet Explorer. The overt changes in the composite
line shape with orbital phase are controlled by the active GO III
star and permit a dissection of the stellar components despite the
obliteration of the central portion of the profile by atomic hydrogen
and deuterium absorption along the 12.5 pc sightline. The Ly-alpha line
shape of the active GO III star is surprisingly asymmetric and possibly
is variable. Both characteristics suggest a stellar wind of moderate
excitation (20,000-100,000 K), a key component of the coronal evolution
scenario of Simon and Drake (1989) for the Hertzsprung-gap giants.

---------------------------------------------------------
Title: Goddard High-Resolution Spectrograph Observations of the Local
Interstellar Medium and the Deuterium/Hydrogen Ratio along the Line
of Sight toward Capella
Authors: Linsky, Jeffrey L.; Brown, Alexander; Gayley, Ken; Diplas,
Athanassios; Savage, Blair D.; Ayres, Thomas R.; Landsman, Wayne;
Shore, Steven N.; Heap, Sara R.
1993ApJ...402..694L Altcode:
HST Goddard High-Resolution Spectrograph observations of the 1216,
2600, and 2800 A spectral regions are analyzed for the spectroscopic
binary system Capella, obtained at orbital phase 0.26 with 3.27-3.57
km/s resolution and high SNR. The column densities of H I, D I, Mg II,
and Fe II for the local interstellar medium along this 12.5 pc line
of sight, together with estimates of the temperature and turbulent
velocity are inferred. It is inferred that the atomic deuterium/hydrogen
ratio by number is 1.65(+0.07, -0.18) x 10 exp -5 for this line of
sight. Galactic evolution calculations indicate that the primordial
D/H ratio probably lies in the range of (1.5-3) x (D/H)LISM. If H0 =
80 km/s Mpc, as recent evidence suggests, then the baryonic density in
units of the Einstein-de Sitter closure density is 0.023-0.031. Thus
the universe is argued to expand forever, unless nonbaryonic matter
greatly exceeds the amount of baryonic matter.

---------------------------------------------------------
Title: A-type and Chemically Peculiar Stars
Authors: Linsky, J. L.
1993ASSL..183..257L Altcode: 1993pssc.symp..257L
No abstract at ADS

---------------------------------------------------------
Title: Debunking the Myth of Two-Temperature Coronae for RS CVn
Systems Using Contemporaneous
Authors: Linsky, Jeffrey L.
1993euve.prop..109L Altcode:
For many years the standard analysis of low energy resolution x-ray
observations of active late-type stars with the IPC, PSPC, TGS,
and SSS has been to assume that the stellar coronae have plasma at
only two temperatures. This type of analysis is constrained by the
small information content and limited bandpass of the data but has NO
PHYSICAL BASIS WHATSOEVER. We propose to test this hypothesis and to
go beyond it to derive continuous emission measure distributions for
the coronae of three very bright RS CVn systems (sigma-2 Cor Bor, UX
Ari and VY Ari) using CONTEMPORANEOUS high resolution EUVE spectra and
the improved x-ray energy resolution of ASCA. EUVE provides Fe lines
with a broad range of ionization to derive the emission measure EM(T)
independent of any uncertainties in the coronal abundances, while ASCA
provides information on the hot plasma as seen in blended features of
Mg, Si, S, and Fe and can test for coronal abundances different from
the photosphere. We will model the quiescent and flare emission with
magnetic loops.

---------------------------------------------------------
Title: The Distant Future of Solar Activity: A Case Study of beta
Hydri. III. Transition Region, Corona, and Stellar Wind
Authors: Dravins, D.; Linde, P.; Ayres, T. R.; Linsky, J. L.;
Monsignori-Fossi, B.; Simon, T.; Wallinder, F.
1993ApJ...403..412D Altcode:
The paper investigates the secular decay of solar-type activity
through a detailed comparison of the present sun with the very old
solar-type star, Beta Hyi, taken as a proxy of the future sun. Analyses
of successive atmospheric layers are presented, with emphasis of the
outermost parts. The FUV emission lines for the transition zone are
among the faintest so far seen in any solar-type star. The coronal soft
X-ray spectrum was measured through different filters on EXOSAT and
compared to simulated X-ray observations of the sun seen as a star. The
flux from Beta Hyi is weaker than that from the solar corona and has
a different spectrum. It is inferred that a thermally driven stellar
wind can no longer be supported, which removes the mechanism from
further rotational braking of the star through a magnetic stellar wind.

---------------------------------------------------------
Title: Dynamic phenomena on the RS Canum Venaticorum binary II Pegasi
in August 1989. I. Observational data.
Authors: Doyle, J. G.; Kellett, B. J.; Butler, C. J.; Byrne, P. B.;
Neff, J. E.; Brown, A.; Fox, D.; Linsky, J. L.; Bromage, G. E.;
Avgoloupis, S.; Mavridis, L. N.; Seiradakis, J. H.; Mathioudakis,
M.; Murphy, H. M.; Krzesinski, J.; Pajdosz, G.; Dadonas, V.;
Sperauskas, J.; van Wyk, F.; Marang, F.; Olah, K.; Collier Cameron,
A.; Antonomoulos, E.; Rovithis, P.; Rovithis-Livaniou, H.
1992A&AS...96..351D Altcode:
Observational results are given for two flares in Pi Pegasi that were
detected by the GINGA and IUE satellites, as well as by ground-based
Johnson U-band photometry and optical spectroscopy. The best-fitting
results were obtained for a combination of a single-temperature
plasma together with a power law; for a two-temperature model, the
temperature of the second component was very high due to the tail in
the photon distribution.

---------------------------------------------------------
Title: Stellar Coronal EUV Emission Observed with the ROSAT Wide
Field Camera
Authors: Brown, A.; Bromage, G.; Schmitt, J.; Ambruster, C.; Linsky,
J. L.
1992AAS...181.8012B Altcode: 1992BAAS...24.1251B
The Wide Field Camera (WFC) on the ROSAT satellite conducted the first
all-sky survey in the extreme ultraviolet (EUV) over the six month
period beginning on 1990 July 30. Two survey filters were used peaking
at 95 and 120 Angstroms . Many of the sources detected are coronal
stars. We present detailed results from WFC survey data for a range of
coronal stars, including a complete survey of the RS CVn systems in the
Strassmeier catalog (40% detection rate), the EUV variability of the
flare star EV Lac (including the largest flare seen by the WFC from a
coronal source), the EUV rotation-activity relation for a homogeneous
sample of single early K dwarfs, and WFC results forming part of the
RIASS (ROSAT-IUE-All-Sky-Survey) campaign. This work is supported by
NASA grant NAG 5-1792 to the University of Colorado.

---------------------------------------------------------
Title: Models for the Transition Regions of gamma Draconis and
Capella based on Hubble GHRS Spectra
Authors: Linsky, J. L.; Andrulis, C.; Brown, A.
1992AAS...181.5107L Altcode: 1992BAAS...24.1206L
We have analyzed Goddard High Resolution Spectrometer observations of
the hybrid-chromosphere star gamma Draconis (K5 III) and the long-period
RS CVn system alpha Aurigae (Capella, G8 III + G0 III) observed at phase
0.26. Here we discuss the low resolution spectra obtained with the G140L
grating that cover the 1057--1943 Angstroms region for gamma Dra and the
1161--1710 Angstroms region for Capella. We identify the emission lines
and tabulate their observed fluxes and surface fluxes. Assuming that
most of the emission line flux from Capella is produced by the G0 III
star, we find that the surface fluxes of the transition region lines are
typically 400 times larger than for the Sun and only a factor of 4 below
the saturation limit. By contrast, the surface fluxes of the transition
region lines for gamma Dra are a factor of 40 times smaller than for
the Sun and are the smallest values ever detected for a star. We have
derived models for the transition regions of gamma Dra and the Capella
G0 III star covering the temperature range 20,000--150,000 K by an
emission measure analysis of the emission line surface fluxes. One
interpretation of the gamma Dra model is that the high-temperature
material occurs in magnetically heated active regions that cover ~
10(-4) by area of the surface. Another interpretation is that the very
small amount of hot material occurs in a few very strong shock waves
that can occur when there is a stochastic distribution of acoustic
wave periods. This work is supported by NASA Interagency Transfer
S-56500-D to the National Institute of Standards and Technology. (1)
Staff member, Quantum Physics Division, National Institute of Standards
and Technology.

---------------------------------------------------------
Title: Plasma Flows in the Outer Atmosphere of α Ori
Authors: Carpenter, K.; Robinson, R.; Wahlgren, G.; Brandt, J.;
Linsky, J.; Ebbets, D.; Weymann, R.
1992AAS...181.5111C Altcode: 1992BAAS...24.1207C
No abstract at ADS

---------------------------------------------------------
Title: Radio Continuum and X-Ray Properties of the Coronae of RS
Canum Venaticorum and Related Active Binary Systems
Authors: Drake, Stephen A.; Simon, Theodore; Linsky, Jeffrey L.
1992ApJS...82..311D Altcode:
Data from circular polarization measurements are reported which yield
radio-continuum and X-ray characterizations of the coronae of active
binaries including RS CVn. The circular polarization measurements are
taken at 6 cm for 28 binary systems detected at flux densities of more
than 0.7 mJy, and the data are examined in conjunction with those
by Drake et al. (1989). Optical positions are derived for 8 RS CVn
objects, three previous detections are confirmed, and seven sources
are shown to have circular polarization at levels of 2-13 percent. A
total of 49 X-ray sources are confirmed in a total of 190 positions,
and the correlation between X-ray and radio emissions is analyzed. No
observational evidence exists to support the notion that radio and
X-ray emissions are due to nonthermal electrons, and the data provide
evidence for and against thermal gyrosynchrotron radio emission.

---------------------------------------------------------
Title: Radio Emission from Chemically Peculiar Stars
Authors: Linsky, Jeffrey L.; Drake, Stephen A.; Bastian, T. S.
1992ApJ...393..341L Altcode:
In five VLA observing runs the initial survey of radio emission from
magnetic Bp-Ap stars by Drake et al. is extended to include a total of
16 sources detected at 6 cm out of 61 observed, giving a detection rate
of 26 percent. Of these stars, three are also detected at 2 cm, four at
3.6 cm, and five at 20 cm. The 11 new stars detected as radio sources
have spectral types B5-A0 and are He-weak and Si-strong. No classical
(SrCrEu-type) Ap stars have yet been detected. The 16 detected sources
show a wide range of radio luminosities with the early-B He-S stars on
average 20 times more radio luminous than the late-B He-W stars and 1000
times more luminous than Theta Aurigae. Multifrequency observations
indicate flat spectra in all cases. Four stars have a detectable
degree of circular polarization at one or more frequencies. It is
argued that the radio-emitting CP (chemically peculiar) stars form a
distinct class of radio stars that differs from both the hot star wind
sources and the active late-type stars. The observed properties of radio
emission from these stars may be understood in terms of optically thick
gyrosynchrotron emission from a nonthermal distribution of electrons
produced in a current sheet far from the star. In this model the
electrons travel along magnetic fields to smaller radii and higher
magnetic latitudes where they mirror and radiate microwave radiation.

---------------------------------------------------------
Title: Local Interstellar Medium and D/h Ratio -- Cycle 3 Baseline
Time - Medium Priority
Authors: Linsky, Jeffrey
1992hst..prop.4873L Altcode:
We will observe with 20,000 spectral resolution the stellar Lyman
alpha emission line and interstellar hydrogen and deuterium absorption
towards local late-type stars to derive the H and D column densities
and D/H ratios along different lines of sight. High resolution (90,000)
spectra of the MgII and FeII lines will help determine the interstellar
line broadening and whether material along each line of sight has more
than one velocity component. This is critical for accurate measurements
of D/H, because both the D and H lines are on or near the flat part of
the curve of growth. Previous IUE and Copernicus observations, which
had low signal/noise and inadequate spectral resolution, provided very
crude D/H values and suggested that the D/H ratio may vary within a
few parsecs of the Sun. We will measure D/H with at least one order of
magnitude improved precision and determine whether the proposed local
variations are real. The local value(s) of D/H may be extrapolated
to zero metal abundance to estimate the primordial value, which is
valuable for constraining cosmological models.

---------------------------------------------------------
Title: Dynamics and Energy Balance in Stellar Transition Regions
Cycle 3 Augmentation - High Priority
Authors: Linsky, Jeffrey
1992hst..prop.4874L Altcode:
We will observe with 20,000 spectral resolution the stellar Lyman
alpha emission line and interstellar hydrogen and deuterium absorption
towards local late-type stars to derive the H and D column densities
and D/H ratios along different lines of sight. High resolution (90,000)
spectra of the MgII and FeII lines will help determine the interstellar
line broadening and whether material along each line of sight has more
than one velocity component. This is critical for accurate measurements
of D/H, because both the D and H lines are on or near the flat part of
the curve of growth. Previous IUE and Copernicus observations, which
had low signal/noise and inadequate spectral resolution, provided very
crude D/H values and suggested that the D/H ratio may vary within a
few parsecs of the Sun. We will measure D/H with at least one order of
magnitude improved precision and determine whether the proposed local
variations are real. The local value(s) of D/H may be extrapolated
to zero metal abundance to estimate the primordial value, which is
valuable for constraining cosmological models.

---------------------------------------------------------
Title: X ray observations of late-type stars using the ROSAT all-sky
survey
Authors: Linsky, Jeffrey L.; Fleming, Thomas A.
1992colo.rept.....L Altcode:
The ROSAT mission made the first x ray survey of the entire sky using
an imaging detector. Although ROSAT is a joint NASA/German project
and involves direct American participation during its second phase
of pointed observations, the all-sky survey remains the sole property
of the German investigators. NASA grant represented the first use of
ROSAT data analysis funds to support direct American participation
in the ROSAT all-sky survey. The project involved a collaborative
agreement between the Joint Institute for Laboratory Astrophysics
(JILA) and the Max-Planck-Institut fur Extraterrestrische Physik (MPE)
where JILA supplied MPE with a post-doctoral research associate with
experience in the field of stellar (coronal) x ray emission to work
within their ROSAT group. In return, members of the cool star research
group at JILA were given the opportunity to collaborate on projects
involving ROSAT all-sky survey data. Both sides have benefitted (and
still benefit) from this arrangement since MPE suffers from a shortage
of researchers who are interested in x ray emission from 'normal'
stars and white dwarfs. MPE has also drawn upon experience in optical
identification of x ray sources from the Einstein Extended Medium
Sensitivity Survey in planning their own identification strategies for
the ROSAT all-sky survey. The JILA cool stars group has benefitted since
access to all-sky survey data has expanded the scope of their already
extensive research programs involving multiwavelength observations
of late-type stars. ROSAT was successfully launched on 1 June 1990
and conducted the bulk of the survey from 30 July 1990 to 25 January
1991. Data gaps in the survey have subsequently been made up. At
the time of this writing (February 1992), the survey data have been
processed once with the Standard Analysis Software System (SASS). A
second processing will soon begin with improvements made to the SASS to
correct errors and bugs found while carrying out scientific projects
with data from the first processing. We outline the major research
activities of Dr. Fleming over the past year (detailed accounts of his
activities during the first two years of this grant can be found in the
first-year and second-year status reports on this grant). Regarding the
three specific projects which were proposed in the original proposal,
two of them (White Dwarfs and Late M Dwarfs) are near completion. The
results are described in two conference proceedings which are appended.

---------------------------------------------------------
Title: The Chromosphere and Circumstellar Shell of α Orionis as
Observed with the Goddard High Resolution Spectrograph
Authors: Carpenter, K. G.; Robinson, R. D.; Wahlgren, G. M.; Linsky,
J. L.; Brown, A.
1992ESOC...44..387C Altcode: 1992swhs.conf..387C
No abstract at ADS

---------------------------------------------------------
Title: First Results from a Coordinated ROSAT; lUE; VLA Study of RS
CVn Systems
Authors: Linsky, J. L.; Fox, D.; Brown, A.; Dempsey, R.; Schmitt,
C.; Schmitt, J. H. M. M.; Fleming, T.; Rodono, M.; Pagano, I.; Neff,
J. E.; Bromage, G.
1992ASPC...26..106L Altcode: 1992csss....7..106L
No abstract at ADS

---------------------------------------------------------
Title: The Class of RadioEmitting Magnetic B Stars; a Wind-Fed
Magnetospheric Model
Authors: Linsky, J. L.; Drake, S. A.; Bastian, T. S.
1992ASPC...26..325L Altcode: 1992csss....7..325L
No abstract at ADS

---------------------------------------------------------
Title: New Stellar Plasma Density Determinations by the GHRS: the
Transition Regions of Capella and Gamma Draconis
Authors: Linsky, J. L.; Wood, B.; Brown, A.
1992ESOC...44..287L Altcode: 1992swhs.conf..287L
No abstract at ADS

---------------------------------------------------------
Title: Atomic Data Needed for Far Ultraviolet Astronomy with HUT
and FUSE
Authors: Linsky, J. L.
1992LNP...407...33L Altcode: 1992amds.conf...33L
I will summarize the spectroscopic capabilities of existing and planned
space experiments, including HUT and FUSE, that will obtain spectra of
astronomical sources at wavelengths shorter than Lyman-α. The important
atomic and molecular data needed to analyze far and extreme ultraviolet
spectra that will be obtained with these instruments include accurate
wavelengths, oscillator strengths, photoionization cross sections
for six important molecules, and, especially, electron collisional
excitation cross sections for both low and high stages of ionization.

---------------------------------------------------------
Title: The deuterium abundance in the local interstellar medium
Authors: Linsky, J. L.
1992HiA.....9..455L Altcode:
No abstract at ADS

---------------------------------------------------------
Title: GHRS Observations of the Local Interstellar Medium and the
Deuterium/Hydrogen Ratio toward Capella
Authors: Linsky, J. L.
1992ESOC...44...33L Altcode: 1992swhs.conf...33L
No abstract at ADS

---------------------------------------------------------
Title: Ultraviolet observations of stellar coronae : early results
from HST.
Authors: Linsky, Jeffrey L.
1992MmSAI..63..577L Altcode:
The first GHRS spectra of two very different late-type giant stars -
Capella and Gamma Dra are reported. Capella is a 104 day period binary
system consisting of two stars (G9 III and GO III) each of which
shows bright emission lines formed in solar-like transition region
and coronae. By contrast, Gamma Dra is a hybrid-chromosphere star with
very weak emission lines from high-temperature plasma. Low-dispersion
spectra of these stars covering the 1160 to 1717 A spectral range
show unresolved emission lines from neutral species through N V. The
very different surface fluxes detected in the spectra of these stars
suggest different types of heating mechanisms.

---------------------------------------------------------
Title: Atomic data needed for FUV astronomy with HUT and FUSE
Authors: Linsky, J. L.
1992HiA.....9..571L Altcode:
No abstract at ADS

---------------------------------------------------------
Title: HST Observations of the Flare Star AU MIC
Authors: Robinson, R. D.; Shore, S. N.; Carpenter, K. G.; Woodgate,
B. E.; Maran, S. P.; Brandt, J. C.; Kundu, M. R.; White, S. M.;
Linsky, J. L.; Walter, F. M.
1992ASPC...26...31R Altcode: 1992csss....7...31R
No abstract at ADS

---------------------------------------------------------
Title: Relationship of Starspots to Other Indicators of Stellar
Activity (Invited)
Authors: Linsky, Jeffrey L.
1992LNP...397..113L Altcode: 1992sils.conf..113L
No abstract at ADS

---------------------------------------------------------
Title: A Multiwavelength Campaign of Active Stars w/Intermediate
Rotation Rates
Authors: Linsky, Jeffrey L.
1992iue..prop.4255L Altcode:
Although the Sun is a very slowly-rotating (v, sin i = 2 km s^-1)
inactive star, images made in high temperature UV emission lines
reveal bright plage regions located above or near dark sunspots. This
indicates that magnetic fields control the local heating rate, density
and energy balance even for an inactive star. Very active rapidly
rotating stars like AR Lac show bright plage regions that are spatially
correlated with dark starspots. In this proposal we ask the question: Do
moderately active stars with moderately rapid rotation (v sin i = 20-30
km s^-1) show the same pattern? Intuitively, we would answer yes, but
astrophysics is full of non-intuitive surprises, and this question has
never been answered. We will test this hypothesis by obtaining spectra
of the Mg II and C IV 1548, 1550A lines to study the size and location
of plages in the chromosphere and transition region of a dwarf and a
giant star which both have v sin i - 25 km s^-1. We will use the CIII]
1909A and SiIII] 1892A intersystem lines to study the electron density
and the amount of 30,000 to 60,000 K material in the plage transition
regions. A unique aspect of our program will be the simultaneous
ground based and IUE observations to provide details on the spatial,
temperature, pressure and magnetic properties of inhomogeneities in the
outer atmosphere. This will lead to a fairly complete, 3-dimensional
picture of these active stars from the photosphere to the transition
region and, in one case, the corona. The two target systems have the
same rotation rates but very different gravities: IM Peg is a 24 day
system with a K1 giant, primary, whereas V815 Her is a 1.8 day system
with a G5 dwarf primary. We wish to study these different systems to
determine whether a factor of 100 deference in gravity changes the
spatial relation between spots and plages and whether it changes the
temperature-density structures in the plage regions appreciably. It
is important to observe both stars, but the program would still be
interesting if only one target is approved.

---------------------------------------------------------
Title: A High-Sensitivity Survey of Radio Continuum Emission in
Herbig Ae/Be Stars
Authors: Skinner, S. L.; Brown, A.; Linsky, J. L.; Stewart, R. T.
1992ASPC...26..331S Altcode: 1992csss....7..331S
No abstract at ADS

---------------------------------------------------------
Title: Four Years of Monitoring a Orionis with the VLA: Where have
all the Flares Gone?
Authors: Drake, S. A.; Bookbinder, J. A.; Florkowski, D. R.; Linsky,
J. L.; Simon, T.; Stencel, R. E.
1992ASPC...26..455D Altcode: 1992csss....7..455D
No abstract at ADS

---------------------------------------------------------
Title: FUSE - The Far Ultraviolet Spectrograph Explorer
Authors: Linsky, J. L.
1992ASPC...26..622L Altcode: 1992csss....7..622L
No abstract at ADS

---------------------------------------------------------
Title: Ultraviolet observations of stellar coronae: early results
from HST
Authors: Linsky, J. L.
1992HiA.....9..657L Altcode:
No abstract at ADS

---------------------------------------------------------
Title: The distant future of solar activity: a case study of beta
Hydri (abstract)
Authors: Dravins, D.; Linde, P.; Ayres, T. R.; Fredga, K.; Gahm, G.;
Lindegren, L.; Linsky, J. L.; Monsignori-Fossi, B.; Nordlund, Å.;
Simon, T.; Vandenberg, D.; Wallinder, F.
1992sccw.conf..105D Altcode:
No abstract at ADS

---------------------------------------------------------
Title: IUE Observations of Solar-Type Stars in the Pleiades and
the Hyades
Authors: Caillault, Jean-Pierre; Vilhu, Osmi; Linsky, Jeffrey L.
1991ApJ...383..594C Altcode:
An extensive set of IUE observations of solar-type stars (spectral
types F5-G5) in the Pleiades is presented. Spectra were obtained in
January and August 1988 for both the transition region and chromospheric
emission wavelength regions, respectively. Mg II fluxes were detected
for two out of three Pleiades stars and C IV upper limits for two of
these stars. Long-wavelength high-resolution spectra were also obtained
for previously unobserved solar-type stars in the Hyades. With the
inclusion of spectra of additional Hyades stars obtained from the IUE
archives, surface fluxes and fractional luminosities for both clusters'
solar-type stars are calculated; these values provide a better estimate
for the Mg II saturation line for single stars.

---------------------------------------------------------
Title: Studies of H i and D i in the Local Interstellar Medium:
Erratum
Authors: Murthy, J.; Henry, R. C.; Moos, H. W.; Vidal-Madjar, A.;
Linsky, J. L.; Gry, C.
1991ApJ...378..455M Altcode:
No abstract at ADS

---------------------------------------------------------
Title: An Investigation of the Flare Star AU Mic with the Goddard
High Resolution Spectrograph on the Hubble Space Telescope
Authors: Maran, S. P.; Woodgate, B. E.; Carpenter, K. G.; Robinson,
R. D.; Shore, S. N.; Linsky, J. L.; Brown, A.; Byrne, P. B.; Kundu,
M. R.; White, S.; Brandt, J. C.; Shine, R. A.; Walter, F. M.
1991BAAS...23.1382M Altcode:
No abstract at ADS

---------------------------------------------------------
Title: Coordinated IUE/HST Observations of the Flare Star AU mic:
Results from IUE
Authors: Carpenter, K. G.; Maran, S. P.; Brown, A.; Linsky, J. L.;
Robinson, R. D.; Byrne, P. B.; Judge, P. G.
1991BAAS...23.1383C Altcode:
No abstract at ADS

---------------------------------------------------------
Title: Time Resolved Observations of the Lyman-Alpha Region in AU
Mic with the Goddard High Resolution Spectrograph
Authors: Woodgate, B. E.; Maran, S. P.; Carpenter, K. G.; Robinson,
R. D.; Shore, S. N.; Linsky, J. L.; Byrne, P. B.; Kundu, M. R.
1991BAAS...23.1383W Altcode:
No abstract at ADS

---------------------------------------------------------
Title: GHRS Observations of the Local Interstellar Medium and the
D/H Ratio Along the Line of Sight towards Capella
Authors: Linsky, J. L.; Brown, A.; Gayley, K.; Landsman, W.; Heap,
S. R.; Savage, B. D.; Diplas, A.
1991BAAS...23.1341L Altcode:
No abstract at ADS

---------------------------------------------------------
Title: First Results from the Goddard High-Resolution Spectrograph:
The Chromosphere of alpha Tauri
Authors: Carpenter, Kenneth G.; Robinson, Richard D.; Wahlgren,
Glenn M.; Ake, Thomas B.; Ebbets, Dennis C.; Linsky, Jeffrey L.;
Brown, Alexander; Walter, Frederick M.
1991ApJ...377L..45C Altcode:
The K5 III star Alpha Tau was observed with the Goddard High Resolution
Spectrograph on November 27, 1990 as part of the Science Assessment
Program for the HST. The spectra show intersystem and permitted
chromospheric emission lines of semiforbidden C II and Si II, Fe II,
Fe I, Ni II, and Co II. Resolved profiles of the semiforbidden C II
lines indicate a complex chromospheric turbulent velocity distribution
with mean value of roughly 24 km/s, while their observed wavelengths
indicate a 4 km/s downflow of the semiforbidden C II plasma. Twenty-five
new emission lines have been found in the 2320-2370 A region, 17 of
which have been identified with the aid of Skylab data obtained above
the solar limb, including four lines from Co II (UV 8) and an Fe I
(UV 12) line.

---------------------------------------------------------
Title: Radiative transfer in the dynamic atmospheres of Mira-type
variables
Authors: Linsky, Jeffrey L.; Luttermoser, Donald G.
1991colo.reptQ....L Altcode:
This NASA grant covers our ADP research program, which involved detailed
radiative transfer calculations of hydrodynamic models of pulsating
asymptotic giant branch stars. Synthetic spectra resulting from these
calculations are compared with International Ultraviolet Explorer
(IUE) observations of these stars to test the validity of the models.

---------------------------------------------------------
Title: Dynamics and Energy Balance in Stellar Transition Regions
Cycle 2
Authors: Linsky, Jeffrey
1991hst..prop.3964L Altcode:
Late-type stars with convective zones and magnetic fields have plasma
above the photosphere heated to temperatures above 10,000 K. We will
use the GHRS to study the dynamics, energy balance, and nonradiative
heating rates in these hot regions for a sample of late-type stars
spanning a range of spectral type and luminosity. We will study the
dynamics of stellar transition regions by measuring the redshifts,
indicative of downflows, with high precision in lines of C III, C
IV, Si IV, and O IV. The energy balance and local heating rates in
stellar transition regions will be derived from an emission measure
analysis of emission line fluxes and electron densities inferred from
density-sensitive line ratios. Cycle 0 observations of the RS CVn
system Capella show that the GHRS can measure ALL of the UV intersystem
lines of Si III, C III, O III, N III, O IV, and S IV, which are useful
density diagnostics. These data may require atmospheric models with
two components (quiet and active regions).

---------------------------------------------------------
Title: Local Interstellar Medium and D/h Ratio -- Cycle 2
Authors: Linsky, Jeffrey
1991hst..prop.3943L Altcode:
We will observe with 20,000 spectral resolution the stellar Lyman
alpha emission line and interstellar hydrogen and deuterium absorption
towards local late-type stars to derive the H and D column densities
and D/H ratios along different lines of sight. High resolution (90,000)
spectra of the MgII and FeII lines will help determine the interstellar
line broadening and whether material along each line of sight has more
than one velocity component. This is critical for accurate measurements
of D/H, because both the D and H lines are on or near the flat part of
the curve of growth. Previous IUE and Copernicus observations, which
had low signal/noise and inadequate spectral resolution, provided very
crude D/H values and suggested that the D/H ratio may vary within a
few parsecs of the Sun. We will measure D/H with at least one order of
magnitude improved precision and determine whether the proposed local
variations are real. The local value(s) of D/H may be extrapolated
to zero metal abundance to estimate the primordial value, which is
valuable for constraining cosmological models.

---------------------------------------------------------
Title: Hybrid Star Winds and Transition Regions Cycle 2
Authors: Linsky, Jeffrey
1991hst..prop.1179L Altcode:
Hybrid-chromosphere stars are G-K bright giants that show weak
high-temperature emission lines and blue-shifted absorption in
low-temperature lines indicating mass loss. We will determine the
temperature distribution and densities in the outer atmosphere, and
measure the outflow velocity and mass loss rate in a representative
hybrid star, Alpha TrA. We will determine whether the hot plasma
participates in the outflow or whether the wind consists entirely of
cool gas. Atmospheric models will be derived for both the hot and
cool gas using an emission measure analysis and density-sensitive
line ratios. This work will settle the question of whether the hybrid
nature of these stars is due to two distinct components in the stellar
atmosphere (perhaps one with strong, closed magnetic fields and the
other with weak, open fields) or whether a more complex geometry is
needed to explain the data.

---------------------------------------------------------
Title: X-Ray Emission from Hybrid-Chromosphere Stars
Authors: Brown, Alexander; Drake, Stephen A.; van Steenberg, Michael
E.; Linsky, Jeffrey L.
1991ApJ...373..614B Altcode:
The observations of hybrid stars made by the Exosat X-ray satellite
are considered, and emphasis is placed on the hybrid star alpha
TrA. Attention is focused on the determination of the column density of
IS hydrogen toward the stars in order to interpret X-ray observations
of stellar coronal emission. The coronal properties of alpha TrA are
discussed as well as implications of the general coronal properties
of hybrid stars. An analysis of the X-ray data, in conjunction with
transition region properties of the star, shows that the X-ray emitting
plasma is likely to have a temperature of at least 10 to the 6th K. The
X-ray luminosity of the star is calculated to be about 5 x 10 to the
29th ergs/s over the 1-300 A spectral region and 7 x 10 to the 28th
ergs/s in the 0.2-4 keV energy range for N(H) = 5 x 10 to the 19th
/sq cm and a temperature of 10 to the 6th K.

---------------------------------------------------------
Title: Rotationalmodulation and flares on RS Canum Venaticorum and BY
Draconis stars. XVI. IUE spectroscopy and VLA observations of GL 182
(=V 1005 Orionis) in October 1983.
Authors: Mathioudakis, M.; Doyle, J. G.; Rodono, M.; Gibson, D. M.;
Byrne, P. B.; Avgoloupis, S.; Linsky, J. L.; Gary, D.; Mavridis,
L. N.; Varvoglis, P.
1991A&A...244..155M Altcode:
A large flare was detected simultaneously with IUE and VLA on Gl 182 on
October 5, 1983, this event showing the largest C IV flare enhancement
yet observed by IUE. A smaller flare was also detected on October 4,
although only with the IUE satellite. Line ratio and emission measure
techniques are used to derive various physical parameters of the
flares. The radiative losses in the temperature region log T(e) =
4.3-5.4 in the two flares are 2.9 x 10 to the 33rd and 8.4 x 10 to
the 32nd ergs, respectively. Total radiative losses over the whole
temperature range log T(e) = 4.0-8.0 are estimated to be of the order
of 6.4 x 10 to the 34th and 1.1 x 10 to the 34th ergs, respectively. In
the October 5, flare, a very strong ultraviolet continuum is present
with a total energy of 1.9 x 10 to the 33rd ergs over the wavelength
range 1250-1950 A.

---------------------------------------------------------
Title: Basic research in solar physics
Authors: Linsky, Jeffrey L.
1991jila.reptQ....L Altcode:
This grant, dating back more than 20 years has supported a variety of
investigations of the chromospheres and coronae of the Sun and related
cool stars by the Principal Investigator, his postdocs and graduate
students, and colleagues at other institutions. This work involved
studies of radiative transfer and spectral line formation theory, and
the application of these techniques to the analysis of spectra obtained
from space and ground-based observatories in the optical, ultraviolet,
x-ray and radio portions of the spectrum. Space observations have
included the analysis of spectra from OSO-7, Skylab, SMM, and the HRTS
rocket experiments. Recent work has concentrated on the interaction
of magnetic fields, plasma and radiation in the outer atmospheres of
the Sun and other magnetically active stars with different fundamental
parameters. Our study of phenomena common to the Sun and stars, the
'solar-stellar connection', can elucidate the fundamental physics,
because spatially-resolved observations of the Sun provide us with the
"groundtruth," while interpretation of stellar data permit us to isolate
those parameters critical to stellar activity. Recently, we have studied
the differences in physical properties between solar regions of high
magnetic flux density and the surrounding plasma. High-resolution
CN and CO spectroheliograms have been used to model the thermal
inhomogeneities driven by unstable CO cooling, and we have analyzed
spatially resolved UV spectra from HRTS to model the thermal structure
and energy balance of small-scale structures. The study of nonlinear
relations between atmospheric radiative losses and the photospheric
magnetic flux density has been continued. We have also proposed a new
model for the decay of plages by random walk diffusion of magnetic
flux. Our analysis of phenomena common to the Sun and stars included
the application of available spectroscopic diagnostics, establishing
evidence that the atmospheres of the least active stars are heated at a
'basal' rate that is also found in the centers of solar supergranules,
and using the Doppler-imaging technique to measure the position,
size, and brightness of stellar active regions. We are computing
multi-component models for solar and stellar atmospheres, and models
for coronal loops and for the transition-region down flows. The study
of solar and stellar flares permits us to assess the role of turbulent
energy transport, to pinpoint the mechanism behind Type I radio bursts,
to determine whether plasma radiation or cyclotron maser is responsible
for microwave flares on M dwarfs, and to extend our knowledge of the
basic physics pertinent to cyclotron-maser processes operating on
the Sun.

---------------------------------------------------------
Title: GHRS Spectroscopy of Cool Stars. II.
Authors: Brown, A.; Linsky, J.; Carpenter, K.; Robinson, R.; Ebbets, D.
1991BAAS...23R.910B Altcode: 1991BAAS...23..910B
No abstract at ADS

---------------------------------------------------------
Title: GHRS Far-Ultraviolet Spectra of the Coronal Giant Capella
Binary
Authors: Linsky, J. L.; Brown, A.; Carpenter, K.; Robinson, R.
1991BAAS...23..910L Altcode:
No abstract at ADS

---------------------------------------------------------
Title: GHRS Spectroscopy of Cool Stars. I.
Authors: Carpenter, K.; Robinson, R.; Ebbets, D.; Brown, A.; Linsky, J.
1991BAAS...23..910C Altcode:
No abstract at ADS

---------------------------------------------------------
Title: GHRS / Goddard High Resolution Spectrograph / Far Ultraviolet
Spectra of Coronal and Noncoronal Stars - Capella and Gamma-Draconis
Authors: Linsky, J. L.; Brown, A.; Carpenter, K. G.
1991fyho.conf...70L Altcode:
No abstract at ADS

---------------------------------------------------------
Title: Peeking through the picket fence: What astrophysical surprises
may be present in the 100-1200 Å region?
Authors: Linsky, Jeffrey L.; Luttermoser, Donald G.
1991AdSpR..11k...5L Altcode: 1991AdSpR..11....5L
In anticipation of more sensitive EUV and FUV spectroscopic instruments,
we simulate spectra, including interstellar absorption, of solar-like,
RS CVn, and flare stars as folded through the instrument parameters
of the EUVE, Lyman/FUSE Phase A, and a desirable next-generation
spectrometer. We find that even the relatively insensitive EUVE
spectrometer will be able to detect sufficient spectral lines from
many active binary and dMe stars to determine their coronal emission
measure distributions. The Lyman/FUSE or next-generation spectrometers
are needed to study solar-type stars or flaring stars with high time
resolution. The high throughput and effective area of a next-generation
spectrometer is needed for Doppler imaging studies, stellar wind
and downflow measurements, and high time and spectral resolution of
stellar flares.

---------------------------------------------------------
Title: Ghrs/ Goddard High Resolution Spectroscopy Chromospheric
Emission Line Spectra of the Red Giant Alpha-Tauri
Authors: Carpenter, K. G.; Robinson, R. D.; Ebbets, D. C.; Brown,
A.; Linsky, J. L.
1991fyho.conf..212C Altcode:
No abstract at ADS

---------------------------------------------------------
Title: Radio Continuum Observations of a Variety of Cool Stars
Authors: Drake, S. A.; Linsky, J. L.; Judge, P. G.; Elitzur, M.
1991AJ....101..230D Altcode:
Radio-continuum observations at 2 and 6 cm are presented for 26
cool stars (F0 and later), including 10 F-K main-sequence stars and
16 F-M giant and supergiant stars. The detection of two M giants,
g Her and R Lyr, is reported for the first time; a redetection of
the unusual infrared carbon star IRC + 10216 is also reported. Some
general conclusions are made concerning the radio-emission properties
of the various types of cool stars observed. For both the detected and
nondetected stars, constraints are obtained on the ionized component
of their mass-loss rates.

---------------------------------------------------------
Title: X-rays from stellar flares.
Authors: Linsky, Jeffrey L.
1991MmSAI..62..307L Altcode:
A summary of X-ray observations of flares on dMe, active spectroscopic
binaries and young stars is presented. Consideration is given to
the energy associated with the X-ray emission and its relation to
other components of the flare energy budget, the time behavior of the
flaring plasma as seen by the X-ray emission, and comparisons of stellar
flare parameters with solar compact and two ribbon flares. Flares are
easily detected when the contrast in the emission from the flaring
plasma relative to the stellar photosphere is large as in the X-ray,
microwave, and UV regions of the spectrum.

---------------------------------------------------------
Title: Recent Advances in Our Understanding of Chromospheric and
Coronal Heating Mechanisms
Authors: Linsky, Jeffrey L.
1991LNP...380..452L Altcode: 1991sacs.coll..452L; 1991IAUCo.130..452L
I will summarize some of the principal scientific results presented
at the Conference on Mechanisms of Chromospheric and Coronal Heating
held on 5-8 June 1990 in Heidelberg, Germany. The Conference included
invited and contributed papers on observations that point to specific
heating mechanisms and theoretical papers on the heating mechanisms
themselves. There were many opportunities for useful interaction
between proponents of these two approaches to understanding stellar
chromospheres and coronae. I will concentrate on what is being learned
from the empirical side, and then summarize the heating mechanisms
discussed and for which types of stars they may be applicable.

---------------------------------------------------------
Title: What Can Solar and Stellar Ultraviolet Observations Tell
About Chromospheric and Coronal Heating Mechanisms? (With 1 Figure)
Authors: Linsky, J. L.
1991mcch.conf..166L Altcode:
No abstract at ADS

---------------------------------------------------------
Title: Dynamics and Energy Balance in Stellar Transition Regions -
AU MIC
Authors: Linsky, Jeffrey
1990hst..prop.4234L Altcode:
We propose to study the dynamics of stellar transition regions by
measuring the redshifts, indicative of downflows, in lines of C III,
C IV, Si IV, and O IV.The energy balance and heating rates in stellar
chromospheres and transition regions will be derived from an emission
measure analysis of emission line fluxes and densities inferred from
density sensitive line ratios. Stars of interest include dwarf stars
of spectral type F-M, active G and K giants, and RS CVn binary systems.

---------------------------------------------------------
Title: The First GHRS Spectra of a Cool Star: The Chromosphere of
Alpha Tau
Authors: Carpenter, K.; Robinson, R.; Ebbets, D.; Linsky, J.; Walter,
F.; Wahlgren, G.; Ake, T.
1990BAAS...22.1277C Altcode:
No abstract at ADS

---------------------------------------------------------
Title: The Large Earth-Based Solar Telescope (LEST) - Its Scientific
Objectives and Status
Authors: Linsky, J. L.; Leibacher, J.; Smithson, R.; Dunn, R. B.
1990BAAS...22.1238L Altcode:
No abstract at ADS

---------------------------------------------------------
Title: The distant future of solar activity - A case study of
Beta Hydri
Authors: Dravins, D.; Linde, P.; Ayres, T. R.; Fredga, K.; Gahm, G.;
Lindegren, L.; Linsky, J. L.; Monsignori-Fossi, B.; Nordlund, A.;
Simon, T.; Vandenberg, D.; Wallinder, F.
1990ESASP.310..323D Altcode: 1990eaia.conf..323D
No abstract at ADS

---------------------------------------------------------
Title: The intrinsic H-I Lyman-Alpha line profiles of late-type stars
Authors: Neff, J. E.; Landsman, W. B.; Bookbinder, J. A.; Linsky, J. L.
1990ESASP.310..341N Altcode: 1990eaia.conf..341N
No abstract at ADS

---------------------------------------------------------
Title: New Radio Detections of Early-Type Pre--Main-Sequence Stars
Authors: Skinner, Stephen L.; Brown, Alexander; Linsky, Jeffrey L.
1990ApJ...357L..39S Altcode:
Results of VLA radio continuum observations of 13 early-type
pre-main-sequence stars selected from the 1984 catalog of Finkenzeller
and Mundt are presented. The stars HD 259431 and MWC 1080 were detected
at 3.6 cm, while HD 200775 and TY CrA were detected at both 3.6 and 6
cm. The flux density of HD 200775 has a frequency dependence consistent
with the behavior expected for free-free emission originating in a fully
ionized wind. However, an observation in A configuration suggests that
the source geometry may not be spherically symmetric. In contrast,
the spectral index of TY CrA is negative with a flux behavior
implying nonthermal emission. The physical mechanism responsible
for the nonthermal emission has not yet been identified, although
gyrosynchrotron and synchrotron processes cannot be ruled out.

---------------------------------------------------------
Title: Ground-truth observations of stellar surface structure from
the lunar surface
Authors: Linsky, Jeffrey L.
1990AIPC..207..168L Altcode: 1990am...proc..168L
Using increasingly sophisticated observing strategies, astronomers have
begun to observe brightness inhomogeneities on the surfaces of stars
indicative of starspots, active regions, and chemically-anomalous
patches with size scales far smaller than the diffraction limits
of the present generation of telescopes. While tantalizing, these
first glimpses of stellar surface structures are very crude and not
unique. Modest-sized optical and ultraviolet inteferometers located on
the lunar surface could resolve these surface structures on nearby,
bright stars to provide `ground truth' to the present crude images and
to extend these studies to much smaller and physically interesting
scales. The combination of broad and narrow-band imaging (where
feasible) will provide qualitatively new information on the physical
processes that occur in stellar atmospheres by observing phenomena
on stars with properties (mass, radius, convective zone depth,
rotation rate) far different from the Sun. An intermediate scale
optical/ultraviolet interferometer on the lunar surface with 10-3 to
10-4 arcsecond angular resolution would provide unique and spectacular
results concerning stellar surface structures. This intermediate scale
interferometer could be a very useful device for learning how to build
larger interferometers that could address more difficult questions.

---------------------------------------------------------
Title: Studies of H i and D i in the Local Interstellar Medium
Authors: Murthy, J.; Henry, R. C.; Moos, H. W.; Vidal-Madjar, A.;
Linsky, J. L.; Gry, C.
1990ApJ...356..223M Altcode:
High-dispersion IUE spectra are presented of the hydrogen Ly-alpha
chromospheric emission line of two nearby late-type stars, Capella
and Lambda And. Both interstellar H I and D I Ly-alpha absorption
can be seen against the chromospheric line, and the density, velocity
dispersion, and bulk velocity of the gas in those lines of sight are
derived. Limits are placed on the D/H ratio. The results are consistent
with the current picture of the local interstellar medium.

---------------------------------------------------------
Title: Goals for the application of high-resolution X-ray spectroscopy
to the diagnosis of stellar coronal plasmas
Authors: Linsky, Jeffrey L.
1990hrxr.conf...94L Altcode: 1990IAUCo.115...94L
Examples are provided of how high-resolution X-ray spectra may be
used to determine the temperature and emission measure distributions,
electron densities, steady and transient flow velocities, and location
of active regions in stellar coronas. For each type of measurement,
the minimum spectral resolution required to resolve the most useful
spectral features is estimated. In general, high sensitivity is
required to obtain sufficient signal-to-noise to exploit the high
spectral resolution. Although difficult, each measurement should be
achievable with the instrumentation proposed for AXAF.

---------------------------------------------------------
Title: Some concluding thoughts for Cool Star VI.
Authors: Linsky, J. L.
1990ASPC....9..500L Altcode:
No abstract at ADS

---------------------------------------------------------
Title: First ultraviolet observations of the transition regions of
X-ray bright solar-type stars in the Pleiades
Authors: Caillault, J. -P.; Vilhu, O.; Linsky, J. L.
1990AdSpR..10b..17C Altcode: 1990AdSpR..10Q..17C
Nearby clusters, such as Ursa Major, the Hyades, and the Pleiades,
have been extensively studied in the X-ray regime. The first two
clusters have also been studied with the IUE. However, the younger,
fainter Pleiades cluster, which contains the youngest, and presumably
most active, main sequence stars in the solar vicinity, had not been
observed in the ultraviolet. Observations of such young clusters provide
the best method of studying the evolution of stellar parameters as
a star ages on the main sequence. Hence, we present here the first
ultraviolet study of the transition regions of two X-ray bright
solar-type stars from the Pleiades in an attempt to extend the main
sequence age baseline for the transition region activity-age relation
over more than two orders of magnitude. However, no emission lines
were detected from either star; the upper limits to the fluxes are
consistent with previously determined saturation levels, but do not
help to further constrain evolutionary models.

---------------------------------------------------------
Title: EINSTEIN and Stellar Sources
Authors: Linsky, J. L.
1990ixra.conf...39L Altcode: 1990ixra.symp...39L
Contents: Perspective. O-type and early B-type stars. Magnetic B-type
and A-type stars. A-type and early F-type stars: where does stellar
activity begin? Pre-main sequence and active main sequence stars. M-type
stars. Active post-main sequence binaries. AXAF and the future.

---------------------------------------------------------
Title: Coronal temperatures of selected active cool stars as derived
from low resolution EINSTEIN observations
Authors: Vilhu, Osmi; Linsky, Jeffrey L.
1990AdSpR..10b.139V Altcode: 1990AdSpR..10..139V
Mean coronal temperatures of some active G-K stars were derived from
Rev1-processed EINSTEIN-observatory's IPC-spectra. The combined X-ray
and transition region emission line data are in rough agreement with
static coronal loop models. Although the sample is too small to derive
any statistically significant conclusions, it suggests that the mean
coronal temperature depends linearly on the inverse Rossby-number,
with saturation at short rotation periods. For an individual active
star (VW Cep) the IPC-temperature was found to depend on the (variable)
X-ray flux.

---------------------------------------------------------
Title: Solar and stellar observations from the South Pole
Authors: Linsky, Jeffrey L.
1990AIPC..198..205L Altcode: 1989AIPC..198..205L; 1990asan.conf..205L
An astronomical observatory located at the geographic South Pole could
provide important new insights into the physcial bases of stellar
variability by monitoring stars for long periods of time with minimal
interruptions by the day-night cycle. I summarize here three broad
topics that could be studied with monitoring techniques-magnetic
phenomena on stars, helioseismology, and asteroseismology.

---------------------------------------------------------
Title: The Near-Stellar Environment of Cool, Evolved Stars
Authors: Judge, G. P.; Stencel, E. R.; Linsky, J. L.
1990ASSL..158..179J Altcode: 1990suas.conf..179J
The authors discuss relationships between spectral indicators of
chromospheric heating, winds and dust for "low" and "intermediate"
mass stars evolving up the RGB and AGB, and suggest new observations
from infrared to mm wavelengths which are needed. A full discussion
of these relations, which are important for theoretical studies of
heating and mass-loss processes, is in preparation.

---------------------------------------------------------
Title: The distant future of solar activity - a case study of
Beta Hydri.
Authors: Dravins, D.; Linde, P.; Ayres, T. R.; Fredga, K.; Gahm, G.;
Lindegren, L.; Linsky, J. L.; Monsignori-Fossi, B.; Nordlund, Å.;
Simon, T.; Vandenberg, D.; Wallinder, F.
1990apsu.conf...17D Altcode:
No abstract at ADS

---------------------------------------------------------
Title: A Three Dimensional Picture of RS CVN Stellar Atmospheres
Authors: Linsky, Jeffrey L.
1990iue..prop.3715L Altcode:
The ROSAT all-sky survey provides a unique opportunity to study an
RS CVn system simultaneously at x-ray, EUV, UV, optical, and radio
wavelengths at many phases throughout an orbital period. ROSAT can
detect the x-ray flux of each candidate system during each 30 second
viewing 16 times per day for at least 2 days. We request a block of 7
IUE shifts to obtain NEAR SIMULTANEOUS emission line fluxes (SWP-LO)
and Mg IT line profiles (LWP-HI), and we will obtain contemporaneous
optical photometry and spectroscopy and VLA radio fluxes (3.6, 6, and 20
cm). one objective of this PROPOSAL is to obtain the FIRST 3-D MODEL OF
THE INHOMOGENEOUS PHOTOSPHERE, CHROMOSPHERE, AND CORONA OF A STAR OTHER
THAN THE SUN. We will use optical photometry and spectroscopy to map
the spotted photospheres of each star, and the Mg II line profiles to
DOPPLERIMAGE their chromospheres, to determine the location, size,
and surface flux of the active regions. We will then use the time
variation of the UV emission line and x-ray fluxes to determine what
fluxes are due to the quiet and active regions separately. These
data will provide SURFACE FLUXES for the quiet and active regions
separately. We will then will model BOTH REGIONS independently using an
emission measure analysis. We will also model any flares observed. The
second part of the program will be a simultaneous UV/X-ray SURVEY with
the objective of DETERMINING THE RANGE OF PHYSICAL MODELS APPLICABLE
TO THE CHROMOSPHERES AND CORONAE OF RS CVN SYSTEMS. We propose to
obtain emission line fluxes (SWP-LO) and Mg II line profiles (LWP-HI)
of all bright RS CVns observed by ROSAT from mid-July through September
1990 that meet the IUE observing constraints. About 17 systems in the
Strassmeier catalog will likely be observed during this period. While
many RS CVn systems have been observed separately by IUE and x-ray
satellites, SIMULTANEOUS UV and x-ray observations are required to
model these spatially inhomogenous and timevariable systems. This
research program and the ROSAT RS CVn survey will constitute most of
the data for the Ph.D. Thesis of the Lead Investigator, Anthony Veale.

---------------------------------------------------------
Title: Extension of the Class of Magnetic B-Star Nonthermal Radio
Sources
Authors: Linsky, Jeffrey L.; Drake, Stephen A.; Bastian, Timothy S.
1990ASPC....9..189L Altcode: 1990csss....6..189L
A large VLA survey of radio emission from magnetic B stars is conducted
at 2, 3.6, 6, and 20 cm to identify and classify the stars and check
for the existence of classical Ap stars. Observations of 30 previously
unidentified stars in the Sco-Cen association are reported, and 10
stars are found which have spectral types B5-A0, measured magnetic
fields, and are He-weak and Si-strong. No radio emission is detected
from stars later than spectral type A1, and the extreme magnetic field
strength and large magnetosphere of GL Lac make it a good test for
magnetosphere theories.

---------------------------------------------------------
Title: Modelling the Coronae and Chromospheres of Rs-Canum Systems
by the Analysis of Ultraviolet X-Ray and Radio Observations
Authors: Linsky, J. L.
1990ASIC..319..747L Altcode: 1990acb..proc..747L
No abstract at ADS

---------------------------------------------------------
Title: A Survey of the Radio Continuum Emission of RS Canum
Venaticorum and Related Active Binary Systems
Authors: Drake, Stephen A.; Simon, Theodore; Linsky, Jeffrey L.
1989ApJS...71..905D Altcode:
Observations of 77 RS CVn and related active binary systems were made
with VLA at a continuum frequency of 4.86 GHz. The results are combined
with other VLA observations to produce a total number of observed
sources of 122. A search for correlations of radio properties with
various systemic and stellar parameters is performed. Significant
correlations are found between the normalized radio luminosity
L(6)/L(bol) and the normalized soft X-ray luminosity L(x)/L(bol). It is
suggested that the close correlation between low-level 6-cm emission and
the hot component of the soft X-ray emission observed by the Einstein
solid state spectrometer is caused by both emissions being produced
by the same thermal electrons.

---------------------------------------------------------
Title: Radio-Continuum Emission from the Ionized Stellar Winds of
Warm Supergiants
Authors: Drake, S. A.; Linsky, J. L.
1989AJ.....98.1831D Altcode:
The Very Large Array has been used at an observing wavelength of 6 cm to
survey 25 supergiants of spectral types between B2 and F8. Only one of
these stars (Beta Ori, or Rigel) has been detected as a radio-continuum
source, with an inferred 6 cm luminosity L6 of 7 x 10 to the 16th
ergs/sec per Hz. Rigel may also be an X-ray source (and, if it were,
would be the only X-ray detected star out of the 12 stars in this
sample that were observed by Einstein. An extended source of more than
10 mJy flux density with the same angular dimensions and location
as He 1-5, the planetary nebula surrounding the peculiar supergiant
FG Sge, and a weak localized source of roughly 0.1-0.2 mJy somewhat
offset from the center of the extended radio emission have also been
detected. The upper limits to L6 for the F Ib stars are as much as an
order of magnitude below the level at which Rigel was detected. If
the radio emission from Rigel is interpreted as free-free radiation
from its stellar wind, the inferred ionized mass-loss rate is 2.5 x
10 th the 7th solar mass/yr. The most stringent upper limits to the
ionized mass-loss rates obtained for the F and A supergiants are not
greater than 10 to the -8th solar mass/yr and less than or equal to
10 to the -7th solar mass/yr, respectively.

---------------------------------------------------------
Title: X-ray Emission From Hybrid-Chromosphere Stars
Authors: Brown, A.; Linsky, J. L.; Drake, S. A.; van Steenberg, M.
1989BAAS...21Q1115B Altcode: 1989BAAS...21.1115B
No abstract at ADS

---------------------------------------------------------
Title: IUE observations of the M dwarfs CM Draconis and Rossiter
137B : magnetic activity at saturated levels.
Authors: Vilhu, O.; Ambruster, C. W.; Neff, J. E.; Linsky, J. L.;
Brandenburg, A.; Ilyin, I. V.; Shakhovskaya, N. I.
1989A&A...222..179V Altcode:
IUE observations of two active M dwarfs with known rotation rate or age
and presumed to be almost totally convective are presented. The first
of these stars, CM Draconis (Gl 630.1), is an old Population II binary
with its components in tidally induced rapid rotation (P = 1.27 d, dM
4 + dM 4). The other one, Rossiter 137 B, forms with HD 36705 (AB Dor)
a visual pair of young active stars. The activity of CM Dra is due to
the forced rotation in a close binary, while Rst 137 B is assumed to
rotate fast enough to generate its magnetica activity. These results
are compared with those for M dwarfs, particularly AU Mic and YZ CMi,
that have known rotational periods and measured ultraviolet emission
line fluxes. The chromospheric-coronal saturation levels of cool dwarfs
between 0.3 less than B-V less than 1.6 is determined. It is found
that saturated F stars have stronger chromospheres than saturated
M stars, but the opposite is true for the corona. Results of these
observations seem to favor a rotation-dependent distributed dynamo
generating magnetic flux in totally convective stars.

---------------------------------------------------------
Title: Rotational modulation and flares on RS Canum Venaticorum and
BY Draconis stars. XI. Ultraviolet spectral images of AR Lacertae
in September 1985.
Authors: Neff, J. E.; Walter, F. M.; Rodono, M.; Linsky, J. L.
1989A&A...215...79N Altcode:
High-resolution IUE SWP and LWP spectra of the bright eclipsing RS
CVn system AR Lac, obtained during 40 h of continuous observations on
September 18-19, 1985, are compiled and used to derive chromosphere
images. The data and results are presented graphically and discussed in
detail. The K 0 IV star is found to have a globally brighter trailing
hemisphere and at least three distinct plage regions; the G 2 IV star
has a flaring region with significant redshift and line-emission
broadening and exhibits factor-of-3 variability in total emission,
attributed to the presence of a large chromospherically inactive region.

---------------------------------------------------------
Title: Extension of the Class of Magnetic B Star Nonthermal Radio
Sources
Authors: Linsky, J. L.; Drake, S. A.; Bastian, T. S.
1989BAAS...21Q.742L Altcode: 1989BAAS...21..742L
No abstract at ADS

---------------------------------------------------------
Title: Solar and Stellar Magnetic Fields and Structures - Observations
Authors: Linsky, Jeffrey L.
1989SoPh..121..187L Altcode: 1989IAUCo.104..187L
This review of stellar magnetic field measurements is both a critique of
recent spectral diagnostic techniques and a summary of important trends
now appearing in the data. I will discuss both the Zeeman broadening
techniques that have evolved from Robinson's original approach and
techniques based on circular and linear polarization data. I conclude
with an ambitious agenda for developing self-consistent models of the
magnetic atmospheres of active stars.

---------------------------------------------------------
Title: Rotational modulation and flares on RS Canum Venaticorum and BY
Draconis.stars. X. The 1981 October 3 flare on V711 Tauri (= HR 1099).
Authors: Linsky, J. L.; Neff, J. E.; Brown, A.; Gross, B. D.; Simon,
T.; Andrews, A. D.; Rodono, M.; Feldman, P. A.
1989A&A...211..173L Altcode:
We present a unique set of high resolution spectra of V71 1 Tauri =
HR 1099 (G5 V + K1 IV) obtained with both the SWP and LWR cameras
of lUE, together with simultaneous 6.4 GHz microwave emission and
optical photometry, during a bright flare on 3 October 1981. The
electron density of the flaring plasma at 6 104K was about
11011 cm-3, 15 times higher than quiescent, and
the radiating volume was about 21030 cm-3, 200
times smaller than quiescent. A constrained multigaussian fit to the
Mg II k line profile shows that the flare component profile was very
broad (66 km s-1 FWHM), indicating significant turbulence,
and redshifted by 90 ± 30 km s-1 relative to the center
of mass of the K 1 IV star. We interpret this redshift as due to
downflowing material probably located above a large starspot known
from optical photometry and Doppler imaging to be near disk center of
the K 1 IV star during the flare. The flux of kinetic energy at flare
peak due to the downflow and turbulence was &lt;1 1032 erg
s-1, essentially equal to the flare radiative luminosity. The
microwave emission was probably gyrosynchrotron emission from mildly
relativistic electrons (typical energy 1.7 MeV) trapped in magnetic
flux tubes emerging from the whole area of this spot.

---------------------------------------------------------
Title: IUE Observations of the Interstellar Medium toward beta
Geminorum
Authors: Murthy, J.; Wofford, J. B.; Henry, R. C.; Moos, H. W.;
Vidal-Madjar, A.; Linsky, J. L.; Gry, C.
1989ApJ...336..949M Altcode:
A dispersion IUE spectrum of the hydrogen Ly-alpha emission line of the
nearby late-type star Beta Gem is presented. Values are determined
for the density, velocity, dispersion, and bulk velocity of the
interstellar H I toward the star, showing agreement with previous
IUE results for stars in the same general direction (Murthy et al.,
1987). It is shown that the interstellar medium in the line of sight
to Beta Gem has a total column density of about 2 x 10 to the 18th/sq
cm and a velocity dispersion of 13-16 km/s. The flow vector is in
agreement with the interstellar wind found by Crutcher (1982).

---------------------------------------------------------
Title: Spectral diagnostics from X-ray to radio wavelengths.
Authors: Linsky, Jeffrey L.
1989mse..proc...97L Altcode:
Contents: 1. Introduction: what is a spectral diagnostic? 2. Spectral
diagnostics of the thermodynamic properties of an
atmosphere. 3. Spectral diagnostics of magnetic fields. 4. Concluding
thoughts.

---------------------------------------------------------
Title: Ultraviolet Observations of Two Possible FK Comae Stars
Authors: Linsky, Jeffrey L.
1989iue..prop.3429L Altcode:
The controversial and rare class of FK Comae stars may be examples of
a brief stage of low-mass binary evolution: the point at which the two
cores of a contact binary merge to form a single star. At present,
there are four members of the class (although the appropriateness
of FK Comae as a prototype has been questioned). Optical follow-up
observations of the serendipitous X-ray detections contained in
the Einstein Observatory Extended Medium Sensitivity Survey (EMSS)
have revealed two new candidates for the FK Comae class. Ultraviolet
observations of the known FK Comae stars show that their chromospheric
and transition region line fluxes are relatively stronger than those
of active binaries such as the RS CVn and W UMa types. Ultraviolet
observations of the two candidates from the EMSS could help to verify
their status as FK Comae stars. We propose to make two LWP (high-
and low-resolution) and one low-resolution SWP observation of the
brighter of the two candidates in order to measure its O I, Si II,
C II, He II, C IV, N V, and Mg II emission line fluxes. In addition,
we will use the high-resolution Mg II h &amp; k line profiles to study
the kinematics of the chromosphere and compare it to the kinematical
information obtained from photospheric lines, as well as look for
evidence of an excretion disk. This, in addition to one low-resolution
LWP exposure of the fainter candidate, form a core proposal of 2 US1
shifts and 1 half US2 shift which is extremely feasible for the IUE to
observe. We also ask for an additional US1 shift and US2 half shift
as part of a supplemental proposal to obtain a high-resolution LWP
exposure of the fainter candidate. We realize, based upon previous
observations of other stars which may be similar in nature, that such
an exposure (10 hours maximum) will probably be insufficient to meet
the objectives listed above. However, since such reasoning precludes
the chance to make an unusual discovery and since the potential for
finding unusually strong chromospheric exists, we have decided to ask
for the time. We will not be surprised if the supplemental proposal
is not granted, but are confident in the merits of the core proposal.

---------------------------------------------------------
Title: Book-Review - Cool Stars Stellar System and the Sun - 5TH
Cambridge Workshop
Authors: Linsky, J. L.; Stencel, R. E.; Rudiger, G.
1989AN....310..374L Altcode:
No abstract at ADS

---------------------------------------------------------
Title: VLA observations of stellar flares: a 3-hour flare of the RS
CVn star λ Andromedae and a 5-minute flare of the Bp star HR 5942.
Authors: Drake, S. A.; Linsky, J. L.
1989sasf.confP..41D Altcode: 1989IAUCo.104P..41D; 1988sasf.conf...41D
The authors describe high-sensitivity VLA observations of rapidly
varying radio emission ("flares") from two stars of very different
types, one of which (λ And) is a Long-Period RS CVn system, and the
other (HR 5942) is a magnetic Bp star. In both cases, however, the
physical mechanism producing the radio emission is most likely to be
gyrosynchrotron radiation from mildly relativistic, power-law electrons.

---------------------------------------------------------
Title: A Coordinated Study of Flares and Active Regions on the by
Draconis-Type Star CC Eridani
Authors: Linsky, Jeffrey L.
1989iue..prop.3430L Altcode:
We propose to observe the 1.56 day period spectroscopic binary CC Eri
(K7Ve + dM?) continuously over its complete orbital period in order
(1) to measure the ultraviolet emission from it's active regions and
it's quiescent atmosphere separately and (2) to study flares that
likely will occur during the observing run. CC Eri is the second
brightest member of the BY Draconis class of spotted cool dwarfs,
it has the shortest known orbital and rotational period, and it
has the fastest rotational velocity of the BY Dra class. For these
reasons it is likely a very active member and probably has one of the
brightest ultraviolet emission line spectrum of its class. Since only
one IUE spectrum has so far been obtained of this important object, we
propose to begin a detailed study of its ultraviolet emission properties
leading to a high-dispersion SWP observation next year. We will obtain
a continuous series of SWP-LO and LWP-LO spectra over the full orbital
(= rotational period) in order to identify bright active regions (from
the rotational modulation of emission line fluxes) and to correlate
the location of these active regions with dark starspots, whose
positions will be determined from contemporaneous optical photometry
and spectroscopy. We also will study the time behavior of flares in
different spectral lines and with coordinated optical photometry and
VLA radio observations. Flares with U-magnitude enhancements greater
than I magnitude are known to occur on average once every 12 hours. We
plan to model the quiescent, active, and flaring atmospheres separately
using emission measure diagnostics. CC Eri is an excellent candidate
for this study, because it usually has a large amplitude photometric
variation indicating an asymmetric distribution of spots (and thus
active regions) across its surface, while it's flares are few but
energetic. IUE is particularly well suited for such modulation studies.

---------------------------------------------------------
Title: General properties of ultraviolet flares in RS CVn systems.
Authors: Neff, J. E.; Brown, A.; Linsky, J. L.
1989sasf.confP.111N Altcode: 1989IAUCo.104P.111N; 1988sasf.conf..111N
Approximately 10 very bright flares in RS CVn systems have been
observed with the IUE. In several cases, high-resolution spectra of
the Mg II k line profiles were obtained before, during, and after
the flare. Such data permit the authors to measure the position and
size of the flaring region, the amount of line broadening, and any
systematic flow velocity. In two cases, several spectra were obtained
during the flare decay, permitting the authors to study the change in
these quantities during the flare decay.

---------------------------------------------------------
Title: Book-Review - Cool Stars Stellar Systems and the Sun / 5TH
Cambridge Workshop / Boulder, Colorado 1987JUL
Authors: Linsky, J. L.; Stencel, R. E.; Venkatakrishnan, P.
1988BASI...16..248L Altcode:
No abstract at ADS

---------------------------------------------------------
Title: Book-Review - Cool Stars Stellar Systems and the Sun -
Cambridge - 1987JULY
Authors: Linsky, J. L.; Stencel, R. E.
1988S&T....76..639L Altcode:
No abstract at ADS

---------------------------------------------------------
Title: Rotational modulation and flares on RS CVn and BY DRA
stars. IX. IUE spectroscopy and photometry of II Peg and V711 Tau
during February 1983.
Authors: Andrews, A. D.; Rodono, M.; Linsky, J. L.; Brown, A.; Butler,
C. J.; Catalano, S.; Scaltriti, F.; Busso, M.; Nha, Il-Seong; Oh,
J. Y.; Henry, M. C. D.; Hopkins, J. L.; Landis, H. J.; Engelbrektson,
S.
1988A&A...204..177A Altcode:
Evidence is presented for spots, plages, and flares on the noneclipsing
RS CVn system II Peg and V 711 Tau. The large spot originally found on
II Peg in 1981.8 could still be identified in 1983. Two spectroscopic
flares of II Peg were detected. For the larger flare the fluxes in
the strongest transition-region lines reached about six times their
quiescent values. A comparison of the 1981 and 1983 flux variations
show that active regions or plages are located on one hemisphere. On V
711 Tau at least two flares were observed. Outside of these flares, the
strongest chromospheric and transition-region emission lines exhibited
weak phase-dependent variations that persist over 173 orbital cycles
(1981-1983) and are possibly associated with one of the proposed
spots. For both stellar systems the fluxes from the higher temperature
emission lines showed the greatest variations.

---------------------------------------------------------
Title: IUE Observations of Solar-Type Stars in the Hyades and the
Pleiades
Authors: Caillault, J. -P.; Vilhu, O.; Linsky, J.
1988BAAS...20Q.989C Altcode: 1988BAAS...20..989C
No abstract at ADS

---------------------------------------------------------
Title: C IV fluxes from the Sun as a star, and the correlation with
magnetic flux
Authors: Schrijver, C. J.; Linsky, J. L.; Bennett, J.; Brown, A.;
Saar, S. H.
1988jila.reptR....S Altcode:
A total of 144 C IV wavelength 1548 Solar Maximum Mission (SMM)-UVSP
spectroheliograms of solar plages were analyzed, some of which are
series of exposures of the same region on the same day. Also analyzed
were the C IV wavelength 1551 rasters of plages and C IV wavelength 1548
rasters of the quiet sun. The sample contained data on 17 different
plages, observed on 50 different days. The center-to-limb variations
of the active regions show that the optical thickness effects in the
C IV wavelength 1548 line can be neglected in the conversion from
intensity to flux density. As expected for the nearly optically thin
situation, the C IV wavelength 1548 line is twice as bright as the C
IV 1551 line. The average C IV wavelength 1548 flux density for a quiet
region is 2700 ergs/cm/s and, with surprisingly little scatter, 18,000
erg/cm/s for plages. The intensity histograms of rasters obtained at
disk center can be separated into characteristic plage and quiet sun
contributions with variable relative filling factors. The relationship
between the C IV and magnetic flux densities for spatially resolved
data is inferred to be almost the same, with only an additional factor
of order unity in the constant of proportionality.

---------------------------------------------------------
Title: C 4 fluxes from the sun as a star and the correlation with
magnetic flux
Authors: Schrijver, C. J.; Linsky, J. L.; Bennett, J.; Brown, A.;
Saar, S. H.
1988jila.reptQ....S Altcode:
A total of 144 C 4 wavelength 1548 SMM-UVSP spectroheliograms of
solar plages were analyzed, some of which are series of exposures of
the same region on the same day. Also analyzed were C 4 wavelength
1551 rasters of plages and C 4 1548 rasters of the quiet sun. The
sample contains data on 17 different plages, observed on 50 different
days. The center-to-limb variations of the active regions show that
the optical thickness effects in the C 4 wavelength 1548 line can be
neglected in the conversion from intensity to flux density. As expected
for the nearly optically thin situation, the C 4 1548 line is twice as
bright as the C 4 wavelength 1551 line. The average C 4 wavelength 1548
flux density for a quiet is 2700 erg/cm/s and, with surprisingly little
scatter, 18,000 erg/cm/s for plages. The intensity histograms of rasters
obtained at disk centers can be separated into characteristic plage and
quiet-sun contributions with variable relative filling factors. The
disk-averaged flux density in the C 4 doublet and the disk-averaged
magnitude of the magnetic flux density are related. The relationship
between the C 4 and magnetic flux densities for spatially resolved data
is inferred to be almost the same, with only an additional factor of
order unity in the constant of proportionality.

---------------------------------------------------------
Title: Book-Review - Cool Stars Stellar Systems and the Sun -
Workshop / Boulder, Colo / 1987JUL
Authors: Linsky, J. L.; Stencel, R. E.
1988Sci...241..991L Altcode:
No abstract at ADS

---------------------------------------------------------
Title: Introductory remarks by the Panel Chairman
Authors: Linsky, J. L.
1988ESASP.281b.399L Altcode: 1988duvb.conf..399L
No abstract at ADS

---------------------------------------------------------
Title: Doppler imaging of AR Lacertae at three epochs
Authors: Walter, F. M.; Neff, J. E.; Linsky, J. L.; Rodono, M.
1988ESASP.281a.295W Altcode: 1988uvai....1..295W; 1988IUE88...1..295W
Observations from IUE were used to study the structure of the lower
chromosphere of AR Lacertae in the light of Mg II k. Sequences of
LWR/P-HI images distributed around the binary period at three epochs
were obtained. Discrete plage-like regions of enhanced Mg II surface
flux in this system are identified. There are temporal variations in
the Mg II flux on timescales of hours as well as substantial changes
in chromospheric morphology on timescales of years. Even with the
limited S/N attainable with the IUE, one can map the gross structures
of active stellar atmospheres. With such information, one can begin
to study the true 3-D structure of the atmospheres of late-type stars.

---------------------------------------------------------
Title: IUE's legacy for the future: the final archive and goals for
its implementation
Authors: Linsky, J. L.; Nichols-Bohlin, Joy
1988ESASP.281b.391L Altcode: 1988duvb.conf..391L; 1988uvai....2..391L
Requirements for the IUE archive, and how the signal/noise (S/N) ratio
in photometrically corrected images can be enhanced considerably by
cross-correlating the fixed pattern in a data image with that in a
suitable flat-field image are described. From these cross-correlations
it is feasible to derive an accurate geometrical correction to apply to
the data image before applying the intensity transfer functions. The
standard IUE processing software does not generate a sufficiently
accurate geometric correction so that typical spatial errors of 1
to 2 pixels conspire with the large fixed pattern in raw images to
produce significant misregistration noise. Tests on flat-field images
demonstrate that an explicit geometric correction procedure can avoid
most of the misregistration noise and can thereby improve the S/N
ratio of IUE data by factors of 1.5 to 2.4.

---------------------------------------------------------
Title: Ultraviolet emission lines and optical photometry of the
flare star AT Microscopii.
Authors: Elgaroy, O.; Joras, P.; Engvold, O.; Jensen, E.; Pettersen,
B. R.; Ayres, T. R.; Ambruster, C.; Linsky, J. L.; Clark, M.; Kunkel,
W.; Marang, F.
1988A&A...193..211E Altcode:
Ultraviolet spectra of the dwarf flare star binary AT Mic (dM 4.5e+dM
4.5e) were obtained with the IUE spacecraft on three days in September
1985. A high-resolution short-wavelength spectrum was exposed for 25
hours. Simultaneous optical monitoring in the U-band was performed
during part of the IUE observations. At the time of observation AT
Mic was flaring at an average rate of 1.3 flares per hour. On the
average 9% of the energy in the U-band was due to the detected flare
activity. From the observed high resolution spectra, line wavelengths,
widths and fluxes were derived, and the effects of the binary structure
of AT Mic on the spectral lines were evaluated. The ultraviolet emission
line spectrum is similar in character to that of flare regions on the
Sun and other stars.

---------------------------------------------------------
Title: Far-ultraviolet and X-ray emission of the long period RS CVn
star sigma Geminorum.
Authors: Engvold, O.; Ayres, T. R.; Elgaroy, O.; Jensen, E.; Joras,
P. B.; Kjeldseth-Moe, O.; Linsky, J. L.; Schnopper, H. W.; Westergaard,
N. J.
1988A&A...192..234E Altcode:
The new UV and X-ray observations of σ Gem support the theory that
large active regions associated with starspots are responsible for the
enhanced line emission commonly seen in RS CVn systems. The rotational
modulation of the UV line fluxes increases with temperature of the
line-forming region. The X-ray emission from the stellar corona, on the
other hand, shows only a barely detectable variation with rotational
phase. One may infer that the coronal active regions of the system
are not co-spatial with the activity in the transition region below,
and/or occupy a significantly larger surface area. An equally probable
explanation, however, is that the X-ray emission is emitted from huge,
stellar sized loops.

---------------------------------------------------------
Title: Requirements for Theoretical Models of Outflows.
Authors: Linsky, Jeffrey L.
1988ASSL..142..177L Altcode: 1988mosg.proc..177L
Recent observational and theoretical investigations of astrophysical
mass outflows are reviewed, with a focus on the basic physical
principles. Specific limitations on the observational data and their
interpretation are listed and discussed. Modeling problems considered
include the role of the critical point in determining the mass-loss
rate and terminal velocity, the physical processes controlling density
at the critical point, the possible coexistence of multiple mass-loss
mechanisms, time scales, instabilities and phase changes, multiphase
atmospheres and winds, the definition of geometries, the role of
the environment, explosive transient events, stochastic phenomena,
mode-mode coupling and damping processes, departures from ionization
equilibrium, and nonthermal phenomena.

---------------------------------------------------------
Title: Applications of the Doppler Imaging Technique to the Analysis
of High Resolution Spectra of the 3 October 1981 Flare on V711 Tauri
Authors: Linsky, J. L.; Neff, J. E.
1988IAUS..132..231L Altcode:
An unconstrained four gaussian fit to the Mg II profile near the flare
peak indicates that the flare occurred near the central meridian of
the K1 IV star, perhaps above a spot. A more likely fit to the same
data places the flare at +90±30 km s-1 relative to the K1
IV star, indicating significant downflowing plasma.

---------------------------------------------------------
Title: First Observations of the Pleiades Transition Region Line
Emission
Authors: Linsky, Jeffrey L.
1988iue..prop.3132L Altcode:
Nearby clusters, such as Ursa Major and the Hyades, have already
been studied with the IUE. However, the younger, fainter Pleiades
cluster, which contains the youngest, and presumably most active,
main sequence stars in the solar vicinity, remains to be observed and
analyzed. Observations of such young clusters provide the best method of
studying the evolution of stellar parameters as stars age an the main
sequence. Hence, we propose to make the first study of the transition
region emission of a small, carefully chosen sample of X-ray bright
late F-type stars from the Pleiades, thereby extending the main sequence
baseline for the transition region activity-age relation over more than
2 orders of magnitude. We expect to determine a.) whether or not there
is indeed a plateau of activity extending to ages as young as that of
the Pleiades, b.) what the resulting exponential decay time is for the
transition region line emission, c.) if there is still a dependence
on the Rossby number for such young stars, and d.) whether or not the
plage model explanation is truly unacceptable in this age regime.

---------------------------------------------------------
Title: Coordinated Multiband Space and Groundbased Observations of
Surface Structures and Flares on Late Type Stars
Authors: Foing, B.; Butler, C. J.; Haisch, B. M.; Linsky, J. L.;
Rodono, M.
1988copa.conf..197F Altcode:
The authors discuss the need to coordinate future synoptic observations
at all accessible wavelengths for these objects which are highly
variable on all timescales from seconds to years.

---------------------------------------------------------
Title: Multiwavelength observations of magnetic fields and related
activity on Xi Bootis A.
Authors: Saar, S. H.; Huovelin, J.; Giampapa, M. S.; Linsky, J. L.;
Jordan, C.
1988ASSL..143...45S Altcode: 1988acse.conf...45S
The authors present preliminary results of coordinated observations
of magnetic fields and related activity on the active dwarf, ξ Boo
A. Combining the magnetic fluxes with the linear polarization data,
a simple map of the stellar active regions has been constructed.

---------------------------------------------------------
Title: Spatially resolved flares in RS CVn systems.
Authors: Neff, James E.; Linsky, Jeffrey L.
1988ASSL..143..175N Altcode: 1988acse.conf..175N
The authors have isolated Mg II k emission line profiles arising solely
from the flaring region during flares on AR Lac and V711 Tau. From
several high-resolution spectra obtained during the lifetime of the
flare, they have determined the size and position of the flaring regions
and studied the decay of the emission line width, radial velocity,
and integrated line flux.

---------------------------------------------------------
Title: Simultaneous Multiwavelength Observations of Stellar Flares
Authors: Linsky, Jeffrey L.
1988iue..prop.3133L Altcode:
We request IUE observations as a major portion of a coordinated
observing program to study flares on dMe stars simultaneously at X-ray,
ultraviolet, optical and radio wavelengths. Three well-known flare
stars (GL 182 - V1005 Ori, Gl 206 - Ross 42, and GI 207.1 - V371 Ori)
located near 5 Right Ascension and 30 Declination have been selected
so as to permit 8 hours per night uninterrupted viewing by the IUE and
GINGA satellites and optical and radio observatories in Europe and
South Africa. Observing campaigns with this broad spectral coverage
are rare and exceedingly valuable. One of our scientific goals is to
assess the energy budget of flares including the prompt (presumably
nonthermal) X-rays, the decay phase soft X-ray radiation from the flare
loops, and the heating of the lower layers (detected as optical and
ultraviolet radiation) as a result of high energy particle streams,
blast waves, or reprocessed X-radiation. This task is important to
help identify the mechanisms responsible for different aspects of a
flare and to confirm or refute the hypothesis that flares of all sizes
are responsible for the timeaveraged X-ray luminosity of dMe stars. A
second goal is to study the time variation of these different aspects
of flares using those data (optical, X-ray, and radio) that do have
high time resolution. We will model the chromospheric and transition
region layers during and outside of flares using an emission measure
analysis of the ultraviolet emission lines observed by IUE.

---------------------------------------------------------
Title: Active late-type stars.
Authors: Linsky, Jeffrey L.
1988mwa..work...49L Altcode: 1988mwa..conf...49L
Contents: 1. What is stellar activity? 2. Some basic questions of
stellar activity research: What types of stars are active? What
stellar parameters control activity? What are the physical
mechanisms responsible for activity? 3. Multiwavelength probes
of multilayer activity: Optical and infrared photometry. Optical
spectroscopy. Ultraviolet spectroscopy. X-ray photometry and
spectroscopy. Radio observations. 4. Examples of multiwavelength
studies of active stars: RS Canum Venaticorum systems. M dwarf
stars. 5. Concluding thoughts.

---------------------------------------------------------
Title: The Discovery of Nonthermal Radio Emission from Magnetic
Bp--Ap Stars
Authors: Drake, Stephen A.; Abbott, David C.; Bastian, T. S.; Bieging,
J. H.; Churchwell, E.; Dulk, G.; Linsky, Jeffrey L.
1987ApJ...322..902D Altcode:
In a VLA survey of chemically peculiar B- and A-type stars with strong
magnetic fields, five of the 34 stars observed have been identified
as 6 cm continuum sources. Three of the detections are helium-strong
early Bp stars (Sigma Ori E, HR 1890, and Delta Ori C), and two are
helium weak, silicon-strong stars with spectral types near A0p (IQ
Aur = HD 34452, Babcock's star = HD 215441). The 6 cm luminosities L6
(ergs/s Hz) range from log L6 = 16.2 to 17.9, somewhat less than the
OB supergiants and W-R stars. Three-frequency observations indicate
that the helium-strong Bp stars are variable nonthermal sources.

---------------------------------------------------------
Title: Rotational modulation and flares on RS CVn and BY DRA
stars. IV. The spatially resolved chromosphere of AR Lacertae.
Authors: Walter, F. M.; Neff, J. E.; Gibson, D. M.; Linsky, J. L.;
Rodono, M.; Gary, D. E.; Butler, C. J.
1987A&A...186..241W Altcode:
The authors observed the RS CVn system AR Lacertae systematically
over an orbital period with the International Ultraviolet Explorer in
October 1983. Contemporaneous radio observations were obtained at the
Very Large Array. The spectra of the Mg II k emission line were analyzed
using a Doppler imaging technique. In this way, the authors identified
three discrete regions of emission in the outer atmosphere of the K
star - two "plages" and a chromospheric brightening that was related
to a radio flare. The widths of the plage profiles indicate that the
two plages together cover about 2% of the visible stellar hemisphere,
and their v sin i values indicate that they lie close to the equator
of the K star. The Mg II k surface flux in the plages is about five
times the mean Mg II k surface flux of the K star. The authors then
used the far-ultraviolet spectra obtained at the eclipse phases to
separate the individual contributions of the two stars and the plage
and flare regions in order to estimate their line surface fluxes.

---------------------------------------------------------
Title: A Radio Continuum Survey of the Coolest M and C Giants
Authors: Drake, Stephen A.; Linsky, Jeffrey L.; Elitzur, Moshe
1987AJ.....94.1280D Altcode:
The authors present the results of a sensitive VLA continuum survey
of 22 cool M and C type giants and supergiants, including nine carbon
stars, one S type star, and 12 M stars. The purpose of the survey was
to probe the physical properties of the partially ionized, expanding
chromospheres of the coolest luminous stars. Of the 22 stars observed
at 6 cm, none were detected directly, although extended emission was
detected near NML Cyg and OH 26.5+0.6, and a point source was detected
near AFGL 865. Of the three stars observed at 2 cm, R Aql (M6.5e-9e)
was detected as a 0.54±0.17 mJy source, and a point source was detected
7arcsec from R Cas (M6e-9e) and may be physically associated with the
star. These data imply small upper limits for the ionized-mass-loss
rates and 2 - 6 cm spectral indices that are significantly steeper
than the 0.6 value predicted by the "standard" stellar-wind model. The
nondetection of ο Ceti (Mira) at both 2 and 6 cm, despite a previous
6 cm detection, supports the idea that the radio-continuum emission
of these stars may be variable, perhaps due either to flares or to
the passage of pulsation-generated shock waves through their outer
atmospheres.

---------------------------------------------------------
Title: Detection of X-ray emission from the young low-mass star
Rossiter 137B.
Authors: Vilhu, O.; Linsky, J. L.
1987PASP...99.1071V Altcode:
Rst 137B, a close M-dwarf companion to the active K-star HD 36705, has
been detected in a High Resolution Image in the Einstein Observatory
Archive. The X-ray surface fluxes (0.2-4 keV) from both stars are
close to the empirical saturation level, F(x)/F(bol) of about 0.001,
defined by rapid rotators and very young stars. This supports the
earlier results of the youthfulness of the system. This young couple
is an excellent subject for studies of dependence of early evolution
on stellar mass. Rst 137B is one of the latest spectral types and thus
lowest-mass premain-sequence stars yet detected as an X-ray source.

---------------------------------------------------------
Title: IUE Observations of the Interstellar Medium Toward β Geminorum
Authors: Murthy, J.; Wofford, J. B.; Henry, R. C.; Moos, H. W.;
Vidal-Madjar, A.; Landsman, W. B.; Linsky, J. L.; Gry, C.
1987BAAS...19R1053M Altcode:
No abstract at ADS

---------------------------------------------------------
Title: The Radio Continuum Properties of RS Canum Venaticorum
Binary Systems
Authors: Drake, S. A.; Simon, T.; Linsky, J. L.
1987BAAS...19.1084D Altcode:
No abstract at ADS

---------------------------------------------------------
Title: Rotational modulation and flares on RS CVn and BY DRA
stars. VI. Physical parameters of the chromospheres/transition
regions of V711 Tau (HR 1099), II Peg and AR Lac during october 1981.
Authors: Byrne, P. B.; Doyle, J. G.; Brown, A.; Linsky, J. L.;
Rodono, M.
1987A&A...180..172B Altcode:
Ground-based optical and IUE satellite-ultraviolet observations of
three RS CVn stars are combined with density sensitive line ratios
and differential emission measure curves to describe the physical
conditions in their outer atmospheres. Solar-like densities are found
to be representative of average conditions on two of the stars, V 711
Tau and AR Lac. The total radiative losses from these two stars are
estimated and found to be larger than the sun by at least two orders of
magnitude. Consideration of the volume emitting in two of the principal
transition region lines suggests a possible relation between the disk
'filling factor' for these two lines and the dynamo-related Rossby
number. Only one hemisphere of the star II Peg, the one showing least
evidence of starspots, is similar. On the opposite hemisphere the
presence of a discrete emitting region is deduced which is almost
coincident in phase with the passage of the dominant optical spot
group across the visible disk. The dimensions of this region, and an
illustrative interpretation in terms of a large emitting magnetic loop,
are discussed. It is compared to large active region loops on the sun.

---------------------------------------------------------
Title: The chromospheres and coronae of five G-K main-sequence stars.
Authors: Jordan, C.; Ayres, T. R.; Brown, A.; Linsky, J. L.; Simon, T.
1987MNRAS.225..903J Altcode:
Five main-sequence stars, χ1 Ori (G0 V), α Cen A (G2
V), ξ Boo A (G8 V), α Cen B (K0 V) and ɛ Eri (K2 V) have been
observed at low and high dispersion with the International Ultraviolet
Explorer (IUE) satellite. The data obtained and X-ray observations
reported in the literature are used to make models of the structure
of the atmospheres of these stars, from the high chromosphere to the
corona. The electron pressures and coronal temperatures in these stars
range from being similar to those in the quiet solar atmosphere (α Cen
A) to the higher values found more typically in solar active regions
(e.g. χ1 Ori, ξ Boo A). The models are used to examine
the energy lost by radiation and transferred by thermal conduction,
in order to establish the heating requirements. The results are similar
to those found for the solar atmosphere.

---------------------------------------------------------
Title: Rotational modulation and flares on RS CVn and BY DRA
stars. III. IUEobserations of V711 Tau = (HR 1099), II Peg and AR Lac.
Authors: Rodono, M.; Byrne, P. B.; Neff, J. E.; Linsky, J. L.; Simon,
T.; Butler, C. J.; Catalano, S.; Cutispoto, G.; Doyle, J. G.; Andrews,
A. D.; Gibson, D. M.
1987A&A...176..267R Altcode:
The authors present observations of three RS CVn stars, which
were obtained over the stellar rotation cycles with the IUE
satellite. Emission lines from high-temperature transition regions
and chromospheres analogous to those observed in the solar spectrum
were observed. However, the stellar line surface fluxes are hundreds
of times the solar values. The only visible component of II Peg and
both components of V711 Tau and AR Lac appear to be chromospherically
active. The emission line fluxes for II Peg and, marginally, for the
other two systems were observed to vary in anti-phase with the optical
varations at the time of the authors' IUE observations. By comparing
the results of two-spot models from Paper I with the variation of UV
line flux, the authors find evidence of a close spatial correlation
between spot and plage-like features. They interpret these correlations
in terms of large spot areas in the stellar photospheres with overlying
magnetic loops, which form plages in the outer atmosphere.

---------------------------------------------------------
Title: IUE Observations of Hydrogen and Deuterium in the Local
Interstellar Medium
Authors: Murthy, J.; Henry, R. C.; Moos, H. W.; Landsman, W. B.;
Linsky, J. L.; Vidal-Madjar, A.; Gry, C.
1987ApJ...315..675M Altcode:
The authors present and analyze high-dispersion IUE observations of the
interstellar hydrogen and deuterium Lyα absorption profiles toward
the late-type stars ɛ Eri (3.3 pc), Procyon (3.5 pc), Altair (5.1
pc), Capella (13.2 pc), and HR 1099 (33 pc). They derive values for
the density nH I, the velocity dispersion bH I,
the bulk velocity vH I and determine lower limits on the
deuterium-to-hydrogen ratio (nD I/nH I). The
results are compared with previous Copernicus data. Interstellar
deuterium is detected toward every star except Altair. In
particular, the strong lower limit of D/H ≥ 1.9×10-5
from Copernicus is confirmed for the Capella sightline. A value of
D/H = 2.0×10-5 is consistent with all observations of
late-type stars.

---------------------------------------------------------
Title: X-Ray Sources in Regions of Star Formation. II. The
Pre--Main-Sequence G Star HDE 283572
Authors: Walter, F. M.; Brown, A.; Linsky, J. L.; Rydgren, A. E.;
Vrba, F.; Roth, M.; Carrasco, L.; Chugainov, P. F.; Shakovskaya,
N. I.; Imhoff, C. L.
1987ApJ...314..297W Altcode:
This paper reports the detection of HDE 283572, a ninth-magnitude G star
8 arcmin south of RY Tau, as a bright X-ray source. The observations
reveal this object to be a fairly massive (about 2 solar masses)
pre-main-sequence star associated with the Taurus-Auriga star formation
complex. It exhibits few of the characteristics of the classical
T Tauri stars and is a good example of a 'naked' T Tauri star. The
star is a mid-G subgiant, of about three solar radii and rotates
with a period of 1.5 d. The coronal and chromospheric surface fluxes
are similar to those of the most active late type stars (excluding T
Tauri stars). The X-ray and UV lines most likely arise in different
atmospheric structures. Radiative losses are some 1000 times the quiet
solar value and compare favorably with those of T Tauri stars.

---------------------------------------------------------
Title: Status Report on the SYNOP Project to Monitor Stars with
High-Resolution Spectroscopy
Authors: Linsky, J. L.; Giampapa, M. S.
1987BAAS...19..701L Altcode:
No abstract at ADS

---------------------------------------------------------
Title: VLA Observations of Rapid 6 cm Flux Variations in α Ori
Authors: Stencel, R. E.; Bookbinder, J.; Drake, S. A.; Simon, T.;
Linsky, J. L.; Florkowski, D.
1987BAAS...19..706S Altcode:
No abstract at ADS

---------------------------------------------------------
Title: Rotational modulation and flares on RS CVn and BY DRA
systems. II. IUE observations of BY Draconis and AU Microscopii.
Authors: Butler, C. J.; Doyle, J. G.; Andrews, A. D.; Byrne, P. B.;
Linsky, J. L.; Bornmann, P. L.; Rodono, M.; Pazzani, V.; Simon, T.
1987A&A...174..139B Altcode:
The modulation of the strong chromospheric and transition region lines
over one cycle of the optical light curves of BY Dra and AU Mic is
studied using IUE observations. The IUE observations were made from
October 2-5, 1981 and include 7 short wavelength (SW) spectra and 13
long wavelength (LW) spectra. The integrated line flux data reveal that
for BY Dra in the SW spectra there is modulation in the C IV, C II, O
I, and He II lines and nonflare surface fluxes; and in the LW spectra,
flares are detected in the Mg II and Fe II bands. It is observed that
there is no modulation in AU Mic, and the optical photometry data reveal
a poor correlation between optical flare strength and UV emission line
enhancements. The differential emission measure curves for BY Dra and
AU Mic are compared with solar curves. It is noted that both stars
show the presence of hot material throughout their rotation period.

---------------------------------------------------------
Title: VLA Observations of Rapid 6 cm Flux Variations in α Ori
Authors: Bookbinder, J. A.; Stencel, R. E.; Drake, S. A.; Simon, T.;
Linsky, J. L.; Florkowski, D.
1987LNP...291..337B Altcode: 1987csss....5..337B; 1987LNP87.291..337B
We present a series of VLA observations designed to monitor the
6 cm flux density variations of α Ori. Our results indicate that
variability is present at the 30% - 40% level on timescales of several
weeks. These timescales are probably inconsistent with any global or
large-scale processes.

---------------------------------------------------------
Title: Status Report on the Synop Project to Monitor Stars with High
Resolution Spectroscopy
Authors: Linsky, Jeffrey L.
1987LNP...291..483L Altcode: 1987csss....5..483L
This report summarizes the rationale, scientific programs and design
considerations for a proposed high resolution spectroscopic monitoring
facility.

---------------------------------------------------------
Title: 4 meter FTS observations of photospheric magnetic fields on
M dwarfs.
Authors: Saar, Steven H.; Linsky, Jeffrey L.; Giampapa, Mark S.
1987LIACo..27..103S Altcode: 1987oahp.proc..103S
Much of the observed activity on M dwarfs (e.g., spots, flares,
chromospheric and coronal emission) has been attributed to the
interaction of magnetic fields with the stellar atmosphere. Since data
on the magnetic field parameters of M dwarfs can potentially reveal much
about the physical mechanisms behind these phenomena and, additionally,
about stellar dynamos and the evolution of stellar angular momentum,
the authors have begun a program to measure the mean magnetic field
strength in stellar active regions, and the surface filling factor of
these regions for a sample of M dwarfs. In this paper some preliminary
results of this survey are discussed.

---------------------------------------------------------
Title: An Investigation of Stellar Coronae with AXAF
Authors: Linsky, Jeffrey L.
1987ApL&C..26...21L Altcode: 1987ApL....26...21L
Questions concerning the phenomenon of stellar coronae are discussed
together with the physical parameters essential to model stellar coronae
and the different AXAF instruments assigned for measurements of these
parameters. As an illustration of what AXAF will be able to accomplish,
three specific examples of studies by AXAF are described. These
include coronal modeling for a bright X-ray source such as HR 1099,
using spectra obtained by AXAF; time-resolved spectroscopy of AR
Lacertae and YY Geminormum during their eclipses, to use the spectra
for the identification and modeling of individual geometrical physical
structures on these stars; and time-resolved spectroscopy during
stellar flares to obtain high-resolution spectra which will make it
possible to infer the changes in the flaring plasma temperatures as
a function of time.

---------------------------------------------------------
Title: Chromospheric and Coronal Heating in a Volume Limited Sample
of K Dwarfs
Authors: Neff, D. H.; Bookbinder, J. A.; Linsky, J. L.
1987LNP...291..161N Altcode: 1987csss....5..161N; 1987LNP87.291..161N
We compare the chromospheric and coronal emission levels in an
essentially bias-free sample of K dwarfs. We find a rough power law
relation between the normalized soft x-ray flux and the Mg H h +
k flux, and we find further evidence of a minimum surface flux level
for Mg H h + k emission in cool dwarfs.

---------------------------------------------------------
Title: Measurements of Stellar Magnetic Fields: Empirical Constraints
on Stellar Dynamo and Rotational Evolution Theories
Authors: Linsky, Jeffrey L.; Saar, Steven H.
1987LNP...291...44L Altcode: 1987LNP87.291...44L; 1987csss....5...44L
We explore the implications of empirical stellar magnetic parameters
for dynamo theories, stellar activity theories, and models of the
evolution of stellar angular momentum.

---------------------------------------------------------
Title: Coordinated Observations of Stellar Flares
Authors: Linsky, Jeffrey L.
1987iue..prop.2803L Altcode:
We propose to make coordinated time-resolved IUE, EXOSAT, and
ground-based observations of dMe flare stars to investigate the spectral
distribution of stellar flare energy, simultaneously over a wide range
of wavelengths, from Xrays to microwaves. Recent successful results
strongly motivate our present proposal. In fact, the unique character
of each of the observed flares and the fortunate circumstance of fully
operative IUE and EXOSAT satellites in 1986 give a particularly strong
reason for additional time-resolved multiband data on stellar flares at
this time. Although time resolved observations in several bandpasses
exist for a very small number of flares, no flare has been observed
simultaneously from X-rays to microwaves. We propose to monitor one to
two of the most active stars among those in the target list, so that
the detection of major flares is highly probable. Spectra from quiescent
phases will be co-added to obtain low-noise spectra of faint transition
region and coronal lines to model outer atmospheric layers. Pure flare
spectra will be extracted by subtracting the average quiescent spectrum
from those at active phases. Several important issues will be addressed,
such as the applicability of loop model structure, the energy deposition
in the different atmospheric layers, the nature of flare continua,
and the extent of the similarity of solar and stellar flares.

---------------------------------------------------------
Title: Cool Stars, Stellar Systems, and the Sun
Authors: Linsky, J. L.; Stencel, R. E.
1987LNP...291.....L Altcode: 1987csss....5.....L
No abstract at ADS

---------------------------------------------------------
Title: What is the essential physics of mass loss from late-type
stars?
Authors: Linsky, Jeffrey L.
1987IAUS..122..271L Altcode:
The author considers what clues the data are providing us concerning the
mass loss from late-type stars. He considers in turn the major classes
of mass-loss mechanisms (thermally-driven winds, radiatively-driven
winds, and wave-driven winds), and considers whether the empirical mass
loss rates and other data are consistent with any of these mechanisms
acting alone. It is likely that several mechanisms act together to
produce the large mass loss rates in the Mira and nonpulsating M
supergiants. Studies of the solar atmosphere suggest that thermal
bifurcation driven by molecular condensation instabilities may play
a critical role in cooling the atmospheres of luminous cool stars and
forming silicate dust. It is possible that several metastable modes of
atmospheric structure may exist for a given set of stellar parameters.

---------------------------------------------------------
Title: A VLA Radio-Continuum Survey of a Sample of Confirmed and
Marginal Barium Stars
Authors: Drake, Stephen A.; Simon, Theodore; Linsky, Jeffrey L.
1987AJ.....93..163D Altcode:
Results are reported from a 6-cm VLA survey of five confirmed Ba II
stars and eight mild Ba II stars, undertaken to search for evidence of
gyrosynchrotron emission or thermal emission from the primary star's
wind that is enhanced or photoionized by a white dwarf companion. Of
these 13 stars, only Beta UMi was detected as a possible radio source
at a flux level of 0.11 mJy (3sigma). The 6-cm radio luminosities
(L6) of the other stars are as small as log L6 less than or equal
to 14.0 and are an order of magnitude or more lower than the average
levels found in RS CVn systems, but are consistent with the L6 upper
limits previously found for stars of spectral type similar to the Ba
II stars and normal elemental abundances. The upper limit to the radio
luminosity for the possible mild Ba II star 56 Peg, when combined with
its previously known X-ray luminosity, may provide useful constraints
on the various models that have been proposed for this interesting
object, once its orbital period is known.

---------------------------------------------------------
Title: Intrinsic Hydrogen Lyman Alpha Profile of AR Lacertae
Authors: Linsky, Jeffrey L.
1987iue..prop.2805L Altcode:
We propose to acquire high-resolution spectra of the H I Lyman-alpha
(Ly-alpha) emission line (1216 A) of the eclipsing binary RS CVn system
AR Lacertae. The velocity difference between opposite quadratures
will cause a wavelength shift in the stellar profiles of about 0.6 A
with respect to the interstellar absorption line center. By obtaining
high-dispersion spectra at successive quadratures, we will be able to
recover that portion of the intrinsic stellar Ly-alpha profile that is
generally obscurred by interstellar absorption and thereby determine
the intrinsic profiles of both components of AR Lac. Once we know the
intrinsic shape of the profile, we will be able to correct for the
geocoronal and interstellar contributions in existing SWP-LO spectra of
AR Lac and other active stars so that we can determine the surface flux
of Ly-alpha. We will obtain additional short low-resolution exposures
that will allow us to test and calibrate our techniques for performing
these corrections. We will incorporate the surface flux measurements
into the multi-component models that we are constructing for this
star. Discrete plage emission components seen on the Mg II k lines
might also be visible on the Ly-alpha profile. If so, we will be able
to obtain the Ly-alpha surface flux within the plage regions alone.

---------------------------------------------------------
Title: Chromospheres and Transition Regions
Authors: Jordan, Carole; Linsky, Jeffrey L.
1987ASSL..129..259J Altcode: 1987euwi.book..259J
The properties of stellar chromospheres are examined, summarizing the
results of observations obtained with the IUE satellite since its launch
in 1978. Numerous sample spectra, graphs, and diagrams are presented and
analyzed in detail. Consideration is given to 120-320-nm spectroscopy of
main-sequence stars, giants, and supergiants; the global properties of
main-sequence and post-main-sequence chromospheres; dynamic phenomena
and structures (systematic flows, atmospheric inhomogeneities, and
intrinsic variability); and structural and energy-balance modeling. A
number of outstanding problems are listed, and the potential value of
data from the Hubble Space Telescope and the Lyman FUV Spectroscopic
Explorer in solving them is indicated.

---------------------------------------------------------
Title: High-Dispersion Observations of Alpha Bootis (K1 III) with
the International Ultraviolet Explorer
Authors: Ayres, T. R.; Judge, P.; Jordan, C.; Brown, A.; Linsky, J. L.
1986ApJ...311..947A Altcode:
The authors have obtained very deeply exposed IUE echelle spectrograms
of the bright, early-K giant Arcturus. They did not detect significant
flux in the most prominent high-excitation species of a solar-like
transition zone, C IV λ1548.2. The presence of a weak feature of
Si III] λ1892.0, and possibly also Si IV λ1393.8, indicates the
existence of a small amount of plasma at temperatures as hot as
6×104K. Measurements of C II] multiplet UV0.01 near 2325
Å provide a lower limit of about 5×109cm-3 for
the electron density in the chromospheric layers. C II UV1 (1335 Å)
emission is very weak. These results confirm that the "coronal" activity
of the old red giants is considerably diminished from that of even the
"quietest" of their main-sequence predecessors, stars like the Sun.

---------------------------------------------------------
Title: Recent Progress in Understanding Phenomena in Cool Star
Atmospheres Using High Resolution Spectroscopy &amp;Monitoring
Techniques
Authors: Linsky, J. L.
1986BAAS...18Q1014L Altcode:
No abstract at ADS

---------------------------------------------------------
Title: Corrected observed stellar Lyman Alpha profiles for the
effects of interstellar absorption and geocoronal emission
Authors: Neff, J. E.; Linsky, J. L.; Landsman, W. B.; Carpenter, K. G.
1986ESASP.263..669N Altcode: 1986NIA86......669N; 1986niia.conf..669N
Techniques to compensate for interstellar absorption and geocoronal
emission in IUE studies of late stars atmospheres were developed. Thus
it is possible to determine the Lyman alpha flux from nearby cool stars
using the low-resolution spectra in the IUE archives. The accuracy of
such a procedure depends fundamentally upon the assumptions regarding
the shape of the intrinsic profile and the density and velocity
structure of the local interstellar medium, not upon measurement
uncertainties of the low-resolution spectra. Geocoronal emission
and saturated spectra are fatal only to a one-dimensional spectral
analysis. When both the spatial and the spectral dimensions are
considered, the observed Lyman alpha flux can be recovered.

---------------------------------------------------------
Title: Rotational modulation and flares on RS CVn and BY Dra-type
stars. I. Photometry and SPOT models for BY Dra, AU Mic, AR Lac,
II Peg and V711 Tau (=HR 1099).
Authors: Rodono, M.; Cutispoto, G.; Pazzani, V.; Catalano, S.;
Byrne, P. B.; Doyle, J. G.; Butler, C. J.; Andrews, A. D.; Blanco,
C.; Marilli, E.; Linsky, J. L.; Scaltriti, F.; Busso, M.; Cellino,
A.; Hopkins, J. L.; Okazaki, A.; Hayashi, S. S.; Zeilik, M.; Helston,
R.; Henson, G.; Smith, P.; Simon, T.
1986A&A...165..135R Altcode:
Multicolor wide-band photometry of five active stars is presented. The
observations were carried out at several places before, during and
after the period of IUE observations for the purpose of determining
the location, sizes, and evolution of photospheric spots at the time
when chromospheric, transition region, and coronal activity data were
obtained from UV and radio observations. II Peg, BY Dra, and AU Mic
show fairly stable quasi-sinusoidal light curves, while AR Lac and V
711 Tau show double-peaked light curves. For V 711 Tau, a remarkable
evolution of the spotted area extent and/or longitude distribution
is found. Small, but definite color variations that are consistent
with the cool spot hypothesis have also been detected for BY Dra,
II Peg and V 711 Tau.

---------------------------------------------------------
Title: Activity in warm stars: IUE observations of early F dwarfs
Authors: Walter, F. M.; Linsky, J. L.
1986ESASP.263..103W Altcode: 1986niia.conf..103W; 1986NIA86......103W
Deep low dispersion, short wavelength IUE observations of 69 F dwarfs
were studied by overexposing the long wavelength end of the SWP camera
by up to 100 times in order to bring up the weak chromospheric and
transition region (TR) emission lines. All but one of the stars observed
shows evidence for stellar activity, as defined by the presence of
large C II and C IV surface fluxes, with fluxes greater than 100,000
ergs/sqcm/sec. There is no correlation between surface flux and the
stellar rotation rate in the early F dwarfs. The TR surface fluxes
increase systematically with decreasing B-V color, with no evidence
for any decrease in the activity as the convection zones become very
small. It is argued that there is a fundamental difference in the
atmospheric heating mechanisms between early F dwarfs and solar-like
stars. The heating of the TR in the early F dwarfs may be dominated
by acoustic heating.

---------------------------------------------------------
Title: Where do flares occur in RS CVn systems ? -- Analysis of the
october 3, 1981 flare on V711 Tau = HR 1099 observed by IUE.
Authors: Linsky, J. L.; Neff, J. E.; Gross, B. D.; Simon, T.; Andrews,
A. D.; Rodono, M.
1986ESASP.263..161L Altcode: 1986niia.conf..161L; 1986NIA86......161L
A set of IUE observations of V711 Tau = HR 1099 (K1 IV and G2 V) in
which high-resolution spectra with the SWP and LWR cameras were obtained
during the luminous flare of October 3, 1981 is discussed. Multigaussian
fits to the Mg II k and C IV 1548 A lines are consistent with the
flare radial velocity being identical to that of the K star. Thus,
the flare probably occurred on the K star. There is no evidence for
flows as seen during a flare on UX Ari. The strongest emitters of UV
radiation during the flare were the L alpha and Mg II lines, which
emitted seven times as much energy as all the transition region lines
combined. The peak luminosity of the flare in the UV emission lines is
1.5 times 10 to the 31st power ergs/sec, and the total emission in these
lines during the flare was about 4 times 10 to the 35th power ergs.

---------------------------------------------------------
Title: Ultraviolet and optical variability of RY Tauri.
Authors: Brown, A.; Linsky, J. L.; Drake, S. A.; Herbst, W.
1986ESASP.263..177B Altcode: 1986niia.conf..177B; 1986NIA86......177B
Ultraviolet and optical observations of the T Tauri star RY Tau
were analyzed. They show evidence for strong variability over 1985
to 1986. High dispersion IUE observations of the Mg II emission line
profiles show significant changes in the wind of RY Tau, with the wind
absorption almost disappearing on 1986 March 20. The behavior of the
emission line flux variability when compared to the optical light curve
shows evidence for changes in circumstellar extinction and changes in
starspot/plage distribution on the visible hemisphere of the star.

---------------------------------------------------------
Title: Definition and empirical structure of the range of stellar
chromospheres-coronae across the H-R diagram: Cool stars
Authors: Linsky, J. L.
1986STIN...8632377L Altcode:
Major advances in our understanding of non-radiative heating and other
activity in stars cooler than Teff = 10,000K has occured
in the last few years. This observational evidence is reviewed and
the trends that are now becoming apparent are discussed. The evidence
for non-radiatively heated outer atmospheric layers (chromospheres,
transition regions, and coronae) in dwarf stars cooler than spectral
type A7, in F and G giants, pre-main sequence stars, and close bindary
systems is unambiguous, as is the evidence for chromospheres in the K
and M giants and supergiants. The existence of non-radiative heating
in the outer layers of the A stars remains undetermined despite
repeated searches at all wavelengths. Two important trends in the
data are the decrease in plasma emission measure with age on the main
sequence and decreasing rotational velocity. Variability and atmospheric
inhomogeneity are commonly seen, and there is considerable evidence that
magnetic fields define the geometry and control the energy balance in
the outer atmospheric layers. In addition, the microwave observations
imply that non-thermal electrons are confined in coronal magnetic flux
tubes in at least the cool dwarfs and RS CVn systems. The chromospheres
in the K and M giants and supergiants are geometrically extended, as
are the coronae in the RS CVn systems and probably also in other stars.

---------------------------------------------------------
Title: Tz-Fornacis - an Eclipsing Capella-Like System Observed
with IUE
Authors: Eriksson, K.; Saxner, M.; Gustafsson, B.; Ayres, T. R.;
Linsky, J. L.; Anderson, J.
1986ESASP.263..225E Altcode: 1986niia.conf..225E; 1986NIA86......225E
The IUE observed TZ Fornacis at orbital phases 0.0, 0.25 and 0.79 in
1986. Most of the exposures were LWP-HI or SWP-LO. Results show that:
the surface fluxes for transition region emission lines are similar
to those for the Capella system while that of the Mg II emission is
smaller; the total flux in the Mg II emission lines is constant with
phase, whereas the flux in the C IV emission lines decreases by 1/3
during primary eclipse, indicating that most of the activity is due
to the hotter giant (F7 III), which is also the case for Capella.

---------------------------------------------------------
Title: The proposed LYMAN Far Ultraviolet Spectroscopic Explorer
Authors: Linsky, J. L.; et al.
1986ESASP.263..537L Altcode: 1986niia.conf..537L
The author summarizes the scientific and technical ideas presented
in the proposal for the LYMAN Far Ultraviolet Spectroscopic
Explorer. LYMAN is designed to answer a broad range of exciting
questions in astrophysics that require high resolution, high sensitivity
spectroscopy in the 912 - 1200 Å band and in the EUV, which cannot
be answered by other means.

---------------------------------------------------------
Title: First Results of an IUE Study of the Ultraviolet Spectra of
Short-Period RS CVn Binary Systems
Authors: Drake, S. A.; Simon, T.; Linsky, J. L.
1986BAAS...18..955D Altcode:
No abstract at ADS

---------------------------------------------------------
Title: Mg II Emission Line Variability of Hybrid Chromosphere Stars
Authors: Brown, A.; Linsky, J. L.; Drake, S. A.; Carpenter, K. G.
1986BAAS...18S.983B Altcode:
No abstract at ADS

---------------------------------------------------------
Title: IUE Spectra of Flares on Au-Microscopii
Authors: Butler, C. J.; Rodono, M.; Linsky, J. L.
1986ESASP.263..229B Altcode: 1986NIA86......229B; 1986niia.conf..229B
IUE spectra were obtained in August 1980 through a substantial part
of the optical cycle of the BY Draconis-type, spotted M dwarf star, AU
Mic. No modulation of the ultraviolet emission line fluxes in antiphase
with the optical curve was detected. Simultaneous optical photometry
of AU Mic, when available, shows remarkably poor correlation of optical
flare strength and ultraviolet emission-line enhancements. In general,
the 'flares' detected on AU Mic, show considerable variety in the degree
of enhancement in the various emission lines and optical continuum.

---------------------------------------------------------
Title: IUE study of the very local interstellar medium
Authors: Henry, R. C.; Murthy, J.; Moos, H. W.; Landsman, W. B.;
Linsky, J. L.; Vidal-Madjar, A.; Gry, C.
1986ESASP.263..555H Altcode: 1986NIA86......555H; 1986niia.conf..555H
IUE and Copernicus results are compared, for studies of the very
local interstellar medium. Despite its lower resolution, IUE produces
results of comparable quality, giving important confirmation of
Copernicus results on the density, temperature, turbulence, and
deuterium-to-hydrogen ratio in the region within ≡10 pc of the
sun. The stars observed are in a very low-density quarter of the galaxy:
multi-component structure seen in other directions may not be present
in the direction of most of our observed stars. The exceedingly low
densities observed in certain directions encourages the idea that EUV
(λ &lt; 912 Å) studies of certain normal stars may be possible.

---------------------------------------------------------
Title: High-dispersion IUE observations of hybrid-chromosphere stars
Authors: Brown, A.; Reimers, D.; Linsky, J. L.
1986ESASP.263..169B Altcode: 1986niia.conf..169B; 1986NIA86......169B
High dispersion, wavelength calibrated IUE spectra of the
hybrid-chromosphere stars alpha TrA (K2 IIb-IIa) and upsilon Aql
(K3 II) are presented. These observations allow accurate measurement
of the wind terminal velocities as seen in the Mg II emission line
profiles. The terminal velocities deduced for upsilon Aql and alpha
TrA are 110 and 120 km/sec respectively. The terminal velocity for
alpha TrA is significantly reduced from the 180 km/sec seen in spectra
obtained 2 yr earlier. The intersystem emission lines of C I (1993 A),
C II (2325 A), C III (1908 A), O I (1641 A; fluoresced) and Si III
(1892 A) are at essentially their rest wavelengths. The upsilon Aql C
II intersystem multiplet line fluxes indicate an electron density near
1 billion/cc in their line formation region. Results suggest that the
transition region intersystem lines are unlikely to be formed in the
high velocity wind seen in the Mg II lines but are certainly formed
in a region with significant turbulence.

---------------------------------------------------------
Title: A 6 centimeter radio survey of short-period active binary
stars.
Authors: Drake, S. A.; Simon, T.; Linsky, J. L.
1986AJ.....91.1229D Altcode:
Thirteen binaries with periods in the range of 0.2-2.0 days have been
observed at 6 cm wavelength with the VLA. Eight out of these thirteen
systems were detected, of which seven are RS Canum Venaticorum systems
and one is an Algol system, with observed fluxes in the range of 0.3-5.0
mJy. The individual characteristics of the detected sources are briefly
discussed. As a group, relative to active binaries of longer orbital
periods, the short-period active binaries have a slightly lower mean
radio luminosity. There is also a clear correlation of high radio
luminosity with high X-ray luminosity evident in these short-period
systems, although a functional dependence cannot be determined from
noncontemporary data.

---------------------------------------------------------
Title: IUE Observations of Interstellar Hydrogen and Deuterium toward
Alpha Centauri B
Authors: Landsman, W. B.; Murthy, J.; Henry, R. C.; Moos, H. W.;
Linsky, J. L.; Russell, J. L.
1986ApJ...303..791L Altcode:
A high dispersion profile is presented of the Lyman-alpha emission
toward Alpha Cen B as recorded in two images taken with the IUE
spacecraft. The spectra were examined with a three-parameter Gaussian
or five-parameter solar-type profile to derive the intrinsic background
stellar emission. Voight absorption profiles were calculated for the
intervening H I and D I gas. A uniform, thermally broadened medium
was assumed, with the calculations being based on the free stellar
parameters of density, velocity dispersion and the bulk velocity of
H I, and the density of D I. The use of a small aperture is shown
to have been effective in eliminating geocoronal and interplanetary
diffuse Ly-alpha contamination. The H I absorption profile toward
Alpha Cen B is found to be equivalent to that toward Alpha Cen A,
indicating that the H I profiles derived are essentially independent
of stellar emission. Less success, however, was attained in obtaining
any definitive D I profile, although an asymmetry in the blue and red
wings of the Lyman-alpha emissions did show the presence of absorption
by interstellar deuterium and allow setting a lower limit of 0.00001
for the D I/H I ratio.

---------------------------------------------------------
Title: Ultraviolet, Optical, Infrared, and Microwave Observations
of HR 5110
Authors: Little-Marenin, I. R.; Simon, Theodore; Ayres, T. R.; Cohen,
N. L.; Feldman, P. A.; Linsky, J. L.; Little, S. J.; Lyons, R.
1986ApJ...303..780L Altcode:
HR 5110 is a close binary system (P = 2d.6) with the
characteristics of an Algol system. Because the primary star is
relatively cool (F2 IV) and there is no apparent emission from
an accretion disk, the authors were able to detect in IUE spectra
the emission of an active chromosphere and transition region of the
cooler (K0 IV) secondary. The surface fluxes of the UV emission lines
of the K star are similar to those of active RS CVn binaries. The
line fluxes appear to vary with orbital phase and are interpreted as
emission from an active region on the K star. Two large radio flares
were detected. VLBI observations during one of these flares indicated
that half the emission came from a region more than 4 times the binary
separation.

---------------------------------------------------------
Title: The Magnetic Field of the BY Draconis Flare Star EQ Virginis
Authors: Saar, S. H.; Linsky, J. L.; Beckers, J. M.
1986ApJ...302..777S Altcode:
High resolution, high S/N-ratio line profiles of the BY Draconis-type
flare star EQ Vir obtained with the MMT are presently subjected to
a novel Zeeman analysis procedure which includes radiative transfer
effects and compensation for blends. A mean field of 2500 + or -
300 G covering 80 + or 15 percent of EQ Vir is determined. This
constitutes the first positive detection of a magnetic field in a BY
Draconis-type flare star, confirming that magnetic fields are present
on these stars. The value of 2500 G obtained for the photospheric field
strength is similar to the value derived by assuming equipartition of
magnetic and thermal energy densities in the photosphere and scaling
from the solar network fields, suggesting that equipartition may
determine the mean field strength in the nonspotted portion of the
flare star photosphere.

---------------------------------------------------------
Title: Radio continuum emission from winds, chromospheres and coronae
of cool giants and supergiants.
Authors: Drake, S. A.; Linsky, J. L.
1986AJ.....91..602D Altcode:
The results of a sensitive VLA radio survey of the single cool-wind
giants and super giants stars, having spectral types in the range
(G0-M5), are presented. The survey was carried out at 6 cm using the
NRAO VLA. The results of the observations are discussed in the context
of the various mechanisms which might be producing radio emission in
the cool stars. One coronal giant was detected as well as six cool-wind
giants in the range 2-6 cm at levels of 0.1-2 mJy. The six-cm emission
of the coronal giant alpha Aurigae is shown to be optically thin having
free-free emission from the corona of energy 10 to the 7th K. The
2-cm emission from alpha Aur also contains contribution of about 65
percent from the stellar disk of one or both stars. The radio emission
from all other sources is explained as optically thick emission from
stellar winds. The inferred ionized mass-los rates for the cool wind
stars was about 10 to the 10th solar mass per year for MK III-type
stars and 10 to the -9th solar mass per year for MK II type stars.

---------------------------------------------------------
Title: Modelling Extended Chromospheres
Authors: Linsky, J. L.
1986IrAJ...17..343L Altcode:
The author reports here on calculations by Drake (1985) and Drake
and Linsky (1986) for the Mg II k line of Arcturus (α Boo, K2 III),
assuming a spherically-symmetric chromosphere, two-level Mg+
ion, and angle-averaged redistribution functions. These calculations
were based on an original program kindly provided by Paul Kunasz and
modified to include partial redistribution of this particular type.

---------------------------------------------------------
Title: The Surface Magnetic Fields of dM and dMe Stars
Authors: Saar, S. H.; Linsky, J. L.; Giampapa, M. S.
1986BAAS...18..670S Altcode:
No abstract at ADS

---------------------------------------------------------
Title: Microwave Continuum Measurements and Estimates of Mass-Loss
Rates for Cool Giants and Supergiants
Authors: Drake, S. A.; Linsky, J. L.
1986IrAJ...17..288D Altcode:
Attention is given to the results of a sensitive, 6-cm radio continuum
survey conducted with the NRAO VLA of 39 of the nearest single cool
giants and supergiants of G0-M5 spectral types; the survey was conducted
in order to obtain accurate measurements of the mass loss rates of
ionized gas for a representative sample of such stars, in order to
furnish constraints for, and a better understanding of, the total mass
loss rates. The inferred angular diameters for the cool giant sources
are noted to be twice as large as photospheric angular diameters,
implying that these stars are surrounded by extended chromospheres
containing warm partially ionized gas.

---------------------------------------------------------
Title: Coordinated IUE and ground-based observations of stellar
flares: YZ CMi, Proxima Cen and AD Leo.
Authors: Foing, B. H.; Rodono, M.; Cutispoto, G.; Catalano, S.; Linsky,
J. L.; Gibson, D. M.; Brown, A.; Haisch, B. M.; Butler, C. J.; Byrne,
P. B.; Andrews, A. D.; Doyle, J. G.; Gary, D. E.; Henry, G. W.; Russo,
G.; Vittone, A.; Scaltriti, F.
1986RMxAA..12..213F Altcode:
Coordinated observations of stellar flares were obtained with lUE
and several ground-based facilities in March 1984.The simultaneous
observations allowed it to cover a wide range of wavelengths from ii5nm
to 6cm.We intend to study the effect ofthe observed flares at different
atmospheric heights in order to estimate the energy budget,the time
scales and the cooling processes.Our observations includetime-resolved
IUE spectroscopy at SWP(115-195nm) and LWP(190-320nm),optical
spectroscopy at the ESO 3.6m+IDS (355-440nm),high resolution
spectroscopy at the ESO 1.4m CAT+CES(653-659nm),narrow band H alpha
and wide band optical photometry, infrared photometry at 2.2microns
and microwave observations at 2,6 and 20 cm We present for some
flare events,among the results,the first detection of infrared flux
decrease -or "negative flare"-in coincidence with the flux increase
at the other wavelengths:the broadening and changes of the Balmer H
lines,He and high excitation lines;the appearance of higher members
of the Balmer serie;the enhancements of Mg II doublet and Fe II blend
(260nm);and the flare detection at 2cm and 6cm

---------------------------------------------------------
Title: The outer atmosphere of Procyon (alpha CMi F5IV-V) : evidence
of supergranulation or active regions.
Authors: Jordan, C.; Brown, A.; Walter, F. M.; Linsky, J. L.
1986MNRAS.218..465J Altcode:
Observations made with the Einstein X-ray observatory and Exosat have
shown Procyon (Alpha CMi) to have a measurable X-ray flux. The flux
observed is similar to the upper limits previously reported. The
interpretation of the X-ray data in the context of models made
previously by Brown and Jordan (1981) based on spectra obtained with
the IUE satellite. The X-ray data lead to a higher electron pressure
than does the UV spectrum. These results support the conclusion by Brown
and Jordan that the UV data cannot be reconciled with a hot corona in a
spherically symmetric uniform model. Two types of models are explored;
one in which the X-ray emission originates from an isothermal corona
but the UV emission is restricted to limited regions of the disk,
analogous to solar supergranulation structure; the other in which
hot loop structures are embedded in a cool (T(e) of about 300,000 K)
corona. Monitoring of Procyon to search for variability is urgently
required to distinguish between these models. Some comparisons with
the predictions of scaling laws are made. This hot isothermal coronal
model agrees quite well with the predictions of Hearn's (1977) minimum
flux model.

---------------------------------------------------------
Title: Second Generation Spectrograph for the Hubble Space Telescope
Authors: Maran, S. P.; Woodgate, B. E.; Boggess, A.; Gull, T. R.;
Heap, S. R.; Melcher, R.; Green, R. F.; Wolff, S. C.; Hutchings, J. B.;
Jenkins, E. B.; Linsky, J. L.; Moos, H. W.; Roesler, F.; Shine, R. A.;
Timothy, J. G.; Weistrop, D. E.
1986BAAS...18..636M Altcode:
No abstract at ADS

---------------------------------------------------------
Title: IUE observations of neutral hydrogen and deuterium in the
local interstellar medium.
Authors: Landsman, W. B.; Murthy, J.; Henry, R. C.; Moos, H. W.;
Linsky, J. L.; Vidal-Madjar, A.; Gry, C.
1986AdSpR...6b..87L Altcode: 1986AdSpR...6Q..87L
Small-aperture, high-dispersion IUE spectra have been obtained of
seven late-type stars that, in general, confirm previous Copernicus
results concerning the distribution of hydrogen and deuterium in the
local interstellar medium. In addition, the IUE Ly α spectra of Altair,
and of the α Cen components, suggest that multiple velocity components
exist in these two directions.

---------------------------------------------------------
Title: HR 5110: An Algol System with RS CVn Characteristics
Authors: Little-Marenin, I. R.; Linsky, Jeffrey L.; Simon, Theodore
1986LNP...254..247L Altcode: 1986csss....4..247L
No abstract at ADS

---------------------------------------------------------
Title: The HRS GTO program to study the neutral hydrogen column
density and D/H ratio in the local interstellar medium
Authors: Linsky, J. L.; Landsman, W. B.; Heap, S. R.; Savage, B. D.;
Smith, A. M.; Brandt, J. C.
1986AdSpR...6b..91L Altcode: 1986AdSpR...6...91L
Early in the HST mission the HRS Team will observe the Lyman alpha line
at 100,000 spectral resolution toward 7 late-type local stars. The
purpose is to derive the hydrogen and deuterium column densities and
D/H ratios along lines of sight toward nearby stars. Here we present
theoretical line profiles that demonstrate why 105 spectral
resolution and high signal-to-noise are needed to derive accurate column
densities from spectral lines that lie close to the flat part of the
curve of growth and may contain multiple velocity components. The aim
of the HRS program is to obtain column densities in the hydrogen and
deuterium Lyman alpha lines along a variety of lines of sight within
and extending beyond the local cloudlet in which the Sun is located
near an edge. The broad chromospheric Lyman alpha emission lines of
late-type stars are used as background sources against which to measure
the interstellar absorption features. We will also obtain profiles of
interstellar absorption features in Mg II and Fe II lines to derive
the broadening parameter and/or identify possible multiple velocity
components in the lines of sight.

---------------------------------------------------------
Title: Second generation spectrograph for the Hubble Space Telescope.
Authors: Woodgate, B. E.; Boggess, A.; Gull, T. R.; Heap, S. R.;
Krueger, V. L.; Maran, S. P.; Melcher, R. W.; Rebar, F. J.; Vitagliano,
H. D.; Green, R. F.; Wolff, S. C.; Hutchings, J. B.; Jenkins, E. B.;
Linsky, J. L.; Moos, H. W.; Roesler, F.; Shine, R. A.; Timothy, J. G.;
Weistrop, D. E.; Bottema, M.; Meyer, W.
1986SPIE..627..350W Altcode:
The preliminary design for the Space Telescope Imaging Spectrograph
(STIS), which has been selected by NASA for definition study for future
flight as a second-generation instrument on the Hubble Space Telescope
(HST), is presented. STIS is a two-dimensional spectrograph that
will operate from 1050 A to 11,000 A at the limiting HST resolution
of 0.05 arcsec FWHM, with spectral resolutions of 100, 1200, 20,000,
and 100,000 and a maximum field-of-view of 50 x 50 arcsec. Its basic
operating modes include echelle model, long slit mode, slitless
spectrograph mode, coronographic spectroscopy, photon time-tagging,
and direct imaging. Research objectives are active galactic nuclei,
the intergalactic medium, global properties of galaxies, the origin
of stellar systems, stelalr spectral variability, and spectrographic
mapping of solar system processes.

---------------------------------------------------------
Title: New measurements of photospheric magnetic fields in late-type
stars and emerging trends
Authors: Saar, S. H.; Linsky, J. L.
1986AdSpR...6h.235S Altcode: 1986AdSpR...6..235S
We report on recent results of our program to measure photospheric
magnetic field strengths and filling factors from the analysis of
unpolarized high spectral resolution and S/N line profiles. We have
analyzed spectra obtained with the KPNO 4-m FTS, the MMT, and the
McMath Reticon Spectrograph. With the latter instrument we now have
an extensive data set through our synoptic and survey observing
programs. Photospheric magnetic field parameters are obtained by
comparison of observed and theoretical line profiles using an LTE
code that includes line saturation and the full Zeeman pattern. We
determine the nonmagnetic line broadening parameters for a star by
fitting profiles of low Landé g lines formed under conditions similar
to the high g lines which are used to infer magnetic fields. The
effects of line blending are cancelled to first order by fitting
profiles of the same high g lines in comparison inactive stars of
the same spectral type. We have measured field parameters (outside of
starspots) in dwarf stars of spectral type GO to dM3.5e (Ad Leo). We
find a trend of increasing field strength with later spectral type,
consistent with equal gas and magnetic pressure in the photosphere,
and a trend of increasing filling factor with activity. Our data are
inconsistent with the hypothesis of a constant number of magnetic flux
tubes on active stars. Staff Member, Quantum Physics Division,
National Bureau of Standards.

---------------------------------------------------------
Title: Study of Active Regions on the K Star Components of RS CVN
and HD 5303
Authors: Linsky, Jeffrey L.
1986iue..prop.2488L Altcode:
Our previous IUE observations of RS CVn systems have shown that the
MgII lines exhibit phase-dependent asymmetries. Using such data we
have applied Doppler imaging techniques to reconstruct a large scale
picture of chromospheric active regions on the stellar surfaces of both
components of the RS CVn-type system AR Lac. Photometric observations
of such systems indicate large spotted regions, which are probably
aggregates of small spots. High spatial resolution to permit mapping
of small structures in the MgII bright regions can be achieved only
during the eclipse of the active component. We propose to observe two
RS CVn systems, RS CVn itself and HD 5303, from before first contact
until after fourth contact during the secondary eclipse (when the
active K star is behind). These systems are particularly suitable for
study by IUE because the primary components are of early spectral type
(F6V and F0V) and do not show any MgII emission. Thus any change in
the MgII emission profile can be easily detected as active regions
are eclipsed or reappear. We will observe each system continuously
during secondary eclipse with consecutive ESA-US1 shifts, obtaining
a LWP-HI spectrum every 85 min and 70 min for RS CVn and HD 5303,
respectively. Doppler imaging techniques will allow us to reconstruct
the surface distribution of MgII and to determine the location and
size of active regions in these very active stars. We will compare
these data with photospheric and coronal information obtained from
our photometric, Xray, and radio observations.

---------------------------------------------------------
Title: RY Tau
Authors: Linsky, Jeffrey
1986iue..prop.2624L Altcode:
No abstract at ADS

---------------------------------------------------------
Title: The Time Variability of Magnetic Fields on Epsilon Eridani
Authors: Saar, Steven H.; Linsky, Jeffrey L.; Duncan, Douglas K.
1986LNP...254..275S Altcode: 1986csss....4..275S
No abstract at ADS

---------------------------------------------------------
Title: Chromospheric &amp; Coronal Heating for a Statistically
Complete Sample of K Stars
Authors: Linsky, Jeffrey L.
1986iue..prop.2480L Altcode:
The overall energy balance of the outer atmospheres of solar- and
late-type dwarf stars appears to undergo a dramatic shift as one
proceeds from spectral types G to M. The solar type stars have an
outer atmosphere in which the radiative losses are dominated by the
chromosphere; in the latertype stars the corona dominates. We propose
to study the nature of this transition, and the implications for
the heating mechanisms, using a carefully selected volume-limited
sample of single, X-ray selected K dwarfs. Low resolution, long
wavelength IUE observations of the MgII resonance lines will allow
us to determine the radiative losses of the chromospheres. These
losses can be correlated with the coronal losses; trends dependent
on age and effective temperature can be used to constrain models for
the non-radiative heating that forms the chromospheres and coronae of
these stars. For a subset (consisting of the brightest) of these stars,
we will also measure the luminosities of such transition region lines
as CIV and CII, enabling us to form a comprehensive picture of the
radiative losses of stellar plasmas between 10^4 K and 10^7 K as a
function of age and effective temperature. This information will serve
to further constrain models of non-radiative heating in late-type stars.

---------------------------------------------------------
Title: The Chromospheric and Transition Region Emiss Region Emission
Lines of the Herbig Foe Stars BN ORI and N
Authors: Linsky, Jeffrey L.
1986iue..prop.2486L Altcode:
We propose to obtain long (10 and 12 hours respectively) LWP high
dispersion spectra of the pre-main-sequence Herbig FOe stars BN Ori
and NGC 2264 Walker 158. BN Ori is a 2.5 M(sun) star with an age of
~1.5x10^6 K and strong chromospheric and transition region emission
lines. W158 is a 2.5 Me star with an age of about 1.2x10^6 years. These
spectra in conjunction with SWP-LO spectra obtained in the same shifts
will be used to investigate the outer atmospheric structure of BN
Ori and W158, leading to models of their chromospheres, transition
regions and winds. By comparison of these stars with other high mass
pre-main-sequence stars we shall investigate how the outer atmospheric
structure of such stars evolves as the stars move towards the main
sequence and how this structure depends on stellar mass.

---------------------------------------------------------
Title: The SHIRSOG Workshop. Proceedings of a workshop on prospects
for a new synoptic high resolution spectroscopic observing facility,
held at the National Solar Observatory, National Optical Astronomy
Observatories, Tucson, Arizona, USA, 3 September 1986.
Authors: Giampapa, M. S.; Jefferies, J. T.; Linsky, J. L.
1986swpw.book.....G Altcode:
No abstract at ADS

---------------------------------------------------------
Title: Concluding Session - Shirsog Workshop
Authors: Linsky, J. L.
1986tswo.work..140L Altcode:
No abstract at ADS

---------------------------------------------------------
Title: Progress Report: Precise Measurements of Radial Velocities
of Far-Ultraviolet Emission Lines in Stars of Late Spectral Type
Authors: Ayres, T.; Engvold, O.; Jensen, E.; Linsky, J.
1986LNP...254...94A Altcode: 1986csss....4...94A
Recent high-dispersion, far-ultraviolet IUE spectra of the G-type
supergiant β Draconis contain evidence for organized, persistent
downflows of gas, apparently confined to a high-density component of
the stellar transition zone.

---------------------------------------------------------
Title: Guidelines for Allocation of Observing Time and Scheduling
Authors: Linsky, J. L.
1986tswo.work..102L Altcode:
No abstract at ADS

---------------------------------------------------------
Title: Ultraviolet Emission from Cool Stars with Measured Magnetic
Fields
Authors: Linsky, Jeffrey L.
1986iue..prop.2481L Altcode:
We propose to obtain new UV spectra of about 11 highly active late-type
dwarfs and to reanalyze spectra of roughly 40 stars from the IUE
archives to explore the relationships between chromospheric and
transition-region line emission and surface magnetic flux measurements
which we have made. We are presently engaged in a program to detect
photospheric magnetic field strengths and fractional area coverages,
using proven, advanced techniques, for a broad range of G, K and
M stars. Over 50 measurements have been made. The relationships we
find between the magnetic parameters and UV line fluxes will provide
important input to theories of nonradiative heating of stellar
atmospheres and dynamo activity in late-type stars. By studying
stars over a broad range of physical parameters, we may be able to
determine the mechanisms by which the magnetic energy is deposited in
stellar upper atmospheres, leading to the development of realistic,
multicomponent stellar atmosphere models. Similarly, by analyzing
magnetic activity for stars of widely varying temperature, mass,
age, gravity, and rotation, we will be able to test various theories
of magnetic dynamos and stellar activity in detail. These studies
will lead to a vastly improved understanding of how magnetic flux
is generated, and how it affects the structure and energy balance of
stellar photospheres, chromospheres, transition regions, and coronae.

---------------------------------------------------------
Title: The Advanced X-Ray Astronomical Facility (AXAF) : A Powerful
New Tool for Probing Stellar Coronae
Authors: Linsky, Jeffrey L.; Weisskopf, Martin C.
1986LNP...254..250L Altcode: 1986csss....4..250L
No abstract at ADS

---------------------------------------------------------
Title: The photospheric magnetic field of the dM3.5e flare star
AD Leonis.
Authors: Saar, S. H.; Linsky, J. L.
1985ApJ...299L..47S Altcode:
A high-resolution infrared spectrum of the dM3.5e flare star AD Leo,
obtained with the Kitt Peak 4 m Fourier Transform Spectrometer, clearly
shows the presence of strong magnetic fields. Five absorption lines
in the 4400-4600 per cm region have been modeled, and it is inferred
that 73 percent + or - 6 percent of the surface of AD Leo is covered by
active regions outside of dark spots containing a mean field strength of
3800 + or - 260 G. If these active regions are brighter than the quiet
photosphere, the surface filling factor will be somewhat smaller. Since
simultaneous H-alpha observations exhibited no evidence of flares, the
observations probably represent the quiescent magnetic flux level. The
inferred field strength is consistent with equipartition of magnetic and
thermal pressures in the photosphere and is similar to values derived
using the scaling laws of Golub. The large observed filling factor is
consistent with efficient dynamo generation of magnetic flux in this
rapidly rotating star.

---------------------------------------------------------
Title: Nonradiative Activity across the H-R Diagram - which Types
of Stars are Solar-Like
Authors: Linsky, J. L.
1985SoPh..100..333L Altcode:
Major advances in our understanding of nonradiatively heated outer
atmospheric layers (coronae, transition regions, and chromospheres)
and other solar-like activity in stars has occurred in the past few
years primarily as a result of ultraviolet spectroscopy from IUE,
X-ray imaging from the Einstein Observatory, microwave detections by
the VLA, and new optical observing techniques. I critically review the
observational evidence and comment upon the trends with spectral type,
gravity, age, and rotational velocity that are now becoming apparent. I
define a solar-like star as one which has a turbulent magnetic field
sufficiently strong to control the dynamics and energetics in its
outer atmospheric regions. The best indicator of a solar-like star is
the direct measurement of a strong, variable magnetic field and such
data are now becoming available, but good indirect indicators include
photometric variability on a rotational time scale indicating dark
starspots and nonthermal microwave emission. X-rays and ultraviolet
emission lines produced by plasma hotter than 104 K imply
nonradiative heating processes that are likely magnetic in character,
except for the hot stars where the heating is likely by shocks in the
wind resulting from radiative instabilities. I conclude that dwarf
stars of spectral type G-M and rapidly rotating subgiants and giants
of spectral type F-K in spectroscopic binary systems are definitely
solar-like. Dwarf stars of spectral type A7-F7 are almost certainly
solar-like, and T Tauri and other pre-Main-Sequence stars are probably
solar-like. Slowly rotating single giants of spectral type F to early K
are also probably solar-like, and the helium-strong hottest Bp stars
are interesting candidates for being solar-like. The O and B stars
exhibit some aspects of activity but probably have weak fields and
are not solar-like. Finally, the A dwarfs and the cool giants and
supergiants show no evidence of being solar-like.

---------------------------------------------------------
Title: Solar-like Activity in Warm Stars
Authors: Walter, F. M.; Linsky, J. L.
1985BAAS...17..879W Altcode:
No abstract at ADS

---------------------------------------------------------
Title: Energy Balance in Stellar Coronae
Authors: Linsky, J. L.
1985BAAS...17..864L Altcode:
No abstract at ADS

---------------------------------------------------------
Title: The Bright Pre-main Sequence Variable HR5999
Authors: The, P. S.; Tjun-A-Djie, H. R. E.; Brown, A.; Catala, C.;
Doazan, V.; Linsky, J.; Mewe, R.; Praderie, F.; Talavera, A.; Zwaan, C.
1985IrAJ...17...79T Altcode:
A meeting to review the reduced coordinated observations by EXOSAT, IUE
and ground-based instruments of the bright and variable Herbig A7e star
HR 5999 is summarized. The attempt was to delineate the relationship
between the various observable quantities of its atmosphere (colors,
emission-line fluxes, wind velocities, etc.) in order to develop a
dynamical model of the extended atmosphere. The observations were made
around September 11, 1983.

---------------------------------------------------------
Title: Ultraviolet Observations of Young Stars in the Chameleon
1 Association
Authors: Brown, A.; Linsky, J. L.; Walter, F.; Jordan, C.; Judge,
P.; Gahm, G.; Feigelson, E. D.
1985BAAS...17R.837B Altcode: 1985BAAS...17..837B
No abstract at ADS

---------------------------------------------------------
Title: An extensive survey of photospheric magnetic fields in G and
K dwarfs.
Authors: Saar, S. H.; Linsky, J. L.
1985BAAS...17..879S Altcode:
No abstract at ADS

---------------------------------------------------------
Title: Mass Loss from Red Giants : Results from Ultraviolet
Spectroscopy (Review)
Authors: Linsky, J. L.
1985ASSL..117...31L Altcode: 1985mlrg.proc...31L
New instrumentation in space, primarily the IUE spacecraft, has
enabled the application of ultraviolet spectroscopic techniques to the
determination of physical properties and reliable mass loss rates for
red giant winds. One important result is the determination of where in
the H-R diagram are found stars with hot outer atmospheres and with
cool winds. So far it appears that single cool stars, except perhaps
the so-called hybrid stars, have either hot outer atmospheres or cool
winds but not both. The C II resonance (1335 A) and intersystem (2325
A) multiplets have been used to derive temperatures, densities, and
geometrical extents for the chromospheric portions of red giant winds,
with the result that the red giants and the earlier giants with hot
coronae have qualitatively different chromospheres. Mass loss rates
can now be derived accurately from the analysis of asymmetric emission
lines, such as the Mg II resonance lines, and from P Cygni profile
lines of atoms in the dominant ionization stage when a hot star is
available to probe the wind of a red giant. The Zeta Aur systems,
consisting of a K-M supergiant and a main sequence B star are important
systems for reliable mass loss rates for the red supergiant components
are becoming available.

---------------------------------------------------------
Title: VLA Observations of A and B Stars with Kilogauss Magnetic
Fields
Authors: Drake, S. A.; Abbott, D. C.; Bieging, J. H.; Churchwell,
E.; Linsky, J. L.
1985ASSL..116..247D Altcode: 1985rst..conf..247D
The serendipitous discovery that the star σ Ori E [B2 Vp (He strong)]
is a 3.5 mJy radio continuum source at 6 cm has stimulated a radio
survey of other early-type stars with strong magnetic fields. No
Ap stars have been detected of 8 observed, with typical 3σ upper
limits of 0.5 mJy at 2 cm. Of 6 Bp stars examined, only HR 1890,
also a helium-strong star, was detected. The authors discuss possible
emission mechanisms for the observed radio emission, and conclude
that non-thermal emission seems the most plausible, on the basis of
the present data.

---------------------------------------------------------
Title: A VLA Radio Continuum Survey of Active Late-Type Giants in
Binary Systems: Preliminary Results
Authors: Drake, S. A.; Simon, T.; Linsky, J. L.
1985ASSL..116..253D Altcode: 1985rst..conf..253D
The authors have made a sensitive survey at 6 cm of "active" G and K
giants in binary systems, including the so-called long period RS CVn
stars. The results to date show that strong radio continuum emission
at centimeter wavelengths is a common but not universal property of
this class of stars. The authors discuss possible correlations between
radio luminosity and other properties, such as X-ray luminosity,
rotation period, and type of companion. Binary systems detected for
the first time as radio continuum sources include 12 Cam, HD 185510,
29 Dra, and FF Aqr. Sensitive upper limits are presented for five
other systems including the closest long period RS CVn binary, α Aur.

---------------------------------------------------------
Title: An Extensive Survey of Photospheric Magnetic Fields in G and
K Dwarfs
Authors: Saar, S. H.; Linsky, J. L.
1985BAAS...17..751S Altcode:
No abstract at ADS

---------------------------------------------------------
Title: Beyond Lyman alpha - The new frontier in ultraviolet
spectroscopy
Authors: Linsky, J. L.
1985ComAp..10..247L Altcode:
The development of space-based instruments for spectroscopic
observations beyond the H I Lyman alpha continuum at 1175 A
is discussed. Consideration is given to instruments which are
currently in use, together with instruments under development or in
production. Among the current instruments described are the Copernicus
(OAO-3) platform and the IUE spacecraft. Instruments under development
or in production include the High-Resolution Spectrograph (HRS), the
Faint Object Spectrograph (FOS) and the Faint Object Camera (FOC) on
board the Space Telescope, and the Far Ultraviolet Spectrograph Explorer
(FUSE). Consideration is also given to the spectroscopic capabilities
of the Extreme Ultraviolet Explorer (EUVE) and the Hopkins Ultraviolet
Telescope (HUT), which will be a facility on the Astro 2 spacecraft and
future Spacelab missions. The anticipated operational dates, spectral
ranges, and resolutions of the instruments are given in a table.

---------------------------------------------------------
Title: Coordinated Multiband Observations of Stellar Flares
Authors: Rodono, M.; Foing, B. H.; Linsky, J. L.; Butler, J. C.;
Haisch, B. M.; Gary, D. E.; Gibson, D. M.
1985Msngr..39....9R Altcode:
The March 28, 1984 flare of AD Leo is characterized on the basis of
observations obtained over the spectral range from 200 nm to 20 cm using
the IUE, the VLA, and four ESO telescopes as part of a coordinated
multiband international campaign. The data are presented graphically
and discussed, with consideration of faint negative K-band events
observed simultaneously with the optical flare; an H-alpha precursor
with longer energy-release relaxation than in the U continuum; and
remarkably enhanced UV continuum, Mg II doublet, and 260-nm Fe II
blend during the last secondary optical peak.

---------------------------------------------------------
Title: A Phase-Linked Study of Emission Lines in the Flare Star Ev lac
Authors: Linsky, Jeffrey L.
1985iue..prop.2176L Altcode:
The classical flare star and BY Dra variable EV Lac has, in the last
decade, produced extraordinarily energetic flares at both optical and
X-ray wavelengths which are unmatched among M dwarfs. Two of these
flares, including the 13 July 1980 optical superflare (the largest ever
observed from an M dwarf), occurred when the dominant starspot group
was on the far side of the star. These flares imply the existence
of anomolously intense or large active regions. We propose both LWP
and SWP observations of EV Lac at equal intervals of 0.23 in phase
for two consecutive 4.37 day periods (9 US2 half shifts) in order
to map plage regions on the star. The SWP-LO exposures will in cases
of high background be obtained by co-adding shorter exposures. This
will result in spectra for every ~0.1 in phase. We will also use the
data to compute surface fluxes which will be compared with available
chromospheric and transition region surface fluxes from other active
and quiescent M dwarfs in search of physical clues to this star's
extreme flaring activity. We are submitting a proposal to EXOSAT for
observing time during the IUE observations.

---------------------------------------------------------
Title: Observed and computed stellar line profiles: the roles played
by partial redistribution, geometrical extent and expansion.
Authors: Linsky, J. L.
1985ASIC..152....1L Altcode: 1985pssl.proc....1L
The author reviews partial redistribution (PRD) radiative transfer with
emphasis on the complex interaction of observations and theoretical
predictions of spectral line shapes. He summarizes the work that
has led to "realistic" plane parallel static chromospheric models
for the Sun and other late-type stars. The author then discusses the
various roles played by atmospheric extension and expansion (winds)
in determining resonance line profile shapes, and summarizes the
existing PRD calculations for late-type stars.

---------------------------------------------------------
Title: Stellar Winds in Cool Giants and Supergiants
Authors: Linsky, Jeffrey L.
1985iue..prop.2171L Altcode:
We propose to study the properties of stellar winds in cool giants and
supergiants using both archive and new high-dispersion, long-wavelength
spectra. We aim to investigate the dependence of wind velocity and mass
loss rate as a function of spectral type and luminosity, concentrating
particularly on the K giants. We will use as primary diagnostic tools,
the blue-shifted absorption features seen in the Mg II h and k lines
of stars in this region of the H-R Diagram.

---------------------------------------------------------
Title: Evidence for non-radiative activity in stars with
Teff &lt; 10,000K.
Authors: Linsky, J. L.
1985NASCP2358...24L Altcode: 1985onhm.rept...24L
Major advances in the acquisition of evidence for and the understanding
of nonradiative heating and other activity in stars cooler than
Teff = 10,000K has occurred in the last few years primarily
as a result of the IUE and Einstein spacecraft and the VLA microwave
facility. The author critically reviews this evidence and comments
on the trends that are now becoming apparent. The existence for
nonradiatively heated outer atmospheric layers (chromospheres,
transition regions, and coronae) in dwarf stars cooler than spectral
type A7, in F and G giants, pre-main sequence stars, and close binary
systems is unambiguous, and chromospheres exist in the K and M giants
and supergiants. The existence of nonradiative heating in the outer
layers of the A stars remains undetermined despite repeated searches
at all wavelengths.

---------------------------------------------------------
Title: A Long Look at Zeta Aurigae During Total Eclipse
Authors: Linsky, Jeffrey L.
1985iue..prop.2175L Altcode:
We propose to observe the eclipsing binary system Zeta Aurigae
(K41b-II + B8V) during the total eclipse of its hotter component in
April 1985 and thereby study the density, temperature, and geometric
extent of the K-star chromosphere. The primary data for this analysis
will be a long-duration (~12 hour) LWP high resolution spectrum that
will properly record the intercombination lines of C II multiplet
UV 0.01 near 2325 A. Fe II fluorescent lines near 2508 A will also be
analyzed to provide an estimate of the star's Ly-alpha flux. Other Fe II
lines throughout the LWP wavelength range will be modelled to provide
additional information on the characteristics of the chromosphere of
the cool, luminous component of the Zeta Aurigae system.

---------------------------------------------------------
Title: Magnetic Activity in Very Late M Dwarfs: Enhanced or Reduced?
Authors: Linsky, Jeffrey L.
1985iue..prop.2173L Altcode:
The degree of magnetic activity on very late M dwarfs (roughly dM5
and later) is currently very uncertain. This is because there is
very little data, and because the few observations that do exist
are contradictory. Optical observations suggest both enhanced and
reduced levels of chromospheric activity. An apparent drop-off in
coronal heating for stars cooler than B-V - 1.7 (spectral type M4-M5)
largely disappears if the quantity Lx/Lbol is considered, rather than
Lx. Since stars this late are believed to be fully convective, and since
many theoretical solar and stellar dynamo models postulate magnetic
flux generation or amplification at the base of the convective zone, a
reduction in all magnetically induced phenomena might be expected. Low
dispersion, short wavelength IUE observations of the transition region
lines of eight nearby, very late, single M dwarfs represents perhaps
the most efficient way to resolve this uncertainty. This study extends
previous survey work on M dwarfs to the coolest spectral types. Except
for the particularly active late M stars Prox Cen and UV Cet, there
are no short wavelength IUE observations in this part of the HR diagram.

---------------------------------------------------------
Title: High Resolution Spectroscopy of Late K and M Supergiants
Authors: Linsky, Jeffrey
1985iue..prop.2172L Altcode:
The ultraviolet spectrum of alpha Ori (M2 Iab) in unique in comparison
to spectra of other M stars previously observed with IUE due to
the great breadth and frequently strong self-reversals of the Fe II
emission lines in the 2200-3200 A region. However no other stars of
its spectral type have yet been wellobserved at high resolution with
IUE. We propose to obtain images, exposed to properly record these Fe II
lines, of two stars of very similar spectral type and luminosity class
to alpha Ori to determine whether these lines and the chromosphere
that produces them are unique to alpha Ori or are examples of a more
general phenomenon. The long double-shift (13-15 hour) exposures
required to obtain properly exposed LWP high-resolution spectra of
the next brightest M supergiants (3-4 magnitudes dimmer than alpha Ori
will be obtained during sequential ESA-US1 shifts. These spectra will
also be used to estimate the Ly-alpha flux from these stars, through
measurements of the two Fe II fluorescent lines near 2508 A. Ly-alpha
is not directly observable in these stars due to extensive circumstellar
and interstellar opacity. Modelling of the Al II (UVI) line and analysis
of the C II UV 0.01 emission line multiplet will be performed to further
characterize the chromospheres of these stars. Estimates of the electron
density in, and the geometric extent of, these chromospheres will be
produced from these data using well established techniques.

---------------------------------------------------------
Title: The Ultraviolet Spectrum of the T Tauri Star RY TAU Subsequent
to its 1983 Brightening
Authors: Linsky, Jeffrey L.
1985iue..prop.2182L Altcode:
We propose to obtain new SWP-LO and LWP-HI spectra of the T Tauri
star, RY Tauri. This irregular, pre-main sequence variable has
recently visually brightened by about 1^m.5 to its brightest level
in 20 years due, most probably, to an increase in its photospheric
temperature. In this proposal, we seek to elucidate the effect of
this dramatic brightening on the chromosphere, transition region,
and wind of this star by comparison of new UV data with those obtained
before and at the onset of its visual rise. We will compare, for all
detected lines, pre- and post-outburst measured emission fluxes and
inferred emission measures, and, for the Mg II resonance lines in the
LWP-HI spectra, make a detailed comparison of "before" and "after"
line profile morphologies, in order to find variations in the mass
loss rate and terminal velocity of the wind of this star. So as to
extend the timeline of UV observations of RY Tau and also so as to
help separate short- and long-term variability effects, we request
that the observations be scheduled at two epochs six months apart.

---------------------------------------------------------
Title: Variability of the Winds, Chromospheres and Transition Regions
of Hybrid Stars
Authors: Linsky, Jeffrey L.
1985iue..prop.2180L Altcode:
We propose to investigate the variability of the winds, chromospheres
and transition regions of hybrid stars and, hence by relating the
observed variability to our earlier studies of hybrid star atmospheric
structure, constrain both models of this structure and theories
concerning the winds from these stars. By means of LWP-HI Mg II
spectra (obtained in the 10 US2 shifts) we will derive the level and
timescales of variability of the wind velocity and mass loss rate,
and also of the chromospheric line fluxes. In order to relate the
wind and chromospheric variability to that seen in the transition
region emission lines, we will obtain, at two epochs, transition
region line profiles for the star, alpha TrA, from the SWP-HI images
(to be obtained in the collaborative US1/ESA shifts). The observed
variability will be analysed to search for any systematic behaviour.

---------------------------------------------------------
Title: An Unbiased Distance-Limited Survey of Early-K Bright Giants
Authors: Linsky, Jeffrey L.
1985iue..prop.2179L Altcode:
We propose to study an unbiased sample of early K bright giant
stars, including all such stars within 200 parsec of the sun, so as
to investigate the evolution of the outer atmospheric structure of
intermediate mass (4-6 M[sun]) stars. We will determine the relative
frequency of coronal, non-coronal and hybrid outer atmospheric structure
among these stars. The range of chromospheric and transition region
properties would be quantitatively investigated using emission measure
analysis and other modelling techniques. Changes in outer atmospheric
structure related to major alterations of their internal structure, such
as the deepening of the outer convection zone as the star ascends the
giant branch and the onset of He-core burning, would be studied. Using
our knowledge about the properties of stars of similar mass at earlier
and later evolutionary states, we will construct a coherent picture
of the outer atmospheric evolution of intermediate mass stars.

---------------------------------------------------------
Title: Pannel discussion on radiative transfer methods.
Authors: Kalkofen, W.; Linsky, J.; Rybicki, G.; Scharmer, G.;
Weherse, R.
1985ASIC..152..233K Altcode: 1985pssl.proc..233K
No abstract at ADS

---------------------------------------------------------
Title: Pannel discussion on partial redistribution.
Authors: Freire Ferrero, R.; Frisch, H.; Linsky, J.; Oxenius, J.;
Simonneau, E.
1985ASIC..152..143F Altcode: 1985pssl.proc..143F
No abstract at ADS

---------------------------------------------------------
Title: The Unique Eclipsing Binary System TZ Fornacis
Authors: Linsky, Jeffrey L.
1985iue..prop.2174L Altcode:
TZ For (G5III+F7III) is the only known eclipsing binary system
consisting of two late-type giants. Accordingly, the stellar parameters
can be determined very accurately, especially the stellar masses and the
evolutionary state. As in the similar but non-eclipsing Capella system,
the secondary is a rapidly rotating star. We propose to observe TZ For
(with LWP-HI and SWP-LO exposures) at opposite quadratures (phases
0.25, 0.75) and during primary eclipse (phase 0.) when almost half
of the F giant is occulted. These observations will permit us to (i)
disentangle the UV emission contributions from each star, (ii) study for
the first time the surface distribution of emission on a giant star,
(iii) investigate time variability, and (iv) model the atmosphere of
the active star. Comparing these results with those for Capella will
be very instructive, since the F9III star in Capella might be atypical
in the steadiness of its (high) level of chromospheric and transition
region flux.

---------------------------------------------------------
Title: Atmospheric properties of RU Lupi derived from high- and
low-resolution IUE spectra.
Authors: Brown, A.; Penston, M. V.; Johnstone, R.; Jordan, C.; Kuin,
N. P. M.; Lago, M. T. V. T.; Gross, B.; Linsky, J. L.
1984NASCP2349..338B Altcode: 1984fiue.rept..338B; 1984IUE84......338B
High and low-dispersion IUE spectra of the premain sequence star, RU
Lupi, were obtained using both the short wave prime (SWP) and long wave
redundant (LWR) cameras. Strong P Cygni line profiles are seen in Mg II
and Fe II emission lines, indicating that the lines are formed in the
stellar wind of RU Lupi. An increase in transition region line widths is
seen with increasing temperature, which cannot be due solely to opacity
broadening, thus indicating that kinematic broadening mechanisms are
dominant. The transition region density is approx. 3 x 10 to the 10th
power cubic cm derived from the Si III lambda1892/C III lambda1909 line
ratio. The status of the atmospheric modeling of RU Lupi is discussed.

---------------------------------------------------------
Title: Ultraviolet, radio and X-ray observations of hybrid stars.
Authors: Drake, S. A.; Brown, A.; Linsky, J. L.
1984NASCP2349..472D Altcode: 1984fiue.rept..472D; 1984IUE84......472D
The Mg II profiles of hybrid stars (obtained from spectra available in
the IUE Archives of the Univ. of Colorado RDAF) were reanalyzed. Radio
observations of 3 hybrid stars (iota aur, theta Her and gamma Aq1)
are presented and the available Einstein X-ray data on these stars
are discussed. This observational material is compared with the
properties of the HDR model for hybrids that could form both low-
and high-velocity Mg II absorptions in the extending circumstellar
envelope predicted no X ray emission. From the analysis it is conducted
that interstellar absorption is sufficient to account for the observed
low-velocity features, so that only the high-velocity absorptions are
formed in the winds themselves. What makes the kinematics of hybrid
stellar winds interesting are the observed high wind velocities (70
km to 140 km) compared to other G-K I III stars and not the supposed
twin circumstellar absorptions.

---------------------------------------------------------
Title: A progress report on the analysis of long exposure SWP high
resolution spectra of cool stars.
Authors: Linsky, J. L.; Ayres, T. R.; Brown, A.; Carpenter, K.;
Jordan, C.; Judge, P.; Gustafsson, B.; Eriksson, K.; Saxner, M.;
Engvold, O.; Jensen, E.; Moe, O. K.; Simon, T.
1984NASCP2349..445L Altcode: 1984fiue.rept..445L; 1984IUE84......445L
The IUE is the first experiment with sufficient sensitivity to obtain
high resolution spectra (lambda/delta lambda is approximately 10,000)
of many cool stars in the vitally important 1200 to 2000 A spectral
region. These data provide qualitatively new information with
which to understand the properties of and structures in the outer
atmospheres of these stars. Also, these cool star spectra will be
extremely useful in planning for the Space Telescope High Resolution
Spectrograph, which will be 1000 times more sensitive than IUE but will
be hampered by limited observing time and limited spectral bandwidth
in each exposure. Very long exposure, high disperson SWP spectra of
many stars located throughout the cool half of the HR diagram were
obtained. These 12 to 21 hour exposures were obtained by combining
NASA and Vilspa shifts so as to obtain the longest possible exposures
at times of low background. Included are dwarf stars of spectral type
G0 V to M2 V, G9.5 III to M5 II giants, G2 Ib to M2 Iab supergiants,
a number of RS CVn-type systems, and Barium stars.

---------------------------------------------------------
Title: Precise measurements of radial velocities of emission lines
in the far-ultraviolet spectra of late-type stars.
Authors: Ayres, T. R.; Engvold, O.; Moe, D. K.; Simon, T.; Jordan,
C.; Judge, P.; Brown, A.; Linsky, J. L.
1984NASCP2349..468A Altcode: 1984fiue.rept..468A; 1984IUE84......468A
The radial velocities of emission lines in deep short wave prime camera
echelle exposures of several late-type dwarf and giant stars were
measured. The goal was to search for absolute and differential Doppler
shifts of emission lines formed at different temperatures in the stellar
outer atmospheres analogous to the redshifts of C IV lambda 1548 (10
to the 5th power K) which occur in the solar transition zone. Existing
images, taken without the precise radial velocity precautions, of five
dwarf stars, four giant stars, and three supergiants are reanalyzed.

---------------------------------------------------------
Title: Observations of Interstellar H i Toward Nearby Late-Type Stars
Authors: Landsman, W. B.; Henry, R. C.; Moos, H. W.; Linsky, J. L.
1984NASCP2345...61L Altcode: 1984lism.rept...61L; 1984NASCP2345...60L; 1984IAUCo..81...60L
High-disperson Copernicus and IUE observations of chromospheric Ly
alpha emission are used to study the distribution of HI in the local
interstellar medium. Interstellar parameters are derived toward 3
stars within 5 pc of the Sun, and upper limits are given for the Ly
alpha flux from 9 other stars within 10 pc.

---------------------------------------------------------
Title: Observations of interstellar hydrogen and deuterium toward
Alpha Centauri A.
Authors: Landsman, W. B.; Henry, R. C.; Moos, H. W.; Linsky, J. L.
1984ApJ...285..801L Altcode:
The authors present a composite profile of the Lyα emission line of
α Cen A, obtained from 10 individual spectra with the high-resolution
spectrograph aboard the satellite. There is excellent overall agreement
with two previous Copernicus observations. Interstellar deuterium
is detected, and a lower limit is set on the deuterium to hydrogen
ratio of nDI/nHI &gt; 8×10-6. In
addition, the deuterium bulk velocity appears blueshifted by 8 ± 2
km s-1 with respect to interstellar hydrogen, suggesting
a nonuniform medium along the line of sight.

---------------------------------------------------------
Title: IUE Observations of Interstellar Hydrogen and Deuterium toward
Alpha Centauri B
Authors: Murthy, J.; Henry, R. C.; Moos, H. W.; Landsman, W.; Linsky,
J. L.; Russell, J.
1984BAAS...16..980M Altcode:
No abstract at ADS

---------------------------------------------------------
Title: Chromospheric Expansion Velocities in Late K and M Giants
Authors: Drake, S. A.; Linsky, J. L.
1984BAAS...16..895D Altcode:
No abstract at ADS

---------------------------------------------------------
Title: Atmospheric Structures in AR Lac. I. Mapping Quiescent Features
by Occultations &amp;Doppler Imaging
Authors: Walter, F. M.; Gibson, D. M.; Brown, A.; Carpenter, K.;
Linsky, J. L.; Rodono, M.; Eyles, C.
1984BAAS...16R.896W Altcode: 1984BAAS...16..896W
No abstract at ADS

---------------------------------------------------------
Title: The origin of low-velocity absorption components in the MG
II resonance lines of hybrid-chromosphere stars.
Authors: Drake, S. A.; Brown, A.; Linsky, J. L.
1984ApJ...284..774D Altcode:
It is argued that the low-velocity absorption features seen in
the Mg II resonance lines of seven confirmed and three probable
hybrid-chromosphere stars are interstellar rather than circumstellar in
origin. From a comparison of radial velocities based on all available
spectra in the International Ultraviolet Explorer (IUE) archives with
estimates of the interstellar velocity along each line of sight, a
good correlation between the observed position of the low-velocity
component and the predicted interstellar feature is found. It is
also shown that previous arguments in favor of the circumstellar
origin of the low-velocity absorption features are either incorrect or
implausible. The conclusion of the present study may modify previously
proposed models of hybrid star winds which have assumed a priori that
both Mg II absorption components are circumstellar.

---------------------------------------------------------
Title: Atmospheric Structures in AR Lac. II. A Spatially Chromospheric
Active Region
Authors: Neff, J. E.; Walter, F. M.; Linsky, J. L.; Gibson, D. M.;
Rodono, M.
1984BAAS...16..896N Altcode:
No abstract at ADS

---------------------------------------------------------
Title: The Many Faces of HR 1099
Authors: Ayres, T. R.; Bennett, J. O.; Linsky, J. L.; Simon, T.
1984BAAS...16..893A Altcode:
No abstract at ADS

---------------------------------------------------------
Title: High-resolution, far-ultraviolet study of beta Draconis
(G2 Ib-II) : transition region structure and energy balance.
Authors: Brown, A.; Jordan, C.; Stencel, R. E.; Linsky, J. L.; Ayres,
T. R.
1984ApJ...283..731B Altcode:
High-resolution far ultraviolet spectra of the star Beta Draconis have
been obtained with the IUE satellite. The observations and emission
line data from the spectra are presented, the interpretation of the
emission line widths and shifts is discussed, and the implications
are given in terms of atmospheric properties. The emission measure
distribution is derived, and density diagnostics involving both line
ratios and line opacity arguments is investigated. The methods for
calculating spherically symmetric models of the atmospheric structure
are outlined, and several such models are presented. The extension of
these models to log T(e) greater than 5.3 using the observed X-ray flux
is addressed, the energy balance of an 'optimum' model is investigated,
and possible models of energy transport and deposition are discussed.

---------------------------------------------------------
Title: Atmospheric Modeling of Cool Giant and Supergiant Stars
Authors: Linsky, Jeffrey L.
1984iue..prop.1845L Altcode:
We propose to continue our collaborative program of obtaining and
analysing high dispersion SWP spectra of cool stars. We request
high dispersion, short wavelength IUE spectra of the stars alpha Tau
(K5III), gamma Cru (M3III), epsilon Peg (K2Ib) and beta Cam (G0Ib)
with exposure times of 16 hours or more. These spectra will provide
measurements of line profiles, widths and Doppler shifts in addition
to density-sensitive and opacity-sensitive line ratios. Models of
chromospheric and transition region (where present) structure will
be calculated by a combination of emission measure analysis, line
opacity/probability of escape methods and model atmosphere calculations
for optically thick resonance lines such as MgII h and k, including
partial redistribution radiative transfer. These models will be used
to investigate the atmospheric energy balance and the nature of energy
transport and nonradiative energy deposition processes. The results
will be considered in relation to stellar evolution and compared with
the chromospheric properties of other stars previously studied by the
authors and their collaborators.

---------------------------------------------------------
Title: Rotational modulation of spots and plages on RS CVn stars.
Authors: Byrne, P. B.; Doyle, J. G.; Andrews, A. D.; Butler, C. J.;
Marstad, N.; Linsky, J. L.; Simon, T.; Rodono, M.; Catalano, S.;
Blanco, C.; Marilli, E.; Pazzani, V.
1984ESASP.218..343B Altcode: 1984iue..conf..343B
Observations of three RS CVn stars made with the IUE satellite are
presented. Emission line fluxes are found to vary in anti-phase with the
stars' optical variations. The authors interpret these correlations in
terms of large-scale spots in the stellar photospheres with overlying
magnetic loops, giving rise to non-thermal heating of the layers above
the spots. Evidence of nonthermal gas motions is also presented which
appear to be associated with the most active regions of the stars.

---------------------------------------------------------
Title: Coordinated IUE and ground-based observations of active stars:
flare events on YZ CMi, V1005 Ori, AD Leo and AR Lac.
Authors: Rodonò, M.; Cutispoto, G.; Catalano, S.; Linsky, J. L.;
Gibson, D. M.; Brown, A.; Haisch, B. M.; Butler, C. J.; Byrne, P. B.;
Andrews, A. D.; Doyle, J. G.; Gary, D. E.; Henry, G. W.; Russo, G.;
Vittone, A.; Scaltriti, F.; Foing, B.
1984ESASP.218..247R Altcode: 1984iue..conf..247R
Observations of stellar flares were obtained with IUE and ground-based
facilities simultaneously over a wide range of wavelengths in order
to study the effect of the flare radiation at different atmospheric
levels. Observations include time-resolved IUE and optical spectroscopy,
narrow and wide-band optical photometry, IR photometry, and microwave
observations. Results include detection of IR flux decrease, or negative
flare, in coincidence with flux increase at all other wavelengths.

---------------------------------------------------------
Title: Lyman Alpha Emission from Cool Dwarf Stars
Authors: Linsky, Jeffrey L.
1984iue..prop.1842L Altcode:
In late-type dwarf stars Lyman-alpha is an extremely bright emission
line comparable in strength to the sum of all transition region
lines. We propose to investigate the energy balance in the outer
atmospheres of late-type dwarf stars by first determining whether
the Ly-alpha emission is correlated best with emission features
from the chromosphere, transition region, or corona (X-rays). This
empirical result will then permit us to attempt to answer three
theoretical questions: (1) Is the Lyman-alpha region heated from below
(chromosphere) or above (corona)?, (2) Which mechanism determines
the location of the transition region in late-type stars?, and (3)
Are major revisions necessary for all existing theoretical models of
magnetically closed and open coronal regions? We will use data from
the archives and request observing time primarily for very short SWP-LO
exposures. We discuss how to minimize problems due to noncontemporaneous
observations, geocoronal emission, and interstellar absorption.

---------------------------------------------------------
Title: Corona models tested with IUE and Einstein observations.
Authors: Hammer, R.; Linsky, J. L.
1984ESASP.218...25H Altcode: 1984iue..conf...25H
Compilations of IUE and Einstein observations which show that
the emissions from the outer layers of cool stars are nonlinearly
correlated are discussed. This result can be used to test theoretical
corona models as well as hypotheses on the mechanism that determines
the location of the transition region. In stars in which most of the
X-ray emission originates in small coronal loops it may be necessary
that part of the emitting plasma is hotter than 20 million K or that
the transition region is not only heated by thermal conduction, but
also by downflows. Observational evidence for both these effects,
and methods for analyzing the geometrical structure of outer stellar
atmospheres are considered.

---------------------------------------------------------
Title: Beyond the T-1/2 Chromospheric Scaling Law
Authors: Linsky, Jeffrey L.
1984iue..prop.1847L Altcode:
We propose to study the effects of evolution off the main sequence on
the chromospheres and transition regions of solar mass stars using both
archive and new SWP-LO and LWR-HI exposures of G to K subgiants. We
will measure the strengths of the strongest emission features of
ions such as OI, CI, CII, CIV, SiII, SI-IV, and NV accessible in
the short wavelength region, and the strength and shape of the MgII
resonance lines in the long wavelength region. We will investigate
correlations of these observable quantities with factors such as age,
metallicity, vsini, and mass. This should enable us to extend the
chromospheric/transition region activity versus age relationships
known for main sequence stars to greater stellar ages.

---------------------------------------------------------
Title: High Dispersion Wavelength-Calibrated Spectra of
Hybrid-Chromosphere Stars
Authors: Linsky, Jeffrey L.
1984iue..prop.1841L Altcode:
No abstract at ADS

---------------------------------------------------------
Title: Ultraviolet Study of the Chamaeleon T-Association
Authors: Linsky, Jeffrey L.
1984iue..prop.1843L Altcode:
The Chamaeleon T1 association is a nearby compact star-forming region
which has been extensively studied at optical, infrared and X-ray
wavelengths. We propose to observe the brightest pre-main sequence
stars in this association with IUE. SWP low dispersion and LWP low and
high dispersion spectra would be obtained for these stars which have
formed essentially coevally (within the free-fall collapse time of
the single cloud from which they originate). Their chromospheric and
coronal properties will be studied using emission measure modelling
techniques based on these IUE spectra and -the extensive database from
other spectral regions. The derived properties of -the outer atmospheres
will be investigated in relation to the general propertie's of the
stars, particularly position in the HR diagram, mass loss rate and
stellar mass. Detailed comparison of apparently similar stars from
different star formation regions will be made.

---------------------------------------------------------
Title: Determination Size/Physical Properties of Active Regions inRS
CVn Sys Rotational Modulation/Doppler Imaging
Authors: Linsky, Jeffrey
1984iue..prop.1848L Altcode:
The primary objective of this proposal is to determine the geometric
size and physical properties of active regions in two properly chosen
bright RS CVn systems.. Previous observing campaigns by this group, and
especially our observations of II Peg in October 1981, have indicated
that RS CVn systems with simple, nearly sinusoidal photometric waves
of large amplitude have one dominant active region and large amplitude
variations in the transition region and chromospheric ultraviolet
emission lines as the active region rotates on to and off of the
visible hemisphere. We propose to determine the size of this active
region by rotational modulation of the line fluxes obtained at least
12 times over a period. We will confirm the existence of this active
region by observing the Doppler shift of the emission lines when
the active region -is near both limbs, a technique called Doppler
imaging. Once the size, latitude, and longitude of the active region
are determined, we can determine the emission line surface fluxes for
the active region alone from the line flux enhancements. We can then
compute models of the active region and quiet components separately
using emission measure techniques or by matching computed and observed
surface fluxes in lines of Mg II, Si II-IV, C II-IV, and N V and by
comparison with density-sensitive line ratios. As before, we will set
up a major coordinated observing campaign to obtain radio observations
(VLA), optical photometry, and optical spectroscopy.

---------------------------------------------------------
Title: Completion of F Dwarf Activity Relations Study
Authors: Linsky, Jeffrey L.
1984iue..prop.1835L Altcode:
We propose to complete our study of chromospheric and transition region
fluxes in early F dwarfs begun under program AFFJL. We are studying
the correlations between chromospheric surface fluxes and rotation,
age, and color (indicative of the depth of the convective zone), using
SWP spectra to obtain fluxes for emission lines formed at temperatures
of -8000 K (01) through 200,000 K (NV). We need a complete grid of
stars in the (BV)-(Vsini) plane to determine at what color the dynamo
turns on (the activity begins to correlate with Vsini), and to see how
activity levels at a fixed Vsini are affected by convection zone depth
and stellar age, in case of a contribution from a decaying primordial
magnetic field in the youngest stars. Completion of the program (25%
of the SWP spectra requires 6 shifts. We also request 4 shifts to
observe four young (~7x10^7 yrs) F dwarfs in the Pleiades Cluster,
specifically to study the dependence of activity levels upon age in
very young stars not available in the field or in the Ursa Major or
Hyades Clusters which have already been studied. We believe that the
completion of this program during the seventh year of IUE will lead
to a major increase in our understanding of F dwarf chromospheres and
transition regions, and provide real guidance in formulating observing
strategies for the observation of these stars by Space Telescope.

---------------------------------------------------------
Title: Models for the active and quiescent regions on the RS CVn-type
systemII Pegasi (HD 224085).
Authors: Linsky, J. L.; Brown, A.; Marstad, N. C.; Rodono, M.; Andrews,
A. D.; Butler, C. J.; Byrne, P. B.
1984ESASP.218..351L Altcode: 1984iue..conf..351L
The IUE observations of the RS CVn binary system II Pegasi obtained
during the period 1981 October 1-7 were used to derive the emission
measure distributions and to calculate transmission region models
of the quiescent and plage (active) regions of II Peg. Active region
models were calculated assuming area coverages of 10%, 6%, 3% and 1%
of the visible hemisphere. These models are used to provide lower
limits to the electron pressure in the quiescent and plage regions,
which are compared with the available density diagnostics. The amount
of mechanical energy deposition required to account for the observed
radiative losses is very large.

---------------------------------------------------------
Title: High Dispersion Line Profile Studies of TW HYA and Other
Pre-Main Sequence Stars
Authors: Linsky, Jeffrey L.
1984iue..prop.1849L Altcode:
We propose to extend our study of line profiles in T Tauri stars by
obtaining a 16 hour SWP-HI spectrum of TW Hya and 6-8 hour LWP-HI
spectra of TW Hya, AK Sco, CoD -35 10525 and CoD -33 10685. High
dispersion spectra of pre-main sequence (PMS) stars provide unique
information on line widths, shifts, and asymmetries, as well as
evidence for mass outflow, circumstellar absorption, and diagnostics
for the temperature structure of the outer atmosphere layers of these
complex yet incredibly important objects. We have previously obtained
and studied line profiles in RU Lupi and the prototype star T Tau. RU
Lupi has line profiles that are dominated by the wind expansion, for
example the MgII and FeII multiplet UV1 profiles are unique in that
they have a classical P Cygni shape, whereas T Tau has more symmetric
emission profiles indicative of a chromosphere and hotter layers not
dominated by expansion. TW Hya is different from these two previously
studied stars in that it may be the brightest known example of a post-T
Tauri star, and hence less active and older than the other PMS stars. We
intend to compare its line profiles with those of RU Lupi and T Tauri
in order to understand the differences in the non-thermal mass motions,
wind expansion, and thermal structures of these three very different
T Tau stars. The requested LWPHI spectra are to obtain MgII and FeII
multiplet UV1. profiles of 4 different T Tauri objects so as to infer
the expansion and thermal structure in their chromospheric layers.

---------------------------------------------------------
Title: IUE observations of BY Draconis.
Authors: Butler, C. J.; Doyle, J. G.; Andrews, A. D.; Byrne, P. B.;
Linsky, J. L.; Simon, T.; Marstad, N. C.; Rodono, M.; Pazzani, V.;
Cutispoto, C.
1984ESASP.218..243B Altcode: 1984iue..conf..243B
Phased IUE low resolution observations of BY Draconis are
discussed. They show no significant modulation of the prominent
SWP emission lines over one rotation period. However a marginally
significant anticorrelation of the MgII flux, and the flux in the LWR
continuum, with the V light curve is observed, and is interpreted as
due to plage type areas over the photospheric spots. Two SWP spectra
show sporadic enhancements of the emission lines, as seen in other
IUE spectra of flares.

---------------------------------------------------------
Title: Properties of Stellar Winds: FE II, C II, and Variability
Authors: Linsky, Jeffrey L.
1984iue..prop.1837L Altcode:
We propose to use both archival and new seventh-year high resolution
IUE spectra to investigate the cool, extended winds around a sample
of late-type giant and supergiant stars. The primary goals of this
study are to determine for each star the radial structure of its wind,
the primary channels for radiative cooling of its outer atmosphere,
and the density and geometrical extent. of its wind. We shall also
examine the long-term stability of the wind in a subset of these
same stars. The density and geometrical extent of the winds will be
estimated from the C II intercombination emission lines near 2325 A.,
using an improved version of the technique developed by Stencel et
al. (1981). Fluxes of the Fe II emission lines, found throughout the
long-wavelength region of IUE, will be used in a probability-of-escape
modelling of the wind structure. The range of opacities and temperature
sensitivities represented by the numerous Fe II lines will allow the
computation of models with much greater radial discrimination than
is possible solely on the basis of the frequently used Mg II or Ca II
resonance lines. The acquisition of wavecal images immediately after
each new high resolution spectrum will also allow us to measure very
accurate absolute radial velocities of the emission features and thus
to determine the speed and radial dependence of the material in the
outer layers of these stars.

---------------------------------------------------------
Title: Eclipsing Coverage of the RS CVn System AR Lac
Authors: Linsky, Jeffrey
1984iue..prop.1967L Altcode:
No abstract at ADS

---------------------------------------------------------
Title: Stellar chromospheres and coronae in the Ursa Major cluster
stars.
Authors: Walter, F. M.; Linsky, J. L.; Simon, T.; Golub, L.; Vaiana,
G. S.
1984ApJ...281..815W Altcode:
IUE spectra of 18 proposed members of the Ursa Major Cluster and
Einstein X-ray images of 11 of these stars are discussed. Thirteen
stars, six in the nucleus and seven in the extended comoving stream,
are probably true members of the UMa Cluster in that their bright
ultraviolet and X-ray surface fluxes indicate youth. Four stars, one in
the nucleus and three in the stream, exhibit weak ultraviolet and/or
X-ray emission suggesting that they are old field stars that have
the same space motion as the UMa Cluster. The X-ray surface fluxes of
the UMa Cluster stars appear to be brighter than those of the Hyades
Cluster stars, consistent with their relative ages. It is argued that
chromospheres and transition regions could be present in dwarf stars
hotter than B-V of about 0.30, but are unobservable in IUE spectra
due to the rapid increase in photospheric flux in hotter stars.

---------------------------------------------------------
Title: Sigma Geminorum (K1 III + ?) : variability of the ultraviolet
emission lines near conjunction.
Authors: Ayres, T. R.; Simon, T.; Linsky, J. L.
1984ApJ...279..197A Altcode:
Far-ultraviolet IUE echelle spectra are reported of the moderate-period
RS CVn system σ Geminorum. Despite the location of the red giant
primary of σ Gem in a portion of the H-R diagram where cool stellar
winds are common, no evidence is found for circumstellar absorption
features or blueward asymmetries in the chromospheric O I emission
cores. However, observations on two consecutive days indicate
significant changes in the profiles of high-excitation species, such
as Si IV and C IV which probably were produced by the rotation off of
the visible hemisphere of the primary of a large-scale magnetic active
region identified in a previous photometric study.

---------------------------------------------------------
Title: Analysis of the 1981 October 3 Flare on HR 1099 Based on High
and Low Resolution IUE Spectra
Authors: Gross, B.; Linsky, J.; Marstad, N.; Byrne, P. B.; Butler,
C. J.; Andrews, A. D.; Rodono, M.; Simon, T.
1984BAAS...16..473G Altcode:
No abstract at ADS

---------------------------------------------------------
Title: First Measurement of Magnetic Fields on a BY Draconis Flare
Star: EQ Virginis
Authors: Saar, S. H.; Linsky, J. L.; Beckers, J. M.
1984BAAS...16Q.517S Altcode: 1984BAAS...16..517S
No abstract at ADS

---------------------------------------------------------
Title: In-Orbit Test and Calibration of the High Resolution
Spectrograph for the Hubble Space Telescope
Authors: Maran, S. P.; Brandt, J. C.; Savage, B. D.; Ebbets, D.;
Beaver, E. A.; Boggess, A.; Heap, S. R.; Hutchings, J. B.; Jura,
M. A.; Leckrone, D. S.; Linsky, J. L.; Smith, A. M.; Trafton, L. M.;
Weymann, R. J.
1984BAAS...16..477M Altcode:
No abstract at ADS

---------------------------------------------------------
Title: Laboratory test results on the High Resolution Spectrograph
(HRS) forthe Space Telescope (ST).
Authors: Brandt, J. C.; Boggess, A.; Heap, S. R.; Maran, S. P.;
Smith, A. M.; Beaver, E. A.; Hutchings, J. B.; Jura, M. A.; Linsky,
J. L.; Savage, B. D.; Trafton, L. M.; Weymann, R. J.; Melcher, R.;
Rebar, F.; Vitagliano, H. D.; Shannon, J.; Krueger, V.; Yagelowich,
J.; Devine, E.; Flemming, K.; Fowler, W.; Leckrone, D.; Yurka, G.;
Meyer, W.; Chodil, J.; Becker, I.; Bottema, M.; Cushman, G.; Eck, H.;
Holmes, A.; Kelly, T.; Gallegos, J.; Garner, H.; Roybal, W.; West,
V.; Williams, B.; Ebbets, D.; Lindler, D. J.; Walter, F.
1984SPIE..445..427B Altcode:
We report some of the laboratory measured performance parameters of
the HRS. We then describe three aspects of performance of particular
importance to astronomers: (1) the capability of detecting very
weak features against a continuum, (2) the capability of producing
reliable line profiles, and (3) the capability of assigning accurate
wavelengths to spectral features. Specific technical descriptions of
the performance of the HRS detectors (Eck and Beaver, this volume),
gratings (Bottema et al., this volume), and control and data-handling
system (Becker, this volume) are reported separately.

---------------------------------------------------------
Title: The Proposed Columbus Mission: High and Low Resolution
Spectroscopy in the 100-2000 Å Spectral Region
Authors: Linsky, J. L.
1984uxsa.coll...72L Altcode: 1984IAUCo..86...72L; 1984uxsa.conf...72L
No abstract at ADS

---------------------------------------------------------
Title: Preliminary Results from Studies of High Resolution Line
Spectra in Late-type Giant and Supergiant Stars
Authors: Engvold, O.; Kjeldseth Moe, O.; Jensen, E.; Jordan, C.;
Stencel, R.; Linsky, J.
1984LNP...193..359E Altcode: 1984csss....3..359E
No abstract at ADS

---------------------------------------------------------
Title: Better Determinations of Mass Loss Rates for Red Giants
and Supergiants
Authors: Drake, Stephen A.; Linsky, Jeffrey L.
1984LNP...193..350D Altcode: 1984csss....3..350D
No abstract at ADS

---------------------------------------------------------
Title: RS CVn Binary Systems
Authors: Linsky, J. L.
1984LNP...193..244L Altcode: 1984csss....3..244L; 1984STIN...8513704L
In this review I will attempt to place in context the vast amount of
data obtained in the last few years as a result of X-ray, ultraviolet,
optical, and microwave observations of RS CVn and similar spectroscopic
binary systems. Since this topic is now very broad, I will concentrate
on the RS CVn systems and their long period analogs, and restrict
the scope by attempting to answer on the basis of the recent ata
and theory the following questions: (1) Are the original defining
characteristics still valid and still adequate? (2) What is the evidence
for discrete active regions? (3) Have we derived any meaningful
physical properties for the atmospheres of RS CVn systems? (4) What
are the flare observations telling us about magnetic fields in RS CVn
systems? (5) Is there evidence for systematic trends in RS CVn systems
with spectral type?

---------------------------------------------------------
Title: Definition and Empirical Structure of the Range of Stellar
Chromospheres-Coronae across the HR Diagram: Cool Stars
Authors: Linsky, J. L.
1984rcch.conf...55L Altcode:
No abstract at ADS

---------------------------------------------------------
Title: Microwave emission from the coronae of late-type dwarf stars.
Authors: Linsky, J. L.; Gary, D. E.
1983ApJ...274..776L Altcode:
VLA microwave observations of 14 late-type dwarf and subgiant stars
and binary systems are examined. In this extensive set of observations,
four sources at 6 cm (Chi-1 Ori, UV Cet, YY Gem, and Wolf 630AB) were
detected and low upper limits for the remaining stars were found. The
microwave luminosities of the nondetected F-K dwarfs are as small as
0.01 those of the dMe stars. The detected emission is slowly variable
in all cases and is consistent with gyroresonant emission from thermal
electrons spiraling in magnetic fields of about 300 gauss if the source
sizes are as large as R/R(asterisk) = 3-4. This would correspond to
magnetic fields that are probably in the range 0.001-0.0001 gauss at the
photospheric level. An alternative mechanism is gyrosynchrotron emission
from a relatively small number of electrons with effective temperature.

---------------------------------------------------------
Title: Outer atmospheres of cool stars. XV. High-dispersion
ultraviolet studies of active chromospheric G-K dwarfs.
Authors: Ayres, T. R.; Linsky, J. L.; Simon, T.; Jordan, C.; Brown, A.
1983ApJ...274..784A Altcode:
The authors have obtained IUE ultraviolet echelle spectra of the three
late-type active-chromosphere dwarf stars χ1 Ori, ξ Boo A
and ɛ Eri. These are compared with previously published observations
of the quiet chromosphere dwarfs α Cen A and α Cen B. The spectra
indicate a gross strengthening of chromospheric and transition-region
line fluxes from quiet to active dwarf stars without a fundamental
change in the line shapes. Qualitatively the same spectroscopic behavior
is seen in detail on the solar surface between regions of strong and
weak magnetic fields. They believe that the correspondence between
the stellar and solar behavior is not accidental, but instead affirms
that enhanced chromospheric and coronal emission on late-type main
sequence stars is a result of increased surface coverage of magnetic
active regions.

---------------------------------------------------------
Title: Redshifts of high-temperature emission lines in the
far-ultraviolet spectra of late-type stars.
Authors: Ayres, T. R.; Stencel, R. E.; Linsky, J. L.; Simon, T.;
Jordan, C.; Brown, A.; Engvold, O.
1983ApJ...274..801A Altcode:
High-dispersion IUE spectra of six late-type stars exhibit small but
statistically significant differential redshifts of high-temperature
emission lines, like Si IV and C IV, with respect to low-temperature
lines like S I and O I. A well-exposed, small-aperture spectrum of
the active chromosphere binary Capella (Alpha Aurigae A: G6 II+F9
III) establishes that the high-temperature lines are redshifted in an
absolute sense with respect to the accurately determined photospheric
velocity of the system at single-line phase 0.50. Several possible
explanations for the stellar redshifts are discused, including a warm
wind (100,000 K) in which aparent redshifts are produced in optically
thick lines by an accelerating outfow, and the downflowing component
of a vertical circulation system for which the up-leg portion of the
flow is too cool, too hot, or too tenuous to be visible in Si IV and C
IV. If the second scenario is true, the stellar redshifts may provide
an important phenomenological link to the downflows observed in 100,000
K species over magnetic active regions in the sun.

---------------------------------------------------------
Title: First detection of winds in red giants by microwave continuum
techniques.
Authors: Drake, S. A.; Linsky, J. L.
1983ApJ...274L..77D Altcode:
Eight red giants and supergiants have been observed at 4885 MHz
(6 cm) with the Very Large Array in an attempt to detect continuum
emission. The bright giant Alpha-1 Her (M5 II) was detected at an
average flux density of 0.9 + or - 0.13 mJy. Since the likely source
of this emission is an ionized, optically thick component of a stellar
wind, this detection implies a mass loss rate of 2 x 10 to the -9th
solar masses per yr for the ionized gas. The fraction of the outflow
in Alpha-1 Her that is ionized (0.002-0.02) seems to be similar to
that previously found for Alpha Ori and Alpha Sco A. Alpha Boo (K2
IIIp) and Beta Gem (K0 III) are probable and definite detections,
respectively. The derived ionized mass loss rates for these two stars
are about 1 x 10 to the -10th solar masses per yr, implying in the
case of Alpha Boo that the wind is largely ionized.

---------------------------------------------------------
Title: The formation of emission lines in the expanding chromospheres
of lumonous cool stars. I. The importance of atmospheric extension
and partial redistribution effects.
Authors: Drake, S. A.; Linsky, J. L.
1983ApJ...273..299D Altcode:
Most late-type luminous stars are losing mass in cool stellar winds,
although the mass-loss rates and mechanisms of these outflows
remain uncertain. In many red giants the only evidence for mass
loss is the presence of a characteristic asymmetry in the strongest
ultraviolet resonance lines, such as the Mg II k line. In this paper,
we discuss the available methods for treating radiative transfer
in such chromospheric lines in an expanding, extended medium and
select the comoving frame method (including partial redistribution)
as the most suitable. We briefly outline this technique in the context
of a two-level atom. Prior to applying this technique to deriving
atmospheric properties from observed line profiles, we present some
schematic examples to illustrate the sensitivity of the calculated line
profiles to the outflow velocity, chromospheric temperature gradient,
physical extent of the atmosphere, line-to-continuum strength, and
the incoherence fraction. In this paper, we illustrate the difference
in the computed line profiles between assuming partial and complete
redistribution for a wide range of atmospheric and wind parameters.

---------------------------------------------------------
Title: Why is Capella Not a Microwave Source?
Authors: Drake, S. A.; Linsky, J. L.
1983BAAS...15..947D Altcode:
No abstract at ADS

---------------------------------------------------------
Title: Outer atmospheres of cool stars. XIV. A model for the
chromosphere and transition region of beta Ceti (G9.5 III).
Authors: Eriksson, K.; Linsky, J. L.; Simon, T.
1983ApJ...272..665E Altcode:
In the present chromospheric and transition region model for Beta
Ceti, which is consistent with IUE spectra of the Mg II, C II,
and C IV resonance lines, the Mg II h and k lines are treated
in partial redistribution and the C II and C IV lines in complete
redistribution. Computed line fluxes are presented for a range of models
to show the range of permitted temperature structures. A comparison
of the Beta Ceti model to models previously computed in a similar way
for other stars shows a trend of decreasing chromospheric pressures
and increasing geometric scales as single stars evolve across the
transition region boundary. The present analysis also suggests that
transition region pressures drastically decrease and geometric scales
rapidly increase as single giant stars evolve to the right, toward
the boudnary. Beta Ceti's exceptional X-ray brightness is discussed.

---------------------------------------------------------
Title: Outer atmospheres of cool stars. XIII. Capella at critical
phases.
Authors: Ayres, T. R.; Schiffer, F. H., III; Linsky, J. L.
1983ApJ...272..223A Altcode:
The results are presented of a program of high-dispersion spectroscopy
of Capella at critical orbital phases utilizing the International
Ultraviolet Explorer. The considered program had the objective
to establish as carefully as possible the relative ultraviolet
emission levels of the Capella primary and secondary in order to
obtain an understanding regarding the nature of their chromospheres
and coronae. The results of the program confirm the earlier study
of the Capella by Ayres and Linsky (1980), which was limited to
orbital phases 0.50 and 0.75. Both programs found that the Capella
secondary is considerably brighter than the primary, in surface flux,
in all of the prominent far-ultraviolet emissions, particularly the
high-excitation CII-CIV lines. In addition, the present study has
revealed several puzzling aspects of the system. It is concluded that
the Capella primary is comparatively bright, for a yellow giant, in
far-ultraviolet and perhaps also in soft X-ray normalized fluxes. The
implications of this conclusion are evaluated.

---------------------------------------------------------
Title: IUE Observations of a Peculiar Flare Event on the dM0. 5e
Star G1 182
Authors: Haisch, B. M.; Linsky, J. L.; Bornmann, P. L.; Rodono, M.
1983BAAS...15..948H Altcode:
No abstract at ADS

---------------------------------------------------------
Title: The narrow ultraviolet emission lines of the red dwarf AU
Microscopii(dM1.6e).
Authors: Ayres, T. R.; Eriksson, K.; Linsky, J. L.; Stencel, R. E.
1983ApJ...270L..17A Altcode:
It is pointed out that the red dwarfs are the smallest, coolest,
faintest, least massive, but most common of normal main-sequence
stars. The dMe (H-alpha emission) subclass of the red dwarfs
exhibits the largest median soft X-ray to bolometric luminosity
ratio of any group of late-type stars. In connection with the present
investigation, attention is given to the first high-dispersion spectra
of the chromospheric (6000 K) and higher temperature (up to 100,000
K) emissions of a dMe star, AU Microscopii in the far-ultraviolet
(1150-2000 A) and middle-ultraviolet (2000-3000 A) bands accessible to
the International Ultraviolet Explorer (IUE). AU Mic is one of the most
luminous of lower main-sequence stars in C IV and soft X-ray emission.

---------------------------------------------------------
Title: Coordinated Einstein and IUE observations of a disparitions
brusques type flare event and quiescent emission from Proxima
Centauri.
Authors: Haisch, B. M.; Linsky, J. L.; Bornmann, P. L.; Stencel,
R. E.; Antiochos, S. K.; Golub, L.; Vaiana, G. S.
1983ApJ...267..280H Altcode:
The Einstein Imaging Particle Counter observed a major X-ray flare
in its entirety during a 5-hr period of simultaneous observations,
with the IUE, of the dM5e flare star Proxima Centauri in August,
1980. The detailed X-ray light curve, temperature determinations
during various intervals, and UV line fluxes obtained before, during,
and after the flare indirectly indicate a 'two-ribbon flare' prominence
eruption. The calculated ratio of coronal to bolometric luminosity for
the event is about 100 times the solar ratio. The Proxima Cen corona
is analyzed in the context of static loop models, in light of which
it is concluded that less than 6% of the stellar surface seems to be
covered by X-ray emitting active regions.

---------------------------------------------------------
Title: First Detection of Winds in Red Giants by Microwave Techniques
Authors: Drake, S. A.; Linsky, J. L.
1983BAAS...15R.646D Altcode: 1983BAAS...15..646D
No abstract at ADS

---------------------------------------------------------
Title: Coordinated Ultraviolet, Microwave, and Optical Observations
of Flares on YZ CMi and AD Leo
Authors: Linsky, J. L.; Bornmann, P.; Brown, A.; Gary, D. E.; Rodono,
M.; Pazzani, V.; Andrews, A. D.; Butler, C. J.; Byrne, P. B.
1983BAAS...15..650L Altcode:
No abstract at ADS

---------------------------------------------------------
Title: IUE spectra of the BY Dra/flarestar AU MIC
Authors: Butler, C. J.; Andrews, A. D.; Doyle, J. G.; Byrne, P. B.;
Linsky, J. L.; Simon, T.; Marstad, N.; Rodono, M.; Pazzani, V.
1983ASSL..102..249B Altcode: 1983ards.proc..249B; 1983IAUCo..71..249B
Ground-based optical and IUE observations of BY Dra variables undertaken
to follow the spectral variation of these stars over one cycle are
discussed. It is noted that in the first series, 20 LWR and 19 SWP
trailed spectra were taken of AU Mic over a three-day period, August
4-6, 1980. The mean integrated flux are shown here for the strong
emission lines in th SWP spectra of AU Mic over the observed phase
interval of 0.14 to 0.8, together with an approximate V light curve
determined by the FES and IUE. Several points emerge from comparing
the emission line intensities and FES magnitudes. The first is that
the light curve at this time had at least three and possibly four
minima. If this is to be interpreted as deriving from the rotation of
a spotted star, several spotted regions would be required, distributed
in stellar longitude. The second point is that repeated flaring of AU
Mic makes it difficult to perceive any clearly defined modulation of
the emission line intensities owing to plage regions in the vicinity
of the spots. The third point is that following flare activity during
SWP 9695 and WP 9698, it appears that the intensity of the HeII and
SiII lines has remained high for some time after the drop in intensity
of the CIV line.

---------------------------------------------------------
Title: Book-Review - Stellar Turbulence
Authors: Gray, D. F.; Linsky, J. L.; Elste, G. H.
1983ApL....23..174G Altcode:
No abstract at ADS

---------------------------------------------------------
Title: Mass Loss Rates for K-M Giants and Supergiants
Authors: Linsky, Jeffrey L.
1983iue..prop.1481L Altcode:
This proposal is an essential component of a larger program aimed
at deriving for the first time accurate mass loss rates from K-M
giants and supergiants. The program consists of the development of a
PRD radiative transfer code to model spherically symmetric expanding
atmospheres and to compute emergent line profiles, the application of
this code to determining mass loss rates and atmospheric properties of
a selected sample of K-M giants and supergiants, and a VLA observing
program to obtain mass loss rates for these stars independently from
their free-free microwave emission. This proposal is to obtain new
IUE high dispersion spectra of the Mg II h and k and Mg I 2852 A
resonance lines and spectra of these lines from the IUE archives,
and then to use our radiative transfer code to derive the mass loss
rates and atmospheric properties. An important selection criterion for
the target stars is that the circumstellar and interstellar absorption
features be widely separated so as not to be confused. This selection
criterion is essential for the unambiguous analysis of the data,
but it does limit the stars that can be studied.

---------------------------------------------------------
Title: The quiescent chromospheres and transition regions of active
dwarf stars - What are we learning from recent observations and
models?
Authors: Linsky, J. L.
1983ASSL..102...39L Altcode: 1983IAUCo..71...39L; 1983ards.proc...39L
Progress in understanding active dwarf stars based on recent IUE,
Einstein, and ground-based observations is reviewed. The extent of
magnetic field control over nonflare phenomena in active dwarf stars is
considered, and the spatial homogeneity and time variability of active
dwarf atmospheres is discussed. The possibility that solar like flux
tubes can explain enhanced heating in active dwarf stars in examined,
and the roles of systematic flows in active dwarf star atmospheres are
considered. The relation between heating rates in different layers of
active dwarf stars is summarized, and the mechanism of chromosphere and
transition region heating in these stars are discussed. The results
of one-component and two-component models of active dwarf stars are
addressed.

---------------------------------------------------------
Title: IUE spectra of RS CVn stars
Authors: Andrews, A. D.; Byrne, P. B.; Butler, C. J.; Linsky,
J. L.; Simon, T.; Marstad, N.; Rodono, M.; Blanco, C.; Catalano, S.;
Marilli, E.
1983ASSL..102..443A Altcode: 1983IAUCo..71..443A; 1983ards.proc..443A
Three RS CVn stars are observed during the period October 1-7,
1981. Eight spectra of II Peg, 10 of HR1099, and four of AR Lac are
obtained. The observations are well distributed with respect to the
phase of the optical light curves. The ground-based data reveal that
all three stars had well established wavelike variations. Evidence
is presented that in RS CVn stars the UV chromospheric and transition
region line fluxes vary in such a way that maximum line flux corresponds
to optical minimum or maximum spot visibility. This, it is pointed out,
is consistent with a solar-type dark spot model.

---------------------------------------------------------
Title: VLA observations of quiescent and flare microwave emission
from late-type stars - A unique probe of coronal magnetic fields
Authors: Gary, D. E.; Linsky, J. L.; Dulk, G. A.
1983IAUS..102..387G Altcode:
No abstract at ADS

---------------------------------------------------------
Title: Coordinated Ultraviolet, Optical and Radio Observations of
RS CVn and Flare Stars
Authors: Byrne, P. B.; Butler, C. J.; Andrews, A. D.; Rodono, M.;
Catalano, S.; Pazzani, V.; Linsky, J. L.; Bornman, P.; Haisch, B. M.
1983IBVS.2258....1B Altcode:
No abstract at ADS

---------------------------------------------------------
Title: Surface Structure of Eclipsing and Non-Eclipsing RS CVN Systems
Authors: Linsky, Jeffrey L.
1983iue..prop.1482L Altcode:
This proposal is to extend our collaborative IUE study of chromospheric
and transition region line flux variations in RS CVn-stars by observing
and analyzing periodic emission line flux changes out-of-phase with
respect to the noneclipse sinusoidal distortion of the light curve, as
well as studying changes during eclipses. In 1981 we observed with IUE
three RS CVn systems (HR 1099, II Peg, and AR Lac) at regular intervals
throughout their 2.0-6.7 day periods (collaborative NASA-ESASERC
program). We found clear evidence for chromospheric and TR line flux
variability, correlated in antiphase with the photometric variability,
and of variable line profile asymmetries with phase. By subtracting
the minimum from the maximum fluxes, we obtained approximate spectra
of the plage region and of the quiet component. The resulting plage
surface fluxes are up to several orders of magnitude larger than those
of chromospheric and TR lines in solar plages. The primary objective
of the present proposal is to use the moving screen of one star as it
eclipses a spotted star to determine the fractional area coverage of
active regions (plages), the atmospheric properties and structures
of these resolved active regions and how they differ from quiescent
regions, and the extent to which the active regions do overlie the
dark spots. We propose to compute models of the plage and quiet
components separately by matching observed fluxes in lines of Mg II,
Si II-IV, C II-IV and N V and by comparison with density-sensitive
line ratios. moreover, line profile asymmetry vs. orbital phase will be
investigated for the purpose of studying the active region geometry and
mass flow in loops in binary systems. We will also model the spectra
of any flare-like event observed. Coordinated ground-based coverage
in optical and radio hands is being organized.

---------------------------------------------------------
Title: The Rotation-Activity Correlations for Early F Dwarfs
Authors: Linsky, Jeffrey L.
1983iue..prop.1474L Altcode:
As one proceeds down the main sequence, convection first becomes
important in the early F stars. It is now well established that by
spectral type F8V, dynamogenerated magnetic fields are an important
factor in heating stellar chromospheres and coronae. Stars later than
F8V exhibit clear relations between the stellar rotation rate and the
level of chromospheric and coronal activity as measured by the strength
of emission features. On the other hand, F2-F5 dwarfs exhibit no such
relations at coronal temperatures, despite coronal activity levels
(Lx/Lbol ) two orders of magnitude larger than for the A-B stars. We
propose to investigate the transition from the early type atmospheres
to the chromospheres and coronae of the later type stars by studying
the UV line emission from a sufficiently large and representative
sample of Fl-F7 dwarfs with known Vsini. We seek to determine at what
effective temperature (as indicated by B-V or V-R) the rotation-activity
relations become apparent. With a sample of stars of similar Vsini, we
shall study how the increasing depth of the convective zone influences
the activity levels. Among the bluest stars that will likely exhibit no
rotation-activity correlation, we also plan to investigate how stellar
age may influence stellar activity levels. Finally, we will investigate
the relationship between chromospheric and transition region emission
in early F stars, in order to test current theoretical ideas about
the structure and energy balance of stellar atmospheres.

---------------------------------------------------------
Title: The role of magnetic fields in stellar chromospheres and
transition regions
Authors: Linsky, J. L.
1983IAUS..102..313L Altcode:
Consideration is given to the different roles that magnetic fields
play in the control of the structure and energy balance in the
chromospheres and transition regions of late-type stars, in view of
IUE and Einstein satellite observations. The rotational modulation of
structures ('plages') that are bright in UV emission lines and overlie
dark star spots suggests that magnetic flux tubes are the dominant
structural elements in late-type stellar atmospheres, as well. It is
proposed that the existence of a boundary between solar-type stars and
those with little or no plasma, as well as the different types of G-K
giants and supergiants, may be understood in terms of the fractional
surface coverage by closed magnetic structures. Models computed for
active and quiet regions of the sun are compared with those for active
and quiet stars.

---------------------------------------------------------
Title: UV Variability and Rotational Modulation of T Tauri Stars
Authors: Linsky, Jeffrey L.
1983iue..prop.1477L Altcode:
T Tauri stars show high levels of chromospheric activity and they
have the largest surface fluxes of chromospheric and transition region
emission lines of any class of stars. (Only the RS CVn binary systems
show equivalent levels of emission.) As low mass premain-sequence stars,
their outer atmospheres are the precursors of the chromospheres and
coronae of main sequence stars and hence are highly relevant to the
evolution and causes of such phenomena. The available X-ray data imply
that the coronae of T Tauri stars are of small extent compared to their
stellar radii, while optical and infrared observations show large
extended regions of relatively cool circumstellar gas and dust. We
propose to study the changes in emission lines formed in the upper
chromospheres and transition regions of three T Tauri stars (SU Aur,
RY Tau, DR Tau) over a period of 5 days. This period was chosen since
it is close to the expected rotational period for these stars. The
data will be examined for the effects of rotational modulation due to
chromospheric structures (plages, active regions) as they pass across
the visible disc of the star. Many examples of such behavior are seen
in other cool stars. Observation of modulation would demonstrate that
the transition region also has a small extent, similar to the coronal
findings. Even if significant rotational modulation is not detected,
we will examine the nature of any other types of variability detected
and deduce the implied constraints on chromospheric structure. To
our knowledge there has been no systematic search for variability or
rotational modulation in the IUE short-wavelength region for T Tauri
stars and this program represents a new approach in the study of these
stars. As a byproduct we should obtain the best set of low-dispersion
SWP observations of T Tauri stars so far made that will allow detailed
modelling of the chromospheric structure of these stars.

---------------------------------------------------------
Title: Coordinated Observations of Flares on UV Ceti-Type Stars
Authors: Linsky, Jeffrey L.
1983iue..prop.1479L Altcode:
We propose to monitor 2 UV Ceti-type flare stars at times of maximum
flare activity simultaneously in the ultraviolet (IUE), X-rays (the
EXOSAT satellite to be launched by ESA in early 1982), optical, and
radio portions of the spectrum. The objectives of this coordinated
program are: (1) to estimate the energy budget for a typical sample of
flares including radiative losses from the corona (X-rays), conductive
loss to the transition region and chromosphere (ultraviolet and
optical), and expansion (optical spectra); (2) to determine whether
flares are cooled primarily by radiation, conduction, or expansion;
(3) to estimate the temperatures, densities, and volumes of the hot
flaring plasma, (4) to study the correlation of optical and radio
flares, and (5) to deter-mine the mechanism by which the ultraviolet
flare continuum is formed. We request 6 US#2 shifts to obtain low
dispersion SWP and LWR spectra either by discrete time trailing along
the aperture or individual spectra depending on exposure times and
background levels. A very successful coordinated observation of the
August 20, 1980 flare on Prox Cen using IUE and Einstein demonstrates
the feasibility of this type of coordinated observing program.

---------------------------------------------------------
Title: High Dispersion Study of Two T Tauri Stars: RU Lupi and
Cod-34 7151
Authors: Linsky, Jeffrey L.
1983iue..prop.1483L Altcode:
High dispersion, short wavelength IUE spectra with exposure times of 16
hours or more are sought for the two T Tauri stars which are brightest
in the ultraviolet, RU Lupi and CoD-34 7151. These spectra will provide
vital information on emission line profiles and widths for resonance
and intersystem lines formed at temperatures between 2xlO^4 and 2xlO^5
K. These data can then be used to examine the energy deposition
processes present in the chromospheres and transition regions of
these stars. In particular, the Alfven wave-powered wind-outflow model
proposed by Lago (1979, 1982) can be tested in terms of its proposed
velocity and density structure. The relative importance of turbulence,
opacity and Doppler shifts in an outflowing wind as line broadening
mechanisms will be investigated for these stars. Low resolution IUE
spectra of T Tauri stars indicate that RU Lupi and CoD-34 7151 are the
only members of this class for which such observations are possible
with IUE.

---------------------------------------------------------
Title: High Dispersion Study of Luminous Cool Stars
Authors: Linsky, Jeffrey L.
1983iue..prop.1480L Altcode:
We propose to obtain 16-20 hour high dispersion SWP spectra, as well
as high dispersion LWR spectra, of four late-type giants. The targets
are Alpha Her (M5 II + G5 III), Zeta Cyg (G8 III, Ba 0.6), Beta Peg
(M2.5 II-III) and Beta And (MO IIIa). The observations of Alpha Her
will extend our understanding of stellar winds, circumstellar material
and binary interaction in cool stellar atmospheres. The existence of
the hotter secondary star (actually a spectroscopic binary) provides a
unique opportunity for studying the circumstellar material in absorption
far into the ultraviolet. The observations of Zeta Cygni should present
further evidence for s-enriched material in the stellar atmosphere and
in the circumstellar gas and may give new information on the probable
compact companion of the star and the interaction between the two
components of the system. The observations of Beta Peg and Beta And
should increase our knowledge dramatically as regards the dynamical
state of chromospheres of M giants and lead to interesting conclusions
when compared with the corresponding observations of the M supergiant
Alpha Ori, and the dMe star AU Mic.

---------------------------------------------------------
Title: High Resolution Spectroscopy of Two FK Comae Stars
Authors: Linsky, Jeffrey L.
1983iue..prop.1478L Altcode:
The FK Comae stars are a class of extremely rapidly rotating G-K
giants that exhibit among the brightest UV and X-ray emission seen in
late type stars. Previous IUE and optical observations have indicated
that the activity (the extreme surface fluxes) in FK Comae may be
qualitatively different from that in "normal" late type stars, and
that the other four members of the class are far less bizarre than
FK Comae itself. A definitive method for determining the structure of
the outer atmospheres of these stars, and deciding whether the heating
mechanism is normal chromospheric heating or accretion heating is by
analysis of high resolution SWP spectra. We propose, in collaboration
with S. Rucinski, to obtain 16-20 hour collaborative NASA-ESA SWP-HI
spectra of FK Comae, which exhibits Hot and MgII line widths of ∼500
kms^-1, and HD 36705, which appears to be a far less bizarre member
of this class. These observations would be the first high dispersion
SWP spectra ever obtained of FK Comae stars.

---------------------------------------------------------
Title: Studies of Spots &amp; Plages in by Draconis-Type Variable
Stars
Authors: Linsky, Jeffrey L.
1983iue..prop.1475L Altcode:
The activity phenomena that are observed in BY Draconis stars closely
resemble those observed in the Sun. Bright and dark spots have been
inferred from their quasi-sinusoidal light variations. Also, powerful
flare phenomena are occasionally observed in the radio, optical, UV and
X-ray wavelength regions. The present proposal is aimed at studying in
a more quantitative way the several activity phenomena observed with
particular emphasis on the variability of chromospheric and transition
region flux and their correlation with photospheric variability. These
observations should provide comprehensive diagnostics, which are
necessary in attempting to infer the physical conditions of the outer
atmospheres of BY Dra stars in their quiescent and active phase. In
order to reach this objective, we are proposing to observe with IUE some
typical representatives of the group in the low and high dispersion
mode with the SWP and the LWR camera, respectively. Coordinated
ground-based coverage in the optical and radio bands, as well as soft
X-ray observations with EXOSAT are planned. We plan to compute models
of the chromospheres, transition regions, and coronae of these stars
for the quiescent and active portions of their surfaces separately.

---------------------------------------------------------
Title: Achievements in space astrophysics : proceedings of the topical
meeting of the COSPAR Interdisciplinary Scientific Commission E of
the COSPAR twenty-fourth plenary meeting held in Ottawa, Canada,
16th May-2nd June 1982
Authors: Hudson, Hugh S.; Dupree, Andrea K.; Linsky, Jeffrey L.
1983asap.book.....H Altcode: 1983QB495.A38v2n9..
No abstract at ADS

---------------------------------------------------------
Title: Measurements of chromospheric densities and geometrical
extensions of late-type giant and super-giant stars
Authors: Wing, R. F.; Carpenter, K. G.; Stencel, R. E.; Linsky, J. L.
1983osuc.rept.....W Altcode:
The density sensitivity of the emission lines within the UV 0.01
multiplet of C II near 2325 A was examined in additional late type
giants and supergiants with deep LWR high dispersion exposures. The
new data support the original contention based on these lines that
noncoronal red giants possess geometrically extended chromospheres.

---------------------------------------------------------
Title: An unusual microwave flare with 56 second oscillations on
the M dwarf L726-8 A.
Authors: Gary, D. E.; Linsky, J. L.; Dulk, G. A.
1982ApJ...263L..79G Altcode:
Using the VLA, an unusual flare event has been observed on L726-8
A (dM5.5e), the primary star in the M dwarf system containing the
prototype flare star UV Cet. This flare had a peak flux of 8 mJy
at 6 cm and a corresponding brightness temperature greater than 10
to the 10th K, was almost entirely right-hand circularly polarized,
showed large flux variations on the 10 s time resolution of the VLA,
and exhibited quasi-periodic oscillations with a period of about 56 +
or - 5 s. While periodic flux variations have been detected during
solar flares and RS CVn type stellar flares, this is apparently the
first detection of periodicity in microwaves from M dwarf stars. It is
proposed that the observed radiation was due to maser action, probably
an electron maser, and that the energy release mechanism was modulated.

---------------------------------------------------------
Title: Ultraviolet and X-ray detection of the 56 Peg system (K0
II p+WD) : evidence for accretion of a cool stellar wind onto a
white dwarf.
Authors: Schindler, M.; Stencel, R. E.; Linsky, J. L.; Basri, G. S.;
Helfand, D. J.
1982ApJ...263..269S Altcode:
IUE spectra of the slowly rotating mild barium star 56 Peg (HD 218356;
K0 IIp) show excess continuum emission from 1300 to 2000 Å, a broad
Lyα absorption feature, and emission lines usually associated with a
l04-(2 × l05) K plasma. The best fit blackbody
curve to the dereddened continuum gives a temperature of 32000 ± 4000
K and a radius for the object of (2.7 ± 1.0) × l09 cm,
consistent with that of a white dwarf. Einstein IPC observations of this
system yield Lx ≍ 3 × 1O31 ergs s-1,
which is as bright as the RS CVn binary systems. The X-rays can be
fitted to a bremsstrahlung spectrum with kT = 0.45 ± 0.3 keV, or a
blackbody spectrum with kT ≍ 0.2 keV. Since bright X-ray and high
temperature emission lines are unusual for single stars in this region
of the H-R diagram, we do not believe that the 56 Peg primary has a
hot corona and transition region. Instead, we propose that the observed
X-ray luminosity is due to accretion onto the white dwarf of ∼0.1% of
the wind from the primary, which we assume has a reasonable mass loss
rate of 2 × 10-7 to 4 × l0-9 Msun
yr-1. The ultraviolet emission lines likely result from
reprocessed X-radiation absorbed by the wind. The Mg II K line exhibits
a time-varying emission core, that may be explained by ionization of
Mg+ in the wind by X-rays from the white dwarf.

---------------------------------------------------------
Title: Evolution of chromospheres and coronae in solar mass stars
: a far-ultraviolet and soft X-ray comparison of Arcturus (K2III)
and alf CEN A (G2V).
Authors: Ayres, T. R.; Simon, T.; Linsky, J. L.
1982ApJ...263..791A Altcode:
IUE far-UV and Einstein Observatory soft X-ray observations for the red
giant Arcturus and the nearby yellow dwarf Alpha-Centauri A, which are
archetypes of solar mass stars in different stages of evolution, are
compared. Evidence is found for neither coronal soft X-ray emission
from the red giant, at surface flux levels of only 0.0006 that
detected previously for the yellow dwarf, nor C II and IV resonance
line emission at surface flux levels of only 0.02 those of the yellow
dwarf. The resonance line upper limits and previous detections of the
C II intersystem UV multiplet 0.01 near 2325 A provide evidence for an
Arcturus outer atmosphere that is geometrically extended, tenuous and
cool. The red giant has, in addition, a prominent cool stellar wind. An
extensive tabulation of line identifications, widths and fluxes for
the IUE far-UV echelle spectra of the two stars is given, and two
competing explanations for the Wilson-Bappu effect are discussed.

---------------------------------------------------------
Title: Outer atmospheres of cool stars. XII. A survey of IUE
ultraviolet emission line spectra of cool dwarf stars.
Authors: Linsky, J. L.; Bornmann, P. L.; Carpenter, K. G.; Wing,
R. F.; Giampapa, M. S.; Worden, S. P.; Hege, E. K.
1982ApJ...260..670L Altcode:
Quantitative information is obtained on the chromospheres and
transition regions of M dwarf stars, in order to determine how the outer
atmospheres of dMe stars differ from dM stars and how they compare with
the outer atmospheres of quiet and active G and K type dwarfs. IUE
spectra of six dMe and four dM stars, together with ground-based
photometry and spectroscopy of the Balmer and Ca II H and K lines,
show no evidence of flares. It is concluded, regarding the quiescent
behavior of these stars, that emission-line spectra resemble that of
the sun and contain emission lines formed in regions with 4000-20,000 K
temperatures that are presumably analogous to the solar chromosphere,
as well as regions with temperatures of 20,000-200,000 K that are
presumably analogous to the solar transition region. Emission-line
surface fluxes are proportional to the emission measure over the range
of temperatures at which the lines are formed.

---------------------------------------------------------
Title: Stellar Activity and the Connection Between Chromospheric
and Coronal Energy Losses
Authors: Hammer, R.; Linsky, J. L.
1982BAAS...14..866H Altcode:
No abstract at ADS

---------------------------------------------------------
Title: Models for the Plage and Quiescent Chromosphere and Transition
Region on II Peg
Authors: Marstad, N.; Linsky, J. L.
1982BAAS...14..866M Altcode:
No abstract at ADS

---------------------------------------------------------
Title: Observations of Neutral Hydrogen and Deuterium toward Cen
Authors: Landsman, W. B.; Henry, R. C.; Moos, H. W.; Linsky, J. L.
1982BAAS...14..893L Altcode:
No abstract at ADS

---------------------------------------------------------
Title: Cool Stellar Winds: Modeling of the Ultraviolet Resonance
Lines to Derive Mass Loss Rates
Authors: Drake, S. A.; Linsky, J. L.
1982BAAS...14..894D Altcode:
No abstract at ADS

---------------------------------------------------------
Title: The Narrow Ultraviolet Emission Lines of the Red Dwarf AU
Microscopii (dM1.6e)
Authors: Ayres, T. R.; Eriksson, K.; Gustafsson, B.; Linsky, J. L.;
Saxner, M.; Stencel, R. E.
1982BAAS...14Q.865A Altcode:
No abstract at ADS

---------------------------------------------------------
Title: Chromospheric Activity Near the ZAMS: Ultraviolet and X-ray
Observations of the UMa Cluster
Authors: Walter, F. M.; Linsky, J. L.; Simon, T.
1982BAAS...14..866W Altcode:
No abstract at ADS

---------------------------------------------------------
Title: Stellar model chromospheres. XIII. M dwarf stars.
Authors: Giampapa, M. S.; Worden, S. P.; Linsky, J. L.
1982ApJ...258..740G Altcode:
Single-component, homogeneous model chromospheres that are consistent
with high-resolution profiles of the Ca II K line calibrated in surface
flux units for three dMe and 2 dM stars observed at quiescent times
are constructed. The models reveal several systematic trends. Large
values of the ratio of T(min) to T(eff) are derived, indicating a large
amount of nonradiative heating present in the upper photospheres of M
dwarf stars. It is also found that the lower chromospheric temperature
gradient is similar for all the M dwarf stars. Since for the models here
the chromospheric K line emission strength is most sensitive to the
total amount of chromospheric material present within the approximate
temperature range T(min)-6000 K, increasing the emission strength is not
simply due to increasing chromospheric temperature gradients. It is also
found that both the electron density and electron temperature at one
thermalization length in the K line below the top of the chromospheres
are greater in the dMe stars than in the dM stars. The M dwarf models
here have microturbulent velocities between 1 and 2 km/sec, which are
much smaller than for solar chromosphere models.

---------------------------------------------------------
Title: Variability of cool stars at optical and ultraviolet
wavelengths. II - The binary (?) flare star AU Mic.
Authors: Linsky, J. L.; Bornmann, P. L.; Rodono, M.; Pazzani, V.;
Andrews, A. D.; Butler, C. J.; Byrne, P. B.
1982ESASP.176..165L Altcode: 1982IUE3r.R....129L; 1982iue..conf..165L
Ground based optical, and IUE observations of AU Mic are described. One
definite flaring event, remarkable changes of the BY Dra-type optical
light curve and evidence of slow variability in the chromospheric and
transition region line fluxes (probably due to the rotational modulation
of photospheric starspots and plages, respectively), was found. The
fractional surface area covered by active regions (filling factor) shows
a definite variability with the temperature of line formation, i.e.,
with atmospheric height. This suggests significant surface and vertical
structuring of active regions in the outer atmosphere of AU Mic.

---------------------------------------------------------
Title: Outer atmospheric properties of beta Draconis (G2 Ib-II)
Authors: Brown, A.; Jordan, C.; Ayres, T. R.; Linsky, J. L.; Stencel,
R. E.
1982ESASP.176..142B Altcode: 1982IUE3r......142B; 1982iue..conf..142B
Observations of the supergiant Beta Draconis made by IUE are
discussed. Electron pressure is comparable with that found in the quiet
solar atmosphere. The X-ray fluxes from previous observations suggest
T = 10 to 20 million k, when combined with the analysis of the IUE
spectra; this would be greater than the proton escape velocity. The
radiation losses between 10,000 and 100,000 K exceed those from the
Sun by an order of magnitude, but in the absence of a stellar wind the
energy losses from the corona would be lower than in the Sun. The line
profile widths indicate substantial (M=2) nonthermal broadening. If
interpreted as energy associated with a wave flux, they would imply
more coronal energy than required by radiation and conduction losses,
suggesting an energetic mass loss. However, line asymmetries can also
be interpreted as motions within the atmosphere.

---------------------------------------------------------
Title: On the reality of a boundary in the H-R diagram between
late-type stars with and without high temperature outer atmospheres.
Authors: Simon, T.; Linsky, J. L.; Stencel, R. E.
1982ApJ...257..225S Altcode:
The Linsky-Haisch hypothesis (1979) that a boundary exists in the H-R
diagram separating yellow giants from red giants and supergiants is
tested. IUE 1150-2000 A low-resolution spectra of 10 stars chosen to
constitute a reverse bias sample are presented and discussed. Despite
the bias, weak C IV emission indicative of high-temperature plasma was
observed in four of the six stars chosen to be probable red stars,
while no C IV emission was detected in the four stars chosen to be
yellows. In a second test using the entire sample of 39 stars, nearly
all of the yellow giants and supergiants were found to have an emission
feature at 1549 A, which is attributed to C IV. The large magnitude
dispersion could be attributed to temporal or spatial variability,
differing magnetic field strengths and geometries, or age-related
effects during post-main-sequence evolution. It is concluded that the
Linsky-Haisch transition region boundary is a real phenomenon.

---------------------------------------------------------
Title: Rotational modulation of chromospheric features in late-type
stars.
Authors: Byrne, P. B.; Butler, C. J.; Andrews, A. D.; Linsky,
J. L.; Simon, T.; Marstad, N.; Rodono, M.; Blanco, C.; Catalano, S.;
Marilli, E.
1982ESASP.176..125B Altcode: 1982iue..conf..125B; 1982IUE3r......125B
Three RS CVn-type binaries (HR 1099, II Peg, and AR Lac) and the
prototype BY Dra binary system were observed by IUE at regular intervals
throughout their 2.0 to 6.7 day periods. Ground based photometry and
radio observations were also made. Flux variations of emission lines
formed in the chromospheres and transition regions of two of these
stars are discussed. The phase relationship between the photometric
observations and the line variations and their relevance to the
location of dark star spots are considered. The evidence suggests
that in the spotted variables the fluxes of the chromospheric and
transition region lines vary in a manner such that maximum line flux
corresponds to optical minimum or maximum spot visibility. This is
consistent with a model of a solar-like dark spot distribution on the
surface of these stars.

---------------------------------------------------------
Title: The structure, energy balance, and winds of cool stars.
Authors: Linsky, J. L.
1982ESASP.176....3L Altcode: 1982iue..conf....3L; 1982IUE3r........3L
Solar magnetic field phenomena which occur in cool stars are
summarized. Factors which can produce magnetic fields in stars
are listed. Information on cool star atmospheres, provided by high
dispersion spectra, is discussed. These spectra show that in Beta Dra
(G2 Ib) the transition lines are red shifted (an antiwind), perhaps
indicating downflows in closed magnetic flux tubes, as seen in the
solar flux tubes above sunspots. The G and K giants and supergiants
are classed as active, quiet, or hybrid, depending on whether their
atmospheres are dominated by closed magnetic flux tubes, open field
geometries, or a predominantly open geometry with a few closed flux
tubes embedded.

---------------------------------------------------------
Title: Current NASA studies for a far-ultraviolet spectrographic
Explorer (FUSE)
Authors: Linsky, J.; Boggess, A.; Bowyer, S.; Caldwell, J.; Cash, W.;
Cohen, J.; Dupree, A.; Green, R.; Jenkins, E.; Jura, M.; Leckrone,
D.; Moos, H. W.; Savage, B.; Shull, M.; Snow, T.; Timothy, J. G.;
Weiler, E.; York, D.
1982ESASP.176..473L Altcode: 1982iue..conf..473L; 1982IUE3r......473L; 1982IUE3E.R....473L
The NASA plans for FUSE, a satellite which obtains spectra with
resolutions between 100,000 and 100 in the spectral regions from 912
to 1216A and 100 to 912A, are outlined. Scientific problems which
can be tackled by FUSE, but not by IUE or the Space Telescope, are
discussed. A grazing incidence echelle and a hybrid echelle design
are presented. They have high throughput, large simultaneous spectral
range, and low background photon counting statistics. The satellite
operational organization is similar to that of IUE.

---------------------------------------------------------
Title: High resolution EUV spectroscopy of 56 Pegasi (K0II P + wd).
Authors: Jordan, C.; Brown, A.; Ayres, T. R.; Linsky, J. L.; Stencel,
R. E.
1982ESASP.176..161J Altcode: 1982iue..conf..161J; 1982IUE3r......161J
The hypothesis that X-ray and UV emission by 56 Pegasi (K0II p + wd)
originates in a conventional chromosphere, transition region and corona,
as opposed to Schindler's hypothesis of accretion of the cool stellar
wind onto the white dwarf companion, is discussed. Analysis of IUE data
indicates that within the uncertainties associated with determining the
stellar radius and abundances, the chromosphere, transition region, and
corona of 56 Peg are similar to that of Beta Draconis both in structure
and energy balance. The accretion hypothesis is not a unique explanation
of the observed spectral properties and the white dwarf companion may
not play a direct role. Furthermore, 56 Peg, according to current
values of V-R and luminosity class, is on the nonsolar side of the
Linsky-Haisch dividing line whereas Beta Draconis is on the solar side.

---------------------------------------------------------
Title: Outer atmospheres of cool stars. XI. High-dispersion IUE
spectra of five late-type dwarfs and giants.
Authors: Ayres, T. R.; Linsky, J. L.; Basri, G. S.; Landsman, W.;
Henry, R. C.; Moos, H. W.; Stencel, R. E.
1982ApJ...256..550A Altcode:
We present high-dispersion, far-ultraviolet (1150-2000 Å) spectra
of five late-type dwarfs and giants obtained with the International
Ultraviolet Explorer. The chromospheric (T ≲104K)
emission lines in the giants tend to be about twice as broad as
the corresponding features of the dwarf star spectra, suggesting a
width-luminosity relation similar to the Wilson-Bappu effect for Ca
II H and K. The Si III λ1892 and C III λ1909 intercombination lines
formed in hotter layers (T ≍ 5 × 104K) also broaden
by a factor of 2 from the main-sequence stars to the evolved stars,
and the permitted resonance doublets of C II(3 × 104
K), Si IV (6 × 104 K), and C IV (105 K) are as much as
a factor of 4 broader in the giants than in the dwarfs. However, we
find no evidence for asymmetric or shifted emission profiles that
might indicate the presence of warm (T≪105K) stellar
winds. We conclude that broad C iv profiles, in particular, are typical
of active chromosphere giant stars and are unlikely to be a unique
signature of an extended, expanding warm wind. Since the resonance
lines tend to be wider than the intersystem lines formed at similar
temperatures in the chromosphere and in hotter layers, we conclude
that opacity must be an important broadening enhancement mechanism in
active chromosphere giant stars. Nevertheless, the intercombination
line widths do indicate a general increase in the outer atmosphere
Doppler motions from the dwarfs to the giants. Application of
the density sensitive line ratio C III λ1909/Si III λ1892 suggests
that the outer atmosphere pressures (T ≍ 5 × 104K)
are similar in the active chromosphere subgiant λ And and the quiet
chromosphere dwarfs, α Cen A and B. However, the pressures derived
for the Capella secondary and β Dra are factors of 3 or more lower
than the dwarfs, suggesting geometrically extended, low-density outer
atmosphere structures qualitatively different from the high-pressure,
compact structures typical of solar magnetic active regions. Finally, we have isolated the He II λ1640 emission component
from contaminant blends, and we find that the line strength is well
correlated with soft X-ray fluxes of the sample stars, as predicted
by photoionization-recombination models of the He II Bα formation.

---------------------------------------------------------
Title: Outer atmospheres of cool stars. X. HR 1099 at quadrature.
Authors: Ayres, T. R.; Linsky, J. L.
1982ApJ...254..168A Altcode:
IUE high-dispersion, far-UV spectra of the active-chromosphere RS
CVn binary HR 1099 are reported. The emission features produced by
such high-temperature species as C II and C IV are found to be very
bright, to exhibit structure, change significantly in the one-week
interval separating the two exposures, and generally follow the radial
velocity motion of the K subgiant primary, while the less massive G
dwarf secondary appears only weakly in the composite spectrum. It is
concluded that chromospheric and transition region emission in RS CVn
binaries is a stellar rather than system phenomenon, and the structure
evident in some of the emission line shapes is interpreted as a patchy
brightness distribution on and above the K star surface that is spread
out in velocity by the rapid rotation.

---------------------------------------------------------
Title: A High Resolution EUV Spectrum of α Ori
Authors: Engvold, O.; Kjeldseth Moe, O.; Jensen, E.; Linsky, J. L.;
Stencel, R. E.
1982BAAS...14..651E Altcode:
No abstract at ADS

---------------------------------------------------------
Title: Gas Flow in the Chromosphere of α Ori
Authors: Kjeldseth Moe, O.; Engvold, O.; Jensen, E.; Linsky, J. L.;
Stencel, R. E.
1982BAAS...14..651K Altcode:
No abstract at ADS

---------------------------------------------------------
Title: A heating mechanism for the chromospheres of M dwarf stars.
Authors: Giampapa, M. S.; Golub, L.; Rosner, R.; Vaiana, G. S.;
Linsky, J. L.; Worden, S. P.
1982SAOSR.392A..73G Altcode: 1982csss....2...73G
The atmospheric structure of the dwarf M-stars which is especially
important to the general field of stellar chromospheres and coronae
was investigated. The M-dwarf stars constitute a class of objects
for which the discrepancy between the predictions of the acoustic
wave chromospheric/coronal heating hypothesis and the observations is
most vivid. It is assumed that they represent a class of stars where
alternative atmospheric heating mechanisms, presumably magnetically
related, are most clearly manifested. Ascertainment of the validity
of a hypothesis to account for the origin of the chromospheric and
transition region line emission in M-dwarf stars is proposed.

---------------------------------------------------------
Title: Ultraviolet and X-ray detection of the 56 Peg system (K0 IIp
+ WD).
Authors: Schindler, M.; Stencel, R. E.; Linsky, J. L.; Basri, G.;
Helfand, D.
1982SAOSR.392B.125S Altcode: 1982STIN...8234317S
Both IUE short and long wavelength exposures of the 56 Peg system are
discussed. This mild barium star has an X-ray luminosity of 3 x 10 to
the 31st power ergs/1, comparable to the rapidly rotating RS CVn binary
systems, yet lies in a region of the HR diagram where stellar X-rays
are generally not observed. This cool, bright giant is not a rapid
rotator and the key to understanding its emission lies in the recent
discovery of its white dwarf companion. Accretion onto the white dwarf
of approximately 0.1% of the stellar wind of the primary is sufficient
to power an X-ray source of the observed luminosity. Reprocessing of
the X-rays in the cool dense stellar wind explains the origin of the
UV emission line spectrum, and may explain the time varying asymmetry
of the Mg 2 kappa line profile that is observed. Graphs which show
observed fluxes and wavelengths are discussed.

---------------------------------------------------------
Title: High dispersion IUE spectra of active chromosphere G and
K dwarfs.
Authors: Ayres, T. R.; Linsky, J. L.; Brown, A.; Jordan, C.; Simon, T.
1982NASCP2238..281A Altcode: 1982auva.nasa..281A; 1982NASCP2338..281A; 1982IUE82......281A
IUE far ultraviolet echelle spectra of three active chromosphere
dwarf stars X1 Orionis (GO V), Bootis A (G8 V), and Eridani (K2 V),
are analyzed utilizing spectra of Alpha Cen A (G2 V) and Alpha Cen B
(K1 V) as quiet chromosphere comparisons.

---------------------------------------------------------
Title: Cool luminous stars
Authors: Linsky, J. L.
1982AdSpR...2i.249L Altcode: 1982AdSpR...2..249L
A broad theme emerging from IUE and Einstein observations of cool stars
is that magnetic fields control the structure and energy balance of the
outer atmospheres of these stars. I summarize the phenomena associated
with magnetic fields in the Sun and show that similar phenomena occur
in cool luminous stars. High dispersion spectra are providing unique
information concerning densities, atmospheric extension, and emission
line widths. A recent unanticipated discovery is that the transition
lines are redshifted (an antiwind) in β Dra (G2 Ib) and perhaps other
stars, which I interpret as indicating downflows in closed magnetic
flux tubes as are seen in the solar flux tubes above sunspots. Finally,
I classify the G and K giants and supergiants into three groups -
active stars, quiet stars, and hybrid stars - depending on whether
their atmospheres are dominated by closed magnetic flux tubes, open
field geometries, or a predominately open geometry with a few closed
flux tubes embedded. Staff Member, Quantum Physics Division,
National Bureau of Standards.

---------------------------------------------------------
Title: Results of an IUE program of monitoring the ultraviolet
emission line fluxes of four binary systems: HR 1099, II Peg, AR Lac,
and BY Dra.
Authors: Marstad, N.; Linsky, J. L.; Simon, T.; Rodono, M.; Blanco, C.;
Catalano, S.; Marilli, E.; Andrews, A. D.; Butler, C. J.; Byrne, P. B.
1982NASCP2238..554M Altcode: 1982auva.nasa..554M; 1982NASCP2338..554M; 1982IUE82......558B
A program to obtain IUE spectra and optical photometry and spectra
of three RS CVn-type binaries (HR 1099, II Peg, and AR Lac) and the
prototype BY Dra system is reported. The systems were monitored for
at least one orbital phase, and periodic variations in emission line
flux from II Peg and HR 1099, indicative of notational modulation
of an active region on these stars were detected. It is found that
for II Peg the active region is in phase with photometric minimum as
expected, but for HR 1099 ultraviolet emission maximum occurs at the
time of photometric maximum.

---------------------------------------------------------
Title: Post-T Tauri Stars
Authors: Linsky, Jeffrey
1982iue..prop.1137L Altcode:
We have detected a number of X-ray sources near regions of star
formation that are likely to be stars more evolved than the T Tauri
stars yet younger than the zeroage main sequence (ZAMS). The sample
includes both K7-MO dwarfs with weak H-alpha emission and GS-140 dwarfs
which show H-alpha. filled in with chromospheric emission. The star SAO
76567, a rapidly rotating G0 III-IV, is likely to be a star of more
than 1 M(sun) crossing the Hertzsprung gap from right to left. Also,
a large fraction of the B7-A0 stars in these regions of star formation
have X-ray fluxes well in excess of those predicted for main sequence
B stars, and could be in binary systems with young, active, low mass
stars. We propose to study the outer atmospheres of these stars with IUE
to investigate three basic questions. MgII surface fluxes may be able
to show how the activity level in the late-type dwarfs relates to that
of the T Tauri stars and the dKe stars. Observations of SAO 76567 will
be compared with those of other stars in the Hertzsprung gap which are
presumably evolving in the other direction. This will be an important
test of the rotation-activity relation in G giants, and will show the
importance of evolutionary effects on stellar activity. The requested
IUE observations of the late B stars should be able to tell whether they
are in binaries with active latetype stars or T Tauri stars. Because
the post-T Tauri stars have only recently been discovered this will be
the first systematic investigation of these stars in the ultraviolet,
and should greatly increase our understanding of this poorly understood
phase of stellar evolution.

---------------------------------------------------------
Title: The structure, energy balance, and winds of cool stars
Authors: Linsky, J. L.
1982STIN...8234318L Altcode:
The phenomena associated with magnetic fields in the Sun are summarized
and it is shown that similar phenomena occur in cool stars. High
dispersion spectra are providing unique information concerning
densities, atmospheric extension, and emission line widths. A recent
unanticipated discovery is that the transition lines are redshifted
(an antiwind) in beta Dra (G2 Ib) and perhaps other stars. This is
interpreted as indicating downflows in closed magnetic flux tubes as
are seen in the solar flux tubes above sunspots. The G and K giants
and supergiants are classified as active stars, quiet stars, or hybrid
stars depending on whether their atmospheres are dominated by closed
magnetic flux tubes, open field geometries, or a predominately open
geometry with a few closed flux tubes embedded.

---------------------------------------------------------
Title: Expansion of the disturbing function by factorization
Authors: Linsky, J. L.
1982ASSL...94..337L Altcode: 1982hper.coll..337L; 1982IAUCo..63..337L
Each of the four functions X and Y in the expansion is represented as
a product of two factors rather than the three factors that appeared
in the study by Broucke (1981). Several relations are developed for
the construction of the X and Y series. It is noted that these series
are relatively short and can be computed in advance and stored on
magnetic tape.

---------------------------------------------------------
Title: Achievements in space astrophysics; Proceedings of the Topical
Meeting, Ottawa, Canada, May 16-June 2, 1982
Authors: Hudson, H. S.; Dupree, A. K.; Linsky, J.
1982AdSpR...2i....H Altcode: 1982AdSpR...2.....H
Progress in astrophysics resulting from IUE and Einstein Observatory
studies is reviewed. The topics considered include: the solar corona
as a testing found for plasma astrophysics; seismological studies
of the sun and other stars; magnetic reconnection; IUE and Einstein
observations of cool stars, high-luminosity X-ray binaries, supernovae,
cataclysmic variables, active galactic nuclei, globular clusters and
blue horizontal branch stars, supernova remnants, UV spectra of H
II regions and galaxies, and galactic clusters. Also discussed are:
highly variable X-ray emitting objects in the Rho Oph dark cloud; X-ray
diagnostics of globular clusters; stellar chromospheres and coronae of
solar and late-type dwarfs, active stars and systems, F-, G-, and K-type
stars, hot stars, and cool luminous stars; coronal heating mechanisms;
magnetic flux expulsion as an acceleration mechanism for stellar winds;
and energy balance of the outer atmospheres of solar like stars. For
individual items see A83-33582 to A83-33609

---------------------------------------------------------
Title: A Correlative Study of the Variability of XI BOO A
Authors: Linsky, Jeffrey L.
1982iue..prop.1136L Altcode:
Magnetic field measurements of the young G8 dwarf xi Boo A indicate that
there are at least three distinct states of the stellar magnetic field
(perhaps analogous to solar coronal holes, large scale structures,
and active regions), and that the magnetic field configuration varies
rapidly. The ultraviolet line fluxes and coronal soft X-ray flux are
similarly variable. We propose to continue our investigation of the
role of the magnetic field in heating the outer atmospheric layers
of this star by correlating the variability of the two. Observations
during the past year clearly show variability on timescales shorter
than the 10^d.15 stellar rotation period. We propose simultaneous IUE,
spectrophotometric, and magnetic observations spanning a complete
stellar rotation period, on two occasions separated by six stellar
rotations (two months), to search for correlated variability in the
structure of the outer atmosphere and the stellar magnetic field
configuration.

---------------------------------------------------------
Title: High Dispersion SWP Spectra of Two DME Stars
Authors: Linsky, Jeffrey L.
1982iue..prop.1135L Altcode:
Low dispersion SWP spectra of AU Mic (dM2.5e) and AT Mic (dM4.5e+dM4.5e)
indicate that these two M dwarfs likely have the brightest emission
lines in the ultraviolet, and that it is feasible to obtain line
profiles for lines of C II, Si IV, C IV, He II, and Si II in 8 hour
SWP high dispersion spectra. We propose to extend our previous studies
of dMe stars and high resolution studies of some 15 late-type dwarfs
and luminous stars to include AU Mic and AT Mic. Our objectives are
(1) to obtain widths of chromospheric and transition region lines for
comparison with our previous observations of 5 GO-K2 dwarfs, and to
determine the increase in turbulence with height in the atmosphere
so as to constrain models of atmospheric heating, (2) to determine
which lines are optically thick for comparison with computed model
atmospheres, (3) to determine the flux and formation mechanism of the
blended He II 1640 multiplet so as to derive the coronal soft X-ray
radiation field, and (4) to compute models for the chromospheres and
transition regions of these stars. In computing these models we will
use fluxes and profiles (when available) for lines of Mg II, C II-IV,
Si II-IV, and N V using computer codes that have already been written.

---------------------------------------------------------
Title: Chromospheric Densities and Geometrical Extensions of
Late-Type Giants
Authors: Linsky, Jeffrey L.
1982iue..prop.1132L Altcode:
Our previous deep high-resolution LWR exposures have shown that the C
II intercombination multiplet UV 0.01 near 2325 A is present in the
chromospheric spectra of latetype giants and supergiants. We have
demonstrated that line ratios within this multiplet are sensitive
to electron density in the regime Ne= 10^7-10^9cm^-3, characteristic
of these chromospheres. Furthermore, the temperature of the gas can
be obtained from the intensity ratio of C II 2325 A to C II 1335
A; measurements of the latter line have already been obtained from
low-resolution SWP exposures. When these temperatures and densities are
combined with the total flux in the 2325 A multiplet, the geometrical
extent of the chromosphere can be calculated. Preliminary results
indicate that chromospheres of red giants and supergiants extend
several stellar raidii. Additional deep LWR exposures to record the C
II UV 0.01 multiplet are needed to complete coverage of the appropriate
part of the HR diagram. Measurements of C II line ratios over a wide
range of Ne are needed to calibrate the density diagnostic and to
place constraints on the A-values of the transitions. The available
archival data do not fill these gaps since unusually long exposures are
required. The same deep exposures can be used for several additional
purposes. The multiplet UV 0.01 of Si II (2330-2350 A), which appears
to have potential as a density diagnostic for a slightly higher
density regime than the C II multiplet, will also be well exposed on
these images and will be measured to test this idea. In addition, the
photospheric absorptionline spectra of these stars will be properly
exposed in the 2600-2900 A region and will be compared to the spectrum
of Arcturus which has already been studied in detail. Analysis of the C
II and Si II data will provide badly needed information and constraints
for the main objective of this study: the modeling of the structure
and energy requirements of the outer atmospheres of late-type stars.

---------------------------------------------------------
Title: IUE Spectra of Active Stars in Binary Systems.
Authors: Butler, C. J.; Andrews, A. D.; Byrne, P. B.; Doyle, J. G.;
Linsky, J. L.; Marstad, N.; Simon, T.; Rodono, M.; Blanco, C.;
Catalano, S.; Pazzani, E.; Marilli, V.
1982uxsa.coll...14B Altcode: 1982IAUCo..73...14B
No abstract at ADS

---------------------------------------------------------
Title: Book-Review - Astrophysical Formulae - ED.2
Authors: Lang, K. R.; Linsky, J. L.
1982ApL....22...70L Altcode:
No abstract at ADS

---------------------------------------------------------
Title: The structure and energy balance of cool star atmosphere.
Authors: Linsky, J. L.
1982NASCP2238...17L Altcode: 1982IUE82.......17L; 1982NASCP2338...17L; 1982auva.nasa...17L
The atmospheric structure and energy balance phenomena associated
with magnetic fields in the Sun are reviewed and it is shown that
similar phenomena occur in cool stars. The evidence for the weakening
or disappearance of transition regions and coronae is discussed together
with the appearance of extended cool chromospheres with large mass loss,
near V-R = 0.80 in the H-R diagram. Like the solar atmosphere, these
atmospheres are not homogeneous and there is considerable evidence
for plage regions with bright TR emission lines that overlie dark
(presumably magnetic) star spots. The IUE observations are providing
important information on the energy balance in these atmospheres that
should guide theoretical calculations of the nonradiative heating
rate. Recent high dispersion spectra are providing unique information
concerning which components of close binary systems are the dominant
contributors to the observed emission. A recent unanticipated discovery
is that the transition lines are redshifted (an antiwind) in DRa (G2 Ib)
and perhaps other stars. Finally, the G and K giants and supergiants
are classified into three groups depending on whether their atmospheres
are dominated by closed magnetic flux tubes, open field geometries,
or a predominately open geometry with a few closed flux tubes embedded.

---------------------------------------------------------
Title: High dispersion far ultraviolet spectra of cool stars.
Authors: Stencel, R. E.; Linsky, J. L.; Ayres, T. R.; Jordan, C.;
Brown, A.; Engvold, O.
1982NASCP2238..259S Altcode: 1982auva.nasa..259S; 1982IUE82......259S; 1982NASCP2338..259S
Recent far ultraviolet high dispersion spectra of two cool supergiant
stars, Beta Dra (G2 Ib) and Alpha Ori (M2 Iab) are examined in the
context of current questions regarding stellar chromospheres, coronae
and mass loss. These stars show very different outer atmosphere
structure. Beta Dra has a geometrically thin transition region with
bright emission lines of 100,000 K plasma that are red-shifted,
indicating downflow in magnetic flux tubes. By contrast, Alpha Ori
has a cool extended chromosphere and circumstellar envelope with large
mass loss.

---------------------------------------------------------
Title: High Dispersion SWP Spectra of Yellow and Red Giants
Authors: Linsky, Jeffrey L.
1982iue..prop.1133L Altcode:
We propose to continue our program, in collaboration with 0. Engvold
and C. Jordan, to obtain 15 hour SWP high dispersion spectra of the
few late-type giants and supergiants observable by IUE. On the basis
of low dispersion SWP spectra, Linsky and Haisch (1979) and Simon et
al. (1981) have proposed a boundary in the HR diagram separating stars
with and without detected emission from 10^5 K plasma. We propose
detailed studies of 4 stars -- 2 on either side of the boundary. Our
scientific objectives are to derive the distributions of temperature and
density for the chromospheres and transition regions (if present). We
plan to do this by constructing model chromospheres and transition
regions using lines of Mg II, Si II, C II, Si III, C III, C IV, and
N V, by an emission measure analysis, and using density-sensitive
line ratios. These models will be used to assess the energy balance
in order to learn about the outer atmosphere heating mechanisms and
wind acceleration mechanisms.

---------------------------------------------------------
Title: On the correlation between chromospheric and coronal emission.
Authors: Hammer, R.; Linsky, J. L.; Endler, F.
1982NASCP2238..268H Altcode: 1982NASCP2338..268H; 1982auva.nasa..268H
It is shown that with increasing stellar activity the emission of the
transition region and corona increases faster than the emission of the
chromosphere. It is also explained why the pressure of the transition
region increases with increasing stellar activity. Further, it is
shown that this relation is a necessary requirement for the global
stability of the chromosphere/transition region/corona system.

---------------------------------------------------------
Title: Ultraviolet observations of yellow giant stars.
Authors: Simon, T.; Linsky, J. L.
1982NASCP2238..273S Altcode: 1982IUE82......273S; 1982auva.nasa..273S; 1982NASCP2338..273S
Low-dispersion spectra of 18 yellow giant stars of spectral types
G4-KO were obtained with the short wavelength camera of IUE. Using the
emission strength of the C IV 1550 A multiplet as a measure of high
temperature 100,000K plasma, we find that the normalized C IV flux is
typically 10 to the minus 7th power or smaller, indicating very feeble
stellar transition regions. By combining these results with earlier data
from IUE, it is shown that there is nearly a two orders of magnitude
spread in carbon IV bolometric flux among the yellow giants. Several
likely reasons for the observed range in high-temperature emission
line strengths are discussed; the more likely appears to be that the
majority of the yellow giant stars observed are slow rotators evolving
across the Hertzsprung Gap for the second time along a blue loop.

---------------------------------------------------------
Title: High Dispersion SWP Observations of Two Late-Type Binaries
Authors: Linsky, Jeffrey L.
1982iue..prop.1131L Altcode:
High dispersion far UV exposures of 15-18 hours duration are proposed
for the analysis of two late type binaries: Alpha Her (M5 II + G5 III)
and Zeta Cap (G5 II Ba-2 + wd). Analysis of the far UV emission line
fluxes and profiles will enable us to derive properties of the cool star
outer atmospheres. The properties of the circumstellar material will
be inferred from the blue-shifted resonance lines seen in absorption
against the continuum of the hot secondary star. Alpha Her is an
excellent candidate for studying mass loss and interaction between a
strong stellar wind from the M5 II star and the G5 III star corona;
while Zeta Cap, the prototype Ba II star, is an excellent system for
the analysis of the interaction between a cool giant enriched with
sprocess material and its white dwarf companion.

---------------------------------------------------------
Title: Outer atmospheres of cool stars. VIII. IUE observations
and chromospheric models for the supergiant stars beta Draconis,
epsilon Geminorum and alpha Orionis.
Authors: Basri, G. S.; Linsky, J. L.; Eriksson, K.
1981ApJ...251..162B Altcode:
A semiempirical modeling of stellar chromospheres is extended to
late-type supergiants, where computations match high-resolution,
absolute-flux profiles of the Ca II K and Mg II h and k lines. IUE
UV spectra of Epsilon Gem and Alpha Ori show no evidence of emission
lines formed at temperatures greater than 10,000 K, leading to the
computation of chromospheric models extending to 10 to the -6th g/sq cm
at temperatures that rise to 6500 K for the former star and 7000 K for
the latter. By contrast, the C II-IV, Si IV, and He II and N V strong
emission lines of Beta Dra lead to a tentative chromospheric model
extension to 16,000 K at 0.012 dynes/sq cm. It is pointed out that
the Ca II and Mg II line analyses presented, which assume hydrostatic
equilibrium with only thermal and turbulent components to the pressure,
imply nearly plane-parallel chromospheres even in the case of Alpha Ori.

---------------------------------------------------------
Title: Coronae of nondegenerate single and binary stars: A survey
of our present understanding and problems ripe for solution
Authors: Linsky, J. L.
1981xras.nasa...13L Altcode:
Information about the coronae of stars in different portions of the HR
diagram, and how the characteristics of such coronae compare with what
is known about the solar corona are reviewed. For each type of star,
some unanswered questions and the generic type of X-ray instrument
required to answer these questions are listed. The survey points out
the critical need for a sensitive X-ray instrument with both moderate
spectra resolution and imaging capability that can monitor selected
targets for long periods of time. There is also a need for high
spectral resolution, provided sensitivities can be improved greatly
over Einstein, and near simultaneous ultraviolet spectroscopy.

---------------------------------------------------------
Title: The cool Half of the H-R diagram in soft X-rays.
Authors: Ayres, T. R.; Linsky, J. L.; Vaiana, G. S.; Golub, L.;
Rosner, R.
1981ApJ...250..293A Altcode:
The results of an Einstein Observatory program to map the occurrence
of hot coronae (T greater than 1 million K) in the cool half of the
Hertzsprung-Russell diagram are reported. F-M dwarfs, and late F
through early K star giants characterized by 10,000 K chromospheric
and 20,000-200,000 K FUV emission lines were studied in one region,
while a second region study included red giants later than K2 III and
supergiants later than G5 Ib with weaker chromospheric emission and
no high temperature species. Program goals comprised determination of
the C IV division as seen in soft X-rays, and identification of stellar
parameters which distinguish strong from weak coronal X-ray sources. A
summary of target stars, X-ray fluxes, and UV emission profiles
is provided, and coronal emissions, comparisons of C IV and wind
boundaries, hybrid-spectrum supergiants, the energy balance of stellar
outer atmospheres, stellar rotation and coronae, and evolutionary
considerations are discussed, along with lines of future research.

---------------------------------------------------------
Title: First detection of nonflare microwave emission from the
coronae of single late-type dwarf stars.
Authors: Gary, D. E.; Linsky, J. L.
1981ApJ...250..284G Altcode:
Results are presented of a search for nonflare microwave radiation
from the coronae of nearby late-type dwarf stars comparable to the sun:
single stars without evidence for either a large wind or circumstellar
envelope. The observing program consisted of flux measurements of
six stars over a 24-h period with the VLA in the C configuration
at a wavelength of 6 cm with 50 MHz bandwidth. Positive detections
at 6 cm were made for Chi 1 Ori (0.6 mJy) and the flare star UV Cet
(1.55 mJy), and upper limits were obtained for the stars Pi 1 UMa,
Xi Boo A, 70 Oph A and Epsilon Eri. It is suggested that Chi 1 Ori,
and possibly UV Cet, represent the first detected members of a new
class of radio sources which are driven by gyroresonance emission,
i.e. cyclotron emission from nonrelativistic Maxwellian electrons.

---------------------------------------------------------
Title: Theory of stellar coronae - an interpretation of X-ray emission
from non-degenerate stellar sources
Authors: Linsky, J. L.
1981ASSL...87...19L Altcode: 1981xaes.proc...19L
It is shown that the acoustic wave heating theory of stellar coronae
explains neither Einstein Observatory coronae data nor previous UV and
X-ray observations of the sun and other stars, on the evidence of data
implying that magnetic fields, stellar rotation rates and convection
zone parameters figure in the determination of coronal heating. Einstein
Observatory results suggest that O-type star coronae are heated by the
interaction of turbulent stellar winds with slowly-decaying primordial
magnetic fields or by radiative instabilities in the flow. The
apparent absence of coronae in Ap stars is due to the stability of
atmospheres in which even weak convection is suppressed by the strong
field. Dynamo action is implicated in some normal A-type stars and in
F- and later-type dwarfs. Coronal characteristics of dMe and dM stars,
close binaries, and K- and M-type giants are also considered.

---------------------------------------------------------
Title: Far-ultraviolet fluorenscence of carbon monoxide in the red
giant Arcturus.
Authors: Ayres, T. R.; Moos, H. W.; Linsky, J. L.
1981ApJ...248L.137A Altcode:
Evidence is presented that many of the weak features observed with
International Ultraviolet Explorer (IUE) in the far-ultraviolet
(1150-2000 A) spectrum of the archetype red giant Arcturus (K2 III) are
A-X fourth positive bands of carbon monoxide excited by chromospheric
emissions of O I, C I, and H I. The appearance of fluorescent CO bands
near the wavelength of commonly used indicators of high-temperature
(T greater than 20,000 K) plasma, such as C II at wavelength 1335 and
C IV at wavelength 1548, introduces a serious ambiguity in diagnosing
the presence of hot material in the outer atmospheres of the cool
giants by means of low-dispersion IUE spectra.

---------------------------------------------------------
Title: Relations among stellar X-ray emission observed from Einstein,
stellar rotation and bolometric luminosity.
Authors: Pallavicini, R.; Golub, L.; Rosner, R.; Vaiana, G. S.; Ayres,
T.; Linsky, J. L.
1981ApJ...248..279P Altcode:
The correlation between observed stellar X-ray luminosities, bolometric
luminosities, and projected rotational velocities for stars of various
spectral types and luminosity classes are determined. Early type
stars (O3 to A5) have X-ray luminosities independent of rotational
velocities, and correlating with bolometric luminosities. Late type
stars of spectral type G to M have luminosities well correlated to
equatorial rotational velocities, and are independent of luminosity
class. The dependence of late type stars is found to be equivalent
to a relation between the X-ray surface flux and the stellar angular
velocity. F stars are intermediate with X-ray luminosities higher
than would be predicted on the basis of the early type star relation,
although lower than expected from the late type velocity dependence. The
location of RS CVn stars as a class is also discussed, and it is found
that the heating of late type stellar coronas does not result from
direct conversion of ratational energy.

---------------------------------------------------------
Title: Density sensitive C II lines in cool stars of low gravity.
Authors: Stencel, R. E.; Linsky, J. L.; Brown, A.; Jordan, C.;
Carpenter, K. G.; Wing, R. F.; Czyzak, S.
1981MNRAS.196P..47S Altcode:
It is shown that the relative intensities of emission lines within the
multiplet UV 0.01 of C II, around 2325 A, are sensitive to electron
density in the range 10 to the 9th to 10 to the 7th per cu cm. The lines
therefore offer a valuable method for measuring electron densities in
the chromospheres of late-type giants and supergiants. Calculated line
ratios are compared with those observed in a range of objects.

---------------------------------------------------------
Title: Outer atmospheres of cool stars. IX. A survey of ultraviolet
emission from F-K dwarfs and giants with the IUE.
Authors: Ayres, T. R.; Marstad, N. C.; Linsky, J. L.
1981ApJ...247..545A Altcode:
Low-dispersion ultraviolet spectra (1150-2000 A) of a representative
sample of cool stars, including dwarfs and giants of spectral types
F-K, obtained with the IUE, are examined. The observation and the
absolute calibration procedures are described. Correlation diagrams
are constructed that compare chromospheric and transition-region
emission line strengths and broadband coronal soft X-ray fluxes. The
transition-region and coronal emission in the G-K dwarfs and G
giants is well correlated with the Mg II (wavelength 2800) doublet
emission strength, which is symptomatic of chromospheric energy
losses. The power-law slopes are steeper than unity, particularly for
soft X-rays. The implications of the correlations are discussed with
respect to the weakening or disappearance of transition regions and
hot coronae in the cool half of the red-giant branch and possible
chromospheric and coronal heating mechanisms. It is proposed that
the weakness of outer atmospheres in the red giants compared with the
yellow giants can be understood as a consequence of stellar evolution,
since it is possible that stars of slightly different spectral type
in the giant branch have very different main-sequence progenitors.

---------------------------------------------------------
Title: Simultaneous X-ray, ultraviolet, optical, and radio
observations of the flare star Proxima Centauri
Authors: Haisch, B. M.; Slee, O. B.; Siegman, B. C.; Nikoloff, I.;
Candy, M.; Harwood, D.; Verveer, A.; Quinn, P. J.; Wilson, I.; Linsky,
J. L.
1981ApJ...245.1009H Altcode:
Results of coordinated program of observations in the X-ray, UV,
optical and radio regions of the dM5e flare star Proxima Centauri
are presented. Simultaneous observations of the star were obtained
on March 6 and March 7, 1979, by the Einstein Observatory IPC, the
IUE SWP and LWR cameras at low dispersion, three ground-based optical
telescopes in Australia and the Parkes 64-m radio telescope. A total
of 10 radio bursts and six optical flares was detected during three
nights of simultaneous radio and optical observations, which appear
to be broadly correlated. A major X-ray flare event was detected with
temperatures of 1.7 x 10 to the 7th and 1.2 x 10 to the 7th K during
the rise and decay phases, respectively, respective X-ray fluxes of
3.0 x 10 to the -11th and 3.7 x 10 to the -11th ergs/sq cm per sec,
and changes in spectral flux distribution. No radio, optical or UV flare
emission corresponding to the X-ray flare was detected. The X-ray flare
is interpreted in terms of an arch model with cooling predominantly by
X-ray radiation, with an electron density of 1.0 x 10 to the 11th/cu
cm during the decay phase and a total arch length comparable to the
size of the star itself. The X-ray flare observed is thus more similar
to a typical strong solar flare than heretofore seen on a flare star.

---------------------------------------------------------
Title: Results from an extensive Einstein stellar survey.
Authors: Vaiana, G. S.; Cassinelli, J. P.; Fabbiano, G.; Giacconi,
R.; Golub, L.; Gorenstein, P.; Haisch, B. M.; Harnden, F. R., Jr.;
Johnson, H. M.; Linsky, J. L.; Maxson, C. W.; Mewe, R.; Rosner, R.;
Seward, F.; Topka, K.; Zwaan, C.
1981ApJ...245..163V Altcode:
The preliminary results of the Einstein Observatory stellar X-ray survey
are presented. To date, 143 soft X-ray sources have been identified with
stellar counterparts, leaving no doubt that stars in general constitute
a pervasive class of low-luminosity galactic X-ray sources. Stars along
the entire main sequence, of all luminosity classes, pre-main sequence
stars as well as very evolved stars have been detected. Early type
OB stars have X-ray luminosities in the range 10 to the 31st to 10 to
the 34th ergs/s; late type stars show a somewhat lower range of X-ray
emission levels, from 10 to the 26th to 10 to the 31st ergs/s. Late type
main-sequence stars show little dependence of X-ray emission levels upon
stellar effective temperature; similarly, the observations suggest weak,
if any, dependence of X-ray luminosity upon effective gravity. Instead,
the data show a broad range of emission levels (about three orders of
magnitude) throughout the main sequence later than F0.

---------------------------------------------------------
Title: BH Canum Venaticorum (HR 5110 = HD 118216)
Authors: Feldman, P. A.; MacLeod, J. M.; Linsky, J. L.; Weiler, E.
1981IAUC.3591....2F Altcode:
P. A. Feldman, Herzberg Institute of Astrophysics, Ottawa, reports
the detection of a large radio outburst from the RS CVn-type binary
HR 5110 = HD 118216 with the 46-m telescope of the Algonquin Radio
Observatory. The flare was first detected on Apr. 4.36 UT with a flux
density of 250 mJy at 10.46 GHZ. The radio flare reached a plateau
of ~ 400 mJy at 10.46 GHZ (1.3 x 10**11 J s**-1 Hz**-1) during
Apr. 5.33-5.56, overlapping a three-station Mark III VLBI-network
observation at 5 GHz during Apr. 5.50-5.62. During Apr. 5.96-6.56 the
flux density remained relatively constant at ~ 200 mJy, overlapping
a four-station VLBI observation during Apr. 6.00-6.17 and the IUE
observations described below. Several subsequent measurements by
J. M. MacLeod at 10.46 GHZ indicate that the flaring has continued
at the 160-mJy level until at least Apr. 7.50. J. L. Linsky, Joint
institute for Laboratory Astrophysics, telexes: "E. Weiler obtained IUE
spectra of HR 5110 during Apr. 6.42-6.75 UT. A 6-hr high-dispersion
exposure with the short-wavelength camera showed exceptionally broad
profiles of L-alpha 122 nm, C II 133.4-133.5 nm, C IV 154.8-155.0
nm and He II 164 nm. The bright emission lines of L-alpha, C IV and
He II are asymmetric, with broad emission wings extending to longer
wavelengths. These profiles indicate large line-of-sight motions in the
system and probably hot plasma falling on to one or both stars. Similar
infalling material was indicated by asymmetric Mg II lines during a
flare on UX Ari (Simon et al. 1980, Ap.J. 239, 911)."

---------------------------------------------------------
Title: High-resolution spectra of five late-type dwarfs and giants
obtained with the IUE satellite.
Authors: Ayres, T. R.; Basri, G. S.; Henry, R. C.; Landsman, W.;
Linsky, J. L.; Moos, H. W.; Stencel, R. E.
1981BAAS...13..546A Altcode:
No abstract at ADS

---------------------------------------------------------
Title: The unusual outer atmosphere of 56 Pegasi (K0 IIp).
Authors: Schindler, M.; Stencel, R. E.; Linsky, J. L.; Helfand, D. J.;
Basri, G.
1981BAAS...13..547S Altcode:
No abstract at ADS

---------------------------------------------------------
Title: Detection of Magnetic Fields in Late-Type Stars with the KPNO
McMath Telescope and MAMA Detector System
Authors: Timothy, J. G.; Joseph, C. L.; Linsky, J. L.
1981BAAS...13..828T Altcode:
No abstract at ADS

---------------------------------------------------------
Title: A Boundary in the H-R Diagram between Late-Type Stars with
and without High Temperature Outer Atmospheres
Authors: Simon, T.; Linsky, J. L.; Stencel, R. E.
1981BAAS...13..885S Altcode:
No abstract at ADS

---------------------------------------------------------
Title: A model of the outer atmosphere of beta Ceti.
Authors: Eriksson, K.; Simon, T.; Linsky, J. L.
1981BAAS...13..547E Altcode:
No abstract at ADS

---------------------------------------------------------
Title: Thermal Bifurcation in Solar Calcium Plages
Authors: Ayres, T. R.; Linsky, J. L.; Testerman, L.; Brault, J.
1981BAAS...13..915A Altcode:
No abstract at ADS

---------------------------------------------------------
Title: Results of an IUE Program of Monitoring the Ultraviolet
Emission Line Fluxes of Four Binary Systems
Authors: Linsky, J. L.; Simon, T.; Marstad, N.; Rodono, M.; Blanco, C.;
Catalano, S.; Marilli, E.; Andrews, A. D.; Butler, C. J.; Byrne, P. B.
1981BAAS...13R.872L Altcode:
No abstract at ADS

---------------------------------------------------------
Title: Far-Ultraviolet Fluorescence of Carbon Monoxide in the Red
Giant Arcturus
Authors: Ayres, T. R.; Moos, H. W.; Linsky, J. L.
1981BAAS...13..515A Altcode:
No abstract at ADS

---------------------------------------------------------
Title: High-Resolution Studies of Arcturus with IUE &amp;Einstein:
A Sensitive Search for High-Temperature Emission
Authors: Ayres, T. R.; Simon, T.; Linsky, J. L.
1981BAAS...13..811A Altcode:
No abstract at ADS

---------------------------------------------------------
Title: IUE Echelle Mode Observations Contrasting Coronal and
Non-Coronal Late Type Giant and Supergiant Stars
Authors: Brown, A.; Stencel, R. E.; Linsky, J. L.; Jordan, C.;
Engvold, O.
1981BAAS...13..885B Altcode:
No abstract at ADS

---------------------------------------------------------
Title: Stellar Chromosphere, Coronae and Winds: Present Status and
Implications for Solar Astrophysics
Authors: Linsky, J.
1981siwn.conf..180L Altcode:
No abstract at ADS

---------------------------------------------------------
Title: The Corona and Chromosphere of Proxima Centauri during Flare
and Quiescent Times
Authors: Haisch, B. M.; Linsky, J. L.; Slee, O. B.
1981BAAS...13..515H Altcode:
No abstract at ADS

---------------------------------------------------------
Title: The Unusual Outer Atmosphere of 56 Pegasi (KO IIp)
Authors: Schindler, M.; Stencel, R.; Linsky, J.; Helfand, D.; Basri, G.
1981BAAS...13Q.545S Altcode:
No abstract at ADS

---------------------------------------------------------
Title: High-Resolution Spectra of Five Late-Type Dwarfs and Giants
Obtained with the IUE Satellite
Authors: Ayres, T. R.; Basri, G. S.; Henry, R. C.; Landsman, W.;
Linsky, J. L.; Moos, H. W.; Stencel, R. E.
1981BAAS...13R.545A Altcode:
No abstract at ADS

---------------------------------------------------------
Title: Evidence for chromospheres and coronae in stars: recent
observations, some unanswered theoretical questions, and a speculative
scenario.
Authors: Linsky, J. L.
1981ASIC...68...99L Altcode: 1981spss.conf...99L
The paper discusses recent UV and X-ray evidence for the existence
of solar-type chromospheres, transition regions and coronae in
stars other than the sun. The stellar spectral types associated with
emission lines indicative of chromospheres and transition regions and
X-ray fluxes indicative of coronae are examined, and the possibility
of chromospheres and transition regions existing in stars hotter or
cooler than the late-type stars is considered. The stellar parameters
determining the properties of stellar chromospheres, transition regions
and coronae are discussed, including varying magnetic fields, stellar
rotation and convection zone parameters. A speculative scenario for
the source of chromospheres, transition regions and coronae in O,
B and A stars, late-type dwarfs, and G-M giants and supergiants is
then presented which is based on the predominant role of magnetic
fields in the nonradiative heating of outer atmospheres.

---------------------------------------------------------
Title: Book-Review - Stellar Turbulence - I.A.U. Colloquium 51 -
London Ontario, Canada - 1979AUG27-30
Authors: Gray, D. F.; Linsky, J. L.; Hubeny, I.
1981BAICz..32..255G Altcode:
No abstract at ADS

---------------------------------------------------------
Title: Target of Opportunity Observations of Flares on RS CVN-Type
Binary Systems
Authors: Linsky, Jeffrey L.
1981iue..prop..791L Altcode:
RS CVn-type binaries are close but noncontact systems, which exhibit
strong ultraviolet and X-ray emission and which produce extremely
energetic flares lasting, for 1-1.0 days. These flares may result from
magnetic anihilation, which may occur when large magnetic flux tubes
from both stars interact, producing a temporary flux tube connection
between the stars and large mass exchange. Our IUE observations of the
large flare on UX Ari (1/1/79) show Mg II lines with broad emission
wings extending 475 km s^-1 to the red, indicative of a large mass flow
towards the G5 star in this system. We propose to observe two major
flare episodes in these systems as target of opportunity observations
initiated by the detection of radio flares by P. A. Feldman during his
manitoring operations. High dispersion SWP spectra are feasible and
needed for the brighter flares in order to detect the flow velocity and
physical properties (temperature and density) of the 10^4-2.5 x 10^5
K plasma. Observations at different aspect angles during the flares
should determine the geometry of the flaring plasma and the extent of
mass exchange between the stars and mass loss from the system.

---------------------------------------------------------
Title: The Mg II h and k lines in a sample of dMe and dM stars.
Authors: Giampapa, M. S.; Pornmann, P. L.; Ayres, T. R.; Linsky,
J. L.; Worden, S. P.
1981NASCP2171..279G Altcode: 1981uviu.nasa..279G; 1981NASCP3171..279G; 1980IUE80......279G
Both Mg II h and k line fluxes are presented for a sample of 4 dMe and
3 dM stars obtained with the IUE satellite in the long wavelength,
low dispersion mode. The observed fluxes are converted to stellar
surface flux units and the importance of chromospheric non radiative
heating in this sample of M dwarf stars is intercompared. In addition,
the net chromospheric radiative losses due to the Ca II H and K lines in
those stars in the sample for which calibrated Ca II H and K line data
exist are compared. Active region filling factors which likely give
rise to the observed optical and ultraviolet chromospheric emission
are estimated. The implications of the results for homogeneous, single
component stellar model chromospheres analyses are discussed.

---------------------------------------------------------
Title: Book-Review - Stellar Turbulence - I.A.U. Coll. - Ontario,
Canada - 1979AUG27-30
Authors: Gray, D. F.; Linsky, J. L.; Gussmann, E. A.
1981AN....302..208G Altcode:
No abstract at ADS

---------------------------------------------------------
Title: Winds in late-type stars - Mechanisms of mass outflow
Authors: Linsky, J. L.
1981ASSL...89..187L Altcode: 1981emls.proc..187L; 1981IAUCo..59..187L
The four basic mechanisms that have been proposed for explaining
the acceleration of winds in late-type stars are thermal pressure
gradients, radiation pressure on circumstellar dust grains, momentum
addition by Alfven waves, and momentum addition by periodic shock
waves. Recent work in applying these mechanisms to stars is reviewed,
with consideration given to whether these mechanisms can work, even
in principle, and whether they are consistent with recent ultraviolet
and X-ray data from the IUE and Einstein spacecraft. It is noted that
thermally driven winds are likely important for late-type dwarfs,
where the mass loss rates are small, and perhaps also in G giants and
supergiants, but they cannot operate alone in the K and M giants and
supergiants. It is thought that radiatively driven winds are probably
unimportant for all cool stars, even the M supergiants with dusty
circumstellar envelopes. In principle, Alfven waves can accelerate
winds to high speeds so long as the field lines are initially open or
forced open by some mechanism, but detailed calculations are needed. It
is noted that, for the Miras and semiregular variable supergiants,
periodic shock waves provide a simple way of producing rapid mass loss.

---------------------------------------------------------
Title: Studies of the Quiet and Plage Component of the Active Stars
in RS CVN Binary Systems
Authors: Linsky, Jeffrey L.
1981iue..prop..792L Altcode:
The present proposal is aimed at continuing the study of chromospheric
and transition region line intensity variations in RS CVn stars, started
with IUE in 1979, in order to disclose a possible periodic character out
of phase with respect to outside of eclipse sinusoidal distortion of the
light curve. If this prediction will prove to be true, by subtracting
the minimum from the maximum fluxes one can obtain separate spectra
of the plage region and of the quiet component. Then, by reasonably
estimating the plage filling factor, surface fluxes can be readily
obtained and compared with the solar-type models of chromospheric
active regions. We propose to compute models for the chromospheres
and transition regions of the plage and quiet components separately,
and to compare these models with models for plage and quiet regions
on the Sun and models previously computed for Capella, HR 1090, and
UX Ari. We will also model the spectra of any flare-like event observed.

---------------------------------------------------------
Title: Outer atmospheres of late-type stars
Authors: Linsky, J. L.
1981ASSL...88..247L Altcode: 1981pprg.work..247L
Recent observational results concerning chromospheres and coronae in
late-type stars are described. In particular, it is indicated where
in the cool half of the HR diagram chromospheres, transition regions,
coronae, and large mass loss occur and what the important parameters
determining the energy balance of these layers are. The chromospheric
modelling process is summarized and models of the late-type supergiants
Beta Dra, Epsilon Gem, and Alpha Ori recently computed by Basri and
Linsky (1980) are detailed.

---------------------------------------------------------
Title: High resolution flux profiles of the Mg II h &amp; k lines
in evolved F8 to M5 stars.
Authors: Stencel, R. E.; Mullan, D. J.; Basri, G. S.; Linsky, J. L.
1981NASCP2171..317S Altcode: 1980IUE80......317S; 1981uviu.nasa..317S; 1981NASCP3171..317S
The central results of a survey of the Mg II resonance line
emission in a sample of over 50 evolved late type stars, including
spectral-luminosity type F8 to M5 and La to IV are presented. Observed
and surface fluxes are derived and correlations noted. The major
findings include: (1) Mg II k emission core asymmetry transition near
K1 III, analogous to that known for Ca II K; (2) a small gravity and
temperature dependence of the Mg II chromospheric radiative loss rate.

---------------------------------------------------------
Title: Progress report on the high resolution spectrograph for the
Space Telescope
Authors: Brandt, J. C.; Boggess, A.; Heap, S. R.; Maran, S. P.; Smith,
A. M.; Beaver, E. A.; Hutchings, J. B.; Jura, M. A.; Linsky, J. L.;
Savage, B. D.
1981SPIE..279..183B Altcode:
The instrument design is complete and many components and subsystems
have been manufactured and tested. Solar-blind, multichannel, pulse
counting detectors for two ultraviolet spectral bands have been
developed and satisfactory flight units have been chosen. A large,
lightweight graphite-epoxy optical bench, utilizing fingerplate
joints with no metallic parts in order to minimize thermal expansion,
has been built. Tests of the engineering model torque-motor-driven
grating carrousel indicate that this critical system exceeds tight
specifications for accurate and repeatable angular positioning. A
complement of large, high-frequency gratings and an echelle is being
completed in several laboratories. Software resident in a computer on
the spacecraft will control the spectrograph with the capability to
alter procedures in response to real-time evaluation of the data.

---------------------------------------------------------
Title: Modelos de flares fotosféricos y cromosféricos
Authors: Machado, M. E.; Linsky, J. L.
1981BAAA...20..145M Altcode:
Presentamos modelos de fotósferas y cromosferas en flares solares de
diversas importancias, basadas principalmente en el análisis teórico
de las líneas del Ca II pero consistentes también con observaciones
en Hα y las líneas altas de la serie de Balmer. Los modelos están
basados en la solución de las ecuaciones de equilibrio estadístico
y transparente de radiación para un átomo de calcio de 5 niveles
y uno de hidrógeno de 3 niveles. Encontramos que incrementando las
importancia del flare, la altura de la alta cromósfera y región de
transición decrece en la atmósfera solar, produciendo con aumento
de presión 60 y 600 veces respecto del Sol quieto e incrementando
el gradiente de temperatura cromosférico. Estos cambios producen
emisión brillante en las líneas del Ca II e H I con perfiles de
acuerdo a las observaciones si se asume un campo de velocidades
macroturbulento. Encontramos que la parte superior de la fotósfera
en flares experimenta un aumento de temperatura entre 100 y 200 K y el
mínimo de temperatura ocurre más abajo en la atmósfera solar que en
regiones activas. Estos resultados sugieren u calentamiento fotosférico
significante, que no ha sido predicho por anteriores modelos.

---------------------------------------------------------
Title: Book Review - Stellar Turbulence IAU Colloquium no.
Authors: Gray, D. F.; Linsky, J. L.; de Jager, C.
1981SSRv...28..113G Altcode:
No abstract at ADS

---------------------------------------------------------
Title: IUE spectra of a flare in HR 5110: a flaring RS CVn or
Algol system?
Authors: Simon, T.; Linsky, J. L.; Schiffer, F. H., III
1981NASCP2171..435S Altcode: 1980IUE80......435S; 1981NASCP3171..435S; 1981uviu.nasa..435S
Ultraviolet spectra of the RS CVn type binary system HR 5110 were
obtained with IUE on May 31, 1979 during a period of intense radio
flaring of this star. High temperature transition region lines are
present, but are not enhanced above observed quiescent strengths. The
similarities of HR 5110 to the Algol system, As Eri, suggest that
the 1979 May to June flare may involve mass exchange rather than
annihilation of coronal magnetic fields.

---------------------------------------------------------
Title: IUE spectra of F and late A stars.
Authors: Linsky, J. L.; Marstad, N. C.
1981NASCP2171..287L Altcode: 1980IUE80......287L; 1981NASCP3171..287L; 1981uviu.nasa..287L
The International Ultraviolet Explorer (IUE) spectra of alpha CMi (F5
IV-V), beta Cas (F2 IV), alpha Car (F0 Ib), and gamma Boo (A7 III) in
the context of the question as to whether chromospheres disappear in the
early F late A portions of the Hertzsprung-Russell diagram. Both alpha
CMi (Procyon) and beta Cas show bright emission line spectra indicative
of chromospheres and transition regions, but neither alpha Car (Canopus)
nor gamma Boo show any evidence of emission in their SWP spectra or at
the Mg II lines, despite very deep exposures. Alpha CMi has emission
line fluxes roughly 6 times those of the quiet Sun, but the rapidly
rotating delta Scuti type variable beta Cas has surface fluxes 10 to
50 times those of the quiet Sun. Upper limits on emission line fluxes
for alpha Car are 4 to 20 and for gamma Boo 15 to 80 times the quiet
Sun. It is concluded that the apparent absence of emission lines in the
spectra of alpha Car and gamma Boo should not be interpreted as due to
the absence of nonradiatively heated outer atmospheres in stars hotter
than spectral type F0, but rather to the inability to see emission
lines with IUE against a background of scattered light and a bright
photospheric absorption line spectrum either in low or high dispersion.

---------------------------------------------------------
Title: Hr 5110
Authors: Linsky, Jeffrey
1981iue..prop..868L Altcode:
No abstract at ADS

---------------------------------------------------------
Title: Einstein X-ray observations of Proxima Centauri and the
surrounding region
Authors: Haisch, B. M.; Harnden, F. R., Jr.; Seward, F. D.; Vaiana,
G. S.; Linsky, J. L.; Rosner, R.
1980ApJ...242L..99H Altcode:
The first detection of both quiescent and flaring soft X-ray emission
from a dMe flare star, Proxima Centauri (dM5e) is reported. The data
are analyzed for temporal variability and spectral characteristics. The
quiescent state is characterized by a mean X-ray luminosity of 1.5 x 10
to the 27th erg s/s, corresponding to a mean surface flux of 700,000
erg s/sq cm-s, and an inferred temperature of 4-million K. The flare
that is detected has a peak flux of 7.4 x 10 to the 27th erg s/s and
a peak temperature of 17-million K. The implications of these data for
models of the quiescent and flare coronae of dMe stars are discussed.

---------------------------------------------------------
Title: The outher atmospheres of cool stars. VII. High resolution,
absolute flux profiles of the MG II H and K lines in stars of spectral
types F8 to M5.
Authors: Stencel, R. E.; Mullan, D. J.; Linsky, J. L.; Basri, G. S.;
Worden, S. P.
1980ApJS...44..383S Altcode:
We present high-resolution lUE spectra of the emission cores of the
Mg II resonance doublet at 280 nm in a selection of 54 stars covering
a range of spectral type from F8 to MS and of luminosity class from
supergiant (Ia) to subgiant (IV). These spectra were obtained with the
LWR echelle system onboard the IUE satellite, and have been calibrated
in absolute flux units using OAO 2 photometry of Eta UMa as a standard,
plus the Barnes and Evans relations for stellar angular diameters. The
uncertainty in flux is probably of order 20%. We discuss the qualitative
line profile groupings, as determined by Basri and Linsky, and derive
chromospheric radiative losses in the h and k lines; we discuss
these loss rates as functions of effective temperature and luminosity
class. We make further comparisons of these rates with rates derived
for the Ca II H and K lines by Linsky and his colleagues. Chromospheric
velocity fields and indicators of circumstellar envelopes are discussed
in terms of profile asymmetries and other diagnostics. Line width
measures and velocity shifts of the central reversals are tabulated,
among other quantities, and several correlations noted. Finally, we
discuss the relation of the Wilson K index and stellar coronae to Mg
II emission, and note the occurrence of Fe II emission lines in the
middle range of the UV of late-type stars.

---------------------------------------------------------
Title: Book-Review - Stellar Turbulence / Colloquium / London,
Ontario, Canada
Authors: Gray, D. F.; Linsky, J. L.
1980Sci...210..635G Altcode:
No abstract at ADS

---------------------------------------------------------
Title: Outer atmospheres of cool stars. V. IUE observations of
Capella: the rotation-activity connection.
Authors: Ayres, T. R.; Linsky, J. L.
1980ApJ...241..279A Altcode:
UV spectra of Capella (G6 III + F9 III) obtained with the IUE are
analyzed. High-resolution emission-line profiles taken near the
elongation at phase 78 days suggest that virtually all of the emission
in transition-region lines and most of the emission in chromospheric
lines comes from the late-F secondary of the system. It is suggested
that the origin of the extraordinary activity levels on these otherwise
very similar stars can be traced to the one property that is obviously
different, i.e., rotation. The Capella primary is a normal sharp-line
slow rotating giant, whereas the secondary has broader lines and is
a rapid rotator for a late-type giant.

---------------------------------------------------------
Title: IUE ultraviolet spectra and chromospheric models of HR 1099
and UX Ari.
Authors: Simon, T.; Linsky, J. L.
1980ApJ...241..759S Altcode:
IUE spectra in the region 1150-3200 A of the RS CVn-type variables HR
1099 and UX Arietis are presented and analyzed in terms of chromospheric
models. Measurements of Mg h and k lines and Ca II H-K and H alpha
spectra are indicated which are found not to be correlated with orbital
phase or radio flares and which suggest that the strong emission
arises in the K star rather than the G star in these systems. Under the
assumption that the UV emission lines are associated with the K star,
surface gravities of log g = 3.6 and 3.4 and effective temperatures
of 4850 and 5000 K are adopted for HR 1099 and UX Ari, respectively,
along with solar metal abundances for each. Model calculations of the
chromospheric structure necessary to account for observed C(+), Mg(+),
Si(+) and Si(+2) line fluxes are presented which indicate that the
transition region pressure lies in the range 0.18-1.0 dynes/sq cm,
implying transition regions that are more extended than that of the
sun and are not conductively heated. It is noted that pressure scaling
laws and the use of Mg II and C II lines as pressure diagnostics may
be invalid, possibly due to atmospheric inhomogeneities or gas flows.

---------------------------------------------------------
Title: First Detection of Steady 6 cm Emission from Coronae of Single
Dwarf Stars of Spectral Type G-M
Authors: Gary, D.; Linsky, J. L.
1980BAAS...12..898G Altcode:
No abstract at ADS

---------------------------------------------------------
Title: The Chromospheres of M Dwarf Stars
Authors: Giampapa, M. S.; Worden, S. P.; Linsky, J. L.
1980BAAS...12..807G Altcode:
No abstract at ADS

---------------------------------------------------------
Title: The Cool Half of the HR Diagram in Soft X-Rays
Authors: Ayres, T. R.; Linsky, J. L.; Vaiana, G. S.; Golub, L.;
Rosner, R.
1980BAAS...12..870A Altcode:
No abstract at ADS

---------------------------------------------------------
Title: Chromospheric Densities and Geometrical Extensions of Red
Giants and Supergiants using C II Lines as Diagnostics
Authors: Stencel, R. E.; Jordan, C.; Wing, R. F.; Linsky, J. L.;
Carpenter, K. G.; Brown, A.; Czyzak, S. J.
1980BAAS...12..806S Altcode:
No abstract at ADS

---------------------------------------------------------
Title: The Onset of Mass-Loss Among G Supergiants
Authors: Basri, G. S.; Stencel, R. E.; Linsky, J. L.
1980BAAS...12R.805B Altcode:
No abstract at ADS

---------------------------------------------------------
Title: IUE spectra of a flare in the RS Canum Venaticorum-type system
UX Arietis.
Authors: Simon, T.; Linsky, J. L.; Schiffer, F. H., III
1980ApJ...239..911S Altcode:
IUE spectra of UX Ari obtained during the large flare of 1979 January
1 exhibit chromospheric and transition-region emission-line fluxes
about 2.5 and 5.5 times brighter than quiescent fluxes, respectively,
and up to 1400 times brighter than the quiet sun. A high-dispersion
spectrum of the 2000-3000 A region exhibits enhanced Fe II emission,
which is probably associated mainly with the K0 IV star, and enhanced
Mg II emission with asymmetric wings extending to +475 km/s. These line
wings are interpreted as evidence for mass flow from the K0 IV star to
the G5 V star. A speculative scenario of major long-lived RS CVn flares
is proposed in which the component stars have very large corotating
flux tubes, which occasionally interact. Magnetic reconnection results
in flux tubes that temporarily connect the two stars.

---------------------------------------------------------
Title: Book-Review - Stellar Turbulence
Authors: Gray, D. F.; Linsky, J. L.
1980S&T....60...57G Altcode:
No abstract at ADS

---------------------------------------------------------
Title: Outer atmospheres of cool stars. VI. Models for EPS ERI based
on IUE spectra of C II, MG II, SI II, and SI III.
Authors: Simon, T.; Kelch, W. L.; Linsky, J. L.
1980ApJ...237...72S Altcode:
Observations of the ultraviolet line spectrum of the active chromosphere
star, Epsilon Eridani, obtained with the IUE satellite have been
analyzed. The coupled statistical equilibrium and radiative transfer
equations for the prominent transitions of C II, Mg II, Si II, and Si
III. A satisfactory fit to all of the line strengths can be achieved
with a model similar to that recently proposed to explain bright points
on the quiet sun. A surface pressure at the base of the transition
region of 0.5 dynes/sq cm is derived, which is a factor of 3 higher
than the quiet sun value, but a factor of 3 smaller than predicted
by scaling laws, assuming a conductively heated stellar transition
region. It is found that the surface fluxes of the C II 1334, 1335
and Si III 1892 emission lines are good diagnostics of pressure at
the base of the transition region, but line ratio techniques using
the 1892 line for estimating electron densities may be valid.

---------------------------------------------------------
Title: High Resolution Spectrograph (HRS) for the Space Telescope (ST)
Authors: Brandt, J. C.; Boggess, A.; Heap, S. R.; Maran, S. P.;
Smith, A. M.; Beaver, E. A.; Bottema, M.; Hutchings, J. B.; Jura,
M. A.; Linsky, J. L.; Savage, B. D.; Trafton, L. M.; Weymann, R. J.
1980BAAS...12R.488B Altcode:
No abstract at ADS

---------------------------------------------------------
Title: An IUE Survey of the Ultraviolet Emission Line Spectra of
dMe and dM Stars
Authors: Carpenter, K. G.; Wing, R. F.; Bornmann, P. L.; Linsky, J. L.
1980BAAS...12..538C Altcode:
No abstract at ADS

---------------------------------------------------------
Title: HEAO 1 observations of active coronae in main-sequence and
subgiant stars.
Authors: Walter, F. M.; Linsky, J. L.; Bowyer, S.; Garmire, G.
1980ApJ...236L.137W Altcode:
The HEAO 1 data has been searched for evidence of X-ray emission from
105 bright late-type stars of luminosity classes IV and V, selected
on the basis of indirect optical evidence of the presence of a hot
corona. Six of the target stars were detected at the 3-standard
deviation level and 15 were coincident with 2-standard deviation
X-ray sources. On a statistical basis no more than 5 of these 21
sources are spurious, and the probability that the identification
with the class of active chromosphere stars is spurious is less than
0.00001. The sources lie near a line of X-ray/bolometric luminosity
ratio = 0.0001, similar to a solar plage, and it is concluded that the
most active coronae of late-type stars which are not members of close
binary systems are being observed. The RS CVn systems discovered to
date seem to form a distinct class of coronal X-ray sources, but the
lowest X-ray luminosity members of the group, of which Capella may be
the prototype, appear to overlap the domain of these single stars with
active coronae. The data do not fit the coronal model of Gorenstein
and Tucker (1976), but they are consistent with the coronal loop model
of Rosner et al. (1978) as extended by Walter et al. (1980).

---------------------------------------------------------
Title: Observations of the quiescent corona, transition region,
and chromosphere in the dMe flare star Proxima Centauri.
Authors: Haisch, B. M.; Linsky, J. L.
1980ApJ...236L..33H Altcode:
No abstract at ADS

---------------------------------------------------------
Title: Ultraviolet spectroscopy of the outer layers of stars
Authors: Snow, T. P., Jr.; Linsky, J. L.
1980Ap&SS..67..285S Altcode:
Ultraviolet observations of the extended atmospheres and circumstellar
envelopes of early-type and cool stars are reviewed. UV spectra of
OB stars have shown that mass loss occurs in virtually all these
stars and in many Be stars, and the Copernicus satellite has also
provided information on the physical conditions and variability of
the winds. The winds have been interpreted in terms of hot coronal
wind models, imperfect flow models and radiation pressure models,
and estimates of mass loss ranging from 10 to the -10th to 9 x 10 to
the -6th solar masses/year have been obtained. Further UV data of faint
stars, additional wavelengths and time variability are required. Recent
UV and X-ray experiments have detected stellar chromospheres, transition
regions coronas and winds in cool stars. Semiempirical line-profile and
line-flux models and purely theoretical atmospheric models have been
constructed to explain chromosphere, corona and wind data, and future
observations of the physical properties of stellar chromospheres,
coronas and winds, terms in the energy balance equation, stellar
activity and its long-term variability and atmospheric modifications
due to the presence of companion stars are proposed for such missions
as Spacelab.

---------------------------------------------------------
Title: Stellar turbulence
Authors: Gray, D. F.; Linsky, J. L.
1980LNP...114.....G Altcode: 1980sttu.coll.....G; 1980IAUCo..51.....G
The generation, nature, and implications of stellar turbulence are
discussed, considering both the stellar and solar domains. Attention
is given to the generation of motions by convection, rotation,
oscillations, the measurement and observed characteristics of
turbulence, modeling and theoretical interpretation of turbulence,
and the relation of chromospheres, coronae, and mass loss to the
turbulence. In particular, the Wilson-Bappu effect, non-thermal motions,
observations of velocity fields, and micro-, meso- and macroturbulence
are considered. Topics include the generation of oscillatory motions
in the stellar atmosphere, photospheric macroturbulence in late-type
stars, the effects of acoustic waves on spectral line profiles, and
mechanical energy transport.

---------------------------------------------------------
Title: Theory of Stellar Coronae - an Interpretation of X-Ray Emission
from Non-Degenerate Stellar Sources
Authors: Linsky, J. L.
1980SAOSR.389..217L Altcode: 1980csss....1..217L
No abstract at ADS

---------------------------------------------------------
Title: Outer atmospheres of cool stars. IV. A discussion of cool
stellar wind models.
Authors: Haisch, B. M.; Linsky, J. L.; Basri, G. S.
1980ApJ...235..519H Altcode:
Possible wind models for late-type stars which appear not to have hot
coronae and transition regions are investigated; taking Arcturus and
the prototypical star, models with T less than approximately 20,000
K are considered, and solutions with mass loss rates of 10 to the
-9th solar masses per year are sought. The radiation pressure of
L-alpha resonance scattering can exceed the force of gravity in
the chromosphere and initiate a net outflow, but is insufficient
to sustain a wind, except perhaps in the presence of an additional
momentum input term such as Alfven wave pressure. It is concluded that
L-alpha radiation-pressure-initiated winds can occur in stars to the
right of the Linsky-Haisch dividing line in the H-R diagram between
stars with and without transition regions and presumably hot coronae,
and that the existence of these winds may explain energetically the
absence of hot coronae in these stars.

---------------------------------------------------------
Title: Outer atmospheres of cool stars. III. IUE spectra and
transition region models for alf CEN A and B.
Authors: Ayres, T. R.; Linsky, J. L.
1980ApJ...235...76A Altcode:
We describe lUE ultraviolet spectra of two nearby dwarf stars, α
Centauri A (G2 V) and B (K1 V). These data include high-resolution
profiles of the Mg II h and k features and lower- resolution integrated
fluxes of lines from the following species: H I, C I-IV, N V, O I, A1
II, Si II-IV, and Fe II. We find that surface fluxes in chromospheric
and transition-region lines of α Cen A and B are nearly identical
to those of the quiet Sun. In addition, the measured stellar line
fluxes are in good agreement with predictions of a transition-region
scaling law based on conductive heating and pressures estimated from
chromospheric models of α Cen A and B. While this agreement does
not verify the conductive heating hypothesis, it does suggest that
the basic physical processes that control the structure and energy
balance in the chromospheres and transition regions of α Cen A and
B and the Sun are, on a gross scale, very likely the same.

---------------------------------------------------------
Title: On the differences at chromospheric levels between RS CVn-type
binaries, active and quiet chromosphere single stars, and active
and quiet regions in the sun.
Authors: Linsky, J. L.
1980HiA.....5..861L Altcode:
No abstract at ADS

---------------------------------------------------------
Title: Stellar chromospheres
Authors: Linsky, J. L.
1980LNP...114..248L Altcode: 1980IAUCo..51..248L; 1980sttu.coll..248L
The interpretation of stellar chromospheric line intensities and widths
is discussed, and semiempirical chromospheric models of single stars
are reviewed. Theoretical chromospheric models based on the short
period acoustic wave theory are shown to have promise for explaining
the heating of the lower chromospheres of quiet chromosphere stars,
but are inadequate to explain the heating of transition regions and
coronae of active chromosphere stars and solar plages. Attention is
given to the Wilson-Bappu (1957) relation between the widths of the
Ca II H and K line emission cores and stellar absolute luminosity,
while an examination of the calculations of Basri (1979) reveals that
it is essential to solve the transfer equation properly before studying
the physical basis of width-luminosity relations. Also considered are
theoretical calculations of profiles of optically thick chromospheric
lines in the presence of systematic flow patterns.

---------------------------------------------------------
Title: Stellar chromospheres
Authors: Linsky, J. L.
1980STIN...8111969L Altcode:
Developments in the understanding and use of chromospheric diagnostics
are discussed with emphasis on the following aspects: (1) trends
emerging from semiempirical models of single stars; (2) the validity of
claims that theoretical models of chromospheres are becoming realistic;
(3) the correlation between the widths of Ca 2 H and K line emission
cores and stellar absolute luminosity extending over 15 magnitudes
(Wilson-Bappu relation); and (4) the existence of systematic flow
patterns in stellar chromospheres.

---------------------------------------------------------
Title: A Critical Test of the Coronae/Winds Division Among Late-Type
Stars
Authors: Linsky, Jeffrey L.
1980iue..prop..473L Altcode:
One of the significant new results from IUE is the discovery by Linsky
and Haisch (1979) of an apparent sharp division in the H-R diagram
between stars with and without emission lines formed at 2 x 10^4 to
2 x 10^5 K. We propose to extend our previous IUE study to a larger
group of carefully selected stars in order to pose a critical test of
this result. Such a test is possible with a set of SWP low resolution
spectra of stars which have observed He 1 10830 line strengths that
imply characteristics opposite to those expected for the stars based
on their position in the H-R diagram with respect to the Linsky-Haisch
division. The outcome will demonstrate that either the L-H division
is not sharp, or that the coronal recombination origin for He I
10830 in stars is gravely in error. The variation in surface fluxes
in transition region lines near the dividing line is important in
determining whether the absence or large decrease in line emission
strength to the right of the dividing line is a result of physical
changes in the mean atmosphere, or a rapid decrease in the fractional
volume in which transition region temperatures occur. These data are
also important in providing constraints on possible wind solutions
and testing whether the cool wind scenarios discussed by Haisch,
Linsky and Basri (1980) are valid.

---------------------------------------------------------
Title: Prox CEN
Authors: Linsky, Jeffrey
1980iue..prop..546L Altcode:
No abstract at ADS

---------------------------------------------------------
Title: Ultraviolet spectroscopy of the outer layers of stars
Authors: Snow, T. P., Jr.; Linsky, J. L.
1980ASSL...81..291S Altcode: 1980afs..conf..291S; 1980as...book..291S
Recent results of the ultraviolet spectroscopy of the outer layers
of stars are reviewed both for early-type stars and for cool stars;
the discussion is limited to extended atmospheres and circumstellar
envelopes, for which fundamental advantages are offered by ultraviolet
observations. Some important observational work still needed is
outlined, and several useful observations possible with instruments
that are compatible with the Spacelab format are described.

---------------------------------------------------------
Title: Stellar chromospheres
Authors: Linsky, J. L.
1980ARA&A..18..439L Altcode:
Recent observational and theoretical work in the general problem
of stellar chromospheres is summarized. The nature of a stellar
chromosphere is reviewed, along with regions of the H-R diagram where
chromospheres exist, trends emerging from semiempirical chromospheric
models of single stars, and the ability of such models to match
the observational data. Reasons why the Wilson-Bappu relation
works are discussed, the existence of systematic flow patterns in
stellar chromospheres is considered, and possible differences between
chromospheres in close binaries and in single stars are examined. The
general questions of chromospheric variability, the energy balance
in stellar chromospheres, and the physics of chromospheric activity
are described.

---------------------------------------------------------
Title: The 2300-3000A IUE Spectrum of Alpha Orionis
Authors: Haisch, B. M.; van der Hucht, K. A.; Linsky, J. L.
1979BAAS...11..681H Altcode:
No abstract at ADS

---------------------------------------------------------
Title: Lyman Alpha Emission from Altair
Authors: Landsman, W. B.; Henry, R. C.; Anderson, R. C.; Moos, H. W.;
Linsky, J. L.
1979BAAS...11Q.682L Altcode:
No abstract at ADS

---------------------------------------------------------
Title: IUE Spectra of a Flare in the RS CVn System UX Ari
Authors: Simon, T.; Linsky, J. L.; Schiffer, F. H., III
1979BAAS...11..630S Altcode:
No abstract at ADS

---------------------------------------------------------
Title: The Coronae of Main Sequence Stars with Active Chromospheres
Authors: Walter, F.; Bowyer, S.; Linsky, J.
1979BAAS...11..624W Altcode:
No abstract at ADS

---------------------------------------------------------
Title: HEAO 1 observations of X-ray emission from flares in dMe stars.
Authors: Kahn, S. M.; Linsky, J. L.; Mason, K. O.; Haisch, B. M.;
Bowyer, C. S.; White, N. E.; Pravdo, S. H.
1979ApJ...234L.107K Altcode:
The paper reports the detection of two X-ray flares from each of the
nearby dMe stars, AT Mic and AD Leo, with the A-2 experiment on board
HEAO 1. A spectrum obtained during the brighter AT Mic flare, the
first X-ray spectrum of a stellar flare, is well matched by a thermal
model with a temperature 3 x 10 to the 7 K and an iron K-alpha emission
line. The X-ray luminosities derived are in the range 1.3-16 x 10 to
the 30th ergs/s, while emission measures are in the range 1.1-14 x 10
to the 53rd/cu cm. The estimated Lx/Lopt ratios exceed unity and are
inconsistent with Mullan's flare model. Several scenarios to explain
this discrepancy are proposed.

---------------------------------------------------------
Title: Quiescent Chromosphere Models for the RS CVn Systems HR 1099
and UX Ari, and Estimates of Transition Region and Coronal Pressures
Authors: Linsky, J. L.; Simon, T.
1979BAAS...11..629L Altcode:
No abstract at ADS

---------------------------------------------------------
Title: Outer atmospheres of cool stars. II. MG II flux profiles and
chromospheric radiative loss rates.
Authors: Basri, G. S.; Linsky, J. L.
1979ApJ...234.1023B Altcode:
International Ultraviolet Explorer high-resolution spectra of the Mg
II lines at 2796, 2803 A in 15 stars of spectral type G2-M2 including a
wide range of luminosities are presented. These spectra are calibrated
in absolute flux units at earth and at the stellar surface, and the
chromospheric radiative loss rates in the Mg II lines are compared with
corresponding rates in the Ca II H, K, and 8542 lines. The ratio of
Mg II surface flux to total surface flux is found to be independent
of stellar luminosity and thus gravity; may decrease slowly with
decreasing effective temperature, and increases with decreasing period
among RS Canum Venaticorum binaries. The factor of 10 range in this
ratio at each effective temperature may be due to differences in the
fractional surface area covered by plages and may indicate that stars
of all luminosity classes have chromospheric plages. In this small
data sample no evidence is found that the Mg II line surface fluxes
indicate whether a star possesses a transition region and hot corona.

---------------------------------------------------------
Title: Stellar model chromospheres. XI. A survey of CA II lam 8542
line profiles in late-type stars of differing chromospheric activity.
Authors: Linsky, J. L.; Hunten, D. M.; Sowell, R.; Glackin, D. L.;
Kelch, W. L.
1979ApJS...41..481L Altcode:
We have obtained profiles of the Ca II infrared triplet line λ8542
in 49 stars of spectral type F9-K3. These data were obtained with a
silicon diode vidicon detector system on the KPNO McMath telescope
and have a spectral resolution of 0.14 Å. We find no evidence for
distinct emission features in the λ8542 lines, even for the most
active chromosphere stars, but instead find that the line cores are
filled in for active chromosphere stars compared to quiet chromosphere
stars of the same spectral type. We derive chromospheric radiative loss
rates in the A8542 line and find good correlations with chromospheric
radiative loss rates in the Ca II H and K lines and Mg II h and k lines
and with the Wilson-Bappu K-line index. Thus the λ8542 line is a good
diagnostic of chromospheric activity. Computed λ8542 line profiles
for the seven stars for which model chromospheres are available are
not in as good agreement with the data as we would like, and for the
three modeled giants the addition of macroturbulence cannot account
for discrepancies in the line cores. We account for variability in
the α Aur line profile as due to orbital motions of α Aur B, and
we point out circumstellar features, indicating both outflowing and
inflowing material, in six supergiants.

---------------------------------------------------------
Title: Theoretical Interpretation of X-ray Emission from
Non-Degenerate Stellar Sources
Authors: Linsky, J.
1979BAAS...11R.770L Altcode:
No abstract at ADS

---------------------------------------------------------
Title: A search for coronal soft X-ray emission from cool stars with
HEAO 1.
Authors: Ayres, T. R.; Linsky, J. L.; Garmire, G. P.; Cordova, F.
1979ApJ...232L.117A Altcode:
A search of the HEAO 1 A-2 experiment all-sky survey for coronal soft
X-ray emission from a sample of active chromosphere G-M stars including
six dwarfs, eight giants, four supergiants, and 10 dMe flare stars is
summarized. Point sources were detected near the positions of several
of the stars considered. However, of these, only the flare stars BY
Draconis (dM0e) and AD Leonis (dM3.5e) appear to be likely candidates
for the detected X-rays.

---------------------------------------------------------
Title: Stellar model chromospheres. X. High-resolution, absolute
flux profiles of the Ca II H and K lines in stars of spectral types
F0 - M2.
Authors: Linsky, J. L.; Worden, S. P.; McClintock, W.; Robertson, R. M.
1979ApJS...41...47L Altcode:
We present 120 mÅ resolution spectra of the cores and wings of the Ca
II H and K lines in 43 stars covering a wide range of spectral type
and luminosity class. These spectra were obtained with the KPNO 4 m
echelle spectrograph and blue image tube, and are calibrated in absolute
surface flux units using Willstrop's narrow-band photometry and the
Barnes and Evans relations for stellar angular diameters. We estimate
an uncertainty of ±15% in our flux scales. We derive chromospheric
radiative loss rates in the H and K lines, and discuss trends in
these loss rates with effective temperature for dwarfs, giants, and
supergiants. We compare these loss rates with similar rates for the
Mg II h and k lines, and discuss the doublet line ratios for H and
K. The monochromatic surface fluxes for different features in the H
and K lines are presented. From the surface fluxes at K1
we derive the radiation temperature TR(K1). The
TR(K1)/Teff ratio is lower in giants
than in dwarfs, as predicted by partial redistribution calculations,
and this ratio appears to be an empirical age indicator among
dwarfs. Asymmetries in the K line profile provide evidence for a
solar-type supergranulation flow pattern in F5-K5 dwarfs and perhaps
also in G and early K supergiants. Measurements of line widths at
H1, K1, and K2 are presented, together
with FWHM data for the H and K lines. We find rough agreement between
the measured K1 widths and the gravity and chromospheric heating
rate dependences in the scaling law proposed by Ayres. Finally, we
present data on emission lines in the wings of H and K, and discuss
chromospheric radiative loss rates in the HE line compared with loss
rates in the H and K lines.

---------------------------------------------------------
Title: Discovery of X-rays from the 40 Eridani system.
Authors: Cash, W.; Charles, P.; Bowyer, S.; Walter, F.; Ayres, T. R.;
Linsky, J. L.
1979ApJ...231L.137C Altcode:
The detection of a point source of soft X-rays (H0405-08) consistent
with the position of the nearby triple star system 40 Eridani is
reported. The source, which has a temperature near 10 million K,
has a flux of 3 x 10 to the -11th erg/sqcm-sec at earth, implying a
luminosity of 9(+ or -3) x 10 to the 28th erg/s at the distance of 40
Eridani. The likely source of the bulk of the X-rays is considered,
including the K1 dwarf, the DA white dwarf, the dwarf M4 flare star,
or accretion onto the white dwarf.

---------------------------------------------------------
Title: Chromospheric emission lines in the red spectrum of AD
Leonis. II. Physical conditions in flares.
Authors: Schneeberger, T. J.; Linsky, J. L.; McClintock, W.; Worden,
S. P.
1979ApJ...231..148S Altcode:
Simultaneous photometry and time-resolved spectra of the dMe flare star
AD Leo has been used to deduce flare temperatures, electron densities,
and dimensions. Photometric results for two qualitatively different
flares yield estimates of the differences in physical properties
between these flares. Flares on AD Leo are hotter and denser than their
solar counterparts, and spike-like flares occupy smaller volumes than
longer-lived flares. An upper limit to the flare X-ray luminosity is
set atL &lt;4 x l028ergss-1. Subject headings: stars: chromospheres -
stars: emission-line - stars: flare - stars: individual

---------------------------------------------------------
Title: Lyman-alpha rocket spectra and models of the quiet and active
solar chromosphere based on partial redistribution diagnostics.
Authors: Basri, G. S.; Linsky, J. L.; Bartoe, J. -D. F.; Brueckner,
G.; van Hoosier, M. E.
1979ApJ...230..924B Altcode:
Absolute intensity Lyman-alpha profiles with a spatial resolution
of 0.8 min and a spectral resolution of 50 mA were obtained for
network and cell regions in the quiet sun, umbral and penumbral
areas of a sunspot, two plages, and a quiescent prominence of the
limb. Weak limb brightening shown by the Lyman-alpha cores and wings
are consistent with predictions derived from partial redistribution
line transfer calculations. Through use of a comoving two-level partial
redistribution code which conserves mass flux, unequal red and blue
Lyman-alpha peak intensities may be interpreted as flow velocities
near 20,000 K. Outflows in the plages and downflows in the network
are also noted. A model of a mean quiet sun chromosphere consistent
with the Lyman-alpha integrated intensity, the Lyman continuum slope,
and the millimeter continuum is presented.

---------------------------------------------------------
Title: HR 5110 = HD 118216
Authors: Feldman, P. A.; Linsky, J. L.
1979IAUC.3366....1F Altcode:
P. A. Feldman, Herzberg Institute of Astrophysics, reports the
detection of a large radio outburst from the RS-CVn-binary HR
5110 = HD 118216 with the 46-m telescope of the Algonquin Radio
Observatory. The flare was first detected on May 29d08h26m UT with
a flux density of 425 mJy at 10.76 GHz. Measurements made over the
next two days have shown continued flaring activity in the range
0.20-0.35 Jy. Observations at radio, optical, ultraviolet, and x-ray
wavelengths are urged. J. L. Linsky, University of Colorado, reports:
"We obtained International Ultraviolet Explorer spectra of HR 5110
on May 31 at 17h00m UT. A 30-min low-dispersion exposure with the
short-wavelength camera on IUE shows strong emission lines at L-alpha
1216 A, N V 1240 A, O I 1304 A, C II 1335 A, O V 1370 A, Si IV 1400 A,
C IV 1550 A, and He II 1640 A. This high-excitation spectrum indicates
material at temperatures up to 250 000 K, which is likely produced at
the secondary star of the system." He adds that the Algonquin Radio
Observatory reported the 10.76-GHz flux as 215 mJy on May 31d08h36m.

---------------------------------------------------------
Title: IUE and the Search for a Lukewarm Corona
Authors: Pasachoff, J. M.; Linsky, J. L.; Haisch, B. M.; Boggess, A.
1979S&T....57..438P Altcode:
The use of the International Ultraviolet Explorer (IUE) to search
for stars having neither a hot corona nor a cool outer atmosphere,
but a lukewarm corona is outlined. An interactive computer system
permits extensive analysis of the data immediately after transmission
to earth, allowing the results of one exposure to influence the taking
of subsequent exposures. The observation program is illustrated for the
star HR 1099, noting that observations were taken while previous spectra
were being analyzed. Observations of many stars of spectral types G and
K lead to the construction of a border region on the Hertzsprung-Russell
diagram between stars with hot coronas and those with cool outer
atmospheres. Stars lying near this border region were then observed;
however, none with lukewarm coronas was found. The interactive control
facility in the satellite control room is considered an important
factor in the efficient implementation of the search procedure.

---------------------------------------------------------
Title: Outer atmospheres of cool stars. I. The sharp division into
solar-type and non-solar-type stars.
Authors: Linsky, J. L.; Haisch, B. M.
1979ApJ...229L..27L Altcode:
No abstract at ADS

---------------------------------------------------------
Title: Stellar model chromospheres. IX. Chromospheric activity in
dwarf stars.
Authors: Kelch, W. L.; Linsky, J. L.; Worden, S. P.
1979ApJ...229..700K Altcode:
High-resolution Ca II K line profiles are used to model the upper
photospheres and lower chromospheres of eight main-sequence stars
ranging in spectral type from F0 to M0 and exhibiting different degrees
of chromospheric activity. The model chromospheres are studied as a
function of spectral type and activity for stars of similar spectral
type in order to obtain evidence of enhanced nonradiative heating in the
upper-photospheric models and in the ratio of minimum temperature at the
base of the chromosphere to effective temperature, a correlation between
activity and temperature in the lower chromospheres, and a correlation
of the width at the base of the K-line emission core and at the K2
features with activity. Chromospheric radiative losses are estimated
for the modelled stars and other previously analyzed main-sequence
stars. The results obtained strengthen the argument that dMe flare stars
exhibit fundamentally solar-type activity but on an increased scale.

---------------------------------------------------------
Title: HEAO-1 Observations of X-Ray Emission from Stellar Flares
Authors: Linsky, J. L.; Kahn, S. M.; Mason, K. O.; White, N. E.;
Pravdo, S. H.
1979BAAS...11..471L Altcode:
No abstract at ADS

---------------------------------------------------------
Title: Simultaneous X-ray, UV, Optical, and Radio Observations of
the Flare Star Proxima Centauri
Authors: Haisch, B. M.; Linsky, J. L.; Slee, O. B.; Worden, S. P.
1979BAAS...11..471H Altcode:
No abstract at ADS

---------------------------------------------------------
Title: Capella: 1/2 of an RS CVn?
Authors: Ayres, T. R.; Linsky, J. L.
1979BAAS...11..472A Altcode:
No abstract at ADS

---------------------------------------------------------
Title: IUE Ultraviolet Spectra and Chromospheric Models of HR 1099
and UX Ari
Authors: Simon, T.; Linsky, J. L.
1979BAAS...11..472S Altcode:
No abstract at ADS

---------------------------------------------------------
Title: Lyman alpha initiated winds in late-type stars
Authors: Haisch, B. M.; Linsky, J. L.; van der Hucht, K. A.
1979IUE1.symp..383H Altcode: 1979STIN...8016008H
One of the first major results of the IUE survey of late-type stars
was the discovery of a sharp division in the HR diagram between stars
with solar type spectra (chromosphere and transition region lines) and
those with non-solar type spectra (only chromosphere lines). This result
is especially interesting in view of observational evidence for mass
loss from G and K giants and super-giants discussed recently by both
Reimers and Stencel. In the present paper models of both hot coronae
and cool wind flows are calculated using stellar model chromospheres as
starting points for stellar wind calculations in order to investigate
the possibility of having a 'supersonic transition locus' in the HR
diagram dividing hot coronae from cool winds. It is concluded from
these models that the Lyman-alpha flux may play an important role
in determining the location of a stellar wind critical point. The
interaction of Lyman-alpha radiation pressure with Alfven waves in
producing strong, low temperature stellar winds in the star Arcturus
is investigated.

---------------------------------------------------------
Title: High Resolution Spectrograph for the Space Telescope
Authors: Brandt, J. C.; Boggess, A.; Heap, S. R.; Maran, S. P.;
Smith, A. M.; Beaver, E. A.; Bottema, M.; Hutchings, J. B.; Jura,
M. A.; Linsky, J. L.; Savage, B. D.; Trafton, L. M.; Weymann, R. J.
1979SPIE..172..254B Altcode:
The high resolution spectrograph (HRS) for ultraviolet astronomy with
the Space Telescope will provide a spectral resolution of approximately
120,000 over a nominal wavelength range of 110-320 nm, together with
a spatial resolution of about 0.25 arc seconds. The two detectors will
consist of 512-element Digicons with cesium telluride and cesium iodide
photocathodes, respectively. Photoelectrons in transit between the
photocathodes and the diodes within the Digicons can be deflected in
two axes with 12-bit resolution. This feature facilitates a design that
emphasizes reliability since (once a hermetic seal is opened in orbit),
only two moving parts, a grating carrousel and a shutter, are required
for regular operation of the HRS. The instrument will be controlled
by a computer in the spacecraft. The scientific objectives of the
HRS investigation relate to interstellar matter in our own and nearby
galaxies, physical processes of stellar mass loss and mass transfer,
chemical abundances, bright quasars and Seyfert galaxy nuclei, and
solar system phenomena.

---------------------------------------------------------
Title: A broad look at solar physics adapted from the solar physics
study of August 1975
Authors: Parker, E.; Timothy, A.; Beckers, J.; Hundhausen, A.; Kundu,
M. R.; Leith, C. E.; Lin, R.; Linsky, J.; MacDonald, F. B.; Noyes, R.
1979sswp.book....3P Altcode: 1979sswp.book....3B
The current status of our knowledge of the basic mechanisms involved
in fundamental solar phenomena is reviewed. These include mechanisms
responsible for heating the corona, the generation of the solar
wind, the particle acceleration in flares, and the dissipation of
magnetic energy in field reversal regions, known as current sheets. The
discussion covers solar flares and high-energy phenomena, solar active
regions; solar interior, convection, and activity; the structure and
energetics of the quiet solar atmosphere; the structure of the corona;
the solar composition; and solar terrestrial interactions. It also
covers a program of solar research, including the special observational
requirements for spectral and angular resolution, sensitivity, time
resolution, and duration of the techniques employed.

---------------------------------------------------------
Title: Accurate measurement of ultraviolet radiation.
Authors: Linsky, J. L.
1979Dimen..64...10L Altcode:
No abstract at ADS

---------------------------------------------------------
Title: Ultraviolet observations of cool stars. VIII. Interstellar
matter toward Procyon.
Authors: Anderson, R. C.; Henry, R. C.; Moos, H. W.; Linsky, J. L.
1978ApJ...226..883A Altcode:
The profile of the chromospheric L-alpha emission line of the F5
IV-V star Procyon (Alpha CMi, d = 3.5 pc) has been measured using
the high-resolution Princeton spectrometer aboard NASA's Copernicus
satellite. L-alpha absorption lines of interstellar deuterium and
hydrogen are distinctly present. The average number density of
interstellar hydrogen along the line of sight is found to be 0.11 +
or - 0.02 per cu cm, similar to the densities that have been found
in the directions of the stars Epsilon Eri, Epsilon Ind, and Alpha
Cen A. These stars are all within 3.5 pc of the earth. The ratio of
deuterium to hydrogen in the direction of Procyon is found to be 1.3
(+1.2, -0.5) x 10 to the -5th.

---------------------------------------------------------
Title: Electron densities in stellar atmospheres determined from
IUE spectra.
Authors: Doschek, G. A.; Feldman, U.; Mariska, J. T.; Linsky, J. L.
1978ApJ...226L..35D Altcode:
No abstract at ADS

---------------------------------------------------------
Title: Chromospheric emission lines in the red spectrum of AD
Leonis. I. The nonflare spectrum.
Authors: Giampapa, M. S.; Linsky, J. L.; Schneeberger, T. J.; Worden,
S. P.
1978ApJ...226..144G Altcode:
High-resolution red (5300-7300 A) spectra of the flare star AD Leonis
were obtained with the Kitt Peak 4 m echelle spectrograph system
at a spectral resolution of 0.22 A at Ha. A series of time-trailed
plates with 5 hours integration in total were averaged together
to obtain a representation of the star's nonflaring spectrum with
high signal-to-noise ratio. The He i A5876 triplet line and A6678
singlet line appear in emission with measured equivalent widths of
0.312 + 0.016 A and 0.058 + 0.029 A, respectively. The corresponding
triplet-to-singlet line flux ratio is 3.7, close to the ratio of the
level statistical weights. We argue that the He i lines are not produced
by recombination and cascade following photoionization by A &lt; 504
A coronal photons, but are instead collisionally excited. We suggest
that these lines are formed in a geometrically thin chromospheric layer
at 20,000-50,000 K with a column density of nel 6 x 1018 . The sodium
D emission lines (A5890, AS 896) are found to be stellar in origin,
with measured FWHM of 0.7 A for both lines, and the Ha line has a
FWHM of 1.4 A. No other chromospheric emission lines were found in
this spectral region. Subject headings: stars: chromospheres - stars:
emission-line - stars: flare - stars: individual

---------------------------------------------------------
Title: Upper limits on extreme ultraviolet radiation from nearby
main sequence and subgiant stars.
Authors: Ayres, T. R.; Linsky, J. L.; Margon, B.; Bowyer, S.
1978A&A....70..431A Altcode:
Flux upper limits for 44-800 A radiation were measured in a sample
of nearby main sequence stars and one subgiant star with the aid of
the Apollo-Soyuz grazing incidence telescope. Comparisons of emission
measure upper limits with three different methods for predicting coronal
properties cannot yet determine which, if any, are valid. Data for
Alpha Centauri A and B are consistent with recent HEAO-1 soft X-ray
measurements which suggest that the surface flux of coronal emission
from the Alpha Cen system is comparable to that of the 'normal' sun.

---------------------------------------------------------
Title: Ultraviolet observations of cool stars. VII. Local interstellar
hydrogen and deuterium Lyman-alpha.
Authors: McClintock, W.; Henry, R. C.; Linsky, J. L.; Moos, H. W.
1978ApJ...225..465M Altcode:
High-resolution Copernicus spectra of Epsilon Eri and Epsilon Ind
containing interstellar hydrogen and deuterium L-alpha absorption lines
are presented, reduced, and analyzed. Parameters of the interstellar
hydrogen and deuterium toward these two stars are derived independently,
without any assumptions concerning the D/H ratio. Copernicus spectra
of Alpha Aur and Alpha Cen A are reanalyzed, and limits on the D/H
number-density ratio consistent with the data for all four stars are
considered. A comparison of the present estimates for the parameters of
the local interstellar medium with those obtained by other techniques
shows that there is no compelling evidence for significant variations in
the hydrogen density and D/H ratio in the local interstellar medium. On
this basis the hypothesis of an approaching local interstellar cloud
proposed by Vidal-Madjar et al. (1978) is rejected

---------------------------------------------------------
Title: A coordinated X-ray, optical, and microwave study of the
flare star Proxima Centauri.
Authors: Haisch, B. M.; Linsky, J. L.; Slee, O. B.; Hearn, D. R.;
Walker, A. R.; Rydgren, A. E.; Nicolson, G. D.
1978ApJ...225L..35H Altcode:
Results are reported for a three-day coordinated observing program
to monitor the flare star Proxima Centauri in the X-ray, optical, and
radio spectrum. During this interval 30 optical flares and 12 possible
radio bursts were observed. The SAS 3 X-ray satellite made no X-ray
detections. An upper limit of 0.08 on the X-ray/optical luminosity ratio
is derived for the brightest optical flare. The most sensitive of the
radio telescopes failed to detect 6-cm emission during one major and
three minor optical flares, and on this basis an upper limit on the
flare radio emission (1 hundred-thousandth of the optimal luminosity)
is derived.

---------------------------------------------------------
Title: IUE observations of cool stars : alf Aur, HR 1099, lam and
EPS Eri.
Authors: Linsky, J. L.; Ayres, T. R.; Basri, G. S.; Morrison, N. D.;
Boggess, A.; Schiffer, F. H., III; Holm, A.; Cassatella, A.; Heck,
A.; Macchetto, F.; Stickland, D.; Wilson, R.; Blanco, C.; Dupree,
A. K.; Jordan, C.; Wing, R. F.
1978Natur.275..389L Altcode:
Initial IUE observations of four cool stars are reported. Observed
fluxes and surface fluxes are given for several UV emission lines in
the spectral range 1175-2000 A, obtained at low and high dispersion with
the short-wavelength spectrograph and camera. These lines are formed in
the outer atmospheres of these stars, in regions presumably analogous to
the solar chromosphere and transition region. The surface fluxes in the
lines increase along the sequence: quiet sun, Epsilon Eri, Lambda And,
Alpha Aur, and HR1099. The 2.8-d RS CVn-type binary HR1099, observed on
1 March 1978 near the end of a major flaring episode, has line surface
fluxes roughly 100 times that of the quiet sun, similar to those seen in
solar flares. Line profiles and flux ratios in multiplets for Capella
are presented, and comments given on the opacity of the lines and on
a tendency of line width to increase with temperature of formation.

---------------------------------------------------------
Title: Outer Atmospheres of Cool Stars: The Sharp Division into
Solar-Type and Alpha Orionis-Type Stars
Authors: Linsky, J. L.; Haisch, B. M.
1978BAAS...10..647L Altcode:
No abstract at ADS

---------------------------------------------------------
Title: Model Chromospheres for Supergiants: A Progress Report
Authors: Basri, G. S.; Linsky, J. L.
1978BAAS...10..647B Altcode:
No abstract at ADS

---------------------------------------------------------
Title: IUE and BUSS Observations of Alpha Orionis
Authors: Haisch, B. M.; Linsky, J. L.; van der Hucht, K. A.
1978BAAS...10..646H Altcode:
No abstract at ADS

---------------------------------------------------------
Title: Photospheric models of solar active regions and the network
based on the Mg II h and k line wings.
Authors: Morrison, N. D.; Linsky, J. L.
1978ApJ...222..723M Altcode:
From a comparison between observed and computed wings of the Mg
II resonance lines, distributions of temperature versus mass column
density for solar photospheric layers in plages and in the chromospheric
network are derived. The theoretical profiles are computed assuming
partial coherent scattering. In the active regions, temperatures exceed
those in the quiet sun by up to 200 K near the temperature minimum
and up to 400 K in deeper layers. In the observed network structure,
the temperature is enhanced by 200 K at the temperature minimum but is
the same as that in the quiet sun at greater depths. The difference
in the slope of the temperature distribution between the network and
plages is real, but may refer only to long elements of the network
rather than to the brightest portions. Adjacent to the network is a
region in which the temperatures are similar to those in the quiet sun,
except immediately below the temperature minimum, where the temperatures
are depressed by 150 K.

---------------------------------------------------------
Title: The solar XUV He I and He II emission lines. II. Intensity
ratios and distribution functions.
Authors: Glackin, D. L.; Linsky, J. L.; Mango, S. A.; Bohlin, J. D.
1978ApJ...222..707G Altcode:
From high-resolution solar images we show that the He ii A256 line
intensity is very nearly uncorrelated with He ii A3O4 at the same
location on the Sun and that the A256 line is formed mainly by the
photoionization-recombination process. We also derive center-to-limb
variations of He ii A3O4 and A256 and He I A584 and A537 for network and
cell regions separately and find that (1), in both network and cells,
A3O4 and A584 each limb-brighten in the quiet Sun and limbdarken
in coronal holes and (2), for both A3O4 and A584, network and cell
regions are each brighter in the quiet Sun than in coronal holes. We
conclude that the appearance of dark coronal holes in the helium lines
is not a geometrical effect involving the chromospheric network, but
is rather an intrinsic property of the atmosphere in both network and
cell regions. We suggest that the network and cells can be treated as
isolated atmospheres in the solution of the transfer equation in the
helium lines. Subject headings: Sun: chromosphere - Sun: corona - Sun:
spectra - ultraviolet: spectra

---------------------------------------------------------
Title: Ultraviolet observations of cool stars. VI. Lalpha and
Mg II emission line profiles (and a search for flux variability)
in Arcturus.
Authors: McClintock, W.; Moos, H. W.; Henry, R. C.; Linsky, J. L.;
Barker, E. S.
1978ApJS...37..223M Altcode:
High-precision, high-resolution profiles of the L alpha and Mg II k
chromospheric emission lines from Arcturus (alpha Boo) obtained with
the Princeton Experimental Package aboard the Copernicus satellite
are presented. Asymmetries seen in the profiles of these lines are
probably intrinsic to the star, rather than the result of interstellar
absorption. In contrast to previous observations of the Ca II K emission
line, no evidence is found during a three-year period for variability
in the profiles or in the total fluxes from these lines on time scales
ranging from hours to months. Also presented is a flux profile of the
O I 1302 line and flux upper limits for L beta, O VI 1032, Si III 1206,
and O V 1218.

---------------------------------------------------------
Title: Physical properties of solar chromospheric plages. III. Models
based on Ca II and Mg II observations.
Authors: Kelch, W. L.; Linsky, J. L.
1978SoPh...58...37K Altcode:
We compute a new grid of plage models to determine the difference in
temperature versus mass column density structure T(m) between plage
regions and the quiet solar chromosphere, and to test whether the
solar chromosphere is geometrically thinner in plages. We compare
partial redistribution calculations of Mg II h and k and Ca II K
to NRL Skylab observations of Mg II h and k in six active regions
and Ca II K intensities obtained from spectroheliograms taken at
approximately the same time as the Mg II observations. We find that
the plage observations are better matched by models with linear (in
log m) temperature distributions and larger values of m0
(the mass column density at the 8000 K layer in the chromosphere),
than by models with larger low chromosphere temperature gradients
but values of m0 similar to the quiet Sun. Our derived
temperature structures are in agreement with the grid originally
proposed by Shine and Linsky, but our analysis is in contrast to the
study by Kelch which implies that stellar chromospheric geometrical
thickness is not affected by chromospheric `activity'. We conclude
that either the stellar Mg II observations upon which the Kelch study
was based are of poorer quality than had been assumed, or that the
spatial averaging of inhomogeneous structures, which is inherent in
the stellar data, does not lead to a best fit one-component model
similar in detail to that of a stellar or a solar plage.

---------------------------------------------------------
Title: IUE Observations of F, G, and K Stars and Preliminary Models
for Upper Chromospheres based on C II, Si II, and Si III
Authors: Kelch, W. L.; Linsky, J. L.
1978BAAS...10R.443K Altcode:
No abstract at ADS

---------------------------------------------------------
Title: IUE Observations of the RS CVn Stars HR 1099 and λ And
Authors: Ayres, T. R.; Linsky, J. L.; Morrison, N. D.
1978BAAS...10R.444A Altcode:
No abstract at ADS

---------------------------------------------------------
Title: A First Look at IUE Far Ultraviolet Spectra of K and M Stars -
α Ori, α Boo, and ɛ Eri
Authors: Basri, G. S.; Linsky, J. L.
1978BAAS...10R.443B Altcode:
No abstract at ADS

---------------------------------------------------------
Title: The solar XUV He I and He II emission lines. I. Intensities
and gross center-to-limb behavior.
Authors: Mango, S. A.; Bohlin, J. D.; Glackin, D. L.; Linsky, J. L.
1978ApJ...220..683M Altcode:
The center-to-limb variation of the He II 304- and 256-A lines and
He I 584- and 537-A lines is derived for different solar features,
but averaged over the chromospheric supergranulation structure. The
general trend is for limb brightening in quiet-sun regions, limb
neutrality in unipolar magnetic regions (UMR), and limb darkening in
polar coronal holes. The center-to-limb behavior in these optically
thick emission lines indicates collisional excitation and decreasing
transition-region temperature gradients with respect to optical depth
in the sequence quiet sun to UMR to coronal hole.

---------------------------------------------------------
Title: Stellar model chromospheres. VI. Empirical estimates of the
chromospheric radiative losses of late-type stars.
Authors: Linsky, J. L.; Ayres, T. R.
1978ApJ...220..619L Altcode:
A method is developed for estimating the nonradiative heating of
stellar chromospheres by measuring the net radiative losses in strong
Fraunhofer line cores. This method is applied to observations of the Mg
II resonance lines in a sample of 32 stars including the sun. At most
a small dependence of chromospheric nonradiative heating on stellar
surface gravity is found, which is contrary to the large effect
predicted by recent calculations based on acoustic-heating theories.

---------------------------------------------------------
Title: Stellar model chromospheres. VII. Capella (G5 III+), Pollux
(K0 III), and Aldebaran (K5 III).
Authors: Kelch, W. L.; Linsky, J. L.; Basri, G. S.; Chiu, H. -Y.;
Chang, S. -H.; Maran, S. P.; Furenlid, I.
1978ApJ...220..962K Altcode:
Data from high-resolution SEC vidicon spectroscopy with a ground-based
telescope (for the Ca II K line) and from spectral scans made with the
BUSS ultraviolet balloon spectrograph (for the Mg II h and k lines)
are used to derive models of the chromospheres and upper photospheres
of three G-K giants. The models are based on partial-redistribution
analyses of the Ca II K line wings and cores and on the fluxes in the
Mg II lines. The photospheres thus computed are hotter than predicted
by radiative-equilibrium models. The minimum-to-effective temperature
ratio is found to decrease with decreasing effective temperature,
while the mass column density at the top of the chromosphere increases
with decreasing stellar surface gravity. The computed pressure at the
chromosphere top in the primary member of the Capella spectroscopic
binary system is 70 times smaller than the transition-region pressure
derived by Haisch and Linsky (1976), which suggests that additional
terms must be included in the transition-region energy equations for
giant stars. Estimates of the Ca II and hydrogen column densities are
made for the circumstellar envelope of Aldebaran.

---------------------------------------------------------
Title: High Resolution IUE Observations of α AUR: Is the Outer
Atmosphere of Capella Similar to a Sunspot?
Authors: Ayres, T. R.; Linsky, J. L.
1978BAAS...10Q.444A Altcode:
No abstract at ADS

---------------------------------------------------------
Title: The helium triplet-to-singlet ratio in T Tauri stars.
Authors: Schneeberger, T. J.; Linsky, J. L.; Worden, S. P.
1978A&A....62..447S Altcode:
Summary. The He ilines at 5876 and 6678 are used to determine the
triplet-to-singlet ratio for T Tauri stars DF Tau and BP Tau. The
ratio is approximately 3. Line profiles and absolute intensities are
presented. Key words: T Tauri stars helium lines

---------------------------------------------------------
Title: Observations of Chromospheric Emission Lines From F-M Dwarfs
and Giants
Authors: Linsky, Jeffrey L.
1978iue..prop...29L Altcode:
No abstract at ADS

---------------------------------------------------------
Title: A sensitive observation of the far-ultraviolet (1160 - 1700
Å) spectrum of Arcturus and implications for its outer atmosphere.
Authors: Weinstein, A.; Moos, H. W.; Linsky, J. L.
1977ApJ...218..195W Altcode:
A low-resolution far-ultraviolet (1160-1700 A) spectrum of Arcturus
(a Boo, K2 IIIp) has been obtained by using a new very sensitive
rocket-borne spectrograph with a multielement microchannel plate
detector. H I Al2l6, 0 I Al 304, and a broad unresolved emission near
1510 A were detected. A 2 a feature is probably 0 I Al 356. The ratio
of 0 I Al 304 to 0 I Al 356 is similar to the solar ratio. This spectrum
is very different from that of the Sun, with few emission features. The
absence of certain emission lines in the spectrum of Areturus implies
either coronal temperatures outside the 20,000 to 350,000 K range
(except for possibly 180,000 + 20 000 K) or a lower coronal base
pressure than previously assumed. A model of the chromosphere-corona
transition region predicts fluxes too low to be detected at present. The
observation was coordinated with a simultaneous determination of the
Areturus La flux by the U2 detector on the Princeton Experimental
Package aboard OAO-Copernicus. The two measurements agree within 10%
of each other. Subject headings: stars: chromospheres - stars: coronae -
stars: individual - stars: late-type - ultraviolet: spectra

---------------------------------------------------------
Title: Chromospheric Emission Lines in the Quiescent Spectrum of
the Flare Star AD Leo
Authors: Giampapa, M. S.; Linsky, J. L.; Schneeberger, T. J.; Worden,
S. P.
1977BAAS....9..593G Altcode:
No abstract at ADS

---------------------------------------------------------
Title: Modeling of Chromospheric Activity in F-M Dwarf Stars and
the Sun.
Authors: Kelch, W. L.; Linsky, J. L.; Worden, S. P.
1977BAAS....9..651K Altcode:
No abstract at ADS

---------------------------------------------------------
Title: The Ca II λ8542 and λ8498 Lines as Important Indicators of
Stellar Chromospheres.
Authors: Linsky, J. L.; Hunten, D. M.; Sowell, R.; Glackin, D. L.
1977BAAS....9..651L Altcode:
No abstract at ADS

---------------------------------------------------------
Title: Simultaneous Photometry and Time Resolved Spectra of Flare
Star AD Leo
Authors: Schneeberger, T. J.; Worden, S. P.; Linsky, J. L.;
McClintock, W.
1977BAAS....9Q.593S Altcode:
No abstract at ADS

---------------------------------------------------------
Title: Analysis of the chromospheric spectrum of O I in Arcturus.
Authors: Haisch, B. M.; Linsky, J. L.; Weinstein, A.; Shine, R. A.
1977ApJ...214..785H Altcode:
The ultraviolet and near-infrared spectra of O I in Arcturus are
analyzed by a 15-level 14-transition model for O I and the Ayres-Linsky
(1975) model chromosphere. It is found that the anomalously bright O
I resonance lines at 1302, 1305, and 1306 A can be readily explained
by a Ly-beta-pumped fluorescence mechanism as originally proposed by
Bowen (1974). Observed equivalent widths of the near-infrared triplet
and singlet lines are also consistent with the model predictions,
but the intercombination lines at 1355 and 1359 A and near-infrared
quintet lines may pose a problem.

---------------------------------------------------------
Title: Extreme-ultraviolet observations of flare on Proxima Centauri
and implications concerning flare-star scaling theory.
Authors: Haisch, B. M.; Linsky, J. L.; Lampton, M.; Paresce, F.;
Margon, B.; Stern, R.
1977ApJ...213L.119H Altcode:
No abstract at ADS

---------------------------------------------------------
Title: Interstellar Deuterium and Hydrogen in the Direction of
Procyon.
Authors: Anderson, R.; Henry, R. C.; Moos, H. W.; Linsky, J. L.
1977BAAS....9..354A Altcode:
No abstract at ADS

---------------------------------------------------------
Title: Analysis of the Wings of the Mg II h and k Lines in Active
Regions and the Chromospheric Network.
Authors: Morrison, N. D.; Linsky, J. L.
1977BAAS....9..324M Altcode:
No abstract at ADS

---------------------------------------------------------
Title: Evidence for Outward Acceleration of the Circumstellar Shell
of α Orionis Determined by High Resolution Vidicon Spectrocopy.
Authors: Linsky, J. L.; Basri, G. S.; Chiu, H. Y.; Chang, S. W.;
Maran, S. P.
1977BAAS....9R.345L Altcode:
No abstract at ADS

---------------------------------------------------------
Title: Copernicus observations of Nova Cygni 1975.
Authors: Jenkins, E. B.; Snow, T. P.; Upson, W. L.; Starrfield, S. G.;
Gallagher, J. S.; Friedjung, M.; Linsky, J. L.; Anderson, R.; Henry,
R. C.; Moos, H. W.
1977ApJ...212..198J Altcode:
Near-ultraviolet radiation from Nova Cygni 1975 was detected by the
Copernicus satellite on five occasions from 1975 September 1 to 1975
September 9. The nova was not seen in the UV after this date. The
principal result was the observation of a broad emission feature
from the Mg II doublet at 2800 A. The absence of strong UV radiation
at shorter wavelengths suggests that these lines are produced by
collisional excitation in the outer layers of an expanding shell with
electron temperature of approximately 4000 K. The absence of observed
emission lines from highly ionized species indicates that the amount of
material with log T between 4.4 and 5.7 is less than 0.001 times that
which produces the Mg II emission. The continuum flux in the near-UV
decreased as the nova evolved, showing that the total luminosity
decreased as the nova faded in the visible.

---------------------------------------------------------
Title: High-resolution stellar vidicon spectrophotometry. I. Variable
mass loss from Arcturus and the hypothesis of giant convective
elements.
Authors: Chiu, H. Y.; Adams, P. J.; Linsky, J. L.; Basri, G. S.;
Maran, S. P.; Hobbs, R. W.
1977ApJ...211..453C Altcode:
High-resolution spectrophotometry of the variable Ca II K line in the
K2 IIIp star Alpha Boo was performed with the McMath Solar Telescope
at Kitt Peak National Observatory and an experimental SEC vidicon
camera. The results are compared with Copernicus observations of the Mg
II h and k lines and with earlier Ca II data. It is found that either
of two states may typically occur in the Arcturus chromosphere. From
comparison with the results of model calculations for expanding
chromospheres, it is concluded that these correspond respectively to a
'normal' state in which the mass loss is less than one billionth of
a solar mass per year and an 'abnormal' state in which the mass loss
is about 8 billionths of a solar mass per year. In the latter case,
the expansion velocity is around 13 km/s at optical depth unity in the
K-line, which exceeds the local sound speed. It is suggested that the
abnormal state represents the rise to the photosphere of a very large
convective element, as hypothesized for red giants by Schwarzschild
(1975).

---------------------------------------------------------
Title: The Solar Output and Variability Viewed in the Broader Context
of Stellar Activity
Authors: Linsky, J. L.
1977soiv.conf..477L Altcode:
No abstract at ADS

---------------------------------------------------------
Title: Erratum: "Evidence for a corona of Beta Geminorum"
[Astrophys. J., Lett., Vol. 193, p. L107 - L110 (1974)].
Authors: Gerola, H.; Linsky, J. L.; Shine, R.; McClintock, W.; Henry,
R. C.; Moos, H. W.
1977ApJ...218L..32G Altcode:
No abstract at ADS

---------------------------------------------------------
Title: Local interstellar hydrogen and deuterium.
Authors: Henry, R. C.; Anderson, R.; Moos, H. W.; McClintock, W.;
Linsky, J. L.
1977JRASC..71R.396H Altcode:
No abstract at ADS

---------------------------------------------------------
Title: Formation of the he i and he II Resonance and Subordinate
Lines in the Sun and Late-Type Stars.
Authors: Linsky, J. L.
1977uxsa.coll...28L Altcode: 1977IAUCo..43...28L
No abstract at ADS

---------------------------------------------------------
Title: Stellar model chromospheres. V. Alpha Centauri A (G2 V)
and Alpha Centauri B (K1 V).
Authors: Ayres, T. R.; Linsky, J. L.; Rodgers, A. W.; Kurucz, R. L.
1976ApJ...210..199A Altcode:
Models for the upper photospheres and lower chromospheres of Alpha
Centauri A and B are derived from high-dispersion spectrograms of the
Ca II K-line emission cores and damping wings. Effective temperatures,
surface gravities, and ages consistent with the measured broadband
colors, metallicities, and absolute magnitudes are estimated for the
two stars. The spectrograms are calibrated by fitting the far-wing K
profiles with synthetic fluxes based on radiative-equilibrium models,
and the model atmospheres are obtained through a partial-redistribution
analysis of the line cores and damping wings. These models are compared
with those previously proposed for Procyon, Arcturus, and the sun. Many
features in all the models are found to be quite similar, and some
evidence suggests that Alpha Cen A may be significantly older and
more evolved than the sun, even though both stars exhibit similar
chromospheric properties.

---------------------------------------------------------
Title: High Spectral Resolution K Line Observations of Active
Chromosphere Stars.
Authors: Linsky, J. L.; Worden, S. P.
1976BAAS....8..519L Altcode:
No abstract at ADS

---------------------------------------------------------
Title: Model Chromospheres and Photospheres of Selected G and
K Giants.
Authors: Kelch, W. L.; Linsky, J. L.; Basri, G. S.; Chiu, H. Y.;
Maran, S. P.; Furenlid, I.
1976BAAS....8..518K Altcode:
No abstract at ADS

---------------------------------------------------------
Title: Models of Solar Chromosphere Structures Implied by Lyman-α
Rocket Spectra.
Authors: Basri, G.; Linsky, J. L.; Bartoe, J. -D. F.; Brueckner, G.;
van Hoosier, M. E.
1976BAAS....8..534B Altcode:
No abstract at ADS

---------------------------------------------------------
Title: Formation of the HeI and HeII Lines in the Solar Atmosphere.
Authors: Avrett, E. H.; Vernazza, J. E.; Linsky, J. L.
1976BAAS....8..534A Altcode:
No abstract at ADS

---------------------------------------------------------
Title: Extreme Ultraviolet Observations of a Flare on Proxima Centauri
and Implications Concerning Flare Star Scaling Theory.
Authors: Haisch, B. M.; Linsky, J. L.; Bowyer, S.
1976BAAS....8..545H Altcode:
No abstract at ADS

---------------------------------------------------------
Title: Excitation and ionization of helium in the solar atmosphere.
Authors: Avrett, E. H.; Vernazza, J. E.; Linsky, J. L.
1976ApJ...207L.199A Altcode:
The excitation and ionization of He I and He II is investigated for
the case of a realistic solar model. The calculations are based on a
simplified numerical treatment of the He I and He II continua and the
He II 304-A line. The extent to which various proposed mechanisms can
account for the observed line and continuum intensities is discussed.

---------------------------------------------------------
Title: The MG II h and k lines. II. Comparison with synthesized
profiles and Ca II K.
Authors: Ayres, T. R.; Linsky, J. L.
1976ApJ...205..874A Altcode:
Measured high-dispersion center and limb profiles of the solar Mg
II h and k resonance lines are compared with synthetic spectra
computed with a partial-redistribution formalism and based on
several upper-photosphere and lower-chromosphere temperature
distributions. Profiles of the analogously formed Ca II K resonance
line are also synthesized for the same atmospheric models. The
spectrum-synthesis approach is outlined, and the collisional and fixed
radiative rates appropriate to the adopted model atoms and solar
atmosphere are discussed. It is found that the HSRA and VAL models
predict systematically lower intensities in the h, k, and K inner
wings than observed and that models with a somewhat higher minimum
temperature (about 4450 K) can reproduce the measured inner wings and
limb darkening. A 'Ca II' solar model with a minimum temperature of
4450 K is proposed as an alternative to the class of models based on
continuum observations.

---------------------------------------------------------
Title: Properties of the chromosphere-corona transition region
in Capella.
Authors: Haisch, B. M.; Linsky, J. L.
1976ApJ...205L..39H Altcode:
Analysis of recent ultraviolet observations of the Capella binary system
(Alpha Aur) indicates a dense geometrically narrow chromosphere-corona
transition region in the Capella system primary (G5 III) similar in
many respects to a solar active region. An examination of the coronal
energy balance, together with the coronal base pressure derived from
the line fluxes, predicts a corona with a mean temperature of 1.2
million K and a large stellar wind consistent with observations.

---------------------------------------------------------
Title: Preliminary Analysis of NRL Rocket Spectra of the Lα Line
Wings
Authors: Basri, G.; Bartoe, J. -D. F.; Brueckner, G.; Linsky, J.;
van Hoosier, M. E.
1976BAAS....8..331B Altcode:
No abstract at ADS

---------------------------------------------------------
Title: An Analysis of the Chromospheric O I Lines in Arcturus
Authors: Haisch, B. M.; Linsky, J. L.; Weinstein, A.; Shine, R.
1976BAAS....8..303H Altcode:
No abstract at ADS

---------------------------------------------------------
Title: Recent Studies of the Chromospheres and Coronae of K-Type
Stars and the Local Interstellar Medium using the Copernicus Satellite
Authors: Linsky, J. L.; McClintock, W.; Henry, R. C.; Moos, H. W.;
Basri, G. S.
1976BAAS....8Q.354L Altcode:
No abstract at ADS

---------------------------------------------------------
Title: Preliminary Analysis of NRL Skylab Spectroheliograms in Lines
of He I and He II
Authors: Mango, S.; Bohlin, D.; Glackin, D.; Linsky, J.
1976BAAS....8..332M Altcode:
No abstract at ADS

---------------------------------------------------------
Title: Simultaneous High-Dispersion Stellar Spectroscopy with
Copernicus and the McMath Solar Telescope
Authors: Maran, S. P.; Chiu, H. Y.; Linsky, J. L.; Henry, R. C.;
Moos, W.; McClintock, W.; Basri, G. S.
1976BAAS....8R.353M Altcode:
No abstract at ADS

---------------------------------------------------------
Title: Ultraviolet observations of cool stars. V. The local density
of interstellar matter.
Authors: McClintock, W.; Henry, R. C.; Moos, H. W.; Linsky, J. L.
1976ApJ...204L.103M Altcode:
A high-resolution Copernicus observation of the chromospheric Ly-alpha
emission line of the nearby (3.3 pc) K dwarf epsilon Eri sets limits
on the velocity, the velocity dispersion, and the density of atomic
hydrogen in the local interstellar medium. Analysis shows that
the interstellar Ly-alpha absorption is on the flat portion of the
curve of growth. An upper limit of 0.12 per cu cm is derived for the
atomic-hydrogen density. The value of this density is 0.08 (plus or
minus 0.04 per cu cm if the velocity-dispersion parameter is 9 km/s,
corresponding to a temperature of 5000 K. Also, the interstellar
deuterium Ly-alpha line may be present in the spectrum.

---------------------------------------------------------
Title: And Who Will Analyze the Data?" (Editorial)
Authors: Linsky, J. L.
1976ApL....17....1L Altcode:
No abstract at ADS

---------------------------------------------------------
Title: The solar XUV spectrum of He II.
Authors: Linsky, J. L.; Glackin, D. L.; Chapman, R. D.; Neupert,
W. M.; Thomas, R. J.
1976ApJ...203..509L Altcode:
OSO-7 observations of the first five Lyman lines and the Lyman
continuum of He II are given for the quiet sun, a coronal hole,
prominences, filaments, and the flare of August 7, 1972. These data are
calibrated and given in specific intensity units together with color
and brightness temperatures for the He II continuum. It is found that
He II is overionized in all features except the flare and that the
continuum is formed at temperatures near 14,000 K. The He II-He III
ionization equilibrium appears to be dominated by photoionizations
and radiative recombinations. Schematic calculations for realistic
chromosphere and transition-region models can account for the observed
intensities of Ly-beta through Ly-epsilon, the Lyman continuum, and its
color temperature. To account for the intensity of Ly-alpha, either an
implausible 100-km plateau at temperatures near 80,000 K is needed or,
more likely, the diffusion-enhanced collisional excitation should be
incorporated into the models.

---------------------------------------------------------
Title: Ultraviolet observations of cool stars. IV. Intensities of
Lyman-alpha and Mg II in Epsilon Pegasi and Epsilon Eridani, and
line width-luminosity correlations.
Authors: McClintock, W.; Henry, R. C.; Moos, H. W.; Linsky, J. L.
1975ApJ...202..733M Altcode:
A spectrometer on the Copernicus satellite has been used to confirm the
existence of a line width-luminosity relation for the Ly-alpha and Mg II
2800-A chromospheric emission lines in K-type stars by observation of
a K2 dwarf (epsilon Eri) and a K2 supergiant (epsilon Peg). Combined
with previously reported observations of lines in three K giants
(alpha Boo, alpha Tau, and beta Gem), the data are consistent with
an identical dependence of line width on absolute visual magnitude
for the Ca II K, Ly-alpha, and Mg II 2795-A lines. Surface fluxes of
Ly-alpha, Mg II 2800-A, and O V 1218-A (upper limit) for epsilon Eri,
and of Mg II 2800-A for epsilon Peg are also compared with values
reported previously for the three giant stars.

---------------------------------------------------------
Title: Diffusion effects on the line intensities of He I and He II
in the solar transition region.
Authors: Shine, R.; Gerola, H.; Linsky, J. L.
1975ApJ...202L.101S Altcode:
A heuristic treatment of diffusion in the solar chromosphere-corona
transition region is developed. It is shown that diffusion becomes
increasingly important with steeper temperature gradients, in active and
quiet regions relative to coronal holes, and with increasing excitation
potential. Numerical calculations are made for the resonance lines of
He I and He II and show that diffusion can enhance these lines. Thus
the helium lines may appear relatively weak in coronal holes due to a
weakening of the enhancement mechanism. Most transition region lines
will be less affected by diffusion than He I or He II.

---------------------------------------------------------
Title: A new solar carbon abundance based on non-LTE CN molecular
spectra.
Authors: Mount, G. H.; Linsky, J. L.
1975ApJ...202L..51M Altcode:
A detailed non-LTE analysis of solar CN spectra strongly suggest a
revised carbon abundance for the sun. We recommend a value of log
carbon abundance = 8.35 plus or minus 0.15 which is significantly
lower than the presently accepted value of log carbon abundance =
8.55. This revision may have important consequences in astrophysics.

---------------------------------------------------------
Title: Ultraviolet observations of cool stars. III. Chromospheric
and coronal lines in alpha Tauri, beta Geminorum, and alpha Bootis.
Authors: McClintock, W.; Linsky, J. L.; Henry, R. C.; Moos, H. W.;
Gerola, H.
1975ApJ...202..165M Altcode:
The ultraviolet spectrometer of the Princeton Experiment Package
aboard the Copernicus satellite has been used to obtain high-resolution
measurements of La, the Mg ii A2800 doublet, and upper limits on the
Si iii Al 206 line in the K giants a Tau and fl Gem. The intensities
and line shapes are compared with earlier observations of a Boo. The
La and Mg ii profiles for a Tau resemble those for a Boo, in that
they are highly asymmetrical, while fl Gem shows much more symmetrical
profiles. The asymmetries for all lines except for those of a Boo and
the Mg ii lines of a Tau could be due to interstellar absorption. in the
case of p Gem only, the 0 V intercombination line at 1218 A is observed,
suggesting a well-developed corona substantially cooler than that of
the Sun. The La profiles of a Tau and p Gem are consistent with the low
interstellar hydrogen abundance in the solar neighborhood previously
obtained from a similar observation of the a Boo La profile. The
strength of the Mg ii A2796 line can be used to measure transition
region and coronal pressures, and indicates a decrease in both with
later spectral type andlor increasing luminosity. Subject headings:
chromospheres, stellar - coronae, stellar - late-type stars - spectra,
ultraviolet

---------------------------------------------------------
Title: Stellar model chromospheres. IV. The formation of the Hepsilon
feature in the sun (G2 V) and Arcturus (K2 III).
Authors: Ayres, T. R.; Linsky, J. L.
1975ApJ...201..212A Altcode:
The formation of the Balmer-series member H-epsilon in the near-red
wing of the Ca II H line is discussed for two cases: the sun
(H-epsilon absorption profile) and Arcturus (H-epsilon emission
profile). It is shown that although the H-epsilon source functions
in both stars are dominated by the Balmer-continuum radiation field
through photoionizations, the line-formation problems in the two stars
are quantitatively different, owing to a substantial difference in the
relative importance of the stellar chromosphere temperature inversion
as compared with the stellar photosphere.

---------------------------------------------------------
Title: Stellar model chromospheres. III. Arcturus (K2 III).
Authors: Ayres, T. R.; Linsky, J. L.
1975ApJ...200..660A Altcode:
Models are constructed for the upper photosphere and chromosphere of
Arcturus based on the H, K, and IR triplet lines of Ca II and the h
and k lines of Mg II. The chromosphere model is derived from complete
redistribution solutions for a five-level Ca II ion and a two-level
Mg II ion. A photospheric model is derived from the Ca II wings using
first the 'traditional' complete-redistribution limit and then the
more realistic partial-redistribution approximation. The temperature
and mass column densities for the temperature-minimum region and
the chromosphere-transition region boundary are computed, and the
pressure in the transition region and corona are estimated. It is
found that the ratio of minimum temperature to effective temperature
is approximately 0.77 for Arcturus, Procyon, and the sun, and that
mass tends to increase at the temperature minimum with decreasing
gravity. The pressure is found to be about 1 percent of the solar
value, and the surface brightness of the Arcturus transition region and
coronal spectrum is estimated to be much less than for the sun. The
partial-redistribution calculation for the Ca II K line indicates
that the emission width is at least partially determined by damping
rather than Doppler broadening, suggesting a reexamination of previous
explanations for the Wilson-Bappu effect.

---------------------------------------------------------
Title: Detection of Interstellar Deuterium Lyman Alpha
Authors: McClintock, W.; Henry, R. C.; Moos, H. W.; Linsky, J. L.
1975BAAS....7..547M Altcode:
No abstract at ADS

---------------------------------------------------------
Title: A non-LTE analysis of the CN 3883 Å band head in the upper
photosphere of Arcturus.
Authors: Mount, G. H.; Ayres, T. R.; Linsky, J. L.
1975ApJ...200..383M Altcode:
A detailed non-LTE study of the CN(0,0) 3883 A band-head spectrum of
Arcturus (K2 iii) provides an accurate determination of the carbon,
nitrogen, and oxygen abundances in Arcturus. Non-LTE effects are
significant, and we find that the Ayres-Linsky model provides an
adequate fit to the observations for [C,N]* = 13[C,N]0 and [O]* =
0.60[0]o, or for [C,N,O]* = 16[C,N,O]0, but the latter abundances are
unlikely. The upper photospheric microturbulence is found to be 2.5
+ . Subject headings: abundances, stellar - atmospheres, stellar -
late-type stars - molecules - stars, individual (alpha Boo)

---------------------------------------------------------
Title: The MG II H and K lines. II. Comparison with synthesized
profiles and CA II K
Authors: Ayres, T. R.; Linsky, J. L.
1975STIN...7722038A Altcode:
The Mg II h and k resonance line data and profiles of the Ca II K
line are compared with synthetic profiles computed using a partial
redistribution formalism and several single-component solar upper
photosphere and lower chromosphere models. It is found that second
models predict systematically lower intensities in the h, k, and K inner
wings than are observed, but that models with a somewhat larger minimum
temperature (T(min) about 4450 K) can reproduce the measured inner
wing intensities and limb darkening of these resonance lines. A 'hot'
T(min) solar model, which is reasonably consistent with the empirical
emission cores and wing intensities of the Ca II and Mg II resonance
lines is proposed to serve as an alternative to the class of models,
such as the HSRA and VAL, based on continuum observations.

---------------------------------------------------------
Title: Changes in the K-Line of Arcturus Observed at High Resolution
by SEC Vidicon Spectroscopy.
Authors: Chiu, H. Y.; Adams, P.; Linsky, J. L.; Basri, G. S.; Maran,
S. P.; Hobbs, R. W.
1975BAAS....7..469C Altcode:
No abstract at ADS

---------------------------------------------------------
Title: Flare Model Chromospheres and Photospheres
Authors: Machado, M. E.; Linsky, J. L.
1975SoPh...42..395M Altcode:
Homogeneous plane-parallel model atmospheres for solar flares have been
constructed to approximately simulate observations of flares. The wings
of the Ca II lines have been used to derive flare upper photosphere
models, which indicate temperature increases of ∼100 K over the
temperature distribution in the pre-existing facula at a height of
300 km above τ5000 = 1. In the case of flares covering
sunspots the temperature rise seems to occur much higher in the
atmosphere. We solve the transfer and statistical equilibrium equations
for a three-level hydrogen atom and a five-level calcium atom in order
to obtain the chromospheric flare models. The general properties of
flares, including ne, N2, linear thickness, and
Lyman continuum intensity are approximately reproduced. We find that
with increasing flare importance the height of the upper chromosphere
and transition region occur lower in the solar atmosphere, accounting
for the factor of 60-600 increase in pressure in these regions relative
to the quiet Sun. The Ca II line profiles agree with observations
only by assuming a macro-velocity distribution that increases with
height. Also the chromospheric parts of flares appear to be highly
inhomogeneous. We show that shock and particle heated flare models do
not agree with the observations and propose a thermal response model
for flares. In particular, it appears that heating in the photosphere
is an essential aspect of flares.

---------------------------------------------------------
Title: The XUV Spectrum of HeII in Quiet Regions, a Coronal Hole,
Filaments Prominences, and the 7 August 1972 Flare
Authors: Linsky, J. L.; Glackin, D. L.; Chapman, R. D.; Neupert,
W. M.; Thomas, R. J.
1975BAAS....7..353L Altcode:
No abstract at ADS

---------------------------------------------------------
Title: One- and Multi-Component Models of the Upper Photosphere Based
on Molecular Spectra. IV: Non-LTE Treatment of the CN Violet System
Authors: Mount, G. H.; Linsky, J. L.
1975SoPh...41...17M Altcode:
Non-LTE synthetic spectra derived from a detailed analysis of
the formation of the CN (0, 0) λ13883 Å spectrum are compared
with center-limb photoelectric spectra taken at Kitt Peak National
Observatory.1 Significant non-LTE effects are found and the Kurucz,
Altrock-Cannon, Mount-Linsky II, and HSRA models are compared. We
derive a solar carbon abundance of Ac=8.30±0.10 for the
Mount-Linsky model and Ac=8.40±0.10 for the Altrock-Cannon
model, compared to the HSRA value of Ac=8.55±0.10, assuming
a nitrogen abundance of logAN=7.93. In addition we specify
the regions of formation for the CN(0, 0) 3883.35 Å bandhead at disc
center and limb.

---------------------------------------------------------
Title: Stellar Upper Photosphere Models Based on the Ca II
K-wing. II. The Coherent Scattering Approximation
Authors: Ayres, T. R.; Linsky, J. L.; Shine, R. A.
1975BAAS....7..359A Altcode:
No abstract at ADS

---------------------------------------------------------
Title: Flare Model Chromospheres and Photospheres
Authors: Machado, M. E.; Linsky, J. L.
1975BAAS....7Q.362M Altcode:
No abstract at ADS

---------------------------------------------------------
Title: A possible width-luminosity correlation of the Ca II
K1 and Mg II k1 features.
Authors: Ayres, T. R.; Linsky, J. L.; Shine, R. A.
1975ApJ...195L.121A Altcode:
Existing high resolution stellar profiles of the Ca II and Mg II
resonance lines suggest a possible width-luminosity correlation of the
K1 minimum features. It is shown that such a correlation can be simply
understood if the continuum optical depth of the stellar temperature
minimum is relatively independent of surface gravity as suggested by
three stars studied in detail.

---------------------------------------------------------
Title: Evidence for a Corona of Beta Geminorum
Authors: Gerola, Humberto; Linsky, Jeffrey L.; Shine, Richard;
McClintock, W.; Henry, R. C.; Moos, H. W.
1974ApJ...193L.107G Altcode:
A spectrometer was used on the satellite Copernicus to observe a
chromospheric L alpha emission from the K0 giant beta Gem at 1218.4
A. This emission appears to be in the corona at temperatures near
260,000 deg K, since the ion it is identified with requires 77.4 eV
to be produced.

---------------------------------------------------------
Title: Physical Properties of Solar Chromospheric Plages. II:
Chromospheric Plage Models
Authors: Shine, R. A.; Linsky, J. L.
1974SoPh...39...49S Altcode:
We propose chromospheric models of plages to explain profiles of
the Ca II H, K, λl8498, λ8542, and λ8662 lines described in Paper
I. These models are consistent with boundary conditions imposed by
the photosphere and the Lyman continuum. We find that increasing
emission in these lines is consistent with a picture of increasing
temperature gradient in the low chromosphere and the resulting increase
in pressure and electron density at similar line optical depths. With
this picture we suggest how to empirically determine the distribution
of chromospheric parameters across the solar disk directly from Ca
II filtergrams. We also propose that the high density aspects of
solar activity are produced by steep temperature gradients in the low
chromosphere and thus by the enhanced heating mechanisms that steepen
these gradients.

---------------------------------------------------------
Title: An Upper Photosphere Model for Arcturus (K2 III) Based on
Partial Redistribution and the Ca II K-line Inner Wings
Authors: Ayers, T. R.; Linsky, J. L.; Shine, R. A.
1974BAAS....6..457A Altcode:
No abstract at ADS

---------------------------------------------------------
Title: Mass Loss and Winds in K-type Stars ad Derived from
"Copernicus" Spectra.
Authors: Linsky, J. L.; Basri, G.; McClintock, W.; Henry, R. C.;
Moos, H. W.
1974BAAS....6..458L Altcode:
No abstract at ADS

---------------------------------------------------------
Title: Stellar Model Chromospheres. H. Procyon (F5 Iv/v)
Authors: Ayres, Thomas R.; Linsky, Jeffrey L.; Shine, Richard A.
1974ApJ...192...93A Altcode: 1974ApJ...192...95A
No abstract at ADS

---------------------------------------------------------
Title: A facular model based on the wings of the Ca ii lines
Authors: Shine, Richard A.; Linsky, Jeffrey L.
1974SoPh...37..145S Altcode:
We develop a relatively simple procedure for deriving models of upper
photospheric regions based on the damping wings of the Ca II resonance
and infrared triplet lines. The procedure is used to derive a facular
model but can also be applied to late-type stars. We compare our model
to that of Chapman.

---------------------------------------------------------
Title: Non-LTE Models of the Upper Solar Photosphere Based on CN
Molecular Spectra
Authors: Mount, G. H.; Linsky, J. L.
1974BAAS....6Q.347M Altcode:
No abstract at ADS

---------------------------------------------------------
Title: Evidence for a Corona of β Geminorum with the "Copernicus"
Satellite.
Authors: McClintock, W.; Linsky, J.; Gerola, H.; Shine, R.; Henry,
R. C.; Moos, H. W.
1974BAAS....6..315M Altcode:
No abstract at ADS

---------------------------------------------------------
Title: One- and Multi-Component Models of the Upper Photosphere Based
on Molecular Spectra. III: CH (0, 0) λ 3144 of the CH C-X System
Authors: Mount, George H.; Linsky, Jeffrey L.
1974SoPh...36..287M Altcode:
We have obtained accurate center-to-limb photoelectric spectra of
the CH (0, 0) C-X bandhead region λ3143-3148 Å at Kitt Peak National
Observatory. From these spectra and a detailed analysis of the formation
of the CH (0, 0) spectrum we demonstrate that the best-fit upper
photospheric model derived from our previous analyses of CN (0, 0)
and CN (1, 1) spectra adequately explains the CH C-X observations. In
addition we derive a solar carbon abundance of ±0.20 compared to the
HSRA value of log Ac = 8.55. This confirms our previous
CN analyses which demonstrated that if the HSRA nitrogen abundance of
log AN = 7.93 ± 0.10 is assumed, then log Ac =
8.20 ± 0.10. We also specify the regions of formation for the CH(0,
0) λ3143.47 Å band-head at disc center and limb.

---------------------------------------------------------
Title: One- and Multi-Component Models of the Upper Photosphere
Based on Molecular Spectra. II: CN (1, 1) of the CN Violet System
Authors: Mount, George H.; Linsky, Jeffrey L.
1974SoPh...35..259M Altcode:
We have obtained center-to-limb photoelectric spectra of the CN(1,1) B-X
bandhead region λ3868-3872 Å at Kitt Peak National Observatory. From
these spectra and a detailed analysis of the formation of the CN (1,
1) spectrum we derive a best-fit upper photospheric model differing
from the HSRA which is consistent with our previous CN(0, 0) λ3883
spectra. We derive a solar carbon abundance of log Ac =
8.30 ± 0.10 compared to the HSRA value of log Ac = 8.55
± 0.10. In addition we specify the regions of formation for the CN(0,
0) λ3883.35 and CN(1, 1) λ 3871.38 bandheads at disc center and limb.

---------------------------------------------------------
Title: High-Spectral Measurements of the H i λ1216 and MG II λ
2800 Emissions from Arcturus
Authors: Moos, H. W.; Linsky, J. L.; Henry, R. C.; McClintock, W.
1974ApJ...188L..93M Altcode:
High-spectral-resolution scans of H i X1216 and Mg ii XX2796, 2803
obtained using the ultraviolet spectrometer abroad the Copernicus
sateffite show broad and very asymmetrical emission profiles. The
ratio of the line widths to the solar values is consistent with a law
similar to the Wilson-Bappu relation for the calcium K reversal. A fit
of the interstellar absorption profile indicates that the average H
density toward this nearby star is low, 0.02#).1 . Subject headings:
late-type stars - line profiles - spectra, ultraviolet

---------------------------------------------------------
Title: Preliminary Interpretation of Diode Array Simultaneous
Observations of He I and Ca II Line Profiles in Collaboration with ATM
Authors: Linsky, J. L.; Dunn, R. B.; Rust, D. M.
1974BAAS....6S.290L Altcode:
No abstract at ADS

---------------------------------------------------------
Title: The Formation of the Hɛ Emission Feature in
Late-Type Stars.
Authors: Ayres, T. R.; Linsky, J. L.
1974BAAS....6..226A Altcode:
No abstract at ADS

---------------------------------------------------------
Title: Models of the Upper Solar Photosphere Based on CN and CH
Molecular Spectra.
Authors: Mount, G. H.; Linsky, J. L.
1973BAAS....5..444M Altcode:
No abstract at ADS

---------------------------------------------------------
Title: The Chromosphere of α Cen A.
Authors: Hewitt, T. G.; Linsky, J. L.; Rodgers, A. W.
1973BAAS....5..453H Altcode:
No abstract at ADS

---------------------------------------------------------
Title: A Model for the Chromosphere of Arcturus.
Authors: Ayres, T. R.; Linsky, J. L.
1973BAAS....5Q.454A Altcode:
No abstract at ADS

---------------------------------------------------------
Title: Copernicus Observations of Chromospheric Emission Lines in
Arcturus and Other K Giants.
Authors: Linsky, J. L.; Moos, H. W.; Henry, R. C.; McClintock, W. E.
1973BAAS....5..453L Altcode:
No abstract at ADS

---------------------------------------------------------
Title: One- and Multi-Component Models of the Upper Photosphere
Based on Molecular Spectra. I: The Violet System of CN(0,0)
Authors: Mount, George H.; Linsky, Jeffrey L.; Shine, Richard A.
1973SoPh...32...13M Altcode:
Spectroheliograms taken in the CN(0, 0) violet band near λ 3883
Å show very small scale network and cell structures with high
contrast. The bandhead itself, which is a broad feature due to
overlap of several CN lines, allows the diagnostic simplicity of a
continuum since motions, magnetic fields, and broadening mechanisms
are unimportant. We have obtained spectroheliograms in the bandhead
and center-to-limb photoelectric spectra of CN(0, 0) at Kitt Peak
National Observatory. From the photoelectric spectra and a detailed
analysis of the formation of the CN(0, 0) spectrum we derive a best-fit
one-component upper photospheric model differing from that of the
HSRA and recommend a change in solar carbon abundance from the HSRA
value of logAc = 8.55 to logAc = 8.25. From the
calibrated spectroheliograms we consider a multi-component model to
account for the observed fine structure intensity variations.

---------------------------------------------------------
Title: A model for the chromosphere of Arcturus.
Authors: Ayres, T. R.; Linsky, J. L.
1973BAAS....5..336A Altcode:
No abstract at ADS

---------------------------------------------------------
Title: A simple explanation of the Wilson-Bappu effect.
Authors: Ayres, T. R.; Linsky, J. L.; Shine, R. A.; Chipman, E.
1973BAAS....5..364A Altcode:
No abstract at ADS

---------------------------------------------------------
Title: A Model for the Chromosphere of Arcturus.
Authors: Ayres, T. R.; Linsky, J. L.
1973BAAS....5R.336A Altcode:
No abstract at ADS

---------------------------------------------------------
Title: Stellar model chromospheres. I. On the temperature minima of
F,G, and K stars.
Authors: Linsky, J. L.; Ayres, T.
1973ApJ...180..473L Altcode:
Brightness temperatures are deduced for the Hiv and Kiv features of
the Ca ii resonance lines in Procyon (F5 IV-V), Arcturus (K2 IlIp),
and the Sun (G2 V). The brightness temperatures of Procyon and the
Sun are in the same ratio as their effective temperatures, suggesting
a simple scaling law for the temperature minima of F and early G
stars. Arcturus departs from this law in a way that can be explained
by CO line blanketing. Subject headings: Ca ii emission - chromosphere,
solar chromospheres, stellar - late-type stars

---------------------------------------------------------
Title: One- and Multi-Component Models of the Upper Photosphere
based on the 3883 Å Band Head of CN
Authors: Mount, George H.; Linsky, Jeffrey L.
1973BAAS....5V.277M Altcode:
No abstract at ADS

---------------------------------------------------------
Title: A Recalibration of the Quiet Sun Millimeter Spectrum Based
on the Moon as an Absolute Radiometric Standard
Authors: Linsky, Jeffrey L.
1973SoPh...28..409L Altcode:
The solar millimeter continuum between 1 and 20 mm is recalibrated using
observations of the average lunar brightness temperature at the center
of lunar disk and new Moon brightness temperatures. The solar data
are placed on a common scale according to the average lunar brightness
temperature distribution proposed by Linsky. A least-squares parabolic
regression curve is proposed for the solar millimeter continuum. A
small departure from this regression curve near 8 mm may indicate the
existence of an absorption feature.

---------------------------------------------------------
Title: The Moon as a Proposed Radiometric Standard for Microwave
and Infrared Observations of Extended Sources
Authors: Linsky, Jeffrey L.
1973ApJS...25..163L Altcode:
Measured values of the average midnight and morning terminator
infrared brightness temperatures of the central portion of the lunar
disk can quite accurately determine the mean surface temperature
despite likely horizontal and vertical inhomogeneities of the thermal
properties of the lunar soil. These data together with laboratory
measurements on lunar soil and in situ temperature measurements in
and on the lunar surface lead to a mean surface temperature of 220.5
K + 2.5 percent and a mean temperature 35 K hotter at a depth of 1
m. The monthly average brightness temperature is then estimated as
a function of wavelength between 10 m and 100 cm taking into account
likely temperature dependencies of the thermal conductivity and loss
tangent, and the variation of emissivity with wavelength. The accuracy
with which the Moon can be used as an absolute radiometric standard
for extended sources is estimated based on the likely range of lunar
thermal and electromagnetic properties. Subject headings: infrared -
Moon - radio radiation - radio radiation, planetary

---------------------------------------------------------
Title: Discovery of upper photospheric temperature inversions or
chromospheres in early A stars.
Authors: Linsky, J. L.; Shine, R. A.; Ayres, T. R.; Praderie, F.
1973BAAS....5....3L Altcode:
No abstract at ADS

---------------------------------------------------------
Title: Discovery of Chromospheres in Early A Stars.
Authors: Linsky, J. L.; Shine, R. A.; Ayres, T. R.; Praderie, F.
1973BAAS....5R...3L Altcode:
No abstract at ADS

---------------------------------------------------------
Title: Physical Properties of Solar Chromospheric Plages. I. Line
Profiles of the Ca II H, K, and Infrared Triplet Lines
Authors: Shine, Richard A.; Linsky, Jeffrey L.
1972SoPh...25..357S Altcode:
Double pass photoelectric observations are presented of five CaII lines
(H, K, 8498 Å, 8542 Å, and 8662 Å) in a number of solar plages of
different degrees of activity, quiet regions, and a sunspot. The data
are compared with previous work. All five lines show increasing emission
together in plages and the least opaque of the infrared triplet lines
appears to exhibit core emission prior to the more opaque members of
the multiplet. The question of source function equality is considered
and the differences and similarities among plage profiles and between
plage and quiet profiles are shown qualitatively and quantitatively.

---------------------------------------------------------
Title: On the validity of a generalized Kirchhoff's law for a
nonisothermal scattering and absorptive medium
Authors: Linsky, Jeffrey L.; Mount, George H.
1972Icar...17..193L Altcode:
The relationship of directional hemispherical reflectivity to emissivity
is investigated for a nonisothermal medium with isotropic coherent
scattering and absorption. Departures from a generalized Kirchhoff's
Law occur due to the long range nature of the scattering process. Such
departures occur in lunar thermal emission at microwave but not at
infrared frequencies.

---------------------------------------------------------
Title: A Model for the Chromosphere of Procyon.
Authors: Linsky, J. L.; Ayres, T. R.
1972BAAS....4..334L Altcode:
No abstract at ADS

---------------------------------------------------------
Title: Photoelectric Ca II Line Profiles in Solar Plages and a
Sunspot and Their Preliminary Interpretation
Authors: Shine, Richard A.; Linsky, Jeffrey L.
1972BAAS....4T.391S Altcode:
No abstract at ADS

---------------------------------------------------------
Title: A proof of the relation between reflectivity and emissivity
in an isothermal scattering and absorptive atmosphere.
Authors: Linsky, J. L.
1972JQSRT..12..777L Altcode:
No abstract at ADS

---------------------------------------------------------
Title: The Solar H and K Lines
Authors: Linsky, Jeffrey L.; Avrett, Eugene H.
1970PASP...82..169L Altcode:
ASTRONOMICAL SOCIETY OF THE PACIFIC Vol. 82 April 1970 No. 485 THE
SOLAR H AND K LINES JEFFREY L. LINSKY Joint Institute for Laboratory
Astrophysics of the National Bureau of Standards and the University of
Colorado AND EUGENE H. AVRETT Smithsonian Astrophysical Observatory
Harvard College Observatory itory 22, 1970 We review our current
understanding of the formation of the Ca ii H and K resonance and
infi-ared triplet subordinate lines in the sun in view of the wedth
of observations of these lines and the devdopment of non-LTE line
formation theory. We descrihe the low- and high-spatial resolution
data of these lines on the solar disk, off the limb, and in stellar
spectra. We also describe obseiwations of the analogous Mg ii resonance
lines. We review the various explanations proposed for the features
of the lines the reversal, limb darkening, plage and spot profiles,
and the anomalous line ratios. Line profiles are according to a
first-order steady-state theoiy in which we assume a one-component
atmosphere in hydrostatic , noncoherent scattering, and a five -level
atom and 'im representation for Ca ii. The chromospheric model chosen
is to be representative nither than definitive, biit it profiles of
all five a microwave continuum in agreement with observations at the
of the disk. We then extensions of this first-order theory.

---------------------------------------------------------
Title: A Model of the Solar Temperature-Minimum Region
Authors: Avrett, Eugene H.; Linsky, Jeffrey L.
1970BAAS....2R.181A Altcode:
No abstract at ADS

---------------------------------------------------------
Title: Observations of the Infrared Triplet of Singly Ionized Calcium
Authors: Linsky, Jeffrey L.; Teske, Richard G.; Wilkinson, Carol W.
1970SoPh...11..374L Altcode:
Observations are presented of the CaII infrared triplet (8498 Å,
8542 Å, and 8662 Å) at three positions on the solar disk to make
possible direct analyses of the lines and comparisons with theoretical
computations. The source functions for the two strongest lines (8542
Å and 8662 Å) are equal at those heights corresponding to the wings
of the lines (¦Δλ¦ &gt; 0.4 Å) but not to those of the cores. We
suggest that the apparent source function inequality in the cores is
due to limb darkening caused by inhomogeneities in the chromosphere.

---------------------------------------------------------
Title: On the Relative Residual Intensities of the Calcium H and
K Lines
Authors: Linsky, Jeffrey L.
1970SoPh...11..355L Altcode:
We have observed the solar CaII H and K lines to obtain well-calibrated
ratios of their core residual intensities. From three independent
calibrations, one using a standard lamp, we conclude that the residual
intensity ratio r(K3)/r(H3) is 1.048 ± 0.03 in
the quiet chromosphere and 1.20 ± 0.03 in a plage region. These ratios
correspond closely to those observed in stars with quiet and active
chromospheres, respectively. For a chromospheric model suggested by
the calcium lines and a four-level CaII ion, we compute H and K line
profiles varying the direct collisional coupling and indirect radiative
and collisional coupling via the 3 2D level. We conclude
that enhanced chromospheric activity in the sun and late-type stars
results more from a steepening of the chromospheric thermal gradient
than from a change in density.

---------------------------------------------------------
Title: Can the ion H3 + account for missing
opacity in the solar ultraviolet?
Authors: Linsky, Jeffrey L.
1970SoPh...11..198L Altcode:
Limb darkening and specific intensity data imply more continuous
opacity in the solar photosphere between 2000 Å and 3500 Å than
has been predicted theoretically. The temperature dependence and
wavelength dependence of this missing opacity are in qualitative
agreement with those deduced for the ion H3+,
but it is unlikely that H3+ is sufficiently
abundant to account for this opacity.

---------------------------------------------------------
Title: An empirical model of the lower chromosphere based upon
millimeter data calibrated by lunar observations.
Authors: Linsky, J. L.
1969BAAS....1..372L Altcode:
No abstract at ADS

---------------------------------------------------------
Title: H3+, An Important Missing Continuous
Opacity Source in the Sun
Authors: Linsky, Jeffrey L.
1969BAAS....1R.251L Altcode:
No abstract at ADS

---------------------------------------------------------
Title: On the Pressure-Induced Opacity of Molecular Hydrogen in
Late-Type Stars
Authors: Linsky, Jeffrey L.
1969ApJ...156..989L Altcode:
The pressure-induced opacity resulting from binary collisions of
hydrogen molecules with each other and with helium atoms is computed
for temperatures typical of the photospheres of late-type stars. The
opacity is effectively continuous throughout the infrared, and consists
of overlapping translational, rota- tional, and vibrational transitions
in the hydrogen molecule. For temperatures less than roughly 25000
K, depending on the pressure, this should be the primary source of
continuous opacity in stellar photospheres between the wavelengths of
1 and 10 /L. Algorithms are given for this opacity that are useful in
calculations of stellar atmospheres. I. INTRODUCTIO

---------------------------------------------------------
Title: A Critical Evaluation of Temperature Determinations in the
Low Solar Chromosphere as Obtained from the Ultraviolet Continuum Data
Authors: Linsky, Jeffrey L.; Brown, Douglas R.
1969BAAS....1Q.285L Altcode:
No abstract at ADS

---------------------------------------------------------
Title: A Recalibration of Solar Millimeter Brightness Temperatures
Based upon Lunar Observations
Authors: Linsky, Jeffrey L.
1969BAAS....1S.284L Altcode:
No abstract at ADS

---------------------------------------------------------
Title: Toward a Self-Consistent Interpretation of the Calcium Lines
Authors: Linsky, J. L.
1968rla..conf..441L Altcode:
No abstract at ADS

---------------------------------------------------------
Title: Formation of the Calcium H, K, and Subordinate Lines in the
Solar Chromosphere
Authors: Linsky, J. L.
1968SAOSR.274.....L Altcode:
Two important problems of astrophysics are the structure of the
solar chromosphere and the study of spectral line formation without
the assumption of local thermodynamic equilibrium (LTE). In this
research we combine the two problems in the process of analyzing the
Ca II resonance and subordinate lines in terms of self-consistent
model chromospheres. We develop an approach for obtaining line
source functions when the lines are coupled together in a four level
representation of the calcium ion and when the ionization equilibrium
is governed by the solar ultraviolet radiation field. By considering a
number of cases in which we alter the complexity of the model ion, we
determine the accuracy with which we can apply simpler representation
to understanding the solar chromosphere. We compute several models
of the solar chromosphere that assume hydrostatic equilibrium, an LTE
representation of metal ionization, and a non-LTE formulation for the
ionization equilibrium of hydrogen. The temperature distributions are
adjusted to produce H and K line profiles similar to observations. A
general feature of these models is a minimum temperature of ~ 4200°
K in the region 3 X 10-4 &lt; τ5000 &lt; 3 X
10-5 corresponding to 470-650 km above the photosphere. Above
the minimum we find a shallow thermal gradient followed by a steep
gradient beginning at 1400-1700 km. The general features of this
description persist even though we vary the calcium abundance, hydrogen
ionization equilibrium, turbulent velocities, He/H ratio, and include
"turbulent" pressure, although the position of the steep gradient is
affected by these changes.

---------------------------------------------------------
Title: Observations of the CA II H- and K-Line Cores on the Solar
Disk.
Authors: Linsky, Jeffrey L.
1968AJS....73S..68L Altcode:
We have found a qualitative discrepancy between published observations
of the Ca II H and K lines and theoretical profiles computed from models
which we feel are representative of the solar chromosphere. On the
solar disk the residual intensity in the core of the H line (H3) has
been observed to exceed that of the K line (K3) by 10-20%, whereas in
our computations K3 is always brighter than H3. The latter result is a
consequence of the near equality of the H- and K-line source functions
at a common geometrical height and the chromospheric rise in the source
functions needed to produce the H2 and K2 features. Observations
of the solar Mg II resonance lines also exhibit K3 brighter than
H3. The theoretical profiles are obtained by solving the coupled
statistical equilibrium and radiative transfer equations, assuming
complete redistribution of line photons, for a four level Ca II ion
consisting of the 4 25, 3 2D 4 2P_ and 4 2P levels. We find that
the K3/H3 ratio depends only weakly on the 4 2Pi -42P~ collisional
rate, and for published values of this rate is 1.01. To help resolve
this discrepancy we have observed the H and K lines on the solar
disk using the McMath Solar Telescope and Spectrograph of Kitt Peak
National Observatory. The observations of the quiet chromosphere,
plage, and sunspot regions were made in sixth-order double pass with
a spectral resolution of 0.0067 A and spatial resolution of 24 sec of
arc along the slit. We place the spectral scans of the H and K lines
and continuum near 4000 A on the same relative scale by calibrating
the relative sensitivity of the spectrograph using a quartz-iodide
standard lamp. When calibrated in this manner, the scans of the quiet
chromosphere yield the ratio K3/H3 =1.045+0.058. Under poor observing
conditions we also obtained the ratio 1.20+0.13 for a plage region
and 1.44+0.38 over a large resolved sunspot.

---------------------------------------------------------
Title: Formation of the Calcium h, k, and Subordinate Lines in the
Solar Chromosphere.
Authors: Linsky, Jeffrey Lawrence
1968PhDT.........1L Altcode:
No abstract at ADS

---------------------------------------------------------
Title: Model Atmospheres for Late-Type Stars
Authors: Gingerich, Owen J.; Latham, D. W.; Linsky, J. L.; Kumar, S. S.
1967SAOSR.240...11G Altcode:
No abstract at ADS

---------------------------------------------------------
Title: Model atmospheres for cool stars
Authors: Gingerich, O. J.; Latham, D. W.; Linsky, J. L.; Kumar, S. S.
1967SAOSR.240.....G Altcode:
(1) Model Atmospheres for Cool Stars, by O. J. Gingerich. Serious
problems beset the would-be constructor of stellar atmosphere models
for cool stars: molecular absorptions, an involved equation of state,
severe scattering, and convective instability This paper describes
early attempts to build models for Teff = 2500°, including
one with simulated water-vapor absorption. (2) Model Atmospheres for
Late-Type Stars, by O. J. Gingerich, D. W. Latham, J. L. Linsky, and
S. S. Kumar. Five model atmospheres for Teff = 2500° K with
gravities ranging from dwarf to supergiant are presented in detail;
they are among the most nongray models ever computed. We have paid
particular attention to the equation of state for the atomic electron
contributors and to the treatment of scattering, which is a major
opacity source. These radiative equilibrium models are idealized in
that we do not include water-vapor absorption or convection, but we
indicate how these models may differ from more realistic cases. In
all the models molecular hydrogen predominates, and in the dwarf
models the photospheric gas pressure exceeds several hundred earth
atmospheres. Models with low metal abundances appear to mimic normal
models with higher gravities.

---------------------------------------------------------
Title: Model atmospheres for late-type stars
Authors: Gingerich, O.; Latham, D. W.; Linsky, J.; Kumar, S. S.
1967lts..conf..291G Altcode:
No abstract at ADS

---------------------------------------------------------
Title: Surface temperatures in late-type model atmospheres
Authors: Linsky, J.
1966AJ.....71..863L Altcode:
No abstract at ADS

---------------------------------------------------------
Title: A Theoretical Study of the Calcium II H and K Lines and
Infrared Triplet in the Solar Chromosphere.
Authors: Linsky, Jeffrey
1966AJ.....71Q.391L Altcode:
K Lines and Infrared Triplet in the Solar Chromosphere. JEFFREY LINsKY,
Smithsonian Astrophysical Observatory and Department of Astronomy,
Harvard University.-Statistical equilibrium equations have been
formulated for a model calcium ii ion consisting of four discrete
levels (32S, 32D, 42P~, 42P~) and a continuum. These equations have
been solved iteratively, on the basis of the approach of Avrett
and Loeser to yield non-LTE source functions for the H and K lines
as well as for each of the lines in the infrared triplet (8498A,
8542A, and 8660A) under a range of physical conditions appropriate
to the solar chromosphere. A computer program has been written to
solve for these source functions and non-LTE ionization equilibria
and to calculate emergent profiles on and off the disk as well as
for heights and optical depths corresponding to features in these
profiles. Comparison of a number of computed profiles with the data of
Goldberg, Mohler, and Muller (Asfrophys. J. 129, 119, 1958) suggests
the following preliminary conclusions: (1) The emission features H2
and K2 correspond to heights 600-900 km above the photosphere and
optical depths 102 to 10~ in the center of the K line. (2) A natural
consequence of chromospheric temperature distributions is that the
K-line residual intensities are larger than those for the H line. (3)
An upper limit of about 5 km/sec for the turbulent velocities in the
region of formation of H2 and K2, 100O~3000 km is established by the
visibility of the emission features corresponding to the relative
maxima in the source functions. (4) Computed K-line profiles for
the chromospheric models of Bohm-Vitense (Z. Astrophys. 36, 145,
1955) and Thomas and Athay (Physics of the Solar Chromosphere) and
for the Utrecht reference model (Bull. Astron. Inst. Neth. 17, 442,
1964) yield K2 and K8 features that are between a factor of 5 and 10
larger than those observed. Unless the gas and electron densities are
factors of 30 to 100 too high in these models for the low chromosphere,
an electron temperature minimum of 4000 K and temperature less than
50000K at 1000 km are required. (5) When either the 32D level or the
42P+ level is ignored, the resultant source functions differ at most
by a factor of 2, and the residual intensities by 1 % of the continuum
from those computed, including all these levels.

---------------------------------------------------------
Title: Models of the Lunar Surface with Temperature-Dependent
Thermal Properties.
Authors: Linsky, Jeffrey
1966AJ.....71S.168L Altcode:
For the interpretation of recent data on lunar thermal emission, I have
written a Fortran encoded computer program to solve the heat conduction
equation and to compute radio brightness temperatures for a medium
having conductive and radiative energy transport and characterized by
arbitrary temperature- and depth-dependent thermal properties. This
program will also solve periodic heat conduction problems of a more
general nature. A number of models were constructed with a range of
temperature-dependent conductivities and specific heats, but each was
consistent with the minimum surface temperature of 900 K observed l~y
Low (Astrophys. J. 142, 806, 1965) at the morning terminator. All of
these models predict infrared and radio brightness temperatures for
eclipses and lunations which agree favorably with high-resolution data
for the center of the lunar disk. If there are no internal heat sources,
a significant increase in the mean radio brightness temperature with
wavelength occurs when the conductivity, but not the specific heat,
increases with temperature. This increase in the mean radio brightness
temperature results from the nonlinear nature of heat conduction
under these circumstances, and is sufficient to explain the observed
increase with wavelength described by Krotikov and Troitskii (Soviet
Phys. Usp. 6, 841, 1964), without requiring as a postulate an unusually
high level of radioactivity in the moon. The general behavior of
silicates at lunar temperatures and laboratory measurements of probable
lunar materials suggest that radiative energy transport is the most
probable mechanism to account for an increase in the conductivity with
temperature. Several models in which radiative transfer and thermal
conduction are of comparable importance at 3500K agree favorably
with the data of Krotikov and Troitskii. The present findings support
the hypothesis that porous or frothy material characterize the lunar
surface at least to a depth of 20 cm, and are in agreement with radar
depolarization studies. This research was sponsored by NASA.

---------------------------------------------------------
Title: Models of the Lunar Surface Including Temperature-Dependent
Thermal Properties
Authors: Linsky, Jeffrey L.
1966Icar....5..606L Altcode:
The thermal conditions in the lunar surface are considered on a gross
scale in terms of models with temperature-dependent thermal properties,
including radiative energy transport. Agreement is obtained with
infrared mesurements of cold terminator temperatures and radio lunation
data at millimeter wavelengths for a range of postulated parameters of
the surface material. The observed increase of mean radio brightness
temperature with wavelength is interpreted as due to radiative energy
transport and the resultant non-linearity of the heat-conduction
equation, rather than to a large radioactive heat flux. The postulated
existence of radiative energy transport is consistent with a porous or
frothy medium, in agreement with photometric and laboratory simulation
experiments, as well as with recent radar depolarization mesurements. A
distance scale of 0.1-0.3 mm for the effective mean separation of
radiating surfaces is suggested by this interpretation of the data.

---------------------------------------------------------
Title: a Critical Analysis of Lunar Temperature Measurements in
the Infrared
Authors: Ingrao, Hector C.; Young, Andrew T.; Linsky, Jeffrey L.
1965nls..conf..185I Altcode:
No abstract at ADS