Author name code: linsky ADS astronomy entries on 2022-09-14 author:"Linsky, Jeffrey L." ------------------------------------------------------------------------ Title: Inhomogeneity within Local Interstellar Clouds Authors: Linsky, Jeffrey L.; Redfield, Seth; Ryder, Diana; Chasan-Taber, Adina Bibcode: 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. 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 Bibcode: 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. 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 Bibcode: 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. 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 Bibcode: 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. 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 Bibcode: 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. 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. Bibcode: 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. Title: Inhomogeneity in the Local ISM and Its Relation to the Heliosphere Authors: Linsky, Jeffrey; Redfield, Seth; Ryder, Diana; Moebius, Eberhard Bibcode: 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. Title: Are the Skumanich relations the same for chromospheric and coronal diagnostics? Authors: Linsky, J. Bibcode: 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. 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. Bibcode: 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. 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 Bibcode: 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. Title: Interactions between the heliosphere and its environment - important questions for Interstellar Probe Authors: Linsky, Jeffrey Bibcode: 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. 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 Bibcode: 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. Title: Could the Local Cavity be an Irregularly Shaped Strömgren Sphere? Authors: Linsky, Jeffrey L.; Redfield, Seth Bibcode: 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. 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 Bibcode: 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. 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. Bibcode: 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. 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. Bibcode: 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 Bibcode: 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. 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 Bibcode: 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. 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 Bibcode: 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 Bibcode: 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. Bibcode: 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<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>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. 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 Bibcode: 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. Bibcode: 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. Bibcode: 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 Bibcode: 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. Bibcode: 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. Bibcode: 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 Bibcode: 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 L/Lbol, and the Mount Wilson Ca II H&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 L/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 Bibcode: 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&'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&'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. Bibcode: 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. Bibcode: 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 Bibcode: 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 Bibcode: 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 Bibcode: 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. Bibcode: 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. Bibcode: 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 & k, Mg II h & 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. Bibcode: 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. Bibcode: 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 Bibcode: 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 Bibcode: 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 Bibcode: 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 Bibcode: 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 & 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 Bibcode: 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 & 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. Bibcode: 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 Bibcode: 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. Bibcode: 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 Bibcode: 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 Bibcode: 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 >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. Bibcode: 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 >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 Bibcode: 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 Bibcode: 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. 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. Bibcode: 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. Title: Computing Models of M-Type Host Stars and Their Panchromatic Spectral Output Authors: Tilipman, D.; Linsky, J. L.; Vieytes, M.; France, K. Bibcode: 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 Bibcode: 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. 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. Bibcode: 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 (<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. Title: UV astronomy throughout the ages: a historical perspective Authors: Linsky, Jeffrey L. Bibcode: 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 Bibcode: 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. 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. Bibcode: 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 Bibcode: 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: Observations of Strong Magnetic Fields in Nondegenerate Stars Authors: Linsky, Jeffrey L.; Schöller, Markus Bibcode: 2018smfu.book...31L Altcode: No abstract at ADS Title: The Development of New Atmospheric Models for K and M DwarfStars with Exoplanets Authors: Linsky, Jeffrey L. Bibcode: 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 Bibcode: 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. Bibcode: 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 Bibcode: 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 >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 Bibcode: 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 Bibcode: 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 (<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. Bibcode: 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. Bibcode: 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 Bibcode: 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 Bibcode: 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 Bibcode: 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 >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 Bibcode: 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} >~ 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 Bibcode: 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. Bibcode: 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. Bibcode: 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 Bibcode: 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 Bibcode: 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 Bibcode: 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) >= 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 Bibcode: 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. Bibcode: 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 & 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 & 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 Bibcode: 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 Bibcode: 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 & 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. Bibcode: 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 Bibcode: 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 & 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 Bibcode: 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 Bibcode: 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. Bibcode: 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. Bibcode: 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<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. Bibcode: 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 Bibcode: 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 Bibcode: 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<IndexTerm> . Ultraviolet radiation<IndexTerm> , 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<IndexTerm> , 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<IndexTerm> , 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 Bibcode: 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. Bibcode: 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 Bibcode: 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 Bibcode: 2015ASSL..411...19W Altcode: Exposure to stellar winds<IndexTerm> 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 Bibcode: 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 Bibcode: 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 Bibcode: 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. Bibcode: 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. Bibcode: 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 (<=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 & 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. Bibcode: 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 Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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 Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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 >~ 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 Bibcode: 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. Bibcode: 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, >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. Bibcode: 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. Bibcode: 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. Bibcode: 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 Bibcode: 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 Bibcode: 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 < 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 <~ 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 Bibcode: 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. Bibcode: 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 Bibcode: 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 Bibcode: 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. Bibcode: 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. Bibcode: 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 > 2000 K). We describe the light-curve of a chromospheric + transition region flare observed in several far-UV emission lines, with flare/quiescent ratios > 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 Bibcode: 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) > 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 >=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 Bibcode: 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. Bibcode: 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 > 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 Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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 > 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. Bibcode: 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. Bibcode: 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 Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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 > 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) >~ 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 Bibcode: 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 Bibcode: 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. Bibcode: 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 <~ λ <~ 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. Bibcode: 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. Bibcode: 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. Bibcode: 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 Bibcode: 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. Bibcode: 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. Bibcode: 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 >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 Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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 Bibcode: 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. Bibcode: 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 Bibcode: 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. Bibcode: 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. Bibcode: 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 Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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 Bibcode: 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. Bibcode: 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. Bibcode: 2009fohl.book.....L Altcode: No abstract at ADS Title: Foreword Authors: Linsky, Jeffrey; Izmodenov, Vlad; Möbius, Eberhard Bibcode: 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 Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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 Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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 Bibcode: 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. Bibcode: 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. Bibcode: 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 Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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 Bibcode: 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 & 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. Bibcode: 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. Bibcode: 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. Bibcode: 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 >=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<=1.19+0.16-0.15(1σ) or <=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. Bibcode: 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. Bibcode: 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. Bibcode: 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 Bibcode: 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 Bibcode: 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. Bibcode: 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. Bibcode: 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 Bibcode: 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>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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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)<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>500 pc and logN(HI)>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. Bibcode: 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. Bibcode: 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) < 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. Bibcode: 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 α Centauri A (G2 V) Authors: Pagano, I.; Linsky, J. L.; Valenti, J.; Duncan, D. K. Bibcode: 2004A&A...415..331P Altcode: 2003astro.ph.10901P We describe and analyze HST/STIS observations of the G2 V star α Centauri A (α Cen A, HD 128620), a star similar 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, 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 α Cen A and the quiet and active Sun, 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 α Cen A and solar UV spectra 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. 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 Sun observed as a point source when comparing other stars to the Sun.

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. Bibcode: 2004ApJ...602..776R Altcode: 2003astro.ph.10878R Moderate- and high-resolution measurements (λ/Δλ>~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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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 Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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 >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 Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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<~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>~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. Bibcode: 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 Bibcode: 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. Bibcode: 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. Bibcode: 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 Bibcode: 2003ApJ...583..963A Altcode: We describe an extensive search with the Space Telescope Imaging Spectrograph (STIS) for ultraviolet coronal (T>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. Bibcode: 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 Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 2003IAUS..210P.F14L Altcode: No abstract at ADS Title: Atomic Deuterium/Hydrogen in the Galaxy Authors: Linsky, Jeffrey L. Bibcode: 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. Bibcode: 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. Bibcode: 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 Bibcode: 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 Bibcode: 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 >=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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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<0.025" (2.9 AU). Long slit spectra of the t>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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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<~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>=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. Bibcode: 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 Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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 <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 Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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> 107 K) coronae, but nevertheless have curiously depressed X-ray luminosities. The post-braking giants are slow rotators (υ rot< 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. Bibcode: 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. Bibcode: 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. Bibcode: 2002ApJS..139..439R Altcode: High-resolution absorption measurements (λ/Δλ>~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. Bibcode: 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 < 10 eV) like Fe are underabundant, whereas elements with FIP > 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. 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. Bibcode: 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< 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. Bibcode: 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. Bibcode: 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 Bibcode: 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. Bibcode: 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 Bibcode: 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. Bibcode: 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. 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. Bibcode: 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. Bibcode: 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. Bibcode: 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 Bibcode: 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 < 10 eV) like Fe are underabundant, whereas elements with FIP > 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. Bibcode: 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. Bibcode: 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. Bibcode: 2001AJ....121.2999B Altcode: Goddard High Resolution Spectrograph observations of the nucleus of the bright, nearby Seyfert galaxy NGC 4151 are presented andbriefly described. 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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 & 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 <~8°, which at the outer edge of the LIC correspond to physical separations of <~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. Bibcode: 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 <~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<~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. Bibcode: 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. Bibcode: 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. Bibcode: 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 Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 2001ASPC..223.1039P Altcode: 2001csss...11.1039P No abstract at ADS Title: Spectral imaging maps of AR Lacertae . 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. Bibcode: 2001A&A...365..128P Altcode: In October 1994 the RS CVn eclipsing binary AR Lacertae 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 AR Lac 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 AR Lac 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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<=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. Bibcode: 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 Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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 Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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 Bibcode: 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. Bibcode: 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} <= 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. 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. Bibcode: 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. 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. Bibcode: 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 & STIS, FUSE, ASCA). A previous study by Dupree & 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 <= 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 & 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\>km\>s-1) coronal wind. This research is funded by NASA grants NAG5-9010 & NAG5-3226. 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. Bibcode: 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>=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. 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 Bibcode: 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. Title: Microstructure of the Local Interstellar Cloud (LIC) and Identification of the Hyades Interstellar Cloud Authors: Redfield, S.; Linsky, J. L.; Wood, B. E. Bibcode: 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. 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. Bibcode: 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 & 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. 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. Bibcode: 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 & Solar Physics, NASA/GSFC. 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. Bibcode: 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 <=15 minutes appear to be due to a coherent emission process. EUVE spectra reveal coronal material at ne<=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 (>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. 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. Bibcode: 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. Title: FUSE Observations of K--M Stars Authors: Ake, T. B.; Dupree, A. K.; Linsky, J. L.; Harper, G. M.; Young, P. R. Bibcode: 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. 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. Bibcode: 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. 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 Bibcode: 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 Bibcode: 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. 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. Bibcode: 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. 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. Bibcode: 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. 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. Bibcode: 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. Title: HETG Observations of the K Giant Beta Ceti Authors: Linsky, Jeffrey Bibcode: 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. Title: The M 16 Star-Forming Region Authors: Linsky, Jeffrey Bibcode: 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. Bibcode: 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 Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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<0.19 pc, which the Sun will reach in tedge<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. Bibcode: 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. Bibcode: 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. Bibcode: 2000IAUS..177..303L Altcode: No abstract at ADS Title: Stellar flares: How common? How Important? Authors: Linsky, Jeffrey L. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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 > 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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 <=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 Bibcode: 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. Bibcode: 2000ASPC..198..467L Altcode: 2000scac.conf..467L No abstract at ADS Title: Spectroscopic Survey of Cool Stars Authors: Linsky, J. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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 Bibcode: 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 <=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. Bibcode: 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. Bibcode: 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 Bibcode: 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. Bibcode: 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 > 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 < 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 & 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. Bibcode: 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& Solar Physics, NASA/GSFC. Title: Discovery space for stellar astrophysics by small missions Authors: Linsky, Jeffrey L. Bibcode: 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. Bibcode: 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. Bibcode: 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 & Wood, 1996, ApJ, 463, 254; Izmodenov et al. 1999, A&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. Bibcode: 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. Bibcode: 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 Bibcode: 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 Bibcode: 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. Bibcode: 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 Bibcode: 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 Bibcode: 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 Bibcode: 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 Bibcode: 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 Bibcode: 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 Bibcode: 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 Bibcode: 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. Bibcode: 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. Bibcode: 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 <= 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. Bibcode: 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 > 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 Bibcode: 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<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<Z<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<Z<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. Bibcode: 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. Bibcode: 1999ASPC..164...26L Altcode: 1999uosa.conf...26L No abstract at ADS Title: Magnetic Fields in the Hertzsprung-Russell Diagram Authors: Linsky, J. L. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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 & 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 Bibcode: 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 >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. Bibcode: 1999ASPC..158..401L Altcode: 1999ssa..conf..401L No abstract at ADS Title: Transition Regions of PMS and Pleiades-Age Stars Authors: Linsky, J. Bibcode: 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 Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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 Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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 Bibcode: 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. Bibcode: 1998pnge.conf..285L Altcode: No abstract at ADS Title: Dynamics, Winds and Structure in Cool Stars Authors: Linsky, J. L. Bibcode: 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 Bibcode: 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 & 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 Bibcode: 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. Bibcode: 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. Bibcode: 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 < 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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 < 0.6 and α < 2. The latter upper limit corresponds to a limit on the LISM magnetic field of B < 5 μG. These results imply that the plasma Mach number of the interstellar wind flowing into the heliosphere is MA > 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. Bibcode: 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. Bibcode: 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 Bibcode: 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 Bibcode: 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. Bibcode: 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. Bibcode: 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 <~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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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 Bibcode: 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 Bibcode: 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 Bibcode: 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 Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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 Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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 Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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<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 Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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 > -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. Bibcode: 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. Bibcode: 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. Bibcode: 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, & 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. Bibcode: 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 Bibcode: 1996IAUS..168..529L Altcode: No abstract at ADS Title: Summary of IAU Symposium 176 Authors: Linsky, J. L. Bibcode: 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. Bibcode: 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. Bibcode: 1996IAUS..176..411D Altcode: No abstract at ADS Title: Steady Radio Emission from Stars: Observations and Emission Processes Authors: Linsky, J. L. Bibcode: 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. Bibcode: 1996ASPC...93..324L Altcode: 1996ress.conf..324L No abstract at ADS Title: Summary of Cool Stars 9 Authors: Linsky, J. L. Bibcode: 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. Bibcode: 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. Bibcode: 1996IAUS..176.....S Altcode: No abstract at ADS Title: Chromospheres of Coronal Stars Authors: Linsky, J. L.; Wood, B. E. Bibcode: 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 Bibcode: 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. Bibcode: 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 Bibcode: 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. Bibcode: 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 & 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)) > -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. Bibcode: 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: 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, B. E.; Alexander, W. R.; Linsky, J. L. Bibcode: 1995AAS...187.4502W Altcode: 1995BAAS...27.1347W We present new GHRS observations of the Lyman-alpha lines of epsilon Indi (K5 V) and lambda Andromedae (G8 IV-III + ?). 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 properties of the D I lines, unless the H I absorption is assumed to consist of two absorption components. For both lines of sight, one absorption component is produced by interstellar material, with velocities consistent with those predicted by the local flow vector. For the 3.46 pc (23 pc) line of sight to epsilon Ind (lambda And), the average density for the interstellar medium is found to be n_H I=0.094+/- 0.022 cm(-3) (n_H I=0.040+/- 0.014 cm(-3) ). We believe hot hydrogen surrounding epsilon Ind and lambda And is responsible for the second H I absorption component. These ``hydrogen walls'' are produced by the interaction of the winds of these stars with the surrounding interstellar material. An analogous solar hydrogen wall has been predicted by recent models of the heliospheric interface region and confirmed by GHRS observations of alpha Cen. The temperatures we measure for the second components are 100,000+/- 20,000 and 62,000+/- 18,000 K for epsilon Ind and lambda And, respectively. These temperatures are too hot for the solar hydrogen wall, and for epsilon Ind the velocity of the second component is clearly inconsistent with the solar hydrogen wall. Thus, we assume a stellar origin for these components, where the higher temperatures are a consequence of higher interstellar wind velocities in the stellar rest frames. Because the heliospheric models demonstrate the importance of a hot wind in the formation of the solar hydrogen wall, our detection of analogous structures around epsilon Ind and lambda And may constitute a first detection of solar-like winds around dwarf and subgiant stars. This work was sponsored by NASA Interagency Transfer S-56460-D to the National Institute of Standards and Technology 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 Bibcode: 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, M ∼ 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 M ∼ 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, M 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. Bibcode: 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 > 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. Bibcode: 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. Bibcode: 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 Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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 < 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 1994AAS...185.4501W Altcode: 1994BAAS...26.1379W Linsky & 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, & 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 ROSAT All-Sky Survey of Active Binary Coronae. I. Quiescent Fluxes for the RS Canum Venaticorum Systems: Erratum Authors: Dempsey, Robert C.; Linsky, Jeffrey L.; Fleming, Thomas A.; Schmitt, J. H. M. M. Bibcode: 1994ApJS...94..829D Altcode: No abstract at ADS 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. Bibcode: 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. Bibcode: 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. Bibcode: 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 Bibcode: 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. Bibcode: 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 (>= 10(7) K) plasma. This work is supported by NASA Grants NAG5-2259 & 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. Bibcode: 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. Bibcode: 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 & 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. Bibcode: 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. Bibcode: 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. Bibcode: 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 >= 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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 Bibcode: 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 Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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 Bibcode: 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. Bibcode: 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 Bibcode: 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 Bibcode: 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. Bibcode: 1994ASPC...64..690D Altcode: 1994csss....8..690D No abstract at ADS Title: Stellar Coronal Structures (Concluding Review) Authors: Linsky, J. L. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 1993AAS...183.1809B Altcode: 1993BAAS...25R1321B The TLUSTY model code of Hubeny & 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 Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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 Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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 Bibcode: 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 Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 1992ASPC...26..455D Altcode: 1992csss....7..455D No abstract at ADS Title: FUSE - The Far Ultraviolet Spectrograph Explorer Authors: Linsky, J. L. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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 Bibcode: 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 Bibcode: 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 Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 1991mcch.conf..166L Altcode: No abstract at ADS Title: Dynamics and Energy Balance in Stellar Transition Regions - AU MIC Authors: Linsky, Jeffrey Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 1990apsu.conf...17D Altcode: No abstract at ADS Title: A Three Dimensional Picture of RS CVN Stellar Atmospheres Authors: Linsky, Jeffrey L. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 1989BAAS...21Q.742L Altcode: 1989BAAS...21..742L No abstract at ADS Title: Solar and Stellar Magnetic Fields and Structures - Observations Authors: Linsky, Jeffrey L. Bibcode: 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. Bibcode: 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 <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. Bibcode: 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. Bibcode: 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. Bibcode: 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 & 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 1988Sci...241..991L Altcode: No abstract at ADS Title: Introductory remarks by the Panel Chairman Authors: Linsky, J. L. Bibcode: 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. Bibcode: 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 Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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 Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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 &Monitoring Techniques Authors: Linsky, J. L. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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 < 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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 Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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 Bibcode: 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. Bibcode: 1986LNP...254..275S Altcode: 1986csss....4..275S No abstract at ADS Title: Chromospheric & Coronal Heating for a Statistically Complete Sample of K Stars Authors: Linsky, Jeffrey L. Bibcode: 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. Bibcode: 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. Bibcode: 1986swpw.book.....G Altcode: No abstract at ADS Title: Concluding Session - Shirsog Workshop Authors: Linsky, J. L. Bibcode: 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. Bibcode: 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. Bibcode: 1986tswo.work..102L Altcode: No abstract at ADS Title: Ultraviolet Emission from Cool Stars with Measured Magnetic Fields Authors: Linsky, Jeffrey L. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 1985BAAS...17..879W Altcode: No abstract at ADS Title: Energy Balance in Stellar Coronae Authors: Linsky, J. L. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 1985BAAS...17..879S Altcode: No abstract at ADS Title: Mass Loss from Red Giants : Results from Ultraviolet Spectroscopy (Review) Authors: Linsky, J. L. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 1985BAAS...17..751S Altcode: No abstract at ADS Title: Beyond Lyman alpha - The new frontier in ultraviolet spectroscopy Authors: Linsky, J. L. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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 < 10,000K. Authors: Linsky, J. L. Bibcode: 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. Bibcode: 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. Bibcode: 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 Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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: Definition and empirical structure of the range of stellar chromospheres-coronae across the H-R diagram: cool stars. Authors: Linsky, J. L. Bibcode: 1985rbcc.conf...55L Altcode: Major advances in the understanding of non-radiative heating and other activity in stars cooler than Teff = 10000K has occurred in the last few years primarily as a result of the IUE and Einstein spacecraft, the VLA microwave facility, and new optical observing techniques. The author critically reviews this observational evidence and comments on the trends that are now becoming apparent. Title: Pannel discussion on radiative transfer methods. Authors: Kalkofen, W.; Linsky, J.; Rybicki, G.; Scharmer, G.; Weherse, R. Bibcode: 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. Bibcode: 1985ASIC..152..143F Altcode: 1985pssl.proc..143F No abstract at ADS Title: The Unique Eclipsing Binary System TZ Fornacis Authors: Linsky, Jeffrey L. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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 > 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. Bibcode: 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. Bibcode: 1984BAAS...16..895D Altcode: No abstract at ADS Title: Atmospheric Structures in AR Lac. I. Mapping Quiescent Features by Occultations &Doppler Imaging Authors: Walter, F. M.; Gibson, D. M.; Brown, A.; Carpenter, K.; Linsky, J. L.; Rodono, M.; Eyles, C. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 1984iue..prop.1841L Altcode: No abstract at ADS Title: Ultraviolet Study of the Chamaeleon T-Association Authors: Linsky, Jeffrey L. Bibcode: 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 Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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 Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 1984LNP...193..350D Altcode: 1984csss....3..350D No abstract at ADS Title: RS CVn Binary Systems Authors: Linsky, J. L. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 1983ApL....23..174G Altcode: No abstract at ADS Title: Mass Loss Rates for K-M Giants and Supergiants Authors: Linsky, Jeffrey L. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 1983IBVS.2258....1B Altcode: No abstract at ADS Title: Surface Structure of Eclipsing and Non-Eclipsing RS CVN Systems Authors: Linsky, Jeffrey L. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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 & Plages in by Draconis-Type Variable Stars Authors: Linsky, Jeffrey L. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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 Bibcode: 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. Bibcode: 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: 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. Bibcode: 1982IUE82......554M Altcode: No abstract at ADS Title: Expansion of the disturbing function by factorization Authors: Linsky, J. L. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 1982ApL....22...70L Altcode: No abstract at ADS Title: The structure and energy balance of cool star atmosphere. Authors: Linsky, J. L. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 1981BAAS...13..515A Altcode: No abstract at ADS Title: High-Resolution Studies of Arcturus with IUE &Einstein: A Sensitive Search for High-Temperature Emission Authors: Ayres, T. R.; Simon, T.; Linsky, J. L. Bibcode: 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. Bibcode: 1981BAAS...13..885B Altcode: No abstract at ADS Title: Stellar Chromosphere, Coronae and Winds: Present Status and Implications for Solar Astrophysics Authors: Linsky, J. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 1981AN....302..208G Altcode: No abstract at ADS Title: Winds in late-type stars - Mechanisms of mass outflow Authors: Linsky, J. L. Bibcode: 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. Bibcode: 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. Bibcode: 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 & k lines in evolved F8 to M5 stars. Authors: Stencel, R. E.; Mullan, D. J.; Basri, G. S.; Linsky, J. L. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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 Bibcode: 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. Bibcode: 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 Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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 Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 1980HiA.....5..861L Altcode: No abstract at ADS Title: Stellar chromospheres Authors: Linsky, J. L. Bibcode: 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. Bibcode: 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. Bibcode: 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 Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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 Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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 <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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 1979BAAS...11..471H Altcode: No abstract at ADS Title: Capella: 1/2 of an RS CVn? Authors: Ayres, T. R.; Linsky, J. L. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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 < 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 1978BAAS...10..647L Altcode: No abstract at ADS Title: Model Chromospheres for Supergiants: A Progress Report Authors: Basri, G. S.; Linsky, J. L. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 1975BAAS....7..469C Altcode: No abstract at ADS Title: Flare Model Chromospheres and Photospheres Authors: Machado, M. E.; Linsky, J. L. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 1975BAAS....7..359A Altcode: No abstract at ADS Title: Flare Model Chromospheres and Photospheres Authors: Machado, M. E.; Linsky, J. L. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 1973BAAS....5..453H Altcode: No abstract at ADS Title: A Model for the Chromosphere of Arcturus. Authors: Ayres, T. R.; Linsky, J. L. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 1973BAAS....5..364A Altcode: No abstract at ADS Title: A Model for the Chromosphere of Arcturus. Authors: Ayres, T. R.; Linsky, J. L. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 1972JQSRT..12..777L Altcode: No abstract at ADS Title: The Solar H and K Lines Authors: Linsky, Jeffrey L.; Avrett, Eugene H. Bibcode: 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. Bibcode: 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. Bibcode: 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¦ > 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. Bibcode: 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. Bibcode: 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. Bibcode: 1969BAAS....1..372L Altcode: No abstract at ADS Title: H3+, An Important Missing Continuous Opacity Source in the Sun Authors: Linsky, Jeffrey L. Bibcode: 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. Bibcode: 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. Bibcode: 1969BAAS....1Q.285L Altcode: No abstract at ADS Title: A Recalibration of Solar Millimeter Brightness Temperatures Based upon Lunar Observations Authors: Linsky, Jeffrey L. Bibcode: 1969BAAS....1S.284L Altcode: No abstract at ADS Title: Toward a Self-Consistent Interpretation of the Calcium Lines Authors: Linsky, J. L. Bibcode: 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. Bibcode: 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 < τ5000 < 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. Bibcode: 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 Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 1967lts..conf..291G Altcode: No abstract at ADS Title: Surface temperatures in late-type model atmospheres Authors: Linsky, J. Bibcode: 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 Bibcode: 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 Bibcode: 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. Bibcode: 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. Bibcode: 1965nls..conf..185I Altcode: No abstract at ADS