baliunas

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Author name code: baliunas
ADS astronomy entries on 2022-09-14
author:"Baliunas, Sallie"

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Title: Magnetic and Rotational Evolution of ρ CrB from
Asteroseismology with TESS
Authors: Metcalfe, Travis S.; van Saders, Jennifer L.; Basu, Sarbani;
Buzasi, Derek; Drake, Jeremy J.; Egeland, Ricky; Huber, Daniel; Saar,
Steven H.; Stassun, Keivan G.; Ball, Warrick H.; Campante, Tiago L.;
Finley, Adam J.; Kochukhov, Oleg; Mathur, Savita; Reinhold, Timo;
See, Victor; Baliunas, Sallie; Soon, Willie
2021ApJ...921..122M Altcode: 2021arXiv210801088M
During the first half of main-sequence lifetimes, the evolution
of rotation and magnetic activity in solar-type stars appears to be
strongly coupled. Recent observations suggest that rotation rates evolve
much more slowly beyond middle age, while stellar activity continues to
decline. We aim to characterize this midlife transition by combining
archival stellar activity data from the Mount Wilson Observatory
with asteroseismology from the Transiting Exoplanet Survey Satellite
(TESS). For two stars on opposite sides of the transition (88 Leo and
ρ CrB), we independently assess the mean activity levels and rotation
periods previously reported in the literature. For the less active star
(ρ CrB), we detect solar-like oscillations from TESS photometry, and
we obtain precise stellar properties from asteroseismic modeling. We
derive updated X-ray luminosities for both stars to estimate their
mass-loss rates, and we use previously published constraints on magnetic
morphology to model the evolutionary change in magnetic braking
torque. We then attempt to match the observations with rotational
evolution models, assuming either standard spin-down or weakened
magnetic braking. We conclude that the asteroseismic age of ρ CrB is
consistent with the expected evolution of its mean activity level and
that weakened braking models can more readily explain its relatively
fast rotation rate. Future spectropolarimetric observations across a
range of spectral types promise to further characterize the shift in
magnetic morphology that apparently drives this midlife transition in
solar-type stars.

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Title: How much has the Sun influenced Northern Hemisphere temperature
trends? An ongoing debate
Authors: Connolly, Ronan; Soon, Willie; Connolly, Michael; Baliunas,
Sallie; Berglund, Johan; Butler, C. John; Cionco, Rodolfo Gustavo;
Elias, Ana G.; Fedorov, Valery M.; Harde, Hermann; Henry, Gregory W.;
Hoyt, Douglas V.; Humlum, Ole; Legates, David R.; Lüning, Sebastian;
Scafetta, Nicola; Solheim, Jan-Erik; Szarka, László; van Loon,
Harry; Velasco Herrera, Víctor M.; Willson, Richard C.; Yan, Hong;
Zhang, Weijia
2021RAA....21..131C Altcode: 2021arXiv210512126C
In order to evaluate how much Total Solar Irradiance (TSI)
has influenced Northern Hemisphere surface air temperature
trends, it is important to have reliable estimates of both
quantities. Sixteen different estimates of the changes in TSI
since at least the 19th century were compiled from the
literature. Half of these estimates are "low variability" and half are
"high variability". Meanwhile, five largely-independent methods for
estimating Northern Hemisphere temperature trends were evaluated using:
1) only rural weather stations; 2) all available stations whether urban
or rural (the standard approach); 3) only sea surface temperatures; 4)
tree-ring widths as temperature proxies; 5) glacier length records as
temperature proxies. The standard estimates which use urban as well as
rural stations were somewhat anomalous as they implied a much greater
warming in recent decades than the other estimates, suggesting that
urbanization bias might still be a problem in current global temperature
datasets - despite the conclusions of some earlier studies. Nonetheless,
all five estimates confirm that it is currently warmer than the late
19th century, i.e., there has been some "global warming"
since the 19th century. For each of the five estimates
of Northern Hemisphere temperatures, the contribution from direct
solar forcing for all sixteen estimates of TSI was evaluated using
simple linear least-squares fitting. The role of human activity on
recent warming was then calculated by fitting the residuals to the UN
IPCC's recommended "anthropogenic forcings" time series. For all five
Northern Hemisphere temperature series, different TSI estimates suggest
everything from no role for the Sun in recent decades (implying that
recent global warming is mostly human-caused) to most of the recent
global warming being due to changes in solar activity (that is, that
recent global warming is mostly natural). It appears that previous
studies (including the most recent IPCC reports) which had prematurely
concluded the former, had done so because they failed to adequately
consider all the relevant estimates of TSI and/or to satisfactorily
address the uncertainties still associated with Northern Hemisphere
temperature trend estimates. Therefore, several recommendations on how
the scientific community can more satisfactorily resolve these issues
are provided.

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Title: The Evolution of Rotation and Magnetic Activity in 94 Aqr Aa
from Asteroseismology with TESS
Authors: Metcalfe, Travis S.; van Saders, Jennifer L.; Basu, Sarbani;
Buzasi, Derek; Chaplin, William J.; Egeland, Ricky; Garcia, Rafael
A.; Gaulme, Patrick; Huber, Daniel; Reinhold, Timo; Schunker, Hannah;
Stassun, Keivan G.; Appourchaux, Thierry; Ball, Warrick H.; Bedding,
Timothy R.; Deheuvels, Sébastien; González-Cuesta, Lucía; Handberg,
Rasmus; Jiménez, Antonio; Kjeldsen, Hans; Li, Tanda; Lund, Mikkel N.;
Mathur, Savita; Mosser, Benoit; Nielsen, Martin B.; Noll, Anthony;
Çelik Orhan, Zeynep; Örtel, Sibel; Santos, Ângela R. G.; Yildiz,
Mutlu; Baliunas, Sallie; Soon, Willie
2020ApJ...900..154M Altcode: 2020arXiv200712755M
Most previous efforts to calibrate how rotation and magnetic activity
depend on stellar age and mass have relied on observations of clusters,
where isochrones from stellar evolution models are used to determine the
properties of the ensemble. Asteroseismology employs similar models to
measure the properties of an individual star by matching its normal
modes of oscillation, yielding the stellar age and mass with high
precision. We use 27 days of photometry from the Transiting Exoplanet
Survey Satellite to characterize solar-like oscillations in the G8
subgiant of the 94 Aqr triple system. The resulting stellar properties,
when combined with a reanalysis of 35 yr of activity measurements
from the Mount Wilson HK project, allow us to probe the evolution of
rotation and magnetic activity in the system. The asteroseismic age
of the subgiant agrees with a stellar isochrone fit, but the rotation
period is much shorter than expected from standard models of angular
momentum evolution. We conclude that weakened magnetic braking may be
needed to reproduce the stellar properties, and that evolved subgiants
in the hydrogen shell-burning phase can reinvigorate large-scale dynamo
action and briefly sustain magnetic activity cycles before ascending
the red giant branch.

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Title: Waldmeier Effect in Stellar Cycles
Authors: Garg, Suyog; Karak, Bidya Binay; Egeland, Ricky; Soon,
Willie; Baliunas, Sallie
2019ApJ...886..132G Altcode: 2019arXiv190912148G
One of the most robust features of the solar magnetic cycle is that
the stronger cycles rise faster than the weaker ones. This is popularly
known as the Waldmeier Effect, which has been known for more than 100
yr. This fundamental feature of the solar cycle has not only practical
implications, e.g., in predicting the solar cycle, but also implications
in understanding the solar dynamo. Here we ask whether the Waldmeier
Effect exists in other Sun-like stars. To answer this question, we
analyze the Ca II H and K S-index from Mount Wilson Observatory for
21 Sun-like G-K stars. We specifically check two aspects of Waldmeier
Effect, namely, (1) WE1: the anticorrelation between the rise times
and the peaks and (2) WE2: the positive correlation between rise rates
and amplitudes. We show that, except for HD 16160, HD 81809, HD 155886,
and HD 161239, all stars considered in the analysis show WE2, while WE1
is found to be present only in some of the stars studied. Furthermore,
the WE1 correlation is weaker than the WE2. Both WE1 and WE2 exist in
the solar S-index as well. Similar to the solar cycles, the magnetic
cycles of many stars are asymmetric about their maxima. The existence of
the Waldmeier Effect and asymmetric cycles in Sun-like stars suggests
that the dynamo mechanism which operates in the Sun is also operating
in other stars.

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Title: Covariations of chromospheric and photometric variability of
the young Sun analogue HD 30495: evidence for and interpretation of
mid-term periodicities
Authors: Soon, W.; Velasco Herrera, V. M.; Cionco, R. G.; Qiu, S.;
Baliunas, S.; Egeland, R.; Henry, G. W.; Charvátová, I.
2019MNRAS.483.2748S Altcode: 2018MNRAS.tmp.3133S
This study reports the synchronization between the chromospheric and
photometric variability at time-scale of about 1.6-1.8 yr as observed
for the young, rapidly rotating solar analogue HD 30495. In addition,
HD 30495 may be presenting evidence of surface differential rotation
at time-scales of about 11 d and 21 d, as well as the sunspot-like
decadal cycles at 11-12 yr or so. We apply a new gapped wavelet method
of time-frequency analysis for studying the variability in a new
composite of the chromospheric S-index (1967-2018) and the longest
photometric Δ(b + y)/2 index (1993-2018). We discuss and interpret
our results in relation to other observed mid-term periodicities
roughly of the same time-scales that had been found recently from not
only chromospheric and photospheric activity indices but also from
coronal X-ray emissions as observed in a considerably large set of
stellar samples including those young Sun analogues from the Kepler
satellite project. Thus, there is an apparent universality of such
mid-term activity modulation time-scales as this solar-stellar magnetic
phenomenon is well observed directly for a host of solar activity
related indices covering the photopsheric, chromospheric, coronal,
and even the heliospheric (utilizing the measures of incoming galactic
cosmic rays as a probe of activity variations) activity records. This
is why we made a further attempt to interpret the results in search of
a realistic generation mechanism as well as spatio-temporal persistency
of the phenomenon under a wide scenario of dynamo simulations.

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Title: Evolution of Long Term Variability in Solar Analogs
Authors: Egeland, Ricky; Soon, Willie; Baliunas, Sallie; Hall,
Jeffrey C.; Henry, Gregory W.
2017IAUS..328..329E Altcode: 2017arXiv170402388E
Earth is the only planet known to harbor life, therefore we may
speculate on how the nature of the Sun-Earth interaction is relevant
to life on Earth, and how the behavior of other stars may influence the
development of life on their planetary systems. We study the long-term
variability of a sample of five solar analog stars using composite
chromospheric activity records up to 50 years in length and synoptic
visible-band photometry about 20 years long. This sample covers a
large range of stellar ages which we use to represent the evolution in
activity for solar mass stars. We find that young, fast rotators have an
amplitude of variability many times that of the solar cycle, while old,
slow rotators have very little variability. We discuss the possible
impacts of this variability on young Earth and exoplanet climates.

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Title: VizieR Online Data Catalog: Calibrated solar S-index time
series (Egeland+, 2017)
Authors: Egeland, R.; Soon, W.; Baliunas, S.; Hall, J. C.; Pevtsov,
A. A.; Bertello, L.
2017yCat..18350025E Altcode:
The Mount Wilson HK Program observed the Moon with both the HKP-1
and HKP-2 instruments. After removing 11 obvious outliers, there
are 162 HKP-1 observations taken from 1966 September 2 to 1977 June
4 with the Mount Wilson 100 inch reflector, covering the maximum
of cycle 20 and the cycle 20-21 minimum. As mentioned in Baliunas+
(1995ApJ...438..269B), observations of the Moon resumed in 1993 with
the HKP-2 instrument. After removing 10 obvious outliers, there are 75
HKP-2 observations taken from 1994 March 27 to 2002 November 23 with
the Mount Wilson 60 inch reflector, covering the end of cycle 22 and
the cycle 23 minimum, extending just past the cycle 23 maximum. The
end of observations coincides with the unfortunate termination of
the HK Project in 2003. We seek to extend our time series of
solar variability beyond cycle 23 by establishing a proxy to the
NSO Sacramento Peak (NSO/SP) observations taken from 1976 to 2016,
covering cycles 21 to 24. The spectral intensity scale is set by
integrating a 0.53Å band centered at 3934.869Å in the K-line wing
and setting it to the fixed value of 0.162. We extend the S-index
record back to cycle 20 using the composite K time series of Bertello+
(2016SoPh..291.2967B). See section 3 for further explanations. (1
data file).

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Title: The Mount Wilson Observatory S-index of the Sun
Authors: Egeland, Ricky; Soon, Willie; Baliunas, Sallie; Hall,
Jeffrey C.; Pevtsov, Alexei A.; Bertello, Luca
2017ApJ...835...25E Altcode: 2016arXiv161104540E
The most commonly used index of stellar magnetic activity is the
instrumental flux scale of singly ionized calcium H &amp; K line
core emission, S, developed by the Mount Wilson Observatory (MWO)
HK Project, or the derivative index {R}{HK}\prime
. Accurately placing the Sun on the S scale is important for
comparing solar activity to that of the Sun-like stars. We present
previously unpublished measurements of the reflected sunlight from
the Moon using the second-generation MWO HK photometer during solar
cycle 23 and determine cycle minimum {S}23,\min =0.1634+/-
0.0008, amplitude {{Δ }}{S}23=0.0143+/- 0.0012, and mean
&lt; {S}23&gt; =0.1701+/- 0.0005. By establishing a proxy
relationship with the closely related National Solar Observatory
Sacramento Peak calcium K emission index, itself well correlated with
the Kodaikanal Observatory plage index, we extend the MWO S time series
to cover cycles 15-24 and find on average &lt; {S}\min &gt;
=0.1621+/- 0.0008, &lt; {{Δ }}{S}{cyc}&gt; =0.0145+/-
0.0012, &lt; {S}{cyc}&gt; =0.1694+/- 0.0005. Our measurements
represent an improvement over previous estimates that relied on stellar
measurements or solar proxies with non-overlapping time series. We
find good agreement from these results with measurements by the
Solar-Stellar Spectrograph at Lowell Observatory, an independently
calibrated instrument, which gives us additional confidence that we
have accurately placed the Sun on the S-index flux scale.

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Title: Dynamo Sensitivity In Solar Analogs With 50 Years Of Ca II
H &amp; K Activity
Authors: Egeland, Ricky; Soon, Willie; Baliunas, Sallie; Hall,
Jeffrey C.; Pevtsov, Alexei A.; Henry, Gregory W.
2016csss.confE...6E Altcode: 2016csss.confE..73E; 2016arXiv160904756E
The Sun has a steady 11-year cycle in magnetic activity most well-known
by the rising and falling in the occurrence of dark sunspots on the
solar disk in visible bandpasses. The 11-year cycle is also manifest
in the variations of emission in the Ca II H &amp; K line cores, due to
non-thermal (i.e. magnetic) heating in the lower chromosphere. The large
variation in Ca II H &amp; K emission allows for study of the patterns
of long-term variability in other stars thanks to synoptic monitoring
with the Mount Wilson Observatory HK photometers (1966-2003) and Lowell
Observatory Solar-Stellar Spectrograph (1994-present). Overlapping
measurements for a set of 27 nearby solar-analog (spectral types G0-G5)
stars were used to calibrate the two instruments and construct time
series of magnetic activity up to 50 years in length. Precise properties
of fundamental importance to the dynamo are available from Hipparcos,
the Geneva-Copenhagen Survey, and CHARA interferometry. Using these
long time series and measurements of fundamental properties, we do
a comparative study of stellar "twins" to explore the sensitivity
of the stellar dynamo to small changes to structure, rotation, and
composition. We also compare this sample to the Sun and find hints
that the regular periodic variability of the solar cycle may be rare
among its nearest neighbors in parameter space.

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Title: The Solar Dynamo Zoo
Authors: Egeland, Ricky; Soon, Willie; Baliunas, Sallie; Hall,
Jeffrey C.; Pevtsov, Alexei A.; Henry, Gregory W.
2016csss.confE..72E Altcode:
We present composite time series of Ca II H &amp; K line core emission
indices of up to 50 years in length for a set of 27 solar-analog stars
(spectral types G0-G5; within 10% of the solar mass) and the Sun. These
unique data are available thanks to the long-term dedicated efforts
of the Mount Wilson Observatory HK project, the Lowell Observatory
Solar-Stellar Spectrograph, and the National Solar Observatory/Air Force
Research Laboratory/Sacramento Peak K-line monitoring program. The Ca II
H &amp; K emission originates in the lower chromosphere and is strongly
correlated with the presence of magnetic plage regions in the Sun. These
synoptic observations allow us to trace the patterns long-term magnetic
variability and explore dynamo behavior over a wide range of rotation
regimes and stellar evolution timescales.In this poster, the Ca HK
observations are expressed using the Mount Wilson S-index. Each time
series is accompanied by a Lomb-Scargle periodogram, fundemental stellar
parameters derived from the Geneva-Copenhagen Survey, and statistics
derived from the time series including the median S-index value and
seasonal and long-term amplitudes. Statistically significant periodogram
peaks are ranked according to a new cycle quality metric. We find that
clear, simple, Sun-like cycles are the minority in this sample.

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Title: Magnetic cycles at different ages of stars
Authors: Oláh, K.; Kővári, Zs.; Petrovay, K.; Soon, W.; Baliunas,
S.; Kolláth, Z.; Vida, K.
2016A&A...590A.133O Altcode: 2016arXiv160406701O
 Aims: We study the different patterns of interannual magnetic
variability in stars on or near the lower main sequence, approximately
solar-type (G-K dwarf) stars in time series of 36 yr from the Mount
Wilson Observatory Ca II H&amp;K survey. Our main aim is to search
for correlations between cycles, activity measures, and ages. Methods: Time-frequency analysis has been used to discern and
reveal patterns and morphology of stellar activity cycles, including
multiple and changing cycles, in the datasets. Both the results from
short-term Fourier transform and its refinement using the Choi-Williams
distribution, with better frequency resolution, are presented in this
study. Rotational periods of the stars were derived using multifrequency
Fourier analysis. Results: We found at least one activity cycle
on 28 of the 29 stars we studied. Twelve stars, with longer rotational
periods (39.7 ± 6.0 days), have simple smooth cycles, and the remaining
stars, with much faster rotation (18.1 ± 12.2 days) on average, show
complex and sometimes vigorously changing multiple cycles. The cycles
are longer and quite uniform in the first group (9.7 ± 1.9 yr), while
they are generally shorter and vary more strongly in the second group
(7.6 ± 4.9). The clear age division between stars with smooth and
complex cycles follows the known separation between the older and
younger stars at around 2 to 3 Gyr of age.

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Title: Dynamo Sensitivity in Solar Analogs with 50 Years of Ca II
H &amp; K Activity
Authors: Egeland, Ricky; Soon, Willie H.; Baliunas, Sallie L.; Hall,
Jeffrey C.; Pevtsov, Alexei A.; Henry, Gregory W.
2016SPD....4720307E Altcode:
The Sun has a steady 11-year cycle in magnetic activity most well-known
by the rising and falling in the occurrence of dark sunspots on the
solar disk in visible bandpasses. The 11-year cycle is also manifest
in the variations of emission in the Ca II H &amp; K line cores, due to
non-thermal (i.e. magnetic) heating in the lower chromosphere. The large
variation in Ca II H &amp; K emission allows for study of the patterns
of long-term variability in other stars thanks to synoptic monitoring
with the Mount Wilson Observatory HK photometers (1966-2003) and Lowell
Observatory Solar-Stellar Spectrograph (1994-present). Overlapping
measurements for a set of 27 nearby solar-analog (spectral types G0-G5)
stars were used to calibrate the two instruments and construct time
series of magnetic activity up to 50 years in length. Precise properties
of fundamental importance to the dynamo are available from Hipparcos,
the Geneva-Copenhagen Survey, and CHARA interferometry. Using these
long time series and measurements of fundamental properties, we do
a comparative study of stellar "twins" to explore the sensitivity
of the stellar dynamo to small changes to structure, rotation, and
composition. We also compare this sample to the Sun and find hints
that the regular periodic variability of the solar cycle may be rare
among its nearest neighbors in parameter space.

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Title: The Solar Dynamo Zoo
Authors: Egeland, Ricky; Soon, Willie H.; Baliunas, Sallie L.; Hall,
Jeffrey C.; Pevtsov, Alexei A.; Henry, Gregory W.
2016SPD....47.1103E Altcode:
We present composite time series of Ca II H &amp; K line core emission
indices of up to 50 years in length for a set of 27 solar-analog stars
(spectral types G0-G5; within ~10% of the solar mass) and the Sun. These
unique data are available thanks to the long-term dedicated efforts
of the Mount Wilson Observatory HK project, the Lowell Observatory
Solar-Stellar Spectrograph, and the National Solar Observatory/Air Force
Research Laboratory/Sacremento Peak K-line monitoring program. The
Ca II H &amp; K emission originates in the lower chromosphere and is
strongly correlated with the presence of magnetic plage regions in
the Sun. These synoptic observations allow us to trace the patterns
long-term magnetic variability and explore dynamo behavior over a wide
range of rotation regimes and stellar evolution timescales.

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Title: Wilson, Olin Chaddock, Jr.
Authors: Baliunas, Sallie
2014bea..book.2351B Altcode:
No abstract at ADS

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Title: Rotation periods of exoplanet host stars
Authors: Simpson, E. K.; Baliunas, S. L.; Henry, G. W.; Watson, C. A.
2010MNRAS.408.1666S Altcode: 2010arXiv1006.4121S; 2010MNRAS.tmp.1209S
The stellar rotation periods of 10 exoplanet host stars have been
determined using newly analysed CaII H&amp;K flux records from the
Mount Wilson Observatory and Strömgren b, y photometric measurements
from Tennessee State University's automatic photometric telescopes
at the Fairborn Observatory. Five of the rotation periods have not
previously been reported, with that of HD 130322 very strongly detected
at Prot = 26.1 +/- 3.5 d. The rotation periods of five other
stars have been updated using new data. We use the rotation periods
to derive the line-of-sight inclinations of the stellar rotation axes,
which may be used to probe theories of planet formation and evolution
when combined with the planetary orbital inclination found from other
methods. Finally, we estimate the masses of 14 exoplanets under the
assumption that the stellar rotation axis is aligned with the orbital
axis. We calculate the mass of HD 92788 b (28 MJ) to be
within the low-mass brown dwarf regime and suggest that this object
warrants further investigation to confirm its true nature.

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Title: Differential rotation of some HK-Project stars and the
butterfly diagrams
Authors: Katsova, M. M.; Livshits, M. A.; Soon, W.; Baliunas, S. L.;
Sokoloff, D. D.
2010NewA...15..274K Altcode:
We analyze the long-term variability of the chromospheric radiation of
20 stars monitored in the course of the HK-Project at the Mount Wilson
Observatory. We apply the modified wavelet algorithm for this set of
gapped time series. Besides the mean rotational periods for all these
stars, we find reliable changes of the rotational periods from year to
year for a few stars. Epochs of slower rotation occur when the activity
level of the star is high, and the relationship repeats again during
the next maximum of an activity cycle. Such an effect is traced in two
stars with activity cycles that are not perfectly regular (but labeled
"Good" under the classification in [Baliunas, S.L., Donahue, R.A.,
Soon, W.H., Horne, J.H., Frazer, J., Woodard-Eklund, L., Bradford, M.,
Rao, L.M., Wilson, O.C., Zhang, Q. et al., 1995. ApJ 438, 269.]) but
the two stars have mean activity levels exceed that of the Sun. The
averaged rotational period of HD 115404 is 18.5 days but sometimes
the period increases up to 21.5 days. The sign of the differential
rotation is the same as the Sun's, and the value ΔΩ / &lt; Ω &gt; =
- 0.14. For the star HD 149661, this ratio is -0.074. Characteristic
changes of rotational periods occur over around three years when the
amplitude of the rotational modulation is large. These changes can
be transformed into latitude-time butterfly diagrams with minimal a
priori assumptions. We compare these results with those for the Sun
as a star and conclude that epochs when surface inhomogeneities rotate
slower are synchronous with the reversal of the global magnetic dipole.

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Title: Multiple and changing cycles of active stars. II. Results
Authors: Oláh, K.; Kolláth, Z.; Granzer, T.; Strassmeier, K. G.;
Lanza, A. F.; Järvinen, S.; Korhonen, H.; Baliunas, S. L.; Soon,
W.; Messina, S.; Cutispoto, G.
2009A&A...501..703O Altcode: 2009arXiv0904.1747O
Aims: We study the time variations in the cycles of 20 active stars
based on decade-long photometric or spectroscopic observations. Methods: A method of time-frequency analysis, as discussed in a
companion paper, is applied to the data. Results: Fifteen stars
definitely show multiple cycles, but the records of the rest are too
short to verify a timescale for a second cycle. The cycles typically
show systematic changes. For three stars, we found two cycles in each
of them that are not harmonics and vary in parallel, indicating a
common physical mechanism arising from a dynamo construct. The positive
relation between the rotational and cycle periods is confirmed for the
inhomogeneous set of active stars. Conclusions: Stellar activity
cycles are generally multiple and variable.

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Title: Inter-Division IX-X-XI Working Group Astronomy from The Moon
Authors: Baliunas, Sallie L.; Kondo, Yoji; Kaifu, Norio; Engvold,
Oddbjørn; Kaifu, Norio; Okuda, Haruyuki; Terzian, Yervant
2009IAUTA..27..356B Altcode:
During the period the Working Group had proposed and was granted renewed
status by Division XI Space and High-Energy Astrophysics. Additionally
the Working Group requested to be extended to Division IX Optical and
Infrared Techniques, Division X Radio Astronomy, as well as Division XI.

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Title: Long-Term Spectroscopic Monitoring of Arcturus
Authors: Brown, Kevin I. T.; Gray, David F.; Baliunas, Sallie L.
2008ApJ...679.1531B Altcode:
We evaluate observed spectroscopic activity of Arcturus (HR 5340,
K2 III) from 1984 to 2007 using high-resolution spectroscopy and
Ca II H+K emission. Line-depth ratios of the V I λ6251.83 Å to
Fe I λ6252.56 Å lines and line bisectors from Fe I λ6252.56 Å
are used to evaluate spectroscopic activity. Chromospheric emission
within H+K lines is used as a magnetic activity indicator. We observe
a significant portion of what appears to be a magnetic cycle with a
period of &gt;=14 yr. Line-depth ratios show comparable variation, but
with a time lag of 2.0 +/- 0.5 yr with respect to H+K variations. This
time lag is qualitatively similar to previous observations of G and K
dwarfs. No corresponding variation is observed in line bisectors. H+K
and line bisectors also show variability within seasons. A Fourier
analysis reveals periods of 253 and 207 days during the 1984-1989 H+K
seasons. Line bisectors show excess power over the range of ≈115-200
days from 1992 to 2007. We attribute this intraseason variability
to inferred magnetic activity along active longitudes. The range
of periods observed in H+K and line bisectors (≈115-253 days)
may result from migration of active regions within longitude bands,
implying differential rotation. We compare these observations with the
Sun and other solar-type stars. A 1/f noise component to the Fourier
spectrum of the line bisector variations is also observed.

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Title: Changing stellar activity cycles
Authors: Oláh, K.; Strassmeier, K. G.; Granzer, T.; Soon, W.;
Baliunas, S. L.
2007AN....328.1072O Altcode:
We investigated continuous long-term photometric datasets of thirteen
active stars, Ca II variability of one single main-sequence star, and
10.7cm radio data of the Sun, with simple Fourier- and time-frequency
analysis. The data reflect the strength of the activity manifested
in magnetic spots. All studied stars show multiple (2 to 4) cycles of
different lengths. The time-frequency analysis reveals, that in several
cases of the sample one or two of the cycles exhibit continuous changes
(increase or decrease). For four stars (V711 Tau, IL Hya, HK Lac,
HD 100180) and for the Sun we find that the cycle length changes are
strong, amounting to 10-50% during the observed time intervals. The
cycle lengths are generally longer for stars with longer rotational
periods.

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Title: Division XI / Wg: Astronomy from the Moon
Authors: Baliunas, Sallie L.; Kondo, Yoji; Kaifu, Norio; Engvold,
Oddbjorn; Kaifu, Norio; Okuda, Haruyuki; Terzian, Yervant; Wamsteker,
Willem
2007IAUTB..26..208B Altcode:
The Business Meeting opened with a recall of the memory of a member of
the Organizing Committee, Willem Wamsteker. N. Kaifu, past president
of the Working Group, was thanked for his outstanding service.

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Title: Patterns of Photometric and Chromospheric Variation among
Sun-like Stars: A 20 Year Perspective
Authors: Lockwood, G. W.; Skiff, B. A.; Henry, Gregory W.; Henry,
Stephen; Radick, R. R.; Baliunas, S. L.; Donahue, R. A.; Soon, W.
2007ApJS..171..260L Altcode: 2007astro.ph..3408L
We examine patterns of variation of 32 primarily main-sequence Sun-like
stars [selected at project onset as stars on or near the main sequence
and color index 0.42&lt;=(B-V)&lt;=1.4], extending our previous 7-12
yr time series to 13-20 yr by combining Strömgren b, y photometry from
Lowell Observatory with similar data from Fairborn Observatory. Parallel
chromospheric Ca II H and K emission data from the Mount Wilson
Observatory span the entire interval. The extended data strengthen
the relationship between chromospheric and brightness variability at
visible wavelengths derived previously. We show that the full range of
photometric variation has probably now been observed for a majority of
the program stars. Twenty-seven stars are deemed variable according
to an objective statistical criterion. On a year-to-year timescale,
young active stars become fainter when their Ca II emission increases,
while older less active stars such as the Sun become brighter when
their Ca II emission increases. The Sun's total irradiance variation,
scaled to the b and y stellar filter photometry, still appears to be
somewhat smaller than stars in our limited sample with similar mean
chromospheric activity, but we now regard this discrepancy as probably
due mainly to our limited stellar sample.

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Title: Coronal activity cycles in 61 Cygni
Authors: Hempelmann, A.; Robrade, J.; Schmitt, J. H. M. M.; Favata,
F.; Baliunas, S. L.; Hall, J. C.
2006A&A...460..261H Altcode:
Context: .While the existence of stellar analogues of the 11 years
solar activity cycle is proven for dozens of stars from optical
observations of chromospheric activity, the observation of clearly
cyclical coronal activity is still in its infancy. Aims: .In
this paper, long-term X-ray monitoring of the binary 61 Cygni is used
to investigate possible coronal activity cycles in moderately active
stars. Methods: .We are monitoring both stellar components, a K5V
(A) and a K7V (B) star, of 61 Cyg with XMM-Newton. The first four years
of these observations are combined with ROSAT HRI observations of an
earlier monitoring campaign. The X-ray light curves are compared with
the long-term monitoring of chromospheric activity, as measured by the
Mt.Wilson CaII H+K S-index. Results: .Besides the observation
of variability on short time scales, long-term variations of the X-ray
activity are clearly present. For 61 Cyg A we find a coronal cycle
which clearly reflects the well-known and distinct chromospheric
activity cycle. The changes of coronal properties during the cycle
resemble the solar behaviour. The coronal activity of 61 Cyg B also
follows the chromospheric variability, although a pronounced sinusoidal
chromospheric cycle of large amplitude is not noticeable. This is also
reflected in the XMM-Newton observations with a rather complex long-term
variability during that time. Conclusions: .61 Cyg A is the
first star where a persistent coronal activity cycle has been observed.

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Title: Investigating the Rotation Periods of Exoplanet Host Stars
Authors: Simpson, Elaine K.; Baliunas, S.; Henry, G.
2006AAS...20915201S Altcode: 2006BAAS...38.1105S
Of approximately 200 exoplanet host stars, we investigate a
subset of fifty whose fluxes in the Ca II H and K passbands and
b and y photometric passbands have been measured and in several
cases, accumulated over a period of years or longer. The Ca II
records from Mount Wilson Observatory's HK Project and highly precise
photometric measurements from Tennessee State University's Automated
Photoelectric Telescopes at Fairborn Observatory detail variability of
surface magnetic features, leading in some cases to a direct measurement
of periodicities thought to be associated with rotation. We discuss
findings of rotation in the context of surface magnetic activity,
its interannual variability, age and other physical properties of the
star. As possible we infer inclination of the stellar rotation axis
and its influence on exoplanet detection methods. This work has
been supported by NASA grant JPL-1270064.

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Title: The Extrasolar Planet ɛ Eridani b Orbit and Mass
Authors: Benedict, George F.; McArthur, B. E.; Gatewood, G.; Nelan,
E.; Cochran, W.; Hatzes, A.; Endl, M.; Wittenmyer, R.; Baliunas, S.;
Walker, G.; Yang, S.; Kurster, M.; Els, S.; Paulson, D.
2006DPS....38.1009B Altcode: 2006BAAS...38.1294B
Hubble Space Telescope (HST) Fine Guidance Sensor astrometric
observations of the nearby (3.22 pc), K2 V star epsilon Eridani have
been combined with ground-based astrometric and radial velocity data
to determine the mass of its known companion. We model astrometric and
radial velocity measurements simultaneously to obtain the parallax,
proper motion, perturbation period, perturbation inclination,
and perturbation size. Due to the long period of the companion,
epsilon Eridani b, we extend our astrometric coverage to a total
of 14.94 years (including the three year span of the HST data) by
including lower-precision ground-based astrometry from the Allegheny
Multichannel Astrometric Photometer. Radial velocity coverage now spans
1980.8 -2006.3. We obtain a perturbation period, P = 6.85 ± 0.03
yr, semi-major axis α =1.88 ± 0.20 mas, and inclination i = 30.1
± 3.8°. This inclination is consistent with a previously measured
dust disk inclination (Greaves et al. 2005), demonstrating dust disk
and exoplanet co-planarity for the first time. Co-planarity is an
expected consequence of planet formation theories. Assuming a primary
mass M* = 0.83 MΟ, we obtain a companion mass
M = 1.55 ± 0.24MJup. Given the relatively young age of
epsilon Eridani ( 800 Myr), this accurate exoplanet mass and orbit
can usefully inform future direct imaging attempts. We predict the
next periastron at 2007.3 with a total separation, ρ = 0.3” at
position angle, p.a. = 27°. Orbit orientation and geometry dictate
that epsilon Eridani b will appear brightest in reflected light very
nearly at periastron. Radial velocities spanning over 25 years indicate
an acceleration consistent with a Jupiter-mass object with a period in
excess of 50 years, possibly the object responsible for one prominent
feature of the dust morphology, the inner cavity. We gratefully
acknowledge NASA Grants GO-09167, -09347, -09969, -10610, and 10989.

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Title: A Survey of Chromospheric Activity in the Solar-Type Stars
in the Open Cluster M67
Authors: Giampapa, Mark S.; Hall, Jeffrey C.; Radick, Richard R.;
Baliunas, Sallie L.
2006ApJ...651..444G Altcode: 2006astro.ph..7313G
We present the results of a spectroscopic survey of the Ca II H and K
core strengths in a sample of 60 solar-type stars that are members of
the solar-age and solar-metallicity open cluster M67. We adopt the HK
index, defined as the summed H+K core strengths in 1 Å bandpasses
centered on the H and K lines, respectively, as a measure of the
chromospheric activity that is present. We compare the distribution of
mean HK index values for the M67 solar-type stars with the variation
of this index as measured for the Sun during the contemporary solar
cycle. We find that the stellar distribution in our HK index is broader
than that for the solar cycle. Approximately 17% of the M67 Sun-like
stars exhibit average HK indices that are less than solar minimum. About
7%-12% are characterized by relatively high activity in excess of solar
maximum values, while 72%-80% of the solar analogs exhibit Ca II H+K
strengths within the range of the modern solar cycle. The ranges given
reflect uncertainties in the most representative value of the maximum
in the HK index to adopt for the solar cycle variations observed
during the period AD 1976-2004. Thus, ~20%-30% of our homogeneous
sample of Sun-like stars have mean chromospheric H+K strengths that
are outside the range of the contemporary solar cycle. Any cycle-like
variability that is present in the M67 solar-type stars appears to be
characterized by periods greater than ~6 yr. Finally, we estimate a mean
chromospheric age for M67 in the range of 3.8-4.3 Gyr. The results
presented herein are based on data obtained at the WIYN telescope and
at the McMath-Pierce Solar Telescope. The WIYN Observatory is a joint
facility of the University of Wisconsin-Madison, Indiana University,
Yale University, and the National Optical Astronomy Observatory. The
McMath-Pierce Solar Telescope Facility is operated by the National
Solar Observatory for the National Science Foundation. This paper is
WIYN Open Cluster Study XXVIII in the series.

---------------------------------------------------------
Title: The Extrasolar Planet ɛ Eridani b: Orbit and Mass
Authors: Benedict, G. Fritz; McArthur, Barbara E.; Gatewood, George;
Nelan, Edmund; Cochran, William D.; Hatzes, Artie; Endl, Michael;
Wittenmyer, Robert; Baliunas, Sallie L.; Walker, Gordon A. H.; Yang,
Stephenson; Kürster, Martin; Els, Sebastian; Paulson, Diane B.
2006AJ....132.2206B Altcode: 2006astro.ph.10247B
Hubble Space Telescope (HST) observations of the nearby (3.22 pc) K2
V star ɛ Eridani have been combined with ground-based astrometric and
radial velocity data to determine the mass of its known companion. We
model the astrometric and radial velocity measurements simultaneously
to obtain the parallax, proper motion, perturbation period,
perturbation inclination, and perturbation size. Because of the
long period of the companion, ɛ Eri b, we extend our astrometric
coverage to a total of 14.94 yr (including the 3 yr span of the
HST data) by including lower precision ground-based astrometry
from the Allegheny Multichannel Astrometric Photometer. Radial
velocities now span 1980.8-2006.3. We obtain a perturbation period,
P=6.85+/-0.03 yr, semimajor axis α=1.88+/-0.20 mas, and inclination
i=30.1d+/-3.8d. This inclination is consistent with a previously
measured dust disk inclination, suggesting coplanarity. Assuming
a primary mass M*=0.83 Msolar, we obtain a
companion mass M=1.55MJ+/-0.24MJ. Given the
relatively young age of ɛ Eri (~800 Myr), this accurate exoplanet
mass and orbit can usefully inform future direct-imaging attempts. We
predict the next periastron at 2007.3 with a total separation ρ=0.3"
at position angle P.A.=-27deg. Orbit orientation and geometry
dictate that ɛ Eri b will appear brightest in reflected light very
nearly at periastron. Radial velocities spanning over 25 yr indicate
an acceleration consistent with a Jupiter-mass object with a period
in excess of 50 yr, possibly responsible for one feature of the dust
morphology, the inner cavity. 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 NAS5-26555.

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Title: Decadal and Interdecadal Surface Magnetic Variability of
Sunlike and Other Cool Stars
Authors: Baliunas, S. L.
2006IAUJD...8E..65B Altcode:
Cross sectional and time serial surveys of disk-integrated proxies
of surface magnetic features in cool stars - those with non-trivial
subsurface convection zones - have yielded information on stellar
magnetic variability, which may express in one or more modes. For
example, decadal magnetic variability is present on the sun and some
lower-main sequence stars. Additionally, evidence for interdecadal
magnetic variability, for instance, the solar Maunder Minimum of the
17^th century and first noted in the parameter of Sunspot Number,
may also be present. Surface magnetic variability may be viewed as
an expression of the action of a dynamo within or just below the
convective zone that produces large-scale dynamo waves. Consequences
for dynamo models will be discussed, based primarily on results from
the near-four-decades-long monitoring program of Ca II H and K emission
fluxes of lower main sequence stars at Mount Wilson Observatory, the
precision photometry made at Lowell and Fairborn Observatory-Tennessee
State University, and solar modulation imprinted in terrestrial
ecosystems..

---------------------------------------------------------
Title: Anharmonic and standing dynamo waves: theory and observation
of stellar magnetic activity
Authors: Baliunas, S.; Frick, P.; Moss, D.; Popova, E.; Sokoloff,
D.; Soon, W.
2006MNRAS.365..181B Altcode: 2005MNRAS.tmp.1044B
The familiar decadal cycle of solar activity is one expression of
interannual variability of surface magnetism observed in stars on or
near the lower main sequence. From studies of time-series of CaII
H and K emission fluxes that go back more than 35 yr and have been
accumulated for such stars at the Mount Wilson Observatory by the HK
Project, we define a quantitative measure, called anharmonicity, of
the cyclic component of interannual magnetic variability. Anharmonicity
provides a connection between observed variations in magnetic activity
and the two-dimensional description of a Parker dynamo model. We
explore the parameter space of the Parker dynamo model and find an
excellent counterpart in the records of several of the lowest-mass
(late K-type to early M-type) active stars in the HK Project sample to
the solutions containing highly anharmonic, standing dynamo waves. We
interpret anharmonicity apparent in the records as resulting from
non-propagating or standing dynamo waves, which operate in a regime that
is substantially supercriticial. There, for the majority of a cycle, or
pulse of decadal-to-interdecadal variability, the large-scale magnetic
fields are generated and maintained by winding of field by differential
rotation rather than by the joint action of differential rotation and
helical convection. Among the less active stars (the Sun is considered
such a star in the HK Project sample) we find a correspondence between
anharmonicity and Parker dynamo model solutions that include simple
harmonic, migratory and/or intermediate-type dynamo wave patterns over
a broad range of dynamo parameters.

---------------------------------------------------------
Title: VizieR Online Data Catalog: Ca II H and K Measurements Made
at MWO (Duncan+ 1991)
Authors: Duncan, D. K.; Vaughan, A. H.; Wilson, O. C.; Preston,
G. W.; Frazer, J.; Lanning, H. H.; Misch, A.; Mueller, J.; Soyumer,
D.; Woodard, L.; Baliunas, S. L.; Noyes, R. W.; Hartmann, L. W.;
Porter, A.; Zwaan, K.; Middelkoop, F.; Rutter, R.; Mihalas, D.
2005yCat.3159....0D Altcode:
Summaries are presented of the photoelectric measurements of stellar
CaII H and K line intensity made at Mount Wilson Observatory during
the years 1966-1983. These results are derived from 65,263 individual
observations of 1296 stars. For each star, for each observing season,
the maximum, minimum, mean, and variation of the instrumental H and
K index "S" are given, as well as a measurement of the accuracy of
observation. A total of 3110 seasonal summaries are reported. These
observations were obtained with two instruments, HKP-1 and HKP-2. The
HKP-2 instrument is a four-channel chopping spectrometer which records
counts in 1.09{AA} FWHM triangular bandpasses centered in the H and
K lines as well as in two 20{AA} reference bandpasses centered on
3901.067 and 4001.067{AA}. The stellar activity is expressed by the
index S defined as S = {alpha} (Nh+Nk)/(Nr+Nv) where Nh and
Nk are the counts (corrected from background) in the H and K lines,
Nr and Nv those in the reference continuum bandpasses, and {alpha}
is a constant of proportionality used to correct for night-to-night
instrumental variations. Higher values of S generally correspond to
higher levels of chromospehric activities. Factors which effect the
ability to detect stellar activity variations and accurately measure
their amplitudes such as the accuracy of the H and K measurements and
scattered light contamination are discussed. Relations are given which
facilitate intercomparison of "S" values with residual intensities
from ordinary spectrophotometry, and for converting measurements to
absolute fluxes. (1 data file).

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Title: Anharmonicity of Stellar Cycles: A Wavelet Quantification
Authors: Baliunas, S.; Frick, P.; Moss, D.; Popova, E.; Sokoloff,
D.; Soon, W.
2004SoPh..224..179B Altcode: 2005SoPh..224..179B
Two quantitative measures for the anharmonicity of stellar cycles,
as recorded in the Ca II H and K chromospheric activity data as well
as in simple dynamo models, are presented and discussed.

---------------------------------------------------------
Title: Time-spectra of chromospheric activity of old solar-type stars:
detection of rotational signals from double wavelet analysis
Authors: Frick, Peter; Soon, Willie; Popova, Elena; Baliunas, Sallie
2004NewA....9..599F Altcode:
We introduce a novel technique, called the double wavelet analysis
(DWA), for the determination of stellar rotation periods from time
serial data. This first paper aims narrowly at the discussion,
introduction and application of the DWA technique to records
of surface magnetism in solar-type (relatively old) lower main
sequence stars that are obtained by the Mount Wilson Observatory
(MWO) HK Project. The technique takes a series of careful steps
that seek to optimize wavelet parameters and normalization schemes,
ultimately allowing fine-tuned, arguably more accurate, estimates of
rotation-modulated signals (with, e.g., periods of days to months)
in records that contain longer periodicities such as stellar magnetic
activity cycles (with, e.g., period of years). The apparent rotation
periods estimated from the DWA technique are generally consistent
with results from both ;first-pass; (i.e., ordinary) global wavelet
spectrum and earlier classical periodogram analyses. But there are
surprises as well. For example, the rotation period of the ancient
subdwarf Goombridge 1830 (HD 103095), previously identified as ≈31
days, suggests under the DWA technique a significantly slower period
of 60 days. DWA spectra also generally reveal a shift in the cycle
period toward high frequencies (hence shorter periods) compared to
the first-pass wavelet spectrum. For solar-type stars analyzed here,
the character of the DWA spectrum and slope of the first-pass global
wavelet spectrum produce a classification scheme that allows a star's
record to be placed into one of three categories.

---------------------------------------------------------
Title: A Comparison of Solar Irradiance Variations with those of
Similar Stars
Authors: Lockwood, G. W.; Radick, R. R.; Henry, G. W.; Baliunas, S. L.
2004AAS...204.0304L Altcode: 2004BAAS...36..671L
The photometric variations of Sun-like stars, including one bona
fide “solar twin," HD146233 = 18 Sco, have been observed at Lowell
Observatory and Fairborn Observatory in b and y filters of the
uvby photometric system over the past 3-18 years. Parallel HK flux
measurements were made at the Mount Wilson Observatory. Thirty five
stars observed at Lowell and Fairborn for more than a decade combined
define a power law relationship of variability as a function of
mean chromopsheric activity. On this diagram, the Sun lies 3x lower
than stars of similar chromospheric activity. Restricting the sample
to stars observed only at Fairborn but for a shorter length of time
reduces the discrepancy to less than a factor of two. Nevertheless,
the Sun still lies below a fitted power law. We will present an
analysis of the various biases possibly present in our data and show
some example light curves. This work was supported by the National
Science Foundation, the National Aeronautics and Space Administration,
and the Air Force Office of Scientific Research.

---------------------------------------------------------
Title: Stellar magnetic cycles
Authors: Baliunas, S. L.
2004AAS...204.3603B Altcode: 2004BAAS...36..707B
Is hope for understanding the solar magnetic cycle to be found
in stars? Observations of stars with significant sub-surface
convective zones -- masses smaller than about 1.5 solar masses on the
lower main sequence and many types of cool, post-main-sequence stars
-- indicate the presence of surface and atmospheric inhomogeneities
analogous to solar magnetic features, making stellar magnetic
activity a cosmically widespread phenomenon. Observations have been
made primarily in visible wavelengths, and important information has
also been derived from the ultraviolet and x-ray spectrum regions. Interannual to interdecadal variability of spectrum indicators
of stellar magnetic features is common, and in some cases similar
in appearance to the 11-year sunspot cycle. Successful models
of the physical processes responsible for stellar magnetic cycles,
typically cast as a magnetohydrodynamic dynamo, require advances
in understanding not only convection but also the magnetic field's
interaction with it. The observed facts that underpin the hope for
models will be summarized. Properties of stellar magnetic cycles will
be compared and contrasted with those of the sun, including inferences
from paleo-environmental reservoirs that contain information on
solar century- to millennial-scale magnetic variability. Partial
support of this research came from NASA NAG5-7635, NRC COBASE, CRDF 322,
MIT-MSG 5710001241, JPL 1236821, AF 49620-02-1-0194, Richard Lounsberry
Foundation, Langley-Abbot, Rollins, Scholarly Studies and James Arthur
Funds (Smithsonian Institution) and several generous individuals.

---------------------------------------------------------
Title: Stellar Magnetic Activity, the Earth and Exoplanets: How
Future Space Missions Can Contribute to Understanding Solar Activity
and Solar-terrestrial Influences
Authors: Baliunas, S. L.; Soon, W. W. -H.
2004AAS...204.0809B Altcode: 2004BAAS...36..790B
The solar spectral and particle output varies over time scales of
minutes to eons; some of those variations are documented or claimed
to have influenced the terrestrial environment. The origins of solar
variability include the progress of fusion through time and the complex
interaction of the interior gas and magnetic fields. The Mount Wilson
HK Project has yielded information on stellar magnetic activity
on more than 2,000 stars going as far back as 38 years in order to
put solar magnetic activity in a physical perspective unavailable
from theory and models alone. We discuss how future space missions
like Space Interferometry Mission (SIM) and Stellar Imager (SI) would
contribute to understanding solar variability that has influenced -- and
should continue to influence -- life and the environment on earth. This research funded in part by MIT-MSG 5710001241, JPL 1236821, AF
49620-02-1-0194, a grant from NASA HQ and GSFC to SAO for the SI Vision
Mission Study, NASA NAG5-7635, NRC COBASE, CRDF 322, Richard Lounsberry
Foundation, Langley-Abbot, Rollins, Scholarly Studies and James Arthur
Funds (Smithsonian Institution) and several generous individuals.

---------------------------------------------------------
Title: High-amplitude, long-term X-ray variability in the solar-type
star HD 81809: The beginning of an X-ray activity cycle?
Authors: Favata, F.; Micela, G.; Baliunas, S. L.; Schmitt, J. H. M. M.;
Güdel, M.; Harnden, F. R., Jr.; Sciortino, S.; Stern, R. A.
2004A&A...418L..13F Altcode: 2004astro.ph..3142F
We present the initial results from our XMM-Newton program aimed at
searching for X-ray activity cycles in solar-type stars. HD 81809 is
a G2-type star (somewhat more evolved than the Sun, and with a less
massive companion) with a pronounced 8.2 yr chromospheric cycle,
as evident from from the Mt. Wilson program data. We present here
the results from the initial 2.5 years of XMM-Newton observations,
showing that large amplitude (a factor of ≃10) modulation is present
in the X-ray luminosity, with a clearly defined maximum in mid 2002
and a steady decrease since then. The maximum of the chromospheric
cycle took place in 2001; if the observed X-ray variability is the
initial part of an X-ray cycle, this could imply a phase shift between
chromospheric and coronal activity, although the current descent into
chromospheric cycle minimum is well reflected into the star's X-ray
luminosity. The observations presented here provide clear evidence
for the presence of large amplitude X-ray variability coherent with
the activity cycle in the chromosphere in a star other than the Sun.

---------------------------------------------------------
Title: Estimation and representation of long-term (&gt;40 year) trends
of Northern-Hemisphere-gridded surface temperature: A note of caution
Authors: Soon, Willie W. -H.; Legates, David R.; Baliunas, Sallie L.
2004GeoRL..31.3209S Altcode: 2004GeoRL..3103209S
Several quantitative estimates of surface instrumental temperature
trends in the late 20th century are compared by using published
results and our independent analyses. These estimates highlight a
significant sensitivity to the method of analysis, the treatment of
data, and the choice of data presentation (i.e., size of the smoothing
filter window). Providing an accurate description of both quantitative
uncertainties and sensitivity to the treatment of data is recommended
as well as avoiding subjective data-padding procedures.

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Title: Variability in a Large Sample of Sun-Like Stars
Authors: Fekel, F. C.; Henry, G. W.; Baliunas, S. L.; Donahue, R. A.
2004IAUS..219..269F Altcode: 2003IAUS..219E.168F
At Fairborn Observatory we have observed a sample of about 350
nearby late-F to early-K dwarfs and subgiants of various ages. In
particular over half of the sample are G0--G5 dwarfs. For up to a decade
photometric obervations have been obtained with a nightly precision of
0.001 mag and 0.0001 mag for yearly means. Complimentary high-dispersion
spectra obtained at Kitt Peak National Observatory have been used
to determine spectral types radial velocities projected rotational
velocities and estimate metallicities for the stars in the sample. The
photometric results will be examined in the context of contemporaneous
Mt. Wilson Observatory measurements of chromospheric emission a proxy
for magnetic activity. Preliminary results on short-term and long-term
light variability will be discussed. The Sun's position in this stellar
sample will be examined.

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Title: The Variability of Sunlike Stars on Decadal Timescales
Authors: Radick, R. R.; Lockwood, G. W.; Henry, G. W.; Baliunas, S. L.
2004IAUS..219..264R Altcode: 2003IAUS..219E.214R
Thirty-four stars similar to the Sun have been monitored in
chromospheric Ca II HK emission since 1966 from Mount Wilson Observatory
and in Strömgren b and y photometry between 1984-2000 from Lowell
Observatory and since 1993 from Fairborn Observatory. We have just
completed an updated analysis of these time series in which we have
successfully merged the Lowell and Fairborn data. We find that the
precision per observation of these two photometric datasets is almost
identical although the Fairborn observations are considerably more
plentiful. Overall our results confirm what we published previously
(Radick et al. 1998 ApJ Suppl 118 239): the Sun's variability pattern
is not uncommon among sunlike stars. The Sun's current behavior however
may be unusually regular - many of the stars in our sample vary more
erratically than the Sun. We also encounter stars whose chromospheric
and photometric ouputs appear to be uncoupled - one varying but not the
other. Finally we continue to find examples of stars with time-averaged
chromospheric emission levels comparable to that of the present-day Sun
but photometric amplitudes several times larger. Such ""ill-behaved""
stars may be telling us about activity patterns that deviate from the
""standard"" solar model.

---------------------------------------------------------
Title: View from the mountaintop
Authors: Baliunas, Sallie
2003Ast....31i..60B Altcode:
Mount Wilson Observatory offers astronomers some of the best seeing
anywhere.

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Title: Evidence for coronal activity cycles on 61 Cygni A and B
Authors: Hempelmann, A.; Schmitt, J. H. M. M.; Baliunas, S. L.;
Donahue, R. A.
2003A&A...406L..39H Altcode:
We investigate a four-and-one-half year time-series of ROSAT HRI
pointed observations of 61 Cyg A and B and compare the X-ray light
curves with the chromospheric Ca HK variability. The ROSAT sampling
rate was two pointings per year and typical errors lie in the range
of 5-10%. The chromospheric cycles are well-known for both stars from
the Mt. Wilson Ca HK survey. Although the time basis of our ROSAT
observations is shorter than the 7-and 12-year cycles of components A
and B, respectively, we find the long-term trend of coronal activity in
close correlation with the chromospheric activity during the observation
period, between 1993 and 1998. The chromospheric activity increased
through maximum activity down to a minimum for component A, and from
maximum to minimum activity for component B. The same behaviour is
observed for the X-ray light curves but with much higher amplitudes
by factors 2.5-3. The remaining scatter observed around low-order
regression curves of coronal activity is small. We conclude that both
stars do show coronal cycles and that coronal cycles are the dominant
source of variability for 61 Cygni.

---------------------------------------------------------
Title: Chromospheric Activity in Solar-Type Stars
Authors: Giampapa, M. S.; Hall, J. C.; Radick, R. R.; Baliunas, S. L.
2003SPD....34.0710G Altcode: 2003BAAS...35..821G
We present an update on the results of a survey of chromospheric
activity in the solar-age and solar-metallicity open cluster, M67. The
objective of the survey is to gain insight on the potential range of
amplitudes of the solar cycle through observations of solar analogs
that are presumably at random phases in their cycles of magnetic
activity. We find that there is a significant overlap of the levels
of Ca II H and K emission in the sun-like stars in M67 with the
range of activity seen in the contemporary solar cycle. However,
there are also stars that exhibit levels of activity outside of this
range, including stars that are "super-solar" in their Ca II H and
K emission. The implications of these results will be discussed. The data presented in this investigation were obtained with the
WIYN 3.5-m telescope on Kitt Peak. The WIYN Observatory is a joint
facility of the University of Wisconsin-Madison, Indiana University,
Yale University, and the NOAO. The NSO and the NOAO are operated by
AURA for the National Science Foundation.

---------------------------------------------------------
Title: Multispectral analysis of asteroid 3 Juno taken with the
100-inch telescope at Mount Wilson Observatory
Authors: Baliunas, Sallie; Donahue, Robert; Rampino, Michael R.;
Gaffey, Michael J.; Shelton, J. Christopher; Mohanty, Subhanjoy
2003Icar..163..135B Altcode:
High-resolution multispectral images of main-belt asteroid 3 Juno
were taken at visible and near-IR wavelengths with the 100-inch
telescope at Mount Wilson Observatory equipped with an adaptive optics
system. The images show spectral features that may represent a large
relatively recent impact that deeply excavated the coarse-grained
olivine-pyroxene-rich crust of the asteroid.

---------------------------------------------------------
Title: Photometric and Chromospheric Variability of Sun-Like Stars
Authors: Lockwood, G. W.; Radick, R. R.; Henry, G. W.; Baliunas, S. L.
2003AAS...202.3213L Altcode: 2003BAAS...35..745L
By merging Stromgren b and y photometry of a sample of 34 Sun-like
stars measured at the Lowell Observatory and Fairborn Observatory we
can now compare 18 years of photometric data with parallel measurements
of chromospheric activity from the Mount Wilson HK program. Nearly
doubling the length of the 7-11 year time series discussed previously
(Radick et al. 1998, ApJS 118, 239; Lockwood et al. 1992 Nature 360,
653) firms up the statistical significance of previously noted patterns
of variation. The full range of variability has probably now been
observed for most stars in our sample. Stellar brightness and
chromospheric variations follow fairly tight power law relations with
respect to mean chromospheric activity. Both diminish with decreasing
mean chromospheric activity (or increasing stellar age). The Sun's
chromospheric variability lies slightly above the mean stellar power
law, but its brightness variations (less than 0.1% over the 11-year
solar cycle) appear somewhat low compared with stars of similar activity
levels. Stellar brightness variations are negatively or positively
correlated with chromospheric variations depending on mean chromospheric
activity, The Sun lies close to the dividing line. A few stars appear
to violate the general pattern.

---------------------------------------------------------
Title: Theories of solar eruptions: a review
Authors: Lin, J.; Soon, W.; Baliunas, S. L.
2003NewAR..47...53L Altcode:
This review highlights current theoretical research on eruptive
phenomena in the solar atmosphere. We start by looking back upon the
early theories and their development. Any theory and model of solar
eruptions must explain two key aspects of eruption physics. The first
aspect concerns the original cause of the eruption and the second
pertains to the nature of the morphological features that form during
its evolution. Those features include rapid ejection of large-scale
magnetic flux and plasma into interplanetary space, and the separating
of ribbons of H α emission on the solar disk joined by a rising arcade
of soft X-ray and H α loops, with hard X-ray emission at their summits
and feet. We intercompare relevant theories and models by discussing
their advantages as well as by pointing out important aspects that
need improvement.

---------------------------------------------------------
Title: Proxy climatic and environmental changes of the past 1000 years
Authors: Soon, W.; Baliunas, S. L.
2003ClRe...23...89S Altcode:
No abstract at ADS

---------------------------------------------------------
Title: Reconstructing climatic and environmental changes of the past
1000 years: A reappraisal
Authors: Soon, W.; Baliunas, S. L.; Idso, C.; Idso, S.; Legates, D.
2003En&En..14..233S Altcode:
No abstract at ADS

---------------------------------------------------------
Title: Global warming
Authors: Soon, W.; Baliunas, S. L.
2003PrPhG..27..448S Altcode:
No abstract at ADS

---------------------------------------------------------
Title: A False Planet around HD 192263
Authors: Henry, Gregory W.; Donahue, Robert A.; Baliunas, Sallie L.
2002ApJ...577L.111H Altcode:
We present new high-precision Strömgren photometry and Ca II H and K
spectrophotometry of HD 192263. Based on radial velocity variations
detected previously by two groups, this K2 V star was thought to
host a 0.75 MJup (minimum mass) planetary companion
in a 24 day orbit. Our photometric observations reveal periodic
variations that match the purported planetary orbital period, while
the Ca II H and K emission fluxes are modulated on half the planetary
period. This suggests that rotational modulation of the visibility of
stellar surface activity is the source of the observed radial velocity
variations. Therefore, HD 192263 should be removed from lists of stars
with well-established planetary companions unless further observations
and analysis can support the existence of the planet in spite of the
star's intrinsic variations.

---------------------------------------------------------
Title: Gauging the Sun: Comparative photometric and magnetic activity
measurements of sunlike stars, 1984-2001
Authors: Lockwood, G. W.; Hall, J. C.; Skiff, B. A.; Henry, G. W.;
Radick, R. R.; Baliunas, S. L.; Soon, W.; Donahue, R. A.
2002AAS...200.0709L Altcode: 2002BAAS...34..651L
Visible light photometric observations of a small sample of
sunlike stars with mean chromospheric activity levels similar to or
slightly lower than the Sun's suggest that total solar irradiance
variations on activity cycle timescales may be comparatively small
(Lockwood et al. 1992, Nature 360, 653; Radick et al. 1998, ApJS 118,
239). The Sun's irradiance variation over the past two cycles is
0.04% rms compared with 0.1% rms for the stellar sample measured at
Lowell from 1984 to 1995. This assertion can now be tested using new
photometric measurements from Fairborn Observatory automated telescopes
(1993-2001) that extend the duration of stellar observations to 17
years. Chromospheric activity measurements for these stars come from
the Mount Wilson HK program (1966-2001) and the Lowell Observatory
Solar Stellar Spectrograph program (1993-2001). In this presentation
we will describe efforts to merge the overlapping Lowell and Fairborn
photometry and the Mt. Wilson and Lowell HK measurements with the
goal of reducing the uncertainties in previous efforts to characterize
stellar photometric variations near the limit of detection.

---------------------------------------------------------
Title: Sources of solar variability responsibile for global warming
of the upper ocean on decadal period scales
Authors: White, W.; Dettinger, M.; Soon, W.; Baliunas, S.
2002cosp...34E1318W Altcode: 2002cosp.meetE1318W
Global-average warming and cooling of upper ocean temperature on decadal
period scales of ~0.1 K are aligned with decadal changes in the SunSs
irradiance of ~0.5 W m-2 throughout the 20th Century at lags ranging
from 0 to 18 months. This apparent upper ocean temperature response
to solar forcing is ~3 times that expected from the Stefan-Boltzmann
radiation balance for the EarthSs surface. Yet, this global-average
temperature change is a small residual in the spatial integration
of relatively large temperature changes of O(1.0 K) associated with
a global pattern of variability that is similar to that of the El
Nino-Southern Oscillation (Tourre et al., 2001). Since the latter
exhibits global-average warming and cooling of 0.2 K in the absence
of solar forcing (White et al., 2001), the SunSs decadal signal
needs simply to excite this particular decadal mode in the EarthSs
ocean-atmosphere-terrestrial system in order to produce the observed
global-average temperature change. The question is, by what mechanism
does it do this? Here we examine the global-average diabatic heat
storage budget for the upper ocean on decadal period scales using the
NCEP/NCAR atmospheric reanalysis and the SIO oceanic reanalysis. First,
we find the global-average variability dominated by the tropical
global-average. Second, we find the peak tropical warm phase associated
with higher troposphere moisture content and cloud fraction, driven
by an increase in outgoing sensible-plus-latent heat flux and
outgoing longwave-minusshortwave radiative heat flux of comparable
magnitudes. The sources of the anomalous warming tendency during the
onset phase is the reduction in the net poleward Ekman heat flux out
of the tropics and the reduction in outgoing sensible-plus-latent
heat flux of similar magnitude, both in response to reduced trade
wind intensity. Thus, the increase in cloud fraction during the peak
tropical warm phase does not heat the underlying ocean, as assumed
by Marsh and Svensmark (2000). Rather, the reduction in trade wind
intensity during the onset phase is consistent with that simulated
by Haigh (1996) in response to heating of the lower stratosphere by
the UV portion of the total solar irradiance spectrum. Here we find
a slow downward propagation of zonal wind anomalies from the lower
stratosphere to the lower troposphere contributing to this reduction
in trade wind intensity.

---------------------------------------------------------
Title: Global warming
Authors: Baliunas, S.
2002WTGSB..41....4B Altcode:
No abstract at ADS

---------------------------------------------------------
Title: Extrasolar Planet Inferometric Survey (EPIcS)
Authors: Shao, Michael; Baliunas, Sallie; Boden, Andrew; Kulkarni,
Shrinivas; Lin, Douglas N. C.; Loredo, Tom; Queloz, Didier; Shaklan,
Stuart; Tremaine, Scott; Wolszczan, Alexander
2002swsi.conf....7S Altcode:
No abstract at ADS

---------------------------------------------------------
Title: Reply to Comments on "Modeling climatic effects of
anthropogenic CO2 emissions: Unknowns and uncertainties
Authors: Risbey, James; Soon, W.; Baliunas, S.; Idso, S. B.;
Kondratyev, K. Ya.; Posmentier, E. S.
2002ClRe...22..187R Altcode:
No abstract at ADS

---------------------------------------------------------
Title: The scientific case against catastrophic global warming and
the Kyoto Protocol
Authors: Baliunas, S.; Macrae, A.; Patterson, T.
2002PPEGG..30...20B Altcode:
No abstract at ADS

---------------------------------------------------------
Title: No planet for HD 166435
Authors: Queloz, D.; Henry, G. W.; Sivan, J. P.; Baliunas, S. L.;
Beuzit, J. L.; Donahue, R. A.; Mayor, M.; Naef, D.; Perrier, C.;
Udry, S.
2001A&A...379..279Q Altcode: 2001astro.ph..9491Q
The G0 V star HD 166435 has been observed by the fiber-fed spectrograph
ELODIE as one of the targets in the large extra-solar planet survey
that we are conducting at the Observatory of Haute-Provence. We
detected coherent, low-amplitude, radial-velocity variations with
a period of 3.7987 days, suggesting a possible close-in planetary
companion. Subsequently, we initiated a series of high-precision
photometric observations to search for possible planetary transits
and an additional series of Ca II H and K observations to measure
the level of surface magnetic activity and to look for possible
rotational modulation. Surprisingly, we found the star to be
photometrically variable and magnetically active. A detailed study
of the phase stability of the radial-velocity signal revealed that
the radial-velocity variability remains coherent only for durations
of about 30 days. Analysis of the time variation of the spectroscopic
line profiles using line bisectors revealed a correlation between radial
velocity and line-bisector orientation. All of these observations, along
with a one-quarter cycle phase shift between the photometric and the
radial-velocity variations, are well explained by the presence of dark
photospheric spots on HD 166435. We conclude that the radial-velocity
variations are not due to gravitational interaction with an orbiting
planet but, instead, originate from line-profile changes stemming
from star spots on the surface of the star. The quasi-coherence of the
radial-velocity signal over more than two years, which allowed a fair
fit with a binary model, makes the stability of this star unusual among
other active stars. It suggests a stable magnetic field orientation
where spots are always generated at about the same location on the
surface of the star.

---------------------------------------------------------
Title: Modeling climatic effects of anthropogenic CO2 emissions:
Unknows and uncerta inties
Authors: Soon, W.; Baliunas, S.; Demirchan, K. S.; Idso, S. B.;
Kondratyev, K. Ya.; Posmentier, E. S.
2001ClRe...18..259S Altcode:
No abstract at ADS

---------------------------------------------------------
Title: Global Climate Change: Conceptual Aspects, 2001
Authors: Kondratyev, K. Ya.; Adamenko, V. N.; Demirchian, K. S.;
Baliunas, S.; Boehmer-Christiansen, S.; Idso, S. B.; Kukla, G.;
Posmentier, E. S.; Soon, W.
2001rass.rept.....K Altcode:
No abstract at ADS

---------------------------------------------------------
Title: The impact of anthropogenic CO2 emissions: Unknows and
uncertainties
Authors: Soon, W.; Baliunas, S.; Demirchan, K. S.; Idso, S. B.;
Kondratyev, K. Ya.; Posmentier, E. S.
2001PRGS..133....1S Altcode:
No abstract at ADS

---------------------------------------------------------
Title: Evidence for a Long-Period Planet Orbiting ɛ Eridani
Authors: Hatzes, Artie P.; Cochran, William D.; McArthur, Barbara;
Baliunas, Sallie L.; Walker, Gordon A. H.; Campbell, Bruce; Irwin,
Alan W.; Yang, Stephenson; Kürster, Martin; Endl, Michael; Els,
Sebastian; Butler, R. Paul; Marcy, Geoffrey W.
2000ApJ...544L.145H Altcode: 2000astro.ph..9423H
High-precision radial velocity (RV) measurements spanning the years
1980.8-2000.0 are presented for the nearby (3.22 pc) K2 V star ɛ
Eri. These data, which represent a combination of six independent
data sets taken with four different telescopes, show convincing
variations with a period of ~7 yr. A least-squares orbital solution
using robust estimation yields orbital parameters of period P=6.9
yr, velocity amplitude K=19 m s-1, eccentricity e=0.6,
projected companion mass Msini=0.86 MJupiter, and semimajor
axis a2=3.4 AU. Ca II H and K S-index measurements spanning
the same time interval show significant variations with periods of
3 and 20 yr yet none at the RV period. If magnetic activity were
responsible for the RV variations, then it produces a significantly
different period than is seen in the Ca II data. Given the lack of Ca
II variation with the same period as that found in the RV measurements,
the long-lived and coherent nature of these variations, and the high
eccentricity of the implied orbit, Keplerian motion due to a planetary
companion seems to be the most likely explanation for the observed RV
variations. The wide angular separation of the planet from the star
(approximately 1") and the long orbital period make this planet a
prime candidate for both direct imaging and space-based astrometric
measurements. Based on observations collected at McDonald Observatory,
Lick Observatory, European Southern Observatory at La Silla, and the
Canada-France-Hawaii Telescope.

---------------------------------------------------------
Title: The Curious case of the carbon forest source
Authors: Baliunas, S.; Soon, W.
2000WCRp....6f...3B Altcode:
No abstract at ADS

---------------------------------------------------------
Title: Searching for Global oscillations of Jupiter
Authors: Murphy, N.; Smith, E. J.; Rogers, W.; Gillam, S.; Rosner,
R.; Baliunas, S.
2000DPS....32.6516M Altcode: 2000BAAS...32.1642M
The detection of global oscillations of Jupiter would lead to
significant advances in our understanding of giant planet internal
structure, analogous to the enormous increase in knowledge of the
sun's interior facilitated by helioseismology. In particular, the
frequencies of p-mode oscillations will be strongly affected by the
presence of density discontinuities and the planet's core size and
structure. While it is clear from previous observations that such
oscillations probably only exist with very small amplitudes, current
instrumentation may still be able to detect them. We will describe a
proposed experiment to detect (or place a firm upper amplitude limit on)
global p-mode oscillations of Jupiter, using a magneto-optical filter
on the Mt Wilson 100" telescope. We will describe the operation of the
instrument, present preliminary data and describe models of instrument
response which show that with 7 nights of data we can expect to detect
signals with amplitudes less than 20 cm/s.

---------------------------------------------------------
Title: Solar-Stellar Connection: Activity and Brightness Changes of
Solar-Type Stars
Authors: Baliunas, S.
2000eaa..bookE2237B Altcode:
The surface and outer atmosphere of the Sun are dominated by the
presence of localized magnetic fields. They influence the structure
of and energy transport through the solar atmosphere and wind,
outward to the distance of the heliopause (see SOLAR WIND: MAGNETIC
FIELD). In addition, the occurrence of the magnetic features varies
on characteristic time scales. Chief among them is the roughly 11 y...

---------------------------------------------------------
Title: Millennial climate
Authors: Baliunas, S.; Soon, W.
2000WCRp....6b...3B Altcode:
No abstract at ADS

---------------------------------------------------------
Title: 100000110011 (Computer Year 2099)
Authors: Baliunas, S.; Soon, W.
2000WCRp....5v...3B Altcode:
No abstract at ADS

---------------------------------------------------------
Title: Man vs. Milky Way revisited
Authors: Baliunas, S.; Soon, W.
2000WCRp....5s...3B Altcode:
No abstract at ADS

---------------------------------------------------------
Title: A Survey of Activity in the Solar-Type Stars in M67
Authors: Giampapa, M. S.; Radick, R. R.; Hall, J. C.; Baliunas, S. L.
2000SPD....3102120G Altcode: 2000BAAS...32..832G
We present an update on a long-term study of the solar-type stars in
the solar-age and solar-metallicity open cluster, M67. The primary
objective of this program is to gain insight on the possible range of
solar chromospheric activity and the associated, potential long-term
variability of the Sun through the observation of stellar analogs of
the Sun. Spectra in the Ca II H &amp; K line region of over 100 stars
in M67, including 76 `solar-type' stars (with unreddened colors in
the range +0.60 &lt;= B-V &lt;= +0.76) and 21 `solar-twins' (+0.63
&lt;= B-V &lt;= +0.67), were obtained with the 3.5-m WIYN telescope
on Kitt Peak in conjunction with the Hydra multi-fiber positioner
to perform multi-object spectroscopy over a 1 degree field. We find
that the distribution of chromospheric H&amp;K line strengths in
the solar-type stars is broader than the distribution of H&amp;K line
emission recorded in modern observations of the Sun, suggesting that the
potential excursion in the amplitude of the solar cycle is greater than
what we have seen so far in the contemporary record. Approximately 30%
of the solar-type stars in M67 exhibit levels of activity that are
outside the present envelope of solar activity. We interpret this to
mean that the Sun can be in a state of magnetic activity---either
exceptional quiescence similar to the Maunder-minimum episode or
enhanced activity---about 30% of the time. The authors gratefully
acknowledge both the NOAO Telescope Allocation Committee and the
WIYN Queue Program for their support of this investigation. The WIYN
Observatory is a joint facility of the University of Wisconsin-Madison,
Indiana University, Yale University, and the NOAO. The NSO and NOAO are
operated by AURA, Inc., under cooperative agreement with the National
Science Foundation.

---------------------------------------------------------
Title: Climate hypersensitivity to solar forcing?
Authors: Soon, W.; Posmentier, E.; Baliunas, S.
2000AnGeo..18..583S Altcode:
We compare the equilibrium climate responses of a quasi-dynamical
energy balance model to radiative forcing by equivalent changes in
CO2, solar total irradiance (Stot) and solar UV (SUV). The response is
largest in the SUV case, in which the imposed UV radiative forcing is
preferentially absorbed in the layer above 250 mb, in contrast to the
weak response from global-columnar radiative loading by increases in
CO2 or Stot. The hypersensitive response of the climate system to solar
UV forcing is caused by strongly coupled feedback involving vertical
static stability, tropical thick cirrus ice clouds and stratospheric
ozone. This mechanism offers a plausible explanation of the apparent
hypersensitivity of climate to solar forcing, as suggested by analyses
of recent climatic records. The model hypersensitivity strongly depends
on climate parameters, especially cloud radiative properties, but
is effective for arguably realistic values of these parameters. The
proposed solar forcing mechanism should be further confirmed using
other models (e.g., general circulation models) that may better capture
radiative and dynamical couplings of the troposphere and stratosphere.

---------------------------------------------------------
Title: The Trouble with Ozone
Authors: Baliunas, S.; Soon, W.
2000WCRp....5o...3B Altcode:
No abstract at ADS

---------------------------------------------------------
Title: Photometric and Ca II H and K Spectroscopic Variations in
Nearby Sun-like Stars with Planets. III.
Authors: Henry, Gregory W.; Baliunas, Sallie L.; Donahue, Robert A.;
Fekel, Francis C.; Soon, Willie
2000ApJ...531..415H Altcode:
We present the results of an analysis of time-series photometry, Ca
II H and K spectrophotometry, and high-dispersion visible spectra of
nine nearby Sun-like stars recently identified as having planets. For
the six stars whose presumed planets have orbital periods of less than
4 months (τ Boo, 51 Peg, υ And, ρ1 Cnc, ρ CrB, and 70
Vir), sine-curve fits to the photometric data show no variations with
semiamplitude greater than 1 or 2 parts in 104. Photometric
variations in 47 UMa are similarly small, although our photometric data
of this star are slightly affected by variability of the comparison
star. Nonvariability at this level of precision is sufficient to
rule out surface magnetic activity as the cause of the observed
radial-velocity variations in these seven stars and makes nonradial
pulsations unlikely as well. Thus, our photometry provides indirect
but strong support for true reflex motions-planets-in these seven
stars, but cannot yet so support the planetary hypothesis for the two
additional stars, 16 Cyg B and Gl 411. Continued photometric monitoring
of the short-period systems may soon result in the direct detection of
these planets in reflected light. We have used our photometric fluxes
to search for possible transits of the extrasolar planets. Transits
definitely do not occur in τ Boo, 51 Peg, υ And, and ρ1
Cnc, and probably do not occur in ρ CrB and 70 Vir. Our transit-search
results are inconclusive for 47 UMa, and we cannot address the issue for
16 Cyg B and Gl 411. The precision of our photometry is sufficient to
detect transits of planets even if they are not gas giants, as currently
assumed, but much smaller objects with rocky compositions. The chance
of finding at least one transit in the six stars is ~40%. We find
significant year-to-year photometric variability only in τ Boo,
which is not only the youngest star in the sample but also the star
with the shallowest convective zone. The interseasonal range in its
yearly mean photometric flux is ~0.002 mag, roughly twice the 0.0008
mag decadal variation in the Sun's total irradiance. Monitoring of
the relative Ca II H and K fluxes began between 1966 and 1968 for 51
Peg, τ Boo, ρ CrB, and Gl 411, between 1990 and 1993 for 47 UMa,
70 Vir, 16 Cyg B, and ρ1 Cnc, and in 1996 for υ And. The
data have been newly recalibrated for improved long-term instrumental
stability, resulting in better precision of the Ca II records. Five of
the nine stars in this study have little or no detectable year-to-year
variation in Ca II flux. The remaining four show moderate or pronounced
variability: τ Boo, whose radial-velocity and photometric variations
have comparatively high amplitudes; Gl 411, whose planetary companion
was inferred astrometrically, not spectroscopically; ρ1
Cnc, which may undergo decadal cyclic activity; and υ And, which shows
moderate year-to-year variability. Except for 47 UMa, intraseasonal
variability consistent with rotation was detected in the Ca II records
of all stars. However, the rotation periods determined for υ And,
70 Vir, and 16 Cyg B are of low confidence. An examination of the
recalibrated Ca II records for 51 Peg finds a rotation period of 22
days, in contrast to our previous result of 37 days. Ages have been
estimated from the mean Ca II flux and, where possible, the rotation
period. We find general consistency with the ages determined by others
comparing properties determined from high-resolution spectroscopy
to evolutionary models, although the uncertainties are, in general,
large. Based on observations made at Mount Wilson Observatory, operated
by the Mount Wilson Institute, under an agreement with the Carnegie
Institution of Washington and the automatic photoelectric telescope
at Fairborn Observatory in the Patagonia Mountains of southern Arizona.

---------------------------------------------------------
Title: Calculating the Climatic Impacts of Increased CO2:
the Issue of Model Validation
Authors: Soon, W.; Baliunas, S.; Idso, S. B.; Kondratyev, K. Ya.;
Posmentier, E. S.
2000ESASP.463..243S Altcode: 2000sctc.proc..243S
No abstract at ADS

---------------------------------------------------------
Title: Commission 12: Solar Radiation and Structure (Radiation et
Structure Solaires)
Authors: Foukal, Peter; Solanki, Sami; Mariska, J.; Baliunas, S.;
Dravins, D.; Duvall, T.; Fang, C.; Gaizauskas, V.; Heinzel, P.;
Kononovich, E.; Koutchmy, S.; Melrose, D.; Stix, M.; Suematsu, Y.;
Deubner, F.
2000IAUTA..24...73F Altcode:
No abstract at ADS

---------------------------------------------------------
Title: The rains of Ranchipur
Authors: Baliunas, S.; Soon, W.
2000WCRp....5j...3B Altcode:
No abstract at ADS

---------------------------------------------------------
Title: Division XI: Space and High Energy Astrophysics(Astrophysique
Spatiale et Des Hautes Energies)
Authors: Wamsteker, Willem; Baliunas, S.; Brosch, N.; Cesarsky, C.;
Courvoisier, Th. -J. L.; da Costa, J. M.; Domingo, V.; Fransson,
C.; Fabian, A.; Fazio, G.; Hasinger, G.; Inoe, H.; Li, Zhongyuan;
O'Brien, P.; Oertel, G.; Okuda, H.; Quintana, H.; Rangarajan, T. N.;
Schilizzi, R.; Shustov, B.; Thronson, H.; Vilhu, O.; Wang, Zhenru
2000IAUTA..24..357W Altcode:
No abstract at ADS

---------------------------------------------------------
Title: The sun also warms
Authors: Baliunas, S.; Soon, W.
2000stcl.rept...21B Altcode:
No abstract at ADS

---------------------------------------------------------
Title: Variations of solar coronal hole area and terrestrial lower
tropospheric air temperature from 1979 to mid-1998: astronomical
forcings of change in earth's climate?
Authors: Soon, W.; Baliunas, S.; Posmentier, E. S.; Okeke, P.
2000NewA....4..563S Altcode:
The temperature anomaly of the terrestrial lower troposphere,
inferred from the Microwave Sounding Unit (MSU) radiometers, is
found to be inversely correlated with the area of the Sun covered
by coronal holes. The correlation between the monthly time series of
global tropospheric temperature anomaly and total coronal hole area
from January 1979 to April 1998 has a Pearson coefficient of -0.46,
which is different from zero at a 95% confidence level. Physical
reasonings for the explained and unexplained parts of the correlation
are discussed. The coronal hole area is a physical proxy for both the
global-scale, 22-yr geometrical and shorter-term, dynamical components
of the cosmic ray modulation, as well as the corpuscular emission of
the Sun. Other solar parameters that may indicate a solar radiative
effect on climate are also evaluated. It is concluded that variable
fluxes either of solar charged particles or cosmic rays modulated by
the solar wind, or both, may influence the terrestrial tropospheric
temperature on timescale of months to years.

---------------------------------------------------------
Title: Generations of Hurricanes
Authors: Baliunas, S.; Soon, W.
1999WCRp....5f...3B Altcode:
No abstract at ADS

---------------------------------------------------------
Title: Almighty Chance and the Dance of El Nino
Authors: Baliunas, S.; Soon, W.
1999WCRp....5d...3B Altcode:
No abstract at ADS

---------------------------------------------------------
Title: Large asymmetrical temperature trends at Mount Wilson,
California
Authors: Balling, Robert C., Jr.; Periconi, Darlene A.; Cerveny,
Randall S.; Baliunas, Sallie L.
1999GeoRL..26.2753B Altcode:
We compiled and analyzed a daily time series of temperatures and
precipitation totals from Mount Wilson, California from 1918 to
1998. Our results show a large decline in maximum temperature, no change
or an upward trend in minimum temperature, and a substantial decline
in the diurnal temperature range (DTR). The interannual variations
in monthly maximum temperature and DTR are significantly correlated
with monthly precipitation levels, sea-surface temperatures (SSTs)
off the coast of Southern California, and the Southern Oscillation
Index (SOI). El Niño periods and/or months with high SST anomalies
tend to be wet with lower maximum temperatures and DTR while La Niña
periods and/or months of lower SSTs are hotter and drier with higher
DTR values. It is noteworthy that the SOI and SSTs have significant
trends toward more El Niño-like conditions with higher SSTs off
Southern California.

---------------------------------------------------------
Title: Pioneers in the Greenhouse Effect
Authors: Baliunas, S.; Soon, W.
1999WCRp....4s....B Altcode:
No abstract at ADS

---------------------------------------------------------
Title: Pioneers in the Greenhouse Effect
Authors: Baliunas, S.; Soon, W.
1999WCRp....4S...6B Altcode:
No abstract at ADS

---------------------------------------------------------
Title: The Suns of M67
Authors: Giampapa, M. S.; Radick, R. R.; Baliunas, S. L.
1999AAS...194.9212G Altcode: 1999BAAS...31..988G
The results of our program to survey the level of chromospheric Ca II
H&amp;K emission in ~ 100 solar analogs in the galactic cluster M67 are
discussed. This cluster is an appropriate target of observation for
the study of solar-type stars since it is approximately the same age
and has the same chemical composition as the Sun. The key objective
of our program is to investigate the nature of solar variability. In
particular, we interpret the range of Ca II H&amp;K emission observed
in the sun-like stars in M67 as indicative of the possible amplitudes
of cycle-related variability that can occur in the Sun itself. In
this way, we can efficiently gain insights on the potential long-term
variability of the Sun that would not otherwise be possible with the
modern solar Ca II synoptic database of just a few decades. This is
especially important given that the amplitude of long-term solar
(and stellar) variations in brightness are correlated with cycle
variations in chromospheric emission. In view of the fact that the
Sun is the engine that drives climate on the Earth, any variation
in the solar “constant" must be taken into account in the study of
the long-term behavior of the global climate. The NOAO is operated
by the Association of Universities for Research in Astronomy, Inc.,
under cooperative agreement with the National Science Foundation.

---------------------------------------------------------
Title: The Mysteries of Carbon Dioxide
Authors: Baliunas, S.; Soon, W.
1999WCRp....4R...6B Altcode:
No abstract at ADS

---------------------------------------------------------
Title: Aerosols are Cool
Authors: Baliunas, S.; Soon, W.
1999WCRp....4k...6B Altcode:
No abstract at ADS

---------------------------------------------------------
Title: Aerosols are Cool
Authors: Baliunas, S.; Soon, W.
1999WCRp....4Q...6B Altcode:
No abstract at ADS

---------------------------------------------------------
Title: Cycles and Long-Term Variability in Solar-Type Stars
Authors: Giampapa, Mark S.; Radick, Richard R.; Hall, Jeffrey C.;
Baliunas, Sallie L.
1999noao.prop..226G Altcode:
We propose a long-term extension of our current WIYN/Hydra program to
study chromospheric activity cycles in the `Suns of M67.' Our results
thus far have revealed that the distribution of activity among the
solar- type stars in M67 is broader than what would be expected from a
comparison with the solar cycle. The next step is to determine whether
our results arise from the cyclic modulation of activity alone or
if the relative amplitudes of cycles in solar-type stars and the Sun
are actually similar and the spread in M67 is due to differences in
the mean level of activity. Only a long-term monitoring program of
regular observations can address these questions. The results of this
program are expected to reveal all the potential modes and amplitudes
of magnetic cycles in sun-like stars and, by inference, in the Sun
itself, with important implications for dynamo models and models of
global climate change.

---------------------------------------------------------
Title: Extremes of Ecofeminism
Authors: Baliunas, S.
1999frfo.rept.....B Altcode:
No abstract at ADS

---------------------------------------------------------
Title: Natural variability in an-ocean-atmosphere climate model
Authors: Posmentier, E. S.; Soon, W. H.; Baliunas, S. L.
1999JFMal..19..157P Altcode:
No abstract at ADS

---------------------------------------------------------
Title: Extreme Ecomfeminism: The view from Science
Authors: Baliunas, S.
1999exfe.rept....7B Altcode:
No abstract at ADS

---------------------------------------------------------
Title: Silvery-blue Cloudlets of the Night
Authors: Baliunas, S.; Soon, W.
1999WCRp....4....5B Altcode:
No abstract at ADS

---------------------------------------------------------
Title: Environmental effects of increased atmospheric carbon dioxide
Authors: Soon, W.; Baliunas, S.; Robinson, A.; Robinson, Z. W.
1999ClRe...13..149S Altcode:
No abstract at ADS

---------------------------------------------------------
Title: Lifetime of Surface Features and Stellar Rotation: A Wavelet
Time-Frequency Approach
Authors: Soon, Willie; Frick, Peter; Baliunas, Sallie
1999ApJ...510L.135S Altcode: 1998astro.ph.11114S
We explore subtle variations in disk-integrated measurements spanning
&lt;~18 yr of stellar surface magnetism by using a newly developed
time-frequency gapped wavelet algorithm. We present results based on
analysis of the Mount Wilson Ca II H and K emission fluxes in four,
magnetically active stars (HD 1835 [G2 V], HD 82885 [G8 IV-V], HD
149661 [K0 V], and HD 190007 [K4 V]) and sensitivity tests using
artificial data. When the wavelet basis is appropriately modified
(i.e., when the time-frequency resolution is optimized), the results
are consistent with the existence of spatially localized and long-lived
Ca II features (assumed here as activity regions that tend to recur
in narrowly confined latitude bands), especially in HD 1835 and HD
82885. This interpretation is based on the observed persistence of
relatively localized Ca II wavelet power at a narrow range of rotational
timescales, enduring as long as &gt;~10 yr.

---------------------------------------------------------
Title: Cold World: Model Analysis shows icy trend
Authors: Baliunas, S.; Soon, W.
1998WCRp....4g...6B Altcode:
No abstract at ADS

---------------------------------------------------------
Title: Activity in Old Dwarf and Subgiant Stars
Authors: Slesnick, C. L.; Donahue, R. A.; Baliunas, S. L.
1998AAS...193.9903S Altcode: 1998BAAS...30R1395S
Chromospheric Ca \sc ii H and K fluxes of ~ 150 F and G stars on or
near the main sequence were analyzed to determine whether previously
established relationships between stellar magnetic activity and rotation
(age) hold for those stars that have begun to evolve off the Main
Sequence. Each star's time series (up to 33 years) was analyzed year by
year to detect variability which could be attributed to rotation. In
several cases, more than one locus of periods was measured for a
star. These periods were compared to the estimated rotation periods
from a relationship derived by Noyes et al. (1984) using a star's
B-V color and the mean emission flux level of the chromospheric Ca
\sc ii H and K lines. In general, the periods observed correspond to
the predicted rotation period. Those which did not were analyzed in
further detail in order to posit a cause for their values. Rotational
velocities inferred from the observed periods and the calculated radius
of each star were compared to v sin i values collected from the Stellar
Rotational Velocity Catalog (Bernacca &amp; Perinotto 1970, 1971,
1973). In several cases the observed periods are inconsistent with
rotation; however, a few stars which have begun to evolve off the Main
Sequence may show characteristically longer periods than expected,
suggesting that they have either begun to lose angular momentum or
are conserving it by slowing their velocity as they expand.

---------------------------------------------------------
Title: The Miner's Canary is Still Singing
Authors: Baliunas, S.; Soon, W.
1998WCRp....4c...6B Altcode:
No abstract at ADS

---------------------------------------------------------
Title: Patterns of Variation among Sun-like Stars
Authors: Radick, Richard R.; Lockwood, G. W.; Skiff, B. A.; Baliunas,
S. L.
1998ApJS..118..239R Altcode:
We examine the patterns of variation among a sample of 35 stars that
includes the Sun, particularly on the timescale of the 11 yr solar
activity cycle. Our investigation uses contemporaneous photometric and
chromospheric HK emission time series measurements from the Lowell and
Mount Wilson Observatories, and comparable solar data. We find that the
photometric and HK variability of the stars in our sample can be related
to their average level of chromospheric activity by power laws. The
photometric variability of the Sun may be somewhat subdued for its
average activity level. We find that the younger, more active stars
in our sample tend to become fainter as their HK emission increases,
whereas the older, less active stars tend to become brighter as their
HK emission increases, as the Sun does during its activity cycle.

---------------------------------------------------------
Title: The summer of our discontent
Authors: Baliunas, S.; Soon, W.
1998WCRp....3c..10B Altcode:
No abstract at ADS

---------------------------------------------------------
Title: The life and times of Alfonso Nino and family
Authors: Baliunas, S.; Soon, W.
1998WCRp....3s..10B Altcode:
No abstract at ADS

---------------------------------------------------------
Title: The Milky Way and the clouds of Earth
Authors: Baliunas, S.; Soon, W.
1998WCRp....3o..10B Altcode:
No abstract at ADS

---------------------------------------------------------
Title: The Sun as a Star, by Roger J. Tayler
Authors: Baliunas, Sallie
1998PhT....51d..63B Altcode:
No abstract at ADS

---------------------------------------------------------
Title: Nature speaks of many things, Of missing flux and butterfly
wings
Authors: Baliunas, S.; Soon, W.
1998WCRp....3k...6B Altcode:
No abstract at ADS

---------------------------------------------------------
Title: Differential Rotation and Meridional Flow for Fast-rotating
Solar-Type Stars
Authors: Rüdiger, Günther; von Rekowski, Brigitta; Donahue, Robert
A.; Baliunas, Sallie L.
1998ApJ...494..691R Altcode:
Observations indicate that normalized surface differential
rotation decreases for fast-rotating stars, that is, | ΔΩ |/Ω ~
Ω-0.3. An increase of | ΔΩ |/Ω is provided, however, by
the current Reynolds stress theory of differential rotation in stellar
convection zones, without the inclusion of meridional flow. We compute
both the pole-equator difference of the surface angular velocity
and the meridional drift for various Taylor numbers to demonstrate
that the inclusion of meridional flow in the computations for fast
rotation yields a systematic reduction of the resulting differential
rotation. Our model's adiabatic and density-stratified convection
zone, with stress-free surfaces and a thickness of 0.3 stellar radii,
yields the relation | ΔΩ |/Ω ~ Ω-(0.15 ... 0.30) for
stars with faster rotation than the Sun, in agreement with previous
observations. If the Coriolis number rather than the Taylor number is
varied, we find a maximum differential rotation of 20%. For stars with
fast rotation, exponents of up to n' ~= 0.4 are found. All rotation
laws exhibit superrotating equators.

---------------------------------------------------------
Title: An Assessment of the Sun-Climate Relation on Time Scales of
Decades to Centuries: The Possibility of Total Irradiance Variations
Authors: Baliunas, S. L.; Soon, W. H.
1998sers.conf..401B Altcode:
No abstract at ADS

---------------------------------------------------------
Title: Environmental effects of increased atmospheric carbon dioxide
Authors: Robinson, A.; Baliunas, S. L.; Soon, W.; Robinson, Z. W.
1998MeSen...3..171R Altcode:
No abstract at ADS

---------------------------------------------------------
Title: Activity Cycles in Lower Main Sequence and POST Main Sequence
Stars: The HK Project
Authors: Baliunas, Sallie L.; Donahue, Robert A.; Soon, Willie; Henry,
Gregory W.
1998ASPC..154..153B Altcode: 1998csss...10..153B
In 1966, Olin Wilson began making monthly measurements at Mount Wilson
Observatory of the relative fluxes in the Ca II H (396.8 nm) and K
(393.3 nm) emission cores of approximately 100 stars on or near the
lower main sequence. In the late 1970's the Ca II fluxes of nearly
1,000 lower main-sequence stars were sampled, and by 1980 the program
had expanded to include near-nightly observations of the stars in
Wilson's sample. In 1984 the project was again extended to include the
measurement of post-main sequence stars. Today, the project monitors the
Ca II fluxes of 400 dwarf and giant stars, with great emphasis on stars
close in mass and age to the Sun. The relative Ca II fluxes are thought
to closely correspond to the strength and coverage of surface magnetism
on such stars. Three general classes of long-term variations of surface
magnetism have been seen in lower main sequence and post main sequence
stars: 1. substantial fluctuations on time scales of a few years,
with little observed repitition of periodicity; 2. nearly-periodic
variations with time scales of a decade or more, with some variability
in the amplitude, length and shape of each successive cycle; 3. either
low-amplitude modulation on time scales of several decades or more,
or essentially no long-term variability. In the lower main-sequence
stars both the class of long-term variability and the time-averaged
level of Ca II fluxes are influenced primarily by a star's angular
momentum. In a related matter, most of the detected extra-solar planets
(with orbital periods ranging from 3 to 1200 days) orbit sun-like stars
with long-term Ca II flux records that are virtually flat (Class 3,
above). The lack of variability is an observational bias that enhances
detection of extra-solar planets orbiting sun-like stars.

---------------------------------------------------------
Title: Activity in old dwarf and subgiant stars
Authors: Slesnick, C.; Baliunas, S. L.; Donahue, R. A.; Soon, W. H.
1998reu..rept.....S Altcode:
No abstract at ADS

---------------------------------------------------------
Title: Solar activity and temperature data: A wavelet analysis
Authors: Zakharov, V.; Baliunas, S.; Frick, P.; Soon, Wa; Sokoloff, D.
1998geoc.conf.....Z Altcode:
No abstract at ADS

---------------------------------------------------------
Title: Science with the ADOPT system on Mt. Wilson [3126-80]
Authors: Shelton, J. C.; Schneider, T.; Baliunas, S. L.
1997SPIE.3126..321S Altcode:
No abstract at ADS

---------------------------------------------------------
Title: Coronal and chromospheric emission from cool stars in
near-simultaneous ROSAT all-sky survey and Mount Wilson data.
Authors: Piters, A. J. M.; Schrijver, C. J.; Schmitt, J. H. M. M.;
Rosso, C.; Baliunas, S. L.; van Paradijs, J.; Zwaan, C.
1997A&A...325.1115P Altcode:
Mt. Wilson Ca II H&amp;K line-core emission fluxes for 215 F-,
G- and K-type stars were obtained within at most a few days of the
corresponding ROSAT All-Sky Survey observations. These stars cover wide
ranges of stellar activity, spectral type and luminosity class. In
this paper we study the well-known relationship between the Ca II
H&amp;K line-core emission in excess of the minimum emission and the
soft X-ray emission. We find that flux densities normalised with the
bolometric flux densities are the best quantity in which to express
activity when comparing radiative emission in different temperature
regimes. We find a power-law relationship, in which the X-ray normalised
emission varies approximately quadratically with the normalised excess
Ca II H&amp;K line-core emission. This relationship does not depend on
luminosity class at least up to luminosity class III, and it does not
depend on effective temperature. The scatter around this relationship
is consistent with the measurement errors. The X-ray spectral hardness
ratios of main-sequence stars increase with the X-ray flux densities;
a similar trend, but with substantially larger scatter, is also present
for evolved stars. A comparison between values from different passbands
of the Mt. Wilson HK spectrophotometer shows that relatively hot stars
((B-V)&lt;=0.50) appear to have a Ca II line core emission peak about
a factor 2 to 3 wider than cooler stars.

---------------------------------------------------------
Title: Wavelet Analysis of Stellar Chromospheric Activity Variations
Authors: Frick, P.; Baliunas, S. L.; Galyagin, D.; Sokoloff, D.;
Soon, W.
1997ApJ...483..426F Altcode:
Observations of chromospheric activity variations for some lower
main-sequence stars from the Mount Wilson Observatory's HK project
reveal a cyclic behavior comparable to the sunspot cycle. Even in
the relatively short interval that they have been observed, those
stars show stellar cycles and other features, like grand minima. The
quasi-periodic nature of such variations is not completely compatible
with the standard Fourier analysis, so we applied a wavelet analysis
to study the nature of regularities in the data. We computed wavelet
transforms and energy spectra for the 25 yr records of surface magnetic
activity in four stars: HD 3651, HD 10700, HD 10476, and HD 201091. We
present a modified wavelet technique that is suitable for analysis of
data with gaps and find that the common aliasing problems due to the
finite length of the observations and irregularly spaced gaps between
data can be reduced on both large and small scales by applying this
algorithm.

---------------------------------------------------------
Title: Time scales and trends in the central England temperature data
(1659-1990): A wavelet analysis
Authors: Baliunas, Sallie; Frick, Peter; Sokoloff, Dmitry; Soon, Willie
1997GeoRL..24.1351B Altcode:
We have applied the standard wavelet and the adaptive wavelet transform
algorithms to the record of the Central England Temperature (CET) from
1659-1990. Peaks in the CET spectra include 7.5±1.0 yr, 14.4±1.0
yr, 23.5±2.0 yr, as well as a previously unreported variation at
102±15 yr. Our wavelet analysis of CET agrees with previous results
from Singular Spectrum Analysis (SSA) by Plaut et al. [1995] and gives
additional results of variability on longer timescales. The interdecadal
and century-scale variability in CET is strongly dependent on the
interval of analysis. Estimates of a data trend are also shown to
be sensitive to the cutoff timescale of the filter. A cooling of ≈
0.3°C during 1659-1720 is found relative to the temperatures during
the 1800s. The complex time dependence of the actual data cautions
against using model-derived representations of natural variability on
such long timescales.

---------------------------------------------------------
Title: VizieR Online Data Catalog: Near-simultaneous ROSAT and Mt
Wilson data (Piters+ 1997)
Authors: Piters, A. J. M.; Schrijver, C. J.; Schmitt, J. H. M. M.;
Rosso, C.; Baliunas, S. L.; van Paradijs, J.; Zwaan, C.
1997yCat..33251115P Altcode:
Table 1 lists near-simultaneous X-ray data and Ca II H&amp;K line-core
emission data from the ROSAT All-Sky Survey and from the Mt. Wilson
H&amp;K spectrometer, respectively. The stars in this sample are 215
bright F-, G-, and K-type stars. Table 2 lists the derived excess Ca II
H&amp;K line-core and the X-ray flux densities for the same stars. (2
data files).

---------------------------------------------------------
Title: Persistent Sub-Yearly Chromospheric Variations in Lower
Main-Sequence Stars: Tau Booe and alpha COM
Authors: Maulik, Davesh; Donahue, Robert A.; Baliunas, Sallie L.
1997sao..rept.....M Altcode:
The recent discoveries of extrasolar planetary systems around lower
main-sequence stars such as tau Booe (HD 120136) has prompted further
investigation into their stellar activity. A cursory analysis of tau
Booe for cyclic chromospheric activity, based on its 30-yr record of Ca
2 H and K fluxes obtained as part of the HK Project from Mount Wilson
Observatory, finds an intermediate, sub-yearly period (approximately 117
d) in chromospheric activity in addition to, and separate from, both its
rotation (3.3 d) and long-term variability. As a persistent sub-yearly
period in surface magnetic activity is unprecedented, we investigate
this apparent anomaly further by examining chromospheric activity
levels of other stars with similar mass, searching for variability
in chromospheric activity with periods of less than one year, but
longer than measured or predicted rotation. An examination of the time
series of 40 mid-to-late F dwarfs yielded one other star for further
analysis: alpha Com (HD 114378, P approximately 132 d). The variations
for these two stars were checked for persistence and coherence. Based
on these determinations, we eliminate the possibilities of rotation,
long-term activity cycle, and the evolution of active regions as the
cause of this variation in both stars. In particular, for tau Booe we
infer that the phenomenon may be chromospheric in origin; however,
beyond this, it is difficult to identify anything further regarding
the cause of the activity variations, or even whether the observed
modulation in the two stars have the same origin.

---------------------------------------------------------
Title: A Combined MG II/CA II Survey of Stellar Magnetic Activity
in the Solar Neighborhood
Authors: Wicklund, B. M.; Donahue, R. A.; Dobson, A. K.; Baliunas,
Sallie L.
1997sao..rept.....W Altcode:
We use nearly contemporaneus low-resolution IUE observations of Mg II
h + k emission and Mount Wilson Observatory Ca II H + K S indices for
33 pairs of observations of lower main sequence stars to formulate
a relationship that will permit accurate predictions of S values
as a function of (B - V) color and Mg II h + k flux. The resulting
relationship is useful because it will extend the set of solar
neighborhood stars for which a uniform estimate of chromospheric
activity is available to include stars that are not observable from
Mount Wilson as well as providing additional estimates of activity
levels for stars that are on the Mount Wilson HK Project observing list.

---------------------------------------------------------
Title: Stellar Active Region Evolution - I. Estimated Lifetimes of
Chromospheric Active Regions and Active Region Complexes
Authors: Donahue, R. A.; Dobson, A. K.; Baliunas, S. L.
1997SoPh..171..191D Altcode:
The lifetimes of chromospheric active regions and active region
complexes ('active longitudes') for 35 lower-Main-Sequence stars
observed at Mount Wilson Observatory are estimated from the relative
distribution of pooled variance at different time scales. The time
scale of active region evolution (i.e., the lifetime of large active
regions) is approximately 50 days, while the lifetime of active region
complexes is on the order of 1 year. These estimates can be used to
clarify the contribution of active regions to variance in short-term
(i.e., &lt;1 yr) time series data. Previously unpublished mean rotation
periods are documented for several stars.

---------------------------------------------------------
Title: Stellar Active Region Evolution - II. Identification and
Evolution of Variance Morphologies in CA II H+K Time Series
Authors: Donahue, R. A.; Dobson, A. K.; Baliunas, S. L.
1997SoPh..171..211D Altcode:
The relative distribution of pooled variance computed at various time
scales for records of chromospheric activity has been calculated for
approximately 100 stars observed at Mount Wilson Observatory. As shown
in Paper I, analysis of the pooled variance provides a technique
for estimating the lifetimes of stellar active regions and their
influence on chromospheric time series used for determining rotation
and activity cycle periods. Pooled variance diagrams may be divided
into three morphological types which depend to a large extent on a
star's mean level of chromospheric activity (i.e., age) and B-V color
(i.e., mass), and possibly depend on star's evolutionary state.

---------------------------------------------------------
Title: Properties of Sun-like Stars with Planets: 51 Pegasi, 47
Ursae Majoris, 70 Virginis, and HD 114762
Authors: Henry, Gregory W.; Baliunas, Sallie L.; Donahue, Robert A.;
Soon, Willie H.; Saar, Steven H.
1997ApJ...474..503H Altcode:
Radial velocity variations have revealed planets orbiting 51 Peg,
47 UMa, and 70 Vir, and a low-mass companion orbiting HD 114762. We
analyze parallel records of photometric measurements in Strömgren
b and y and Johnson V, R, and I passbands and Ca II H and K fluxes
in those stars. In the case of 51 Peg, the high precision of the
differential photometric measurements made by the 0.75 m Automatic
Photoelectric Telescope and the nonvariability of the star would allow
the detection of a transit of a planet as small as Earth (corresponding
to an amplitude of 0.0001 mag) if its orbit were nearly coplanar with
our line of sight. No transits were observed. For 51 Peg and
70 Vir, the upper limit of nondetection of photometric variability
at their companion's orbital periods is Δ(b + y)/2 &lt; 0.0002 +/-
0.0002 mag. For HD 114762, it is ΔV &lt; 0.0007 +/- 0.0004 mag. Such
small amplitudes of photometric variability seem to eliminate periodic
velocity variations expected from p-mode oscillations. All four
stars are magnetically quiet; that is, they lack the typical Ca II and
photometric variability due to rotation and activity cycles expected
from surface magnetic activity in solar-type stars. Such quiescence
produces an interesting observational bias that favors the detection of
planets from low-amplitude radial velocity or photometric variations
by minimizing the contribution from intrinsic stellar variability. We
discuss the circumstances for which the probability of planet detections
is improved by the reduced level of variability from surface magnetic
activity in G and K stars. Stars with low variability in surface
activity should be the best candidates for planet searches using
radial velocity and photometric techniques. Searches for planets
around younger, more active stars will be impeded by variations in
velocity or brightness caused by time-varying surface features. The Ca II H and K fluxes indicate that all four stars are older
than 5 Gyr. Ages were estimated from the average levels of Ca II
H and K fluxes and an existing relationship of the decrease of Ca
II fluxes with age on the lower main sequence and were drawn from
previous results based on theoretical isochrone fitting. Values of the
projected rotational velocity, v sin i, are determined for 70 Vir and
47 UMa from high-resolution spectra. Based on observations made
at Mount Wilson Observatory, operated by the Mount Wilson Institute
under an agreement with the Carnegie Institution of Washington, and at
the National Solar Observatory, administered by AURA, Inc. for the NSF.

---------------------------------------------------------
Title: Properties of Sun-like Stars with Planets: ρ1
Cancri, τ Bootis, and υ Andromedae
Authors: Baliunas, Sallie L.; Henry, Gregory W.; Donahue, Robert A.;
Fekel, Francis C.; Soon, Willie H.
1997ApJ...474L.119B Altcode:
Planets have been reported orbiting the Sun-like stars ρ1
Cnc, τ Boo, and υ And based on low-amplitude radial velocity
variations. We have derived information on the first two stars from
analysis of spectra, as well as parallel records of high-precision
Strömgren b and y photometry and Ca II H + K fluxes. In the case of
ρ1 Cnc, the upper limit (peak to peak) of nondetection of
photometric variability at the orbital period is Δy ~ 0.0004 mag. The
possibility of a planetary transit cannot be ruled out completely
from the photometric data. Variations of the Ca II fluxes suggest a
rotational period of ~42 days, in agreement with the inferred v sin
i ~ 2 km s-1. The age of ρ1 Cnc is ~5 Gyr,
based on its average Ca II flux and a relation between Ca II flux
and age. The star τ Boo, unlike the other reported solar-type
stars with planets, is relatively young (~2 Gyr). Despite its young
age, it is photometrically nonvariable at the orbital period with
an amplitude of Δ(b + y)/2 ~ 0.0004 mag (peak to peak); however,
small-amplitude interseasonal variability is seen. No planetary
transits were found in the photometry, which limits the inclination of
the planet's orbital plane to Earth's line of sight to less than 83°
(where 90° is coplanar). The Ca II record shows a weakly significant
rotational period near 3.3 days, coincident with the orbital period of
the companion. The Ca II record also shows a period of 116 days that has
persisted for 30 years and is not seen in the photometric record. The
persistence and timescale of this Ca II variation mean that it has no
counterpart in Sun-like magnetic activity. The amplitude of the reflex
velocity of the parent star (~450 m s-1) is much larger
than the radial velocity perturbations expected from the presence of
either surface inhomogeneities or line-bisector variations. Thus the
anticipated perturbations from those stellar effects do not refute
the inference of reflex velocities. We have few Ca II flux
measurements for υ And. Its age and rotational period are estimated
to be ~5 Gyr and 12 days, respectively. Our results for ρ1
Cnc and τ Boo are consistent with the explanation of planets as the
cause of the velocity variations. Based on observations made at
Mount Wilson Observatory, operated by the Mount Wilson Institute under
an agreement with the Carnegie Institution of Washington.

---------------------------------------------------------
Title: Mount Wilson Reborn: A New ERA Dawns for 'America's
Observatory'.
Authors: Jastrow, R.; Baliunas, S. L.
1997ASSL..210...10J Altcode: 1997ilsn.proc...10J
No abstract at ADS

---------------------------------------------------------
Title: The Rotation of the G0 Dwarf β Comae
Authors: Gray, David F.; Baliunas, Sallie L.
1997ApJ...475..303G Altcode:
The rotation of β Comae (HR 4983, HD 114710, G0 V) is studied
using the available information from spectral line broadening
and from rotational modulation. The line broadening yields v sin
i = 4.10 +/- 0.06 km s-1, which agrees with previous
values. Rotational modulation was looked for but not seen in the
photospheric parameters of temperature and granulation, although this
might be a result of data sampling not being well suited for modulation
studies. Rotational modulation is seen in the S index of the Ca II
chromospheric emission. Two period sequences characterize β Comae
between 1981 and 1994. The periods decline monotonically with time,
paralleling the decline in magnetic activity as indicated by the
average strength of the Ca II emission. We interpret the decrease in
period as differential rotation coupled with systematic migration in
latitude of the active regions. It is not possible to separate the
differential rotation profile of β Comae from its rate and sense of
latitude migration. We compare the changes of β Comae with the Sun's
and point out similarities and differences.

---------------------------------------------------------
Title: Inference of Solar Irradiance Variability from Terrestrial
Temperature Changes, 1880--1993: an Astrophysical Application of
the Sun-Climate Connection
Authors: Soon, W. H.; Posmentier, E. S.; Baliunas, S. L.
1996ApJ...472..891S Altcode:
Information can be inferred on the timing and amplitude of solar
total irradiance changes over t880- t993 by simulating the global
terrestrial surface temperature changes produced by these irradiance
changes and comparing them with observed temperatures. The profiles
of solar irradiance variations used in the climate simulations
are adopted from several different proxies: (t) the length of the
sunspot cycle, (2) the mean sunspot number, and (3) a composite proxy
that includes the two previous indicators plus the equatorial solar
rotation rate, the fraction of penumbral spot coverage, and the rate
of decay of the sunspot cycle. We use a seasonal energy-conservation
climate/upwelling-diffusion ocean model, forced by the assumed profiles
of solar total irradiance variations, combined with variations in
anthropogenic greenhouse gases. Optimized cases imply total irradiance
changes during t880-t993 in the range 0.18%-0.77%. If the solar
irradiance profiles found from the climate simulations are required to
be consistent with recent satellite observations, then the composite
solar profile reconstructed by Hoyt &amp; Schatten, combined with the
anthropogenic greenhouse forcing, explains the highest fraction of the
variance of observed global mean temperatures. In this case, the solar
and greenhouse combination accounts for 92% of the observed long-term
temperature variance during t880-t993. The simulation implies that the
solar part of the forcing alone would account for 7t% of the global
mean temperature variance, compared to 5t% for the greenhouse gases'
part alone. It also suggests a solar total irradiance variation of
0.5% during the interval t880-t993. Such an amplitude of solar total
irradiance change is consistent with astrophysical limits of brightness
changes on timescales of decades to centuries independently derived
from observations of solar-type stars (including the Sun).

---------------------------------------------------------
Title: Multiwavelength Activity Profiles of Cool Stars
Authors: Hall, J. C.; Baliunas, S. L.
1996AAS...189.8108H Altcode: 1996BAAS...28.1383H
We have constructed detailed observing histories of a large number of
cool stars by combining measurements of magnetic-activity-sensitive
lines in ground-based data and space archival data into what we term
multiwavelength activity profiles (MAPs) of these stars. To construct a
MAP, we first combine the Mt. Wilson Observatory HK project data and the
Lowell Observatory Solar-Stellar Spectrograph (SSS) near-UV to near-IR
data for a given target into absolute-flux-calibrated records of the
star's chromospheric variability. We then add IUE NEWSIPS-processed
spectra and available EUV and X-ray data to produce the final MAP,
which provides a comprehensive picture of the long-term variability
in the target stars from their low chromospheres to their coronae. In
this poster we present representative MAPs for nine stars with large
space-based data sets (HDs 20630, 22049, 35296, 39587, 61421, 72905,
115383, 131156A, and 201091). We first describe how we combine the
various data into a uniformly calibrated MAP, and then examine the
response of different regions of the stellar atmospheres to cyclic,
rotational, and short-term variability.

---------------------------------------------------------
Title: Possible Detection of a Residual Non-Cyclic Distributed Dynamo
in “Maunder Minimum” Stars
Authors: Saar, S. H.; Deluca, E. E.; Baliunas, S. L.; Donahue, R. A.
1996AAS...189.8104S Altcode: 1996BAAS...28.1382S
We have analyzed HST and IUE ultraviolet spectra of five dwarfs which
have extremely low, non-variable levels of Ca II HK emission. These
stars appear to be in the stellar analog of the solar “Maunder
minimum” - a period when the normal cyclic magnetic dynamo went
into temporary quiescence. The stars all have very low levels of
chromospheric and transition region (TR) emission. The ratio of TR (Si
IV and C IV) to chromospheric emission (C II) is smaller than expected
from published estimates of the “basal” emission, and increases with
decreasing T_eff. This is in contrast to the lack of such a trend in
dwarfs with variable Ca II HK (“normal” operating magnetic dynamos)
and the reverse of the trend expected if the emission was acoustic in
origin. The existence of significant TR emission in “Maunder minimum”
stars suggests that they are still generating magnetic flux, but
it is apparently in some form which enhances chromospheric emission
relative to the TR. A possible explanation for the observations is
that a residual “Maunder minimum” magnetic flux is a generated
by a non-cyclic distributed-type dynamo (a less efficient mechanism
which operates throughout the convective zone, and thus grows with
increased convective zone depth). If this scenario is correct, our
data are the first observational evidence of such a dynamo operating
in a star which is not fully convective.

---------------------------------------------------------
Title: M.I.T. Space Grant Program Photoelectric Observations of
Variable Stars for High School Students
Authors: Baliunas, Sallie
1996sao..reptR....B Altcode:
This progress report covers work by three undergraduate and two advanced
high school students on intensive astrophysical research. Subject areas
included: chromospheric activity in evolved stars, ages of sunlike
stars from IUE satellite observations, Sunlike stars with planets,
adaptive optics - surface features of Vesta, and rotation of lower
main sequence stars.

---------------------------------------------------------
Title: The Stellar Dynamo
Authors: Nesme-Ribes, Elizabeth; Baliunas, Sallie L.; Sokoloff, Dmitry
1996SciAm.275b..46N Altcode:
No abstract at ADS

---------------------------------------------------------
Title: A Relationship between Mean Rotation Period in Lower
Main-Sequence Stars and Its Observed Range
Authors: Donahue, Robert A.; Saar, Steven H.; Baliunas, Sallie L.
1996ApJ...466..384D Altcode:
Chromospheric Ca II H and K fluxes have been measured in a
sample of ~100 stars on or near the main sequence at Mount Wilson
Observatory. Observations were made several times a week and span
more than ten years. Within an observing season, many stars show
periodic variations due to rotation. Thirty-six of the stars have
highly-significant periods in at least five seasons. We compute
the range in the observed period, Delta P, and suggest that it is a
measure of, and a lower limit to, the surface differential rotation
(SDR). Several physical and selection effects can affect the measured
Delta P value. An analysis of the cumulative variance distribution
at various time scales, however, demonstrates that Ca II variations
due to active region growth and decay are of longer period and smaller
amplitude than those due to rotation. We argue that other effects (e.g.,
multiple active regions, latitude bands) are either small, or primarily
act to reduce the measured Delta P relative to its true value. Including
results for the Sun, we find that Delta P depends on the mean seasonal
rotation period , such that Delta P is proportional to to
the power of 1.3 +/- 0.1, independent of mass. We briefly discuss this
in the context of dynamo models, and other observations of surface
differential rotation and active region structure.

---------------------------------------------------------
Title: Magnetic, Photometric, Temperature, and Granulation Variations
of XI Bootis A 1984--1993
Authors: Gray, David F.; Baliunas, Sallie L.; Lockwood, G. W.; Skiff,
Brian A.
1996ApJ...465..945G Altcode:
The magnetically active G8 dwarf star, ξ Boo A = HR 5544 = HD 13 1156
is studied for magnetic- cycle type variations over the 1984-1993
interval. We present measurements of Ca II H and K emission as an
indirect indicator of magnetic activity, blue and visual magnitudes as
an indication of the power output and temperature, line-depth ratios
of V I λ6251.83 to Fe I λ6252.57 as a measure of temperature, and
line bisectors as a measure of the star's granulation. The season
means of all these parameters show the same pattern of variation with
several irregular rises and falls, rather different from the relatively
smooth variations seen for the Sun. As found for several other stars in
previous studies, the magnetic signal leads the others in time. Time
lags relative to the H and K index variation are 1.4±0.4 yr for
the photometric brightness, 1.5±0.5 yr for the b -y color index,
1.8±0.3 yr for the line-depth ratio, and 2.1±0.4 yr for the line
bisectors. The ≍1.7 year temperature lag for ξ Boo A is close to
the linear relation between lag and effective temperature found for
the other stars that have been measured.

---------------------------------------------------------
Title: A Dynamo Interpretation of Stellar Activity Cycles
Authors: Baliunas, S. L.; Nesme-Ribes, E.; Sokoloff, D.; Soon, W. H.
1996ApJ...460..848B Altcode:
Twenty-five-year records of Ca II H and K chromospheric emission fluxes
measured in single lower main-sequence stars at Mount Wilson Observatory
reveal surface magnetic activity cycles in one-third of the sample of
roughly 100 stars. For those stars with cycles, we compare the ratio
of the observed periods of the cycle of magnetic activity and axial
rotation, Pcyc/Prot, to predictions available
from stellar dynamo theory. Theoretical considerations suggest that the
ratio is the observational equivalent of the stellar dynamo number,
D. The stellar sample is comprised of two groups separated by
their mean level of activity, &lt;R'HK&gt;, and rotation,
Prot: one group has high levels of average activity and fast
rotation, while the other group has relatively low levels of activity
and slower rotation. Both groups also occupy different regions on the
diagram of X-ray flux versus stellar dynamo number. For the older
group of stars (ages &amp;#8819 2 Gyr) which includes the current
Sun, we find a statistically significant inverse relation between the
intensity of the cycle, C = ΔRHK/&lt;R'HK&gt;,
and the stellar dynamo number, empirically determined to be D ∼
(Pcyc/Prot)1.35+0.65-0.35.

---------------------------------------------------------
Title: The writing on the wall.
Authors: Baliunas, S. L.
1996Mercu..25a..18B Altcode:
Scientists has two choices: continue to fight for money in the current
system of federal research funding, with diminishing returns, or push
for alternatives. One alternative, in keeping with the spirit of the
age, is to create incentives for private support of research.

---------------------------------------------------------
Title: Magnetic Field and Rotation in Lower Main-Sequence Stars:
an Empirical Time-dependent Magnetic Bode's Relation?
Authors: Baliunas, Sallie; Sokoloff, Dmitry; Soon, Willie
1996ApJ...457L..99B Altcode:
We find a significant correlation between the magnetic and rotational
moments for a sample of 112 lower main-sequence stars. The rotational
moment is calculated from measurements of the rotation period in most
of the stars (not from the projected rotational velocity inferred
from Doppler broadening). The magnetic moment is computed from a
database of homogeneous measurements of the mean level of Ca II H
and K emission fluxes sampled for most of the stars over an interval
of 25 yr. The slope connecting the logarithm of the magnetic moment
and the logarithm of the rotational moment is about +0.5--0.6, with a
Pearson correlation coefficient of about +0.9. The scatter of points
from the mean relation has a component that is natural and caused by
decade-long surface variability.

---------------------------------------------------------
Title: Physical Properties of the Contact Binaries of the Old Open
Cluster NGC 188
Authors: Bradstreet, D. H.; Baliunas, S. L.; Guinan, E. F.
1996ASPC...90..135B Altcode: 1996oedb.conf..135B
No abstract at ADS

---------------------------------------------------------
Title: A Survey of Ca II H and K Chromospheric Emission in Southern
Solar-Type Stars
Authors: Henry, Todd J.; Soderblom, David R.; Donahue, Robert A.;
Baliunas, Sallie L.
1996AJ....111..439H Altcode:
More than 800 southern stars within 50 pc have been observed for
chromospheric emission in the cores of the Ca II H and K lines. Most
of the sample targets were chosen to be G dwarfs on the basis of colors
and spectral types. The bimodal distribution in stellar activity first
noted in a sample of northern stars by Vaughan and Preston in 1980 is
confirmed, and the percentage of active stars, about 30%, is remarkably
consistent between the northern and southern surveys. This is especially
compelling given that we have used an entirely different instrumental
setup and stellar sample than used in the previous study. Comparisons to
the Sun, a relatively inactive star, show that most nearby solar-type
stars have a similar activity level, and presumably a similar age. We
identify two additional subsamples of stars -- a very active group, and
a very inactive group. The very active group may be made up of young
stars near the Sun, accounting for only a few percent of the sample,
and appears to be less than ~0.1 Gyr old. Included in this high-activity
tail of the distribution, however, is a subset of very close binaries
of the RS CVn or W UMa types. The remaining members of this population
may be undetected close binaries or very young single stars. The very
inactive group of stars, contributting ~5%--10% to the total sample,
may be those caught in a Maunder Minimum type phase. If the observations
of the survey stars are considered to be a sequence of snapshots of the
Sun during its life, we might expect that the Sun will spend about 10%
of the remainder of its main sequence life in a Maunder Minimum phase.

---------------------------------------------------------
Title: The Sun-Climate Connection
Authors: Baliunas, Sallie; Soon, Willie
1996S&T....92...38B Altcode:
No abstract at ADS

---------------------------------------------------------
Title: Interpretation of stellar Ca II activity cycles.
Authors: Baliunas, S. L.; Nesme-Ribes, E.; Sokoloff, D.; Soon, W.
1996sube.conf...57B Altcode:
Twenty-five year records of Ca II H and K chromospheric emission
fluxes measured in lower main-sequence stars reveal surface magnetic
activity cycles which are comparable to that of the Sun's. The observed
variations can be interpreted in terms of stellar dynamo theory. The
authors find the ratio of the period of stellar cycle to the period
of stellar axial rotation, Pcyc/Prot, to be
representative of a stellar dynamo number, D.

---------------------------------------------------------
Title: Variations of beta Comae through a Magnetic Minimum
Authors: Gray, David F.; Baliunas, Sallie L.; Lockwood, G. W.; Skiff,
Brian A.
1996ApJ...456..365G Altcode:
The dwarf star β Com = HR 4983 = HD 114710 (GO V, B-V = 0.57) is close
to the Sun in the H-R diagram, being only ≍260 K hotter. We present
measurements done over several years of (1) the line depth ratios
of V I λ6251.83 to Fe I λ6252.57 to establish the temperature,
(2) the line bisectors as a measure of the star's granulation, (3)
Ca II H and K emission as an indirect indicator of magnetic activity,
and (4) the blue and visual magnitudes as an indication of the power
output. All these parameters show a similar variation consisting of a
broad minimum extending over approximately 5 years, but the minima do
not occur at the same epoch. The magnetic signature leads the others
in time. Time lags relative to the magnetic variation are 0.9±0.3
yr for the photometric data, 2.9±0.3 yr for the temperature, and
2.9±0.5 yr for the granulation. A 1% variation in radius during the
5 yr interval is indicated.

---------------------------------------------------------
Title: The chromospheric activity of the many "suns" in M67.
Authors: Giampapa, M. S.; Baliunas, S. L.; Radick, R. R.
1996BAAS...28.1197G Altcode:
No abstract at ADS

---------------------------------------------------------
Title: The stellar dynamo.
Authors: Nesme-Ribes, E.; Baliunas, S. L.; Sokoloff, D.
1996SciAm.275b..30N Altcode:
No abstract at ADS

---------------------------------------------------------
Title: Low-Resolution IUE Observations of Chromospheric MG II H and
K Emissions
Authors: Wicklund, B. M.; Donahue, B.; Baliunas, S.
1995AAS...18710301W Altcode: 1995BAAS...27Q1430W
Low-resolution IUE observations of the 280 nm Mg II h and k lines of 67
G--K type stars are used to formulate a relationship between Mg II and
Ca II chromospheric emission. The resulting relationship can be used
to convert Mg II flux measurements to Ca II flux measurements. This
expands the database currently being compiled by the HK Project at Mount
Wilson Observatory by providing measurements of chromospheric activity
for stars not observable from Mount Wilson. This data will be of use
to projects currently using Ca II H and K fluxed from the HK Project.

---------------------------------------------------------
Title: Are Variations in the Length of the Activity Cycle Related
to Changes in Brightness in Solar-Type Stars?
Authors: Baliunas, Sallie; Soon, Willie
1995ApJ...450..896B Altcode:
We compare the average level of chromospheric activity and cycle
length for solar-type stars as determined from 25 yr records of Ca
II fluxes and from the sunspot record from 1750 to 1990. Both sets
of data show an inverse relation between the cycle length and average
activity level, with only a minor difference in the slopes. In turn,
the amplitude of Ca II variability is positively correlated with
the photometric brightness change during an activity cycle. The
relationship between those observables provides a physical basis for
the close correlation between the length of the sunspot cycle and
mean terrestrial temperature over the last few centuries as shown by
Friis-Christensen &amp; Lassen. Solar brightness variations over
the last several centuries can be estimated from this relationship by
including stars with low Ca II fluxes which, we assume, are in states
resembling the phase of solar activity known as the Maunder minimum
(circa 1645-1715). Although the value of the slope connecting the
mean level of Ca II activity and the cycle length is sensitive to the
statistical treatment of the data, a lower limit to the slope can be
determined reliably. This lower limit yields an increase of 0.4% of
solar brightness from the solar Maunder minimum to the cyclic phase
of sunspot activity which immediately followed the Maunder minimum.

---------------------------------------------------------
Title: First tests of the Cassegrain adaptive optics system of the
Mount Wilson 100-in telescope
Authors: Shelton, J. Christopher; Schneider, T.; McKenna, Daniel;
Baliunas, Sallie L.
1995SPIE.2534...72S Altcode:
In January 1994, we began construction of a modern adaptive optics
system for the newly refurbished 100-inch telescope. The design
philosophy of the adaptive optics system is to achieve a working system
in the visible in a short time at relatively low cost. This means
wavefront sensing with natural guide stars and implementation at the
bent Cassegrain focus of the telescope. The system has an integrated
wavefront sensor and finder camera, and is automated for one-person
operation. It uses off-the-shelf components where possible. The
deformable mirror, which has 241 actuators, is on loan from the U.S. Air
Force. The use of an existing mirror imposes constraints that have
driven some of the design considerations. The system is operating at
the telescope, with early results described below.

---------------------------------------------------------
Title: A Study of Variability in a Sample of G and K Giants
Authors: Choi, Hyung-Jin; Soon, Willie; Donahue, Robert A.; Baliunas,
Sallie L.; Henry, Gregory W.
1995PASP..107..744C Altcode:
Eight years of Ca II surface activity records from Mount Wilson
Observatory measured for 12 bright G-K III stars have been analyzed
in order to detect periodic variations attributable to rotation. We
also present photometric V-band data for these stars from the
Fairborn 0.25m Automatic Photometric Telescope (APT) that yielded
a photometric period in one case and rms deviations from apparently
constant brightness levels for the remaining 11 stars. The Ca II data
yielded rotation periods for 10 out of 12 giant stars. We demonstrate
that the photometric variability and non-variability of these stars
can be predicted from their Rossby numbers calculated from our observed
rotation periods and convective turnover times scaled up from the main
sequence. (SECTION: Stars)

---------------------------------------------------------
Title: Estimated Lifetimes of Chromospheric Active Regions and Active
Region Complexes
Authors: Dobson, A. K.; Donahue, R. A.; Baliunas, S. L.
1995AAS...186.2111D Altcode: 1995BAAS...27..839D
The relative distribution of pooled variance at different time scales
for some 40 lower main sequence stars observed at Mt Wilson Observatory
are used to derive estimates for the lifetimes of chromospheric active
regions and active region complexes. For the sample stars, the time
scale of AR evolution is approximately 50 days, while the lifetime of
AR complexes is on the order of 1 year. These estimates can be used
to clarify the contribution of active regions to short-term (i.e.,
less than 1 y) time series data.

---------------------------------------------------------
Title: Pulsation Timescales and Amplitudes in a Sample of Bright
Semi-Regular Variable Stars
Authors: Cristian, V. -Cristina; Donahue, Robert A.; Soon, Willie H.;
Baliunas, Sallie L.; Henry, Gregory W.
1995PASP..107..411C Altcode:
We have analyzed the differential V-band photometric variations of
records up to 8 years long in ten M III semi-regular (SR) variable
stars. Periodograms constructed from each star's entire record and
seasoned intervals were used to find repetitive occurrences of pulsation
periods in the range of 10 to 250 days. For every star at least one
locus of periods was observed, with many stars showing two distinct
distributions of pulsation timescales. The observed pulsation periods
and differential V-magnitude semi-amplitudes appear to be correlated
such that longer periods correspond to larger semi-amplitudes. (SECTION:
Stars)

---------------------------------------------------------
Title: Identification and Evolution of Variance Morphologies in CA
II H+K Time Series
Authors: Donahue, Robert A.; Dobson, Andrea K.; Baliunas, Sallie L.
1995AAS...186.2213D Altcode: 1995BAAS...27Q.843D
The relative distribution of pooled variance at different time scales
for the chromospheric activity of approximately 100 stars observed at
Mount Wilson Observatory may be divided into three basic morphological
types which depend to a large extent on their mean activity level
(i.e., age) and color (i.e., mass). Analysis of the pooled variance
plots possibly provide a technique for determining the lifetimes of
stellar active regions and their influence on chromospheric time series
used for determining rotation and activity cycle periods.

---------------------------------------------------------
Title: Identification and evolution of variance morphoplogies in Ca
II H+K time series.
Authors: Donahue, R. A.; Dobson, A. K.; Baliunas, S. L.
1995BAAS...27R.843D Altcode:
No abstract at ADS

---------------------------------------------------------
Title: Chromospheric Activity and Age of Solar-Type Stars
Authors: Baliunas, S. L.; Donahue, R. A.; Soon, W.; Gilliland, R.;
Soderblom, D. R.
1995AAS...186.2109B Altcode: 1995BAAS...27..839B
Main-sequence stars near one solar mass show an average level of Ca
II H and K emission and rotation that decrease with age. Although the
mechanism governing surface magnetism and rotation is not theoretically
well-understood, the measurement of rotation or average activity
level can yield an estimate of the age of a solar-mass star. Several
empirically-determined functions of the decay of rotation and activity
have been developed over the last several decades, but more have
concentrated on stars much younger than the Sun, whose Ca II activity
and rotation have been relatively easy to measure. Observations of the
Ca II H and K emission were obtained of solar-mass stars in the old
open clusters NGC 752 and M 67 with the KPNO 4-m telescope and HYDRA
spectrograph. Those spectra yield a large (&gt;50) smaple of stars
close to one solar mass and close to the age of the Sun. Those spectra
have been calibrated to the system of measurement of Ca II H and K
emission fluxes of nearly 1000 lower main sequence stars obtained at
Mount Wilson Observatory. The combined sample of Ca II fluxes yield:
(1) a refined calibration of age as a function of activity, using
rotation as an indicator of age; (2) the range of Ca II activity at a
given age, caused by variations of surface magnetic activity over time
scales of decades to centuries; and (3) an estimate of the uncertainty
of age inferred from a measurement of the instantaneous activity level.

---------------------------------------------------------
Title: Magnetic Activity Variations of epsilon Eridani
Authors: Gray, David F.; Baliunas, Sallie L.
1995ApJ...441..436G Altcode:
The variations in magnetic activity, temperature and granulation of
epsilon Eri (HR 1084, HD 22049, K2 V, B-V = 0.88) in the interval from
1986 to 1992 are discussed in this paper. We monitored the magnetic
activity with the Ca II H and K-line emission, the temperature with
the ratio of depths of two spectral lines, and the granulation with
spectral-line asymmetries. Rotational modulation is seen only in the
H and K emission, and it shows a period of 11.10 +/- 0.03 days, in
agreement with earlier published values. The star has one dominant
activity longitude. The magnetic activity of epsilon Eri is strong
and shows irregular excursions that may be superposed on a cyclic
variation having a period approximately equal to 5 yr. During the
1986-1992 interval the magnetic activity went through a broad relative
minimum. Temperature and granulation changes mimic the variation in
H and K emission, with excursions approximately equal to 15 K and
approximately equal to 35 m/s, repectively. No long-term photometric
observations are available for epsilon Eri, but we calculate a 1.2%
variation in luminosity and 0.014 mag in V to have occurred, assuming
the radius of the star is constant.

---------------------------------------------------------
Title: Is HD 3651 entering a "Maunder minimum" phase?
Authors: Donahue, R. A.; Baliunas, S. L.; Soon, W. H.; McMillan, F. M.
1995IAUS..176P..72D Altcode:
No abstract at ADS

---------------------------------------------------------
Title: Chromospheric Variations in Main-Sequence Stars. II.
Authors: Baliunas, S. L.; Donahue, R. A.; Soon, W. H.; Horne, J. H.;
Frazer, J.; Woodard-Eklund, L.; Bradford, M.; Rao, L. M.; Wilson,
O. C.; Zhang, Q.; Bennett, W.; Briggs, J.; Carroll, S. M.; Duncan,
D. K.; Figueroa, D.; Lanning, H. H.; Misch, T.; Mueller, J.; Noyes,
R. W.; Poppe, D.; Porter, A. C.; Robinson, C. R.; Russell, J.; Shelton,
J. C.; Soyumer, T.; Vaughan, A. H.; Whitney, J. H.
1995ApJ...438..269B Altcode:
The fluxes in passbands 0.1 nm wide and centered on the Ca II H
and K emission cores have been monitored in 111 stars of spectral
type F2-M2 on or near the main sequence in a continuation of an
observing program started by O. C. Wilson. Most of the measurements
began in 1966, with observations scheduled monthly until 1980, when
observations were scheduled sevral times per week. The records, with
a long-term precision of about 1.5%, display fluctuations that can be
identified with variations on timescales similar to the 11 yr cycle of
solar activity as well as axial rotation, and the growth and decay of
emitting regions. We present the records of chromospheric emission and
general conclusions about variations in surface magnetic activity on
timescales greater than 1 yr but less than a few decades. The results
for stars of spectral type G0-K5 V indicate a pattern of change in
rotation and chromospheric activity on an evolutionary timescale, in
which (1) young stars exhibit high average levels of activity, rapid
rotation rates, no Maunder minimum phase and rarely display a smooth,
cyclic variation; (2) stars of intermediate age (approximately 1-2
Gyr for 1 solar mass) have moderate levels of activity and rotation
rates, and occasional smooth cycles; and (3) stars as old as the Sun
and older have slower rotation rates, lower activity levels and smooth
cycles with occasional Maunder minimum-phases.

---------------------------------------------------------
Title: Pulsation and Long-Periods in Three Nearby M Supergiants
Authors: Smith, M. A.; Teays, T. J.; Taylor, L. L.; Wasatonic, R.;
Guinan, E. F.; Baliunas, S.
1995ASPC...83..403S Altcode: 1995IAUCo.155..403S; 1995aasp.conf..403S
No abstract at ADS

---------------------------------------------------------
Title: The Current State of Target Selection for NASA's High
Resolution Microwave Survey
Authors: Henry, T.; Soderblom, D.; Baliunas, S.; Davis, R.; Donahue,
R.; Latham, D.; Stefanik, R.; Torres, G.; Duquennoy, A.; Mayor, M.;
Andersen, J.; Nordstrom, B.; Olsen, E.
1995ASPC...74..207H Altcode: 1995psel.conf..207H
No abstract at ADS

---------------------------------------------------------
Title: Variations in Surface Activity of the Sun and Solar Type Stars
Authors: Soon, W. H.; Baliunas, S. L.; Zhang, Q.
1994SoPh..154..385S Altcode:
Twenty-five-year records of relative CaII H and K emission fluxes
of lower Main-Sequence stars have been measured at Mount Wilson
Observatory and reveal surface activity in most of the older G- and
K-type dwarf stars that is similar to the aperiodical activity cycle
of the contemporary Sun (i.e., the cyclic and the occasional episode
of reduced activity in the past few centuries). We find an inverse
relationship between the amplitude of the activity cycle and the
length of the cycle for the ensemble of those solar-type stars. We
also find a similar relationship using the 250-year sunspot record
(Cycles 1 to 21). The similarity between the two inverse relationships
for the solar-type stars observed for 25 years and the Sun for a longer
interval of time may suggest one common underlying physical mechanism
that is responsible for the variations in surface activity ranging
from decades to centuries.

---------------------------------------------------------
Title: The Activity Cycle of tau Ceti
Authors: Gray, David F.; Baliunas, Sallie L.
1994ApJ...427.1042G Altcode:
The temperature, granulation, and chromospehric emission of tau Ceti (HR
509, HD 10700, G8 V, B-V = 0.72) in the 1984-1992 interval are studied
for magnetic-cycle type variations. Yearly-mean temperature measurements
are determined to +/- 3-4 K using ratios of spectral line depths, and
show no systematic variations over the 9 yr interval. Granulation
is monitored using the asymmetries of spectral lines. There is
some indication of systematic variation in velocity span, but this
variation is not well established. The Ca II H and K line emission,
although weak by stellar standards, may show two cycles of variability
in the 1970-1992 time span with a period of approximately = 11 yr. No
rotation modulation is seen in any of the parameters, but the very
narrow spectral lines of tau Cet points to a nearly pole-on orientation
so that none would be expected.

---------------------------------------------------------
Title: A Method of Determining Possible Brightness Variations of
the Sun in Past Centuries from Observations of Solar-Type Stars
Authors: Zhang, Q.; Soon, W. H.; Baliunas, S. L.; Lockwood, G. W.;
Skiff, B. A.; Radick, R. R.
1994ApJ...427L.111Z Altcode:
Observations of the Sun and a number of stars with mass and age close
to the Sun show that changes in magnetic activity and brightness
are directly correlated over an activity cycle. The ratio of the two
correlated changes shows considerable scatter. If we assume that the
scatter represents variability of the one solar-type star at different
epochs, the aggregate data may represent the range of variation of the
Sun over centuries. We illustrate a technique of inferring possible
brightness variations of the Sun from a sample of solar-type stars. The
observed scatter of the ratio of all 10 solar-type stars in our sample
(stars with (B-V) greater than or approximately equal to 0.55 and less
than or approximately equal to 1.2 and mean level of chromospheric
activity R primeHK less than or approximately equal to -4.75
in the Lockwood et al. 1992 sample) plus the Sun yields a possible
increase of 0.2% - 0.6% in solar brightness as magnetic activity has
increased from the Maunder Minimum (ca. A.D. 1660-1710) to the decade
of the 1980s. The limited sample of solar-type stars will need to be
extended in order to improve the range of the estimate provided.

---------------------------------------------------------
Title: Adaptive Optics at Mount Wilson Observatory
Authors: Shelton, J. C.; Baliunas, S. L.; Russell, J.; Donahue, R. A.
1994ESOC...48...53S Altcode: 1994aao..conf...53S
No abstract at ADS

---------------------------------------------------------
Title: Adaptive Optics at Mount Wilson Observatory: Results from
the 60-inch Telescope.
Authors: Baliunas, S. L.; Shelton, J. C.; Russell, J.; Donahue, R. A.
1994ASPC...55...56B Altcode: 1994oaem.conf...56B
No abstract at ADS

---------------------------------------------------------
Title: Evidence of Surface Differential Rotation (SDR) in Lower
Main-Sequence Stars.
Authors: Donahue, R. A.; Baliunas, S. L.
1994ASPC...64..396D Altcode: 1994csss....8..396D
No abstract at ADS

---------------------------------------------------------
Title: The Evolution of Stellar Dynamo Variations.
Authors: Saar, S. H.; Brandenburg, A.; Donahue, R. A.; Baliunas, S. L.
1994ASPC...64..468S Altcode: 1994csss....8..468S
No abstract at ADS

---------------------------------------------------------
Title: A technique for estimating long-term variations of solar
total irradiance : Preliminary estimates based on observations of
the Sun and solar-type stars
Authors: Soon, W. H.; Baliunas, S. L.; Zhang, Q.
1994seit.conf..133S Altcode:
No abstract at ADS

---------------------------------------------------------
Title: Second Generation Adaptive Optics: Plans for the Mount Wilson
100-Inch Telescope.
Authors: Shelton, J. C.; Baliunas, S.
1994ASPC...55...68S Altcode: 1994oaem.conf...68S
No abstract at ADS

---------------------------------------------------------
Title: The Mount Wilson Story
Authors: Bester, M.; Baliunas, S.; Shelton, C.; Webster, L.
1994vuae.conf..105B Altcode:
No abstract at ADS

---------------------------------------------------------
Title: The Mount Wilson Observatory Metallicity Index, C RV:
Comparison with Other Photometric Systems
Authors: Soon, W. H.; Zhang, Q.; Baliunas, S. L.; Kurucz, R. L.
1993ApJ...416..787S Altcode:
A new spectrophotometric index, CRV, is assessed as a
metallicity indicator for late-type stars. The index is the ratio of
the measured photospheric fluxes in 20 Å wide passbands centered
at 400t and 3901 Å. CRV correlates directly with the
metallicity index, m1, of the Strömgren uvby system and
with the metallicity index hk, of Anthony-Twarog et al. (1991). Using observations of 236 dwarfs and 140 giants combined with
stellar atmosphere models (Kurucz 1991), we compared the sensitivity
of the CRV, m1, and hk indices to metal
abundance. We also studied the sensitivity of the CRV,
C1, and hk indices to surface gravity. The effect of
interstellar extinction on all the indices was also studied from
published mean extinction laws. We find that the CRV
index is sensitive to the variation of metal abundance, [M], over the
range examined (-5.0 ≲ [M] ≲ 0.5). CRV is also more
sensitive than the m1 index at metal-poor conditions ([M]
≲ -2.0). The CRV index has the following advantages: (1)
the passbands of CRV are dominated by Fe lines, which reduce
the uncertainty that may be introduced by the presence of lines of
α-process elements with enhanced abundances at metal-poor conditions;
(2) the effect of interstellar reddening is limited because the two
passbands are separated in wavelength by only 100 Å. We also find
that the atmospheric models produce results that agree qualitatively
with the trends of observed indices on stellar parameters such as
effective temperature, metallicity, and surface gravity.

---------------------------------------------------------
Title: An Interpretation of Cycle Periods of Stellar Chromospheric
Activity
Authors: Soon, W. H.; Baliunas, S. L.; Zhang, Q.
1993ApJ...414L..33S Altcode:
We propose (P(cyc)/P(rot))-squared, the square of the ratio of
the characteristic oscillatory timescales of stellar chromospheric
activity to the rotation period, as a useful parameterization of
the stellar activity cycle and as the observational equivalent of
the theoretical dynamo number, N(D). (P(cyc)/P(rot))-squared can be
obtained observationally from 25-yr activity records of stellar Ca II
H and K chromospheric emission fluxes of the Mount Wilson Observatory
HK Project. Using that parameterization, we study the relationships
between the period of the activity cycle and mass or age (estimated from
the average level of chromospheric emission and its calibration with
age). The quantity (P(cyc)/P(rot))-squared increases as B-V decreases,
in qualitative agreement with the expectation that as the fractional
depth of convective zone decreases (i.e., toward higher mass stars),
N(D) increases (i.e., the variability of stellar activity tends to
be more irregular). (P(cyc)/P(rot))-squared seems independent on age
for young stars but has a well-defined dependence on age for the older
stars. The difference in the behavior of (P(cyc)/P(rot))-squared with
age is another aspect of chromospheric activity that changes as a star
ages; the time of the transition depends on mass but occurs roughly
near stellar age of about 1-3 billion yr.

---------------------------------------------------------
Title: Results of adaptive optics at Mt. Wilson Obseratory
Authors: Shelton, J. Christopher; Baliunas, Sallie L.
1993SPIE.1920..371S Altcode:
We have mounted an early adaptive optics system, the Atmospheric
Compensation Experiment (ACE), on the 60-inch telescope at Mount
Wilson Observatory in California in a program designed to investigate
the performance of ACE at an astronomical site and to evaluate the
usefulness of adaptive optics for astronomy. Despite its development
as a non-astronomical instrument, ACE has produced positive results,
including the obtaining of images of single and double stars with a
resolution (full-width half-maximum) of 117 milliarcseconds at 700
nm. Improvement of image quality is obtained for guide objects with
a B magnitude brighter than 5.9. To deepen this limiting magnitude,
we have embarked on a low-noise high-speed CCD fabrication project
jointly with JPL. First devices have been fabricated. We have applied
post- processing techniques borrowed from speckle methodology to the
adaptive optics images, and find that the pre- and post-processing
techniques complement each other powerfully. We conclude that an
adaptive optics system designed specifically for visible-wavelength
astronomy would be a low-order system with good site thermal control,
combined with post-processing. Such a system could be effective,
robust and relatively low cost.

---------------------------------------------------------
Title: Correlated Optical/UV Variations of α Her and α Sco
Authors: Taylor, L. L.; Smith, M. A.; Teays, T. J.; Guinan, E. F.;
Baliunas, S. L.
1993AAS...182.4624T Altcode: 1993BAAS...25Q1242T
No abstract at ADS

---------------------------------------------------------
Title: Correlated optical/UV variations of alpha HER and alpha Sco.
Authors: Taylor, L. L.; Smith, M. A.; Teays, T. J.; Guinan, E. F.;
Baliunas, S. L.
1993BAAS...25.1242T Altcode:
No abstract at ADS

---------------------------------------------------------
Title: Mount Wilson: America's Observatory
Authors: Jastrow, Robert; Baliunas, Sallie
1993S&T....85...18J Altcode:
New developments at the Mount Wilson Observatory are reviewed. The
renovation of the 100-inch Hooker reflector is described, and projects
involving interferometry and adaptive optics are examined. Major
new programs in support of science education and amateur astronomy
are discussed.

---------------------------------------------------------
Title: CAII H and K Variations of a Sample of Hybrid Stars - do
Hybrids Pulsate
Authors: Rao, L. M.; Baliunas, S. L.; Robinson, C. R.; Frazer, J.;
Woodard, L.; Donahue, R. A.
1993ASPC...45..300R Altcode: 1993lhls.work..300R
No abstract at ADS

---------------------------------------------------------
Title: Longterm Photometric Monitoring of the Yellow Supergiant
89-HERCULIS
Authors: Donahue, R. A.; Rao, L. M.; Baliunas, S. L.; Dupree, A. K.
1993ASPC...45..285D Altcode: 1993lhls.work..285D
No abstract at ADS

---------------------------------------------------------
Title: X-ray/Optical Survey of Late-Type Stars
Authors: Piters, A. J. M.; Schmitt, J. H. M. M.; Schrijver, C. J.;
Baliunas, S.; Zwaan, C.; van Paradijs, J.
1993ASSL..183..377P Altcode: 1993pssc.symp..377P
No abstract at ADS

---------------------------------------------------------
Title: The Activity Cycle of sigma Draconis
Authors: Gray, David F.; Baliunas, Sallie L.; Lockwood, G. W.; Skiff,
Brian A.
1992ApJ...400..681G Altcode:
Investigations of the temperature and granulation of Sigma Draconis
(HR 7462, HD 185144, K0 V) are discussed. Temperature is monitored
using a line-depth ratio, and temperature variations of about 5 K are
seen. Intermediate-band photometry and Ca II H and K-line emission mimic
the temperature changes: a monotonic decline from the 1984 season,
a smooth minimum around 1988, followed by a rise back to the 1984
values at the current time. The temperature variations are physically
compatible with the photometric ones, implying a constant radius
over the activity cycle. Granulation is invariant during this portion
of the activity cycle, at least to the level of about +/- 3 m/s, or
about +/- 5 percent. The temperature variations by themselves can also
be interpreted as rotational modulation with a 20.3-d period, but no
evidence of this period is seen in the photometry, the H and K emission,
or the line asymmetries, and it is argued to be a chance occurrence.

---------------------------------------------------------
Title: Activity cycles in dwarfs: σ Draconis.
Authors: Gray, D. F.; Baliunas, S. L.; Lockwood, G. W.; Skiff, B. A.
1992JRASC..86..277G Altcode:
No abstract at ADS

---------------------------------------------------------
Title: Long-term solar brightness changes estimated from a survey
of Sun-like stars
Authors: Lockwood, G. W.; Skiff, Brian A.; Baliunas, Sallie L.;
Radick, Richard R.
1992Natur.360..653L Altcode:
THE brightness of the Sun varies during the 11-year solar cycle,
typically by less than 0.1% (refs 1, 2), and a larger brightness
variation is thought to have occurred during the Maunder minimum,
from AD 1645 to 1715 (refs 3-5). But because individual solar cycles
are different in form, amplitude and length, and because accurate
solar data have been available only for the most recent two or
three cycles, there is no direct way of understanding long-term
solar variability. Here we present a compilation of eight years of
observations of 33 Sun-like stars and report year-to-year brightness
changes that substantially exceed the analogous solar fluctuations. We
have also measured chromospheric magnetic activity in these stars and
find that it correlates with the brightness variations. During 1980-88,
solar chromospheric variability was comparable to that observed in the
stellar survey, but solar brightness variations were only one-quarter
as large. This suggests that the Sun is in an unusually steady phase
compared to similar stars, which means that reconstructing the past
historical brightness record, for example from sunspot records, may
be more risky than has been generally thought.

---------------------------------------------------------
Title: Periodogram Analysis of 240 Years of Sunspot Records
Authors: Donahue, Robert A.; Baliunas, Sallie L.
1992SoPh..141..181D Altcode:
We have analyzed the direct records of sunspot number between 1749 and
1990 with the same technique currently used in the study of stellar
activity cycles observed with Mount Wilson Observatory's 60-inch
telescope. In order to mimic the stellar time series, which span
only two decades, we analyzed twenty- and fifty-year intervals of the
sunspot data in comparison to the entire record. We also examined the
reliability of the oldest (pre-1850) sunspot records. The mean solar
cycle period determined from the entire record (1749-1990) is 11.04
yr with a computed precision of ± 0.01 yr, but an overall accuracy
of only ±1.1 yr. The large uncertainty is caused by variation of the
cycle period with time and not observational uncertainty.

---------------------------------------------------------
Title: Evidence of Differential Surface Rotation in the Solar-Type
Star HD 114710
Authors: Donahue, Robert A.; Baliunas, Sallie L.
1992ApJ...393L..63D Altcode:
Observations of the chromospheric Ca II H and K emission variability
of the intermediate-age solar-type star HD 114710 obtained at Mount
Wilson Observatory over the past 10 years reveal a secular change in the
seasonal rotation period that can be interpreted as surface differential
rotation. The dependence of rotation period on chromospheric flux
(i.e., activity-cycle phase) suggests that the star may have two
latitudinal zones of activity: one in which changes in rotation period
appear to follow the starspot activity cycle, and another confined
to a narrow range of periods that does not. The pattern of rotation
that depends on stellar cycle phase is opposite that of the sun:
the rotation period increased as activity declined during the last
activity cycle. Active region growth and decay is ruled out as the
explanation for the systematic change of the seasonal rotation periods.

---------------------------------------------------------
Title: The Magnetic Cycle of Kappa Ceti
Authors: Saar, S. H.; Baliunas, S. L.
1992ASPC...27..197S Altcode: 1992socy.work..197S
Observations of chromospheric Mg II and Ca II fluxes and photospheric
magnetic flux (spanning 10, 22, and 6 years, respectively) of the
active G5 dwarf, Kappa Ceti, show long-term variations analogous
to the solar cycle. Ca II emission varies with a period of P_cyc =
5.6 yr, and we detect a decrease in magnetic flux (~ fB) during the
declining phase of a recent cycle (1984-1988) of the form: Delta F_HK ~
(fB)^{0.4 +/- 0.2}. This is the first direct evidence for a magnetic
cycle on a star other than the Sun.

---------------------------------------------------------
Title: The Maunder-Minimum Phase of Old K-Dwarf Stars in the
Ultraviolet
Authors: Baliunas, Sallie L.
1992iue..prop.4208B Altcode:
We propose observations and analysis of chromospheric and
transition-region fluxes of C II, C IV, Mg II and Ca II of a small
sample of old, K-dwarf stars, According to 25 years of Ca II H and
K magnetic activity records from Mount Wilson Observatory, three of
the five target stars currently show periodic magnetic activity on
timescales of a decade, similar to the sun's 11-year cycle. Another
star has been in a Maunder-minimum state (e.g., low and flat magnetic
activity) since roughly 1981; the remaining star had been in the
minimum state since at least 1966, but in 1989, the star began a slow
increase in activity. The ultraviolet spectra of the K-dwarf stars
will be compared to similar IUE observations of solar-type stars made
in 1991. We intend to model and compare the cyclic and Maunder-minimum
states of magnetic activity of the sun, solar-type stars and the old,
K-dwaxf stars.

---------------------------------------------------------
Title: Recent Advances in Stellar Cycle Research
Authors: Saar, S. H.; Baliunas, S. L.
1992ASPC...27..150S Altcode: 1992socy.work..150S
We review recent work on stellar cycles, focusing on a preliminary
analysis of the first 25 years of data from the Mount Wilson Ca II
program. Cyclic variations are generally solar-like (rapid increase,
slow decline), but some stars show multiple cycle periods. About 10-15%
of the stars may be in the stellar equivalent of "Maunder minima":
epochs when cycles, but not all magnetic activity, temporarily
cease. Well-determined cycle periods show no clear dependence on
single stellar parameters, but do show correlations with more complex
formulations (e.g., alpha-Omega dynamo number) when normalized to the
magnetic diffusion timescale. The relation between this normalized cycle
frequency (Omega*_cyc) and dynamo number appears to change with activity
or age. Cycle amplitudes also correlate with Omega*_cyc, and tend to
increase with convection zone depth and P_rot. Giants in young clusters
also exhibit many of these phenomena, suggesting similar, dynamo-related
origins. Stellar differential rotation can differ markedly from the
Sun in both amplitude and form. Photometric variability increases
rapidly with increasing Ca II emission, first reversing, and eventually
eliminating the correlation between brightness and activity. Dynamos
of active stars thus appear to produce a larger spot-to-plage ratio
than inactive stars; more high-latitude spots are also seen. Surface
convective properties may also change during the cycle.

---------------------------------------------------------
Title: Unfolding Mysteries of Stellar Cycles
Authors: Baliunas, S.; Saar, S.
1992Ast....20...42B Altcode:
No abstract at ADS

---------------------------------------------------------
Title: Vulcan's Sun
Authors: Baliunas, S.; Donahue, R.; Nassiopoulos, G.; Roddenberry, G.
1991S&T....82R...5B Altcode:
No abstract at ADS

---------------------------------------------------------
Title: CA II H and K Measurements Made at Mount Wilson Observatory,
1966--1983
Authors: Duncan, Douglas K.; Vaughan, Arthur H.; Wilson, Olin C.;
Preston, George W.; Frazer, James; Lanning, Howard; Misch, Anthony;
Mueller, Jean; Soyumer, David; Woodard, L.; Baliunas, Sallie L.;
Noyes, Robert W.; Hartmann, Lee W.; Porter, Alain; Zwaan, Cornelis;
Middelkoop, Frans; Rutten, Rene G. M.; Mihalas, Dimitri
1991ApJS...76..383D Altcode:
Summaries are presented of the photoelectric measurements of stellar
Ca II H and K line intensity made at Mount Wilson Observatory during
the years 1966-1983. These results are derived from 65,263 individual
observations of 1296 stars. For each star, for each observing season,
the maximum, minimum, mean, and variation of the instrumental H and
K index 'S' are given, as well as a measurement of the accuracy of
observation. A total of 3110 seasonal summaries are reported. Factors
which affect the ability to detect stellar activity variations and
accurately measure their amplitudes, such as the accuracy of the H and K
measurements and scattered light contamination, are discussed. Relations
are given which facilitate intercomparison of 'S' values with residual
intensities derived from ordinary spectrophotometry, and for converting
measurements to absolute fluxes.

---------------------------------------------------------
Title: A Comparision of the Photometric and Chromospheric Variability
of 33 Lower Main-Sequence Stars During the Years 1984-1989
Authors: Radick, R. R.; Lockwood, G. W.; Baliunas, S. L.
1991BAAS...23..876R Altcode:
No abstract at ADS

---------------------------------------------------------
Title: The Maunder-Minimum Phase of Solar-Type Stars in the
Ultraviolet
Authors: Baliunas, Sallie L.
1991iue..prop.3938B Altcode:
We propose observations and analysis of Mg II h and k line profiles
and fluxes as well as the chromospheric and transition-region fluxes
of C II and C IV in a small sample of solar-type stars. The surface
magnetic activity (Ca II H and K relative fluxes) of the selected
solar-type stars has been monitored for over two decades at Mount
Wilson Observatory. Analysis of the Ca II magnetic activity records
suggests that solar-type stars spend most of their time in a cyclic
state, with periodicities roughly on the order of a decade. However,
solar-type stars apparently spend some time in a prolonged lull in
magnetic activity, denoted by low and nearly constant values of magnetic
activity and assumed to be similar to the Sun's Maunder Minimum. We
intend to compare the ultraviolet chromospheric and transition-region
properties of the cyclic magnetic state to the Maunderminimum state of
the solar-type stars, and compare them both to the known range of the
Sun's variability. From the ultraviolet data we will construct model
atmospheres and chromospheres of the solar-type stars and compare them
to models of the Sun.

---------------------------------------------------------
Title: What can other stars tell us about the Sun?
Authors: Noyes, Robert W.; Baliunas, S. L.; Guinan, E. F.
1991sia..book.1161N Altcode:
The authors focus on those aspects of the solar-stellar connection where
observations of other stars give information about the Sun which could
not be obtained from study of the Sun alone. Solar-like phenomena
on other stars with a range of values for key parameters (e.g.,
rotation) yield the dependence on those parameters and hence better
physical insight into the governing mechanisms. A key presumption is
that the Sun is a normal star, so that the same mechanisms govern its
behavior. Also if the Sun is normal, then study of stars with similar
masses but different ages gives information on the evolution of solar
properties, such as structure, internal dynamics, activity, etc. First,
the authors discuss stellar observations which yield information on
the internal structure of solar-like stars, including central density,
and helium abundance. Such results support the standard value for
the solar helium abundance, as well as standard stellar structure
theory. The authors note how stellar seismology can, in principle,
determine the stellar radius, as well as the degree of mixing in stellar
cores, as a function of age. Next, the authors discuss information
on the internal dynamics of the Sun, and its evolution, as inferred
from the study of the time history of surface rotation in solar-type
stars. They use the rotation-activity-age connection to infer how the
Sun's rotation and activity level has changed with age. The authors
discuss what the dependence of activity on mass and rotation can
tell us about the nature and location of the solar dynamo. Finally,
they discuss the solar activity cycle and its likely change over the
lifetime of the Sun, inferred from observation of other stars.

---------------------------------------------------------
Title: The Past, Present and Future History of Solar Magnetism:
Stellar Magnetic Activity
Authors: Baliunas, Sallie
1991suti.conf..809B Altcode:
Many stars show magnetic activity, and of those that do, the majority
appear to show variability that is cyclic, on time scales ranging
roughly from as short as 2 yr to as long as several tens of yr. Studies
of magnetic activity of other stars may yield understanding of the
complex physics underlying solar magnetism. In this regard, two
broad classes of observations of magnetic activity are useful:
(1) studies of the dependence of the mean level of magnetic
activity on stellar properties such as mass, age and rotation; and
(2) studies of the variability with time of magnetic activity of
individual stars. Results from the first class of studies are briefly
described as the underpinning for discussion of the time variability
of stellar magnetism. Solar-type stars display activity in one of
two states: approximately two-thirds of the solar-type stars show
magnetic variability that is cyclic, analogous to the 11-yr sunspot
cycle. About one-third of the solar-type stars have lower mean levels
of magnetic activity and little or no variability. Such prolonged
states of low and constant magnetic activity may be similar to the
sun during the Maunder minimum. These tentative results suggest that
solar-type stars undergo significant changes in magnetic activity
on time scales of centuries. If correlated with magnetic variations,
accompanying brightness changes for solar-type stars could be larger
during entry to and exit from the Maunder minimum state than irradiance
changes observed for the sun during the 11-yr cycle.

---------------------------------------------------------
Title: Evidence for long-term brightness changes of solar-type stars
Authors: Baliunas, Sallie; Jastrow, Robert
1990Natur.348..520B Altcode:
CHANGES in the brightness of the Sun may introduce further uncertainties
into forecasts of global warming by the greenhouse effect. The Sun is
known to vary in brightness, on a timescale of years, by 0.1% in phase
with changes in magnetic activity during the solar cycle1-3,
and variations of up to 0.4%, also correlated with surface magnetic
activity, have been found in stars similar to the Sun4. To
delimit the magnitude of solar luminosity variations on a timescale
of centuries, we have looked at the magnetic behaviour of a number
of solar-type stars over several years. Observed in random phases
of their long-term variability, they give a sample of the behaviour
of a solar-type star over a long period of time. We find indirect
evidence that these stars undergo brightness changes of more than
the 0.1% observed during the last solar cycle, a result that calls
into question the assumption of a constant Sun in calculations using
general circulation models for climate forecasting.

---------------------------------------------------------
Title: A Period Analysis of the Semi-Regular Variable SW Vir
Authors: Armour, J. E.; Henry, G. W.; Baliunas, S. L.
1990IBVS.3521....1A Altcode:
No abstract at ADS

---------------------------------------------------------
Title: 89 Her: The Atmosphere of a Strange Yellow Supergiant
Authors: Dupree, A. K.; Baliunas, S. L.; Zucker, D.; Bond, H. E.;
Meakes, M.
1990BAAS...22.1200D Altcode:
No abstract at ADS

---------------------------------------------------------
Title: Long-Term Variation of Magnetic and Chromospheric Flux on
κ Ceti
Authors: Saar, S. H.; Baliunas, S. L.
1990BAAS...22.1200S Altcode:
No abstract at ADS

---------------------------------------------------------
Title: Magnetic Activity Cycles of the Hyades and Praesepe Giant Stars
Authors: Baliunas, S. L.; Rao, L.; Frazer, J.; Robinson, C.;
Woodard, L.
1990BAAS...22.1199B Altcode:
No abstract at ADS

---------------------------------------------------------
Title: Studies of solar type stars.
Authors: Baliunas, Sallie; Jastrow, Robert
1990NASCP3086....7B Altcode: 1990cisv.nasa....7B
Satellite observations show a change of 0.1 percent in solar irradiance
over the past decade. The question arises as to whether larger changes
in irradiance may occur over century time scales. Researchers approached
this question by looking at changes in surface magnetism, since the
satellite observations also show that irradiance and surface magnetism
are correlated. To obtain information on possible variations in surface
magnetism over century-long intervals, researchers looked at records of
surface magnetism spanning up to 20 years for a sample of 74 stars of
solar type, i.e., of similar age and mass to the sun. The histories of
these stars, observed in random phases of their long-term variability,
give a snapshot at any one time of the behavior of a solar-type star
over long periods of time. Evidence on Maunder Minimum phases and
levels of magnetic activity in these solar-type stars are compared
with information on solar magnetism. Implications for solar irradiance
changes are discussed.

---------------------------------------------------------
Title: Trends in solar variability.
Authors: Jastrow, Robert; Baliunas, Sallie
1990NASCP3086..115J Altcode: 1990cisv.nasa..115J
Radiocarbon (delta C-14) records suggest a 200-year periodicity in solar
activity in the last millennium. Researchers examined the Carbon-14
record going back 8 millennia for this and other periodicities. The
computation differs from that in most previous work in its use of
techniques developed for unevenly spaced sampling without rebinning
the data to equally spaced intervals. A variation with a 200-year
period is a strong feature of the Carbon-14 record going back several
millennia. Periodicities that appear to be significant are listed and
their physical interpretation discussed.

---------------------------------------------------------
Title: Automated Precision Differential Photometry
Authors: Young, A. T.; Boyd, L. J.; Genet, R. M.; Epand, D. H.;
Lockwood, G. W.; Baliunas, S. L.; Pyper Smith, D.; Donahue, R.
1990IAPPP..39....5Y Altcode:
No abstract at ADS

---------------------------------------------------------
Title: Stellar Activity and Brightness Variations: A Glimpse at the
Sun's History
Authors: Radick, Richard R.; Lockwood, G. W.; Baliunas, Sallie L.
1990Sci...247...39R Altcode:
Radiometric measurements during the past decade from the Solar
Maximum Mission and Nimbus 7 satellites have shown that the total
solar irradiance varies in step with the sun's 11-year magnetic
activity cycle. Stellar observations from the Lowell and Mount
Wilson observatories now confirm and elaborate this discovery. These
measurements show that older stars similar to the sun tend to become
brighter as their magnetic activity level increases, just as the sun
does during its 11-year activity cycle. Younger stars, however, tend
to become fainter as their magnetic activity level increases. This
contrasting behavior suggests that the balance between the competing
phenomena that influence solar brightness variability has shifted
during the sun's lifetime.

---------------------------------------------------------
Title: Alpha Ori: evidence for pulsation.
Authors: Dupree, A. K.; Baliunas, S. L.; Guinan, E. F.; Hartmann,
L.; Sonneborn, G.
1990ASPC...11..468D Altcode: 1990cbsp.proc..468D
The bright cool supergiant α Ori (Betelgeuse, M2 Iab) shows a periodic
modulation of the ultraviolet continuum and Mg II emission line fluxes
of about 420 days that has lasted over 6.5 years of observation:
1984.0-1990.5. This modulation is identified with pulsation in the
supergiant's atmosphere. The authors' monitoring program has also
demonstrated that the longer 5.8 year period of variability identified
in the 1930's has disappeared. A longer variation of ≡11 years is
evident, and noted here for the first time. Its origin is obscure.

---------------------------------------------------------
Title: Global Warming Report
Authors: Lindzen, Richard S.; Nierenberg, William A.; Jastrow, Robert;
Baliunas, Sallie; Stuiver, Minze; Roberts, Leslie
1990Sci...247...14L Altcode:
No abstract at ADS

---------------------------------------------------------
Title: 1889 - the Beginnings of Astronomy at Mount-Wilson
Authors: Woodard, L. A.; Baliunas, S. L.
1989PASP..101..889W Altcode:
No abstract at ADS

---------------------------------------------------------
Title: Ca II H and K Flux Monitoring in Cool Stars: Rotation and
Activity Cycles
Authors: Robinson, C. R.; Baliunas, S. L.; Bennett, W.; Briggs, J.;
Frazer, J.; Noyes, R. W.; Shelton, C.; Woodard, L.; Vaughan, A. H.;
Wilson, O. C.
1989BAAS...21.1115R Altcode:
No abstract at ADS

---------------------------------------------------------
Title: Long-term Changes in Surface Activity of Solar-Type Stars
Authors: Baliunas, S.; Jastrow, R.
1989BAAS...21R1115B Altcode:
No abstract at ADS

---------------------------------------------------------
Title: Call for Participation in A Global Network of Automatic
Telescopes
Authors: Baliunas, S. L.
1989IAPPP..35...12B Altcode:
No abstract at ADS

---------------------------------------------------------
Title: Automatic Photoelectric Telescope Service: Third Annual
Summer Workshop
Authors: Baliunas, S. L.; Pyper Smith, D.; Genet, R. M.
1988IAPPP..34...37B Altcode:
No abstract at ADS

---------------------------------------------------------
Title: Methods of period analysis in the study of variable stars
with applications to AF Cygni.
Authors: Robinson, C. R.; Baliunas, S. L.; Mattei, J. A.
1988JAVSO..17Q.147R Altcode:
No abstract at ADS

---------------------------------------------------------
Title: Long-Term Variations in the Light Curve of Beta Lyrae
Authors: Guinan, E. F.; McCook, G. P.; Bergin, E. A.; Robinson, C. R.;
Baliunas, S. L.; Theokas, A. C.
1988BAAS...20..954G Altcode:
No abstract at ADS

---------------------------------------------------------
Title: Starspots Cycles and Paleoclimatology
Authors: Baliunas, S. L.
1988BAAS...20.1030B Altcode:
No abstract at ADS

---------------------------------------------------------
Title: The Mount Wilson Observatory HK Project: The Continuing
Analysis of Rotation and Stellar Magnetic Cycles
Authors: Baliunas, S. L.; Bennett, W.; Briggs, J.; Frazer, J.; Noyes,
R. W.; Robinson, C. R.; Shelton, C.; Woodard, L.; Vaughan, A. H.;
Wilson, O. C.
1988BAAS...20Q.994B Altcode:
No abstract at ADS

---------------------------------------------------------
Title: On the Relation Between Stellar Luminosity Variations and
Chromospheric Activity
Authors: Radick, R. R.; Lockwood, G. W.; Skiff, B. A.; Baliunas, S. L.
1988BAAS...20..995R Altcode:
No abstract at ADS

---------------------------------------------------------
Title: An Analysis of Photometric and Spectroscopic Observations of
the Enigmatic Eclipsing Binary Beta Lyrae
Authors: Robinson, C. R.; Baliunas, S. L.; Bopp, B. W.; Dempsey, R. C.
1988BAAS...20..954R Altcode:
No abstract at ADS

---------------------------------------------------------
Title: Periodic modulation of the atmosphere of alpha Orionis.
Authors: Dupree, A. K.; Baliunas, S. L.; Guinan, E. F.; Hartmann,
L.; Nassiopoulos, G. E.; Sonneborn, G.
1988ESASP.281a.365D Altcode: 1988IUE88...1..365D; 1988uvai....1..365D
Alpha Orionis (Betelgeuse; M2 Iab) was monitored with IUE since
1984. Discovery of a 420-day periodic modulation of the flux in the
optical and ultraviolet continua, and in the Mg II h and k line emission
cores suggests that periodic photospheric pulsations were present
from 1984 to 1986. This behavior continues through 1987. However,
the general flux level of the ultraviolet continuum and the Mg
II lines is decreasing, and the amplitude of the variation may be
reduced. These decreases may be the emerging signature of an additional
longer period. The density sensitive C II diagnostic, 2325.4/2328.1,
indicates the chromospheric densities range between log Ne
(cm-3) = 8.7 and 9.5, but periodicities are not evident.

---------------------------------------------------------
Title: Photometric Variations of Bright Stars Observed with the SAO
0.25m APT
Authors: Robinson, C. R.; Baliunas, S. L.; Boyd, L.; Genet, R.;
Donahue, R. A.
1988BAAS...20..675R Altcode:
No abstract at ADS

---------------------------------------------------------
Title: Stellar Activity Cycles and Rotation in Cool Stars Observed
from Mt. Wilson Observatory
Authors: Baliunas, S. L.; Briggs, J.; Frazer, J.; Noyes, R. W.;
Robinson, C. R.; Carroll, S.; Donahue, R. A.; Shelton, C.; Woodard,
L.; Vaughan, A. H.; Wilson, O. C.
1988BAAS...20Q.697B Altcode: 1988BAAS...20Z.697B
No abstract at ADS

---------------------------------------------------------
Title: APT Monitoring of Luminous Cool Stars
Authors: Dupree, A. K.; Baliunas, S. L.; Robinson, C. R. Donahue, R. A.
1988BAAS...20..674D Altcode:
No abstract at ADS

---------------------------------------------------------
Title: Activity Cycles in Cool Dwarfs
Authors: Baliunas, Sallie L.
1988iue..prop.3059B Altcode:
Our project encompasses both archival and new IUE
measurements. Approximately 100 cool dwarf stars have been monitored
at Mt. Wilson over the past 20 years for long-term chromospheric
Ca II variations. Many of these stars also have archival IUE Mg II
observations spanning the last decade, which we will use to study
long-term variations ("starspot activity cycles" akin to the 11-year
sunspot cycle). We plan to augment the archival Mg II spectra with
new data of several stars at critical phases of their long-term
chromospheric activity curves. We wish to investigate activity cycle
variations in chromospheric radiative losses (using Mg II and Ca
II), magnetic flux (from high-resolution optical spectra) and spot
coverage (from broadband photometry). Our goal is to study the magnetic
dynamodriven cycles as a function of stellar parameters (e.g., mass
and age). The activity cycles are welldefined by the Mt. Wilson Ca
II fluxes; we propose to examine the behavior of the Mg II fluxes, at
extrema in the activity curves in order to extract the chromospheric
radiative losses, which are better identified at Mg II compared to
Ca II due to the smaller photospheric contribution. In addition,
some of the selected stars have a history of magnetic-field strength
and distribution measurements, as well as photometric ("starspots")
coverage.

---------------------------------------------------------
Title: Luminosity and Magnetic Activity Variations on Cool Stars
Authors: Baliunas, S.
1988srov.proc..230B Altcode:
No abstract at ADS

---------------------------------------------------------
Title: Ff Agr
Authors: Baliunas, Sallie L.
1988iue..prop.3060B Altcode:
Our long-term investigations of FF Aqr, an eclipsing binary system with
G8 III and subdwarf component stars reveals that the chromospheric
activity in FF Aqr is intense and extreme, primarily because the G8
III star rotates synchronously with its 9-day orbital period. Using
the hot subdwarf star as a probe of the atmospheric structure of
the G8 III star, we have found that the ultraviolet lineforming
region of the G8 III star extends at least 1.5 stellar radii above
its photosphere. We plan to diagnose the extended atmosphere with a
high-resolution Mg II profile. We propose to investigate the masses
and absolute dimensions of the system and its components with radial
velocities derived from ultraviolet and visible spectra and thereby
study the evolutionary status of this unusual system. In addition,
ground-based spectroscopic and photometric observations of FF Aqr will
be carried out at Oak Ridge and Villanova observatories.

---------------------------------------------------------
Title: Long-Term Variations of Stellar Magnetic Activity in Lower
Main Sequence Stars
Authors: Baliunas, Sallie L.
1988ASIC..241..319B Altcode: 1988felm.conf..319B
No abstract at ADS

---------------------------------------------------------
Title: Shock Heating in V CVN
Authors: Baliunas, Sallie L.
1988iue..prop.3062B Altcode:
We propose to investigate non-radiative heating presumably caused
by relatively slow-moving shock waves through the atmosphere of the
bright, pulsating, semi-regular variable V CVn (M4-M6IIIe). Previous
visible-light investigations show a persistent 192-day pulsation with
a range in V-light of 7^m.0-9^m.5. A second, weaker pulsation often
appears with a period between 170-190 days. H-alpha emission accompanies
both pulsations but is strongest (3x nearby continuum) for the primary
pulsation. The photospheric velocity amplitude is rather modest (4-5
km s^-1) for such bright H-alpha emission. Shock models appropriate
for red, low gravity stars predict significant nonradiative losses in
ultraviolet lines, for example, Mg II (2800) and Si II (1820). While
Mira variables are known to show strong Mg II emission, we would like
to test the shock models by obtaining the ultraviolet emissions from
the less luminous semi-regular variable V CVn.

---------------------------------------------------------
Title: The Sun among the stars: what stars indicate about solar
variability.
Authors: Soderblom, D. R.; Baliunas, S. L.
1988ssgv.conf...25S Altcode:
The authors briefly review the kinds of solar-like phenomena seen on
other solar-type stars, including chromospheric and coronal activity,
spots, and magnetic fields. The stages of evolution of a one solar
mass star are described, particularly with respect to the levels of
magnetic activity that characterize those phases. Finally, the authors
examine evidence for long-term varability in solar-like stars.

---------------------------------------------------------
Title: The Automatic Photoelectric Telescope service.
Authors: Genet, R. M.; Boyd, L. J.; Kissell, K. E.; Crawford, D. L.;
Hall, D. S.; Hayes, D. S.; Baliunas, S. L.
1987PASP...99..660G Altcode:
Automatic observatories have the potential of gathering sizable
amounts of high-quality astronomical data at low cost. The Automatic
Photoelectric Telescope Service (APT Service) has realized this
potential and is routinely making photometric observations of a large
number of variable stars. However, without observers to provide on-site
monitoring, it was necessary to incorporate special quality checks into
the operation of the APT Service at its multiple automatic telescope
installation on Mount Hopkins.

---------------------------------------------------------
Title: Periodic Photospheric and Chromospheric Modulation in Alpha
Orionis (Betelgeuse)
Authors: Dupree, A. K.; Baliunas, S. L.; Guinan, E. F.; Hartmann,
L.; Nassiopoulos, G. E.; Sonneborn, G.
1987ApJ...317L..85D Altcode:
The bright cool supergiant Alpha Orionis has been monitored
spectroscopically and photometrically over the past three years
(1984-1986) in the optical and the ultraviolet wavelength regions. A
420-day periodic modulation of the flux is observed in the optical and
ultaviolet continua, and in the Mg II line emission cores. Periodic
photospheric pulsations are the most likely explanation of these
observations. This identification is based on the large amplitude of the
variation, the correlation of the continuum and chromospheric fluxes,
and the length of the observed period. Pulsation may heat and extend
the atmosphere of Alpha Ori and initiate the mass flow from the star.

---------------------------------------------------------
Title: Photometric light curves for seven rapidly-rotating K dwarfs
in the Pleiades and alpha Persei clusters.
Authors: Stauffer, John R.; Schild, Rudolph A.; Baliunas, Sallie L.;
Africano, John L.
1987PASP...99..471S Altcode:
Light curves and period estimates were obtained for several Pleiades
and Alpha Persei cluster K dwarfs which were identified as rapid
rotators in earlier spectroscopic studies. A few of the stars have
previously-published light curves, making it possible to study the
long-term variability of the light-curve shapes. The general cause of
the photometric variability observed for these stars is an asymmetric
distribution of photospheric inhomogeneities (starspots). The presence
of these inhomogeneities combined with the rotation of the star lead
to the light curves observed. The photometric periods derived are thus
identified with the rotation period of the star, making it possible
to estimate equatorial rotational velocities for these K dwarfs. These
data are of particular importance because the clusters are sufficiently
young that stars of this mass should have just arrived on the main
sequence. These data could be used to estimate the temperatures and
sizes of the spot groups necessary to produce the observed light curves
for these stars.

---------------------------------------------------------
Title: The Automatic Photoelectric Telescope Service - An Update
Authors: Kissell, K. E.; Genet, R. M.; Boyd, L. J.; Baliunas, S. L.;
Hall, D. S.
1987BAAS...19..747K Altcode:
No abstract at ADS

---------------------------------------------------------
Title: Objective Characterization of Stellar Activity
Cycles. I. Methods and Solar Cycle Analyses
Authors: Gilliland, Ronald L.; Baliunas, Sallie L.
1987ApJ...314..766G Altcode:
A large set of high-quality chromospheric activity index data of
sufficient temporal extent to allow quantitative characterization of
stellar cycles now exists thanks to the work, begun two decades ago,
by Olin Wilson. In this paper the authors discuss the methods which can
be used in analyzing the 18 yr records of Ca II H and K index data. It
is shown that derivation of accurate periods and characterization of
cycle morphology (ratio of rise to decay time) is possible, but that
the background noise, especially the growth and decay of activity,
is an important and troublesome factor to consider.

---------------------------------------------------------
Title: Stellar Activity and the Rotation of Hyades Stars
Authors: Radick, Richard R.; Baliunas, Sallie L.
1987LNP...291..217R Altcode: 1987csss....5..217R; 1987LNP87.291..217R
No abstract at ADS

---------------------------------------------------------
Title: Automatic Photometric Monitoring of Cool Stars
Authors: Genet, Russell M.; Boyd, Louis J.; Hayes, Donald S.; Baliunas,
Sallie L.; Crawford, David L.; Hall, Douglas S.; Genet, David R.
1987LNP...291..473G Altcode: 1987csss....5..473G
No abstract at ADS

---------------------------------------------------------
Title: Cool star automated photometry.
Authors: Genet, R. M.; Boyd, L. J.; Baliunas, S. L.; Hall, D. S.
1987PASP...99R1147G Altcode:
No abstract at ADS

---------------------------------------------------------
Title: Broadband photometry of bright stars: the first year of APTS
at the F. L. Whipple Observatory.
Authors: Baliunas, S. L.; Donahue, R. A.; Loeser, J. G.; Guinan,
E. F.; Genet, R. M.; Boyd, L. J.
1987ngst.symp...97B Altcode:
The authors present time series of broadband V, R, and I
photometry. Time serial measurements of photometric variations of
bright stars contain insight into the physical processes of stellar
pulsation, winds, and mass loss in stars of a wide range of spectral
type across the H-R diagram. Additionally, photometric variations in
cool stars have signaled the presence of large starspots.

---------------------------------------------------------
Title: Automated K-line photometry of active chromosphere stars.
Authors: Baliunas, S. L.; Boyd, L. J.; Genet, R. M.; Hayes, D. S.
1987ngst.symp...65B Altcode:
The relative chromospheric emission strength in weak-emission-line
solar-type stars is detectable with a 0.75-meter telescope and the
K-line filter photometer described in the paper. Integration times
for stars as faint as apparent magnitude V = 5.0 are short enough for
about 80 stars to be observed per night.

---------------------------------------------------------
Title: Combined ultraviolet studies of astronomical sources
Authors: Baliunas, S. L.; Dupree, A. K.; Elvis, M.; Huchra, J. P.;
Kenyon, S.; Raymond, J. C.
1986sao..rept.....B Altcode:
Topics addressed include: Cygnus Loop; P Cygni profiles in dwarf novae;
YY Gem; nova shells; HZ Herculis; activity cycles in cluster giants;
Alpha Ori; metal deficient giant stars; ultraviolet spectra of symbiotic
stars detected by the Very Large Array; time variability in symbiotic
stars; blue galaxies; and quasistellar objects with X-ray spectra.

---------------------------------------------------------
Title: Ultraviolet and Visible Observations of the Atmospheric
Structure of the Active G8III Component of FF Aquarii
Authors: Loeser, J. G.; Baliunas, S. L.; Raymond, J. C.; Guinan,
E. F.; Dorren, J. D.
1986BAAS...18..983L Altcode:
No abstract at ADS

---------------------------------------------------------
Title: Period Analysis of Sunspot Data
Authors: Donahue, R. A.; Baliunas, S. L.
1986BAAS...18..981D Altcode:
No abstract at ADS

---------------------------------------------------------
Title: Flares and active sectors on YY Geminorum.
Authors: Baliunas, S. L.; Raymond, J. C.; Loeser, J. G.
1986ESASP.263..181B Altcode: 1986niia.conf..181B; 1986NIA86......181B
With IUE ultraviolet and Hβ emission spectra obtained during one week,
the authors have mapped the atmospheric activity on the component
stars of YY Gem (dM1e+dM1e, P = 19h.5) as a function of
orbital and rotational phases. They have observed several flares in
Hβ on both component stars, as well as two flare-like brightenings
in the ultraviolet. The behavior of the line ratios of the C II,
C IV, and He II features is similar to that of solar surges during
the ultraviolet brightenings. The spatial extent of the ultraviolet
phenomena is likely small. In the ultraviolet and visible, certain
phases or areas of the stars are apparently more active than others.

---------------------------------------------------------
Title: Evidence of large-scale structures in the atmosphere of the
active K-dwarf component of V471 Tauri.
Authors: Guinan, E. F.; Wacker, S. W.; Baliunas, S. L.; Loesser,
J. G.; Raymond, J. C.
1986ESASP.263..197G Altcode: 1986NIA86......197G; 1986niia.conf..197G
The authors have analyzed contemporaneous IUE ultraviolet spectra and
visible photoelectric data of the eclipsing binary V471 Tauri (K2 V+DA)
between 1979 and 1985. The combined data detail the three-dimensional
structure of atmospheric loops and their associated starspots on the
K dwarf. The distribution of starspot regions on the surface of the
K star has been inferred from the visible photometry. When spots are
located near the limb of the K dwarf prior to and shortly after the
total eclipse of the white dwarf, absorption lines such as C II, C
III, C IV, and Si IV appear superimposed on the continuum of the white
dwarf. These absorption lines are likely caused by "cool coronal loops"
overlying the spots in the atmosphere of the K dwarf. Occasionally,
the loops can extend nearly one stellar radius above the surface of
the K2 V star.

---------------------------------------------------------
Title: Longterm Spectroscopic Monitoring of Alpha-Orionis
Authors: Sonneborn, G.; Baliunas, S. L.; Dupree, A. K.; Guinan, E. F.;
Hartmann, L.
1986ESASP.263..221S Altcode: 1986niia.conf..221S; 1986NIA86......221S
Ultraviolet spectroscopy and optical photometry of Alpha Orionis
(M2 Iab) have been obtained at approximately two-week intervals from
January 1984 through April 1986. The ultraviolet (2950 Å - 3050 Å)
and optical continua are found to vary in phase with each other. The
Mg II h and k total emission flux is similarly modulated, but lags
the optical light curve by about 0.25 years. However, the h and k
line fluxes vary by different amounts and in a manner which suggests
a periodicity of about one year. These and other spectral variations
may be causally linked to atmospheric disturbances, possibly related
to a close stellar companion.

---------------------------------------------------------
Title: Short-Term Periodic Variability in Alpha Orionis
Authors: Dupree, A. K.; Baliunas, S. L.; Guinan, E. F.; Hartmann,
L.; Sonneborn, G. S.
1986BAAS...18..982D Altcode:
No abstract at ADS

---------------------------------------------------------
Title: Rotation and Long-term Activity in Evolved Stars
Authors: Baliunas, S. L.; Donahue, R. A.; Noyes, R. W.; Duncan, D. K.;
Frazer, J.; Misch, A.; Mueller, J.; Woodard, L.; Vaughan, A. H.
1986BAAS...18Q.983B Altcode:
No abstract at ADS

---------------------------------------------------------
Title: The surface and atmospheric structure of the active G8III
star FF Aquarii.
Authors: Baliunas, S. L.; Loesser, J. G.; Raymond, J. C.; Guinan,
E. F.; Dorren, J. D.
1986ESASP.263..185B Altcode: 1986niia.conf..185B; 1986NIA86......185B
IUE ultraviolet investigations of the eclipsing binary FF Aquarii (G8
III+sdOB, P = 9d.2) reveal intense and extreme chromospheric
activity in the cool star. The giant star's ultraviolet spectrum can
be observed during total eclipse of the subdwarf. IUE spectra obtained
during ingress and egress of the total eclipse show that some absorption
lines in the subdwarf spectrum, for example, C II and C IV are doubled
in strength relative to quadrature. This excess absorption is likely
caused by a geometrically extended atmosphere of the G8 III star and
the enhancements are present at least to 1.5 stellar radii above the
surface of the G8 III star. Since the enhancements have persisted for
three years, they cannot be transient phenomena.

---------------------------------------------------------
Title: A Prescription for Period Analysis of Unevenly Sampled
Time Series
Authors: Horne, J. H.; Baliunas, S. L.
1986ApJ...302..757H Altcode:
A technique is presented for detecting the presence and significance
of a period in unequally sampled time series data. The calculation of
the modified periodogram for unevenly sampled data is reviewed. The
proper definition of the variance that is used to normalize the
power of the modified periodogram is clarified. It is proven that
the probability that a peak in the periodogram is noise or signal
can be easily assessed by the method given here only when the total
variance of the data is used to normalize the periodogram power. The
crucial choice of independent frequencies in calculating both the
periodogram and the false alarm probability from unevenly sampled
data is discussed. An empirical formula for estimating the number of
independent frequencies is derived. In addition, the formula for the
uncertainty of a frequency identified in the periodogram is reviewed. A
method for detecting the presence of an alias frequency caused by the
interaction of the window and signal is prescribed. With some examples
of periodic signals, the minimum number of points required to measure
reliably a signal are shown. The signal-to-noise ratio and the number
of points required to extract signals when one or two periodicities
are present in the time series are investigated.

---------------------------------------------------------
Title: The Beginnings of the Automatic Photoelectric Telescope Service
Authors: Boyd, Louis J.; Genet, Russell M.; Baliunas, Sallie L.
1986IAPPP..25...15B Altcode:
No abstract at ADS

---------------------------------------------------------
Title: Recent Spectroscopic Observations of Alpha Orionis
Authors: Dupree, A. K.; Baliunas, S. -L.; Guinan, E. F.; Hartmann,
L.; Sonneborn, G. S.
1986LNP...254..411D Altcode: 1986csss....4..411D
No abstract at ADS

---------------------------------------------------------
Title: Light, Velocity, and H-α Variations in the Pulsating Red
Giant V CVn
Authors: Loeser, J. G.; Baliunas, S. L.; Guinann, E. F.; Mattei,
J. A.; Wackern, S.
1986LNP...254..460L Altcode: 1986csss....4..460L
No abstract at ADS

---------------------------------------------------------
Title: A Flare Event on the Quiet dM Star HD 95735
Authors: Donahue, R. A.; Baliunas, S. L.; Frazer, J.; French, H.;
Lanning, H.
1986LNP...254..281D Altcode: 1986csss....4..281D
No abstract at ADS

---------------------------------------------------------
Title: Stellar activity cycles
Authors: Baliunas, Sallie L.
1986LNP...254....1B Altcode:
No abstract at ADS

---------------------------------------------------------
Title: Stellar activity cycles in lower main sequence stars.
Authors: Baliunas, S. L.
1986AdSpR...6h.231B Altcode: 1986AdSpR...6R.231B
No abstract at ADS

---------------------------------------------------------
Title: Two-Dimensional Mapping of the Activity in FF Aquari
Authors: Baliunas, Sallie
1986iue..prop.2412B Altcode:
Our long-term investigations of FF Aqr, an eclipsing binary system with
G8 III and subdwarf component stars reveals that the chromospheric
activity in FF Aqr is intense and extreme, primarily because the G8
III star rotates synchronously with its 9-day orbital period. Using the
hot subdwarf star as a probe of the atmospheric structure of the G8 III
star, we have found that the ultraviolet line-forming region of the GS
III star extends at least 1.5 stellar radii above its photosphere. We
propose to time the disappearance of the G8 III star's influence on
the subdwarf spectrum and thereby measure the geometric extent of the
ultraviolet structure through the G8 III star's atmosphere. We plan to
diagnose the physical structure of the extended atmosphere with line
strengths and ratios. Finally, we plan to investigate the nature of
the H-alpha emission enhancement as a function of orbital phase. The
subdwarf apparently causes H-alpha emission to reach maximum strength
near secondary eclipse, probably by the irradiation of the facing
hemisphere of the cool star by the hotter component. In addition,
ground-based spectroscopic and photometric observations of FF Aqr will
be carried out at Oak Ridge and Villanova observatories.

---------------------------------------------------------
Title: Stellar Activity Cycles
Authors: Baliunas, S. L.
1986LNP...254....3B Altcode: 1986csss....4....3B
No abstract at ADS

---------------------------------------------------------
Title: Automatic Photoelectric Telescope III The Mount Hopkins Site
Authors: Baliunas, S. L.; Boyd, L. J.; Genet, R. M.; Hall, D. S.;
Criswell, S.
1985IAPPP..22...47B Altcode:
No abstract at ADS

---------------------------------------------------------
Title: Design of a Dedicated 1-Meter System for Automatic Ca II
K-Line Photometry of Evolved Stars
Authors: Baliunas, S. L.; Boyd, L. J.; Genet, R. M.; Guinan, E. F.
1985IAPPP..22...32B Altcode:
No abstract at ADS

---------------------------------------------------------
Title: Book-Review - Activity in Red Dwarf Stars
Authors: Baliunas, S. L.
1985JRASC..79..327B Altcode: 1985JRASC..79..320B
No abstract at ADS

---------------------------------------------------------
Title: Post-Main Sequence Evolution of Rotation and Chromospheric
Activity
Authors: Baliunas, S. L.; Donahue, R. L.; Horne, J. H.; Duncan,
D. K.; Frazer, J.; Lanning, H.; Misch, A.; Mueller, J.; Vaughan,
A. H.; Woodward, L.
1985BAAS...17Q.877B Altcode: 1985BAAS...17..877B
No abstract at ADS

---------------------------------------------------------
Title: Book-Review - Cool Stars Stellar Systems and the Sun
Authors: Baliunas, S. L.; Hartmann, L.
1985S&T....70Q.231B Altcode:
No abstract at ADS

---------------------------------------------------------
Title: Combined ultraviolet studies of astronomical source
Authors: Dupree, A. K.; Baliunas, S. L.; Blair, W. P.; Hartmann,
L. W.; Huchra, J. P.; Raymond, J. C.; Smith, G. H.; Soderblom, D. R.
1985sao..reptR....D Altcode:
As part of its Ultraviolet Studies of Astronomical Sources the
Smithsonian Astrophysical Observatory for the period 1 Feb. 1985 to
31 July 1985 observed the following: the Cygnus Loop; oxygen-rich
supernova remnants in 1E0102-72; the Large Magellanic Cloud supernova
remnants; P Cygni profiles in dwarf novae; soft X-ray photoionization of
interstellar gas; spectral variations in AM Her stars; the mass of Feige
24; atmospheric inhomogeneities in Lambda Andromedae and FF Aquarii;
photometric and spectroscopic observation of Capella; Alpha Orionis;
metal deficient giant stars; M 67 giants; high-velocity winds from
giant stars; accretion disk parameters in cataclysmic variables;
chromospheric emission of late-type dwarfs in visual binaries;
chromospheres and transient regions of stars in the Ursa Major group;
and low-metallicity blue galaxies.

---------------------------------------------------------
Title: Time-series measurements of chromospheric CA II H and K
emission in cool stars and the search for differential rotation.
Authors: Baliunas, S. L.; Horne, J. H.; Porter, A.; Duncan, D. K.;
Frazer, J.; Lanning, H.; Misch, A.; Mueller, J.; Noyes, R. W.; Soyumer,
D.; Vaughan, A. H.; Woodard, L.
1985ApJ...294..310B Altcode:
The relative strength of the chromospheric Ca II H and K emission cores
has been monitored on a near- nightly basis during several seasons
in a variety of cool stars, predominantly those lower-main-sequence
stars observed by Wilson for long-term chromospheric activity
fluctuations. From initial data obtained in 1980, rotation rates had
been inferred from the period of modulation of chromospheric flux. We
have analyzed the rotation periods determined from three seasons of
Ca II H and K emission strengths in these stars. In 12 stars we find
evidence for varying periodicities in different seasons or for multiple
periodicities in one season, or both. For about 10 stars, significant
peaks in the power spectrum are found at two different frequencies in
at least one season. Detailed analysis of the chromospheric emission
with time reveals two possibilities consistent with the appearance
of dual periodicities in the observed time series: two distinct
periods arising from active areas rotating differentially with
respect to each other because they are at different latitudes, or
the growth and decay of active areas with subsequent birth of active
areas occurring at a stellar longitude different from the original
site of the activity. Generally, the data from only one season cannot
discriminate between these two explanations of dual peaks in the power
spectra. In four stars, however, differential surface rotation is a
more likely explanation for the observed chromospheric fluctuations
with time during the first three seasons. The fractional differential
surface rotation would be at least 5% in HD 206860, 10% in HD 101501,
11% in HD 190406 and 21% in HD 114710. The analysis of the data for
the GO V star HD 206860, with a relatively rapid rotation period of
about 5 days, indicates an active area persisting for three years.

---------------------------------------------------------
Title: The old galactic cluster NGC 188 and the origin of the W
Ursae Majoris-type contact binaries.
Authors: Baliunas, S. L.; Guinan, E. F.
1985ApJ...294..207B Altcode:
Spectroscopic observations of the four faint, short-period light
variables EP Cep, EQ Cep, ER Cep, and ES Cep confirm that they are
W UMa-type, or contact, binaries. The binaries EP Cep and ES Cep are
members of the old open cluster NGC 188 (age about 5-10 x 10 to the
9th yr) by a radial-velocity criterion; all four are associated with
the cluster by their position in space and in its color-magnitude
diagram. Combined with the light curves of the variables, the inferred
component radial velocities reveal spectroscopic mass ratios that
characterize these binaries as "W-type' systems that are physically
similar to those in the field. The high spatial incidence of these
systems in a cluster of such great age suggests that these stars have
evolved into the contact configuration from detached or semidetached
progenitors that lose orbital angular momentum, perhaps through magnetic
braking in stellar winds. The W UMa-type binaries may coalesce and
form the rapidly rotating yellow giants, the FK Comae stars.

---------------------------------------------------------
Title: Book-Review - Cool Stars Stellar Systems and the Sun
Authors: Baliunas, S. L.; Hartmann, L.; Vetesnik, M.
1985BAICz..36..128B Altcode:
No abstract at ADS

---------------------------------------------------------
Title: Three Dimension Mapping of the Atmosphere of an Active
K-Dwarf Star
Authors: Guinan, E. F.; Wacker, S. W.; Baliunas, S. L.; Loeser, J. G.
1985BAAS...17..569G Altcode:
No abstract at ADS

---------------------------------------------------------
Title: Combined ultraviolet studies of astronomical sources
Authors: Dupree, A. K.; Baliunas, S. L.; Blair, W. P.; Hartmann,
L. W.; Huchra, J. P.; Raymond, J. C.; Smith, G. H.; Soderblom, D. R.
1985sao..reptQ....D Altcode:
Ultraviolet studies of various astronomical entities are reported. Among
the specific phenomena examined were supernova remnants, dwarf novae,
red giant stars, stellar winds, binary stars, and galaxies.

---------------------------------------------------------
Title: Book-Review - Cool Stars Stellar Systems and the Sun
Authors: Baliunas, S. L.; Hartmann, L.; Rudiger, G.
1985AN....306..212B Altcode:
No abstract at ADS

---------------------------------------------------------
Title: A Search for Differential Rotation in Cool Stars Using Ca II
H and K Emission
Authors: Porter, A. C.; Baliunas, S. L.; Horne, J. H.; Noyes, R. W.;
Duncan, D. K.; Frazer, J.; Lanning, H.; Misch, A.; Mueller, J.;
Soyumer, D.; Vaughan, A. H.; Woodard, L.
1985BAAS...17..512P Altcode:
No abstract at ADS

---------------------------------------------------------
Title: Activity Cycles in the Hyades and Praesepe
Authors: Baliunas, Sallie L.
1985iue..prop.2114B Altcode:
The giant stars in the Hyades present a well-studied group of stars
of spectral type KO III. Their optical properties are quite similar,
if not identical. All rotate with the same, slow period. Yet their
chromospheric and coronal emission is different one from another, by as
much as a factor of ten. We conjecture that this disparity results from
sampling during different phases of long-term activity cycles which are
present among dwarf stars. Some variation on a three-year timescale has
been observed, as well as during phases of rotation modulation, however,
at levels too small to explain the discrepancy of the emission strengths
between the stars. We propose to investigate the range of chromospheric
activity from these giants which are similar in the visible three ways:
(a) reobserve the Hyades to search for variability on at least a
seven-year timescale; (b) reobserve another young cluster, Praesepe,
with four KO III stars similar to those in the Hyades to search for
variability on a five-year timescale; (c) extend the sampling to four
Hyades moving group stars with similar photospheric properties. The
ultraviolet spectra provided by IUE represent the longest time frame,
seven years, over which to search for long-term activity variations.

---------------------------------------------------------
Title: Stellar activity cycles.
Authors: Baliunas, S. L.; Vaughan, A. H.
1985ARA&A..23..379B Altcode:
The variety of stellar chromospheric and coronal activity provides a
framework for understanding solar and stellar magnetic activity. It
is pointed out that the recognition of an 11-yr periodicity within the
record of sunspot numbers is a relatively recent discovery of just over
a century ago. The solar activity cycle is examined, taking into account
the sunspot cycle, and solar dynamo models. Time-averaged stellar
chromospheric activity levels are considered along with long-term
activity fluctuations of cool stars. Attention is given to the direct
measurement of stellar magnetic fields, solar luminosity variations,
the RS Canum Venaticorum and BY Draconis variables, continuum variations
in lower main sequence stars, chromospheric variations in lower main
sequence stars, and chromospheric variations in evolved stars.

---------------------------------------------------------
Title: Outer atmospheres of cool stars observed with IUE.
Authors: Baliunas, S. L.
1984NASCP2349...64B Altcode: 1984IUE84.......64B; 1984fiue.rept...64B
Ultrviolet observations of cool stars in conjuction with coronal X-ray
or ground based chromospheric measurements, or both have served both to
refine and define understanding of stellar activity. The sensitivity
of IUE down to a reasonable limiting magnitude made accessible many
different stars' ultraviolet spectra. Understanding of stellar activity
throughout stellar atmospheres has progressed because observation in
the ultraviolet range of particular stars can be done in great detail.

---------------------------------------------------------
Title: Betelgeuse at maximum luminosity.
Authors: Dupree, A. K.; Sonneborn, G.; Baliunas, S. L.; Guinan, E. F.;
Hartmann, L.; Hayes, D. P.
1984NASCP2349..462D Altcode: 1984IUE84......462D; 1984fiue.rept..462D
Betelgeuse (Alpha Ori; M2 Iab) was extremely bright at optical
wavelengths and in the Mg II resonance lines during January and February
1984 when an intrinsic brightening occurred in the photosphere and
chromosphere. Linear polarization in the B-band at this time was not
anomalous when compared to earlier epochs. The core of the Hα line
was redshifted by about 10 km/s with respect to the photospheric lines
during January/February as compared to measurements made five months
previously. There may be periodic variations in the chromospheric flux.

---------------------------------------------------------
Title: Evidence for global oscillations in the K2 dwarf epsilon
Eridani.
Authors: Noyes, R. W.; Baliunas, S. L.; Belserene, E.; Duncan, D. K.;
Horne, J.; Widrow, L.
1984ApJ...285L..23N Altcode:
Evidence of global p-mode oscillations in the K2 V star Epsilon Eridani,
based on observed time variations in the Ca II H and K emission lines,
is presented. Power spectra of time series of Ca II intensity measures
reveal a number of peaks spaced at about 86 and 172 micro-Hz. The
172 micro-Hz spacing is significantly larger than the corresponding
spacing observed for solar p-mode oscillations but is in excellent
agreement with predictions for a star of the known radius of Epsilon
Eri. The amplitude of the oscillations seen in the H and K flux of this
chromospherically active star is much larger than in the sun. Peak
power in the H and K fluctuations occurs at periods near 10 minutes,
in contrast to predictions of peak oscillation amplitude near four
minutes for a K2 dwarf.

---------------------------------------------------------
Title: Activity Cycles of Lower Main-Sequence Stars: Eighteen Years
of Research
Authors: Baliunas, S. L.; Donahue, R. A.; Horne, J. H.; Noyes, R. W.;
Porter, A.; Gilliland, R.; Duncan, D. K.; Frazer, J.; Lanning, H.;
Misch, A.; Mueller, J.; Soyumer, D.; Vaughan, A. H.; Wilson, O. C.;
Woodard, L. A.
1984BAAS...16R.899B Altcode:
No abstract at ADS

---------------------------------------------------------
Title: Chromospheric emission and rotation of the Hyades lower
main sequence.
Authors: Duncan, D. K.; Baliunas, S. L.; Noyes, R. W.; Vaughan, A. H.;
Frazer, J.; Lanning, H. H.
1984PASP...96..707D Altcode:
The identity of chromospheric Ca II H- and K-line emission has
been monitored for two seasons in a large sample of Hyades F and
G dwarfs. Mean emission levels vary smoothly with spectral type,
suggesting that the rotation rate at a given spectral type varies
relatively little, and that the rotation rate decreases smoothly
as a function of mass. In this case the mechanism which controls
pre-main-sequence angular momentum loss in late-type stars must be
self-regulating to a high degree.

---------------------------------------------------------
Title: Objective Characterization of Stellar Cycles
Authors: Gilliland, R. L.; Baliunas, S. L.
1984BAAS...16..899G Altcode:
No abstract at ADS

---------------------------------------------------------
Title: Flares &amp; Activity in FF Aquarii &amp; Lambda Andromedae
Authors: Baliunas, Sallie L.
1984iue..prop.1765B Altcode:
The serendipitous detection of an extremely energetic flare on
the activechromosphere G8 IV-III star lambda And provides a unique
opportunity for comparative flare studies. Our long-term investigations
of A And and FF Aqr, a binary with a G8 III star reveals that the
chromospheric activity in FF Aqr is more intense and extreme than
in lambda And, primarily because the G8 III star FF Aqr rotates six
times faster than lambda And. Some of the UV surface fluxes from FF
Aqr and 20-50 times those of A And. In photometric U-band monitoring
reveals flaring on the G8 III star in FF Aqr as bright as a magnitude
and as frequently as once an hour. We expect, therefore, a flare more
luminous than observed on lambda And. Such a flare would provide strong
and extreme constraints for theoretical models of stellar flares.

---------------------------------------------------------
Title: Ultraviolet flare on lambda Andromedae.
Authors: Baliunas, S. L.; Guinan, E. F.; Dupree, A. K.
1984ApJ...282..733B Altcode:
On November 5, 6, 1982, a luminous, flarelike brightening of the
ultraviolet emissions was observed with IUE from the active RS CVn
type star Lambda And during the phase of rotation period corresponding
to maximum area coverage of the visible hemisphere by starspots and
active regions. Enhancements during the flare in the ultraviolet
emission lines as large as factors of several and in the ultraviolet
continuum up to 80 percent persisted for over 5 hours. The bulk of
the radiative output of the flare occurred in Mg II h and k and H I
Ly-alpha. Because of the long duration and extreme luminosity of the
event, the energy radiated by the flare alone is in excess of 10 to the
35th ergs just in the ultraviolet region. This is the most energetic
stellar flare ever recorded in the ultraviolet. In addition, it is the
first ultraviolet flare observed from a giant star. In comparison to
the largest solar flares, the flare on Lambda And is at least three
orders of magnitude more energetic in similar emission lines.

---------------------------------------------------------
Title: Ultraviolet and visible flare observations of EQ Pegasi B.
Authors: Baliunas, S. L.; Raymond, J. C.
1984ApJ...282..728B Altcode:
EQ Peg AB (dM43+dM5.5e) was monitored in the visible at the Whipple
Observatory and ultraviolet with IUE on September 2, 1981. In the
visible spectrophotometry of EQ Peg B the H-beta emission strengthened
by a factor of 2 relative to the nearby stellar continuum within
a few minutes and decayed over an hour. This flare in EQ Peg B was
coincident with the enhancement of ultraviolet emission lines of C
IV 1550 A, He II 1640 A, and C II 1335 A in the combined light of EQ
Peg AB. The ultraviolet fluxes during the flare can be interpreted
as similar to those either in the thermal phases of large two-ribbon
solor flares where radiative cooling balances thermal conduction or in
gas cooling quickly from X-ray emitting temperatures. The appearance
of the ultraviolet continuum at 1700-1900 A and ratio of H-alpha to
H-beta fluxes during the flare are consistent with models producing
these emissions in the chromosphere.

---------------------------------------------------------
Title: PM. 04 Stars, Atmospheres, and Shells: Potential for
High-Resolution Imaging
Authors: Dupree, A. K.; Baliunas, S. L.; Guinan, E. F.
1984BAAS...16..797D Altcode:
Substantial progress in stellar physics can result from one- or
two-dimensional imaging at a spatial resolution of 10-3 to
10-5arc sec. The direct measurement of stellar diameters,
surface and atmospheric features, and extended shells can significantly
advance the knowledge of stellar structure, activity, and evolution. A
dwarf star - the sun - and a supergiant star - Alpha Orionis - are
used to illustrate the possibilities of measurements with high spatial
resolution. In addition, magnetically sensitive lines can trace the
distribution of activity across a stellar surface.

---------------------------------------------------------
Title: Rotation, convection, and magnetic activity in lower
main-sequence stars.
Authors: Noyes, R. W.; Hartmann, L. W.; Baliunas, S. L.; Duncan,
D. K.; Vaughan, A. H.
1984ApJ...279..763N Altcode:
Rotation periods are reported for 14 main-sequence stars, bringing the
total number of such stars with well determined rotation periods to
41. It is found that the mean level of their Ca II H and K emission
(averaged over 15 years) is correlated with rotation period, as
expected. However, there is a further dependence of the emission
on spectral type. When expressed as the ratio of chromospheric flux
to total bolometric flux, the emission is well correlated with the
parameter P(obs)/tau(c), where P(obs) is the observed rotation period
and tau(c)(B - V) is a theoretically-derived convective overturn time,
calculated assuming a mixing length to scale height ratio alpha of about
2. This finding is consonant with general predictions of dynamo theory,
if the relation between chromospheric emission and dynamo-generated
magnetic fields is essentially independent of rotation rate and spectral
type for the stars considered. The dependence of mean chromospheric
emission on rotation and spectral type is essentially the same for
stars above and below the Vaughan-Preston (1980) 'gap', thus casting
doubt on explanations of the gap in terms of a discontinuity in dynamo
characteristics.

---------------------------------------------------------
Title: A study of the dependence of MG II emission on the rotational
periodsof main-sequence stars.
Authors: Hartmann, L.; Baliunas, S. L.; Duncan, D. K.; Noyes, R. W.
1984ApJ...279..778H Altcode:
International Ultraviolet Explorer satellite measurements of the
Mg II chromospheric emission from a sample of late-type dwarfs with
known rotational periods are presented. The ratio of chromospheric
to photospheric luminosity for the late-G and K type stars in this
sample can be fitted within the probable errors by a single function of
rotational period. The chromospheric emission of early-G and F dwarfs
appears to depend upon rotation in a qualitatively different way, which
suggests that the rapid variation of convective zone properties in this
spectral range affects the dissipation of energy in the chromosphere. Mg
II h and k emission correlates fairly well with Ca II emission. However,
the data sample is not large enough at present to show conclusively
that Mg II emission exhibits precisely the same dependence on rotation
and spectral type as the Ca II H and K line fluxes.

---------------------------------------------------------
Title: Chromospheric Activity and Rotation in the Giant Stars in
the Hyades and Praesepe Clusters
Authors: Baliunas, S. L.; Horne, J.; Noyes, R. W.; Duncan, D. K.;
Frazer, J.; Lanning, H.; Misch, A.; Soyumer, T.; Woodard, L.
1984BAAS...16..508B Altcode:
No abstract at ADS

---------------------------------------------------------
Title: Stars, atmospheres, and shells: potential for high-resolution
imaging.
Authors: Dupree, A. K.; Baliunas, S. L.; Guinan, E. F.
1984BAAS...16..558D Altcode:
No abstract at ADS

---------------------------------------------------------
Title: Book-Review - Cool Stars Stellar Systems and the Sun
Authors: Baliunas, S. L.; Hartmann, L.; Schrijver, C. J.
1984SSRv...39..375B Altcode:
No abstract at ADS

---------------------------------------------------------
Title: Cool Stars, Stellar Systems, and the Sun
Authors: Baliunas, Sallie L.; Hartmann, Lee
1984LNP...193.....B Altcode: 1984csss....3.....B
No abstract at ADS

---------------------------------------------------------
Title: Evolution of Rotation in Main-Sequence Stars
Authors: Baliunas, Sallie L.
1984LNP...193..114B Altcode: 1984csss....3..114B
A review of the classical and modern measurements of axial rotation
and their implications for the evolution of rotation of stars on the
lower main sequence is given. From stars of main-sequence spectral
type A through early K, the dependence of rotation on mass and age
is investigated, from results for stars in open clusters and in the
field. The high-mass, single, normal dwarf stars of spectral type A
display a common mean projected rotational velocity dependent on their
masses and re gardless of their ages. The angular momentum per unit
mass in this range decreases slowly with decreasing mass.

---------------------------------------------------------
Title: Time Series Measurements of Chromospheric Emission and Possible
Evidence for Differential Rotation
Authors: Horne, J. H.; Baliunas, S. L.; Noyes, R. W.; Duncan, D. K.;
Vaughan, A. H.
1984LNP...193..143H Altcode: 1984csss....3..143H
No abstract at ADS

---------------------------------------------------------
Title: Four W Ursae Majoris Contact Binaries in the Old Galactic
Cluster NGC 188
Authors: Baliunas, Sallie L.; Guinan, Edward F.
1984LNP...193..223B Altcode: 1984csss....3..223B
No abstract at ADS

---------------------------------------------------------
Title: Stellar rotation in lower main-sequence stars measured from
time variations in H and K emission-line fluxes. II. Detailed analysis
of the 1980 observing season data.
Authors: Baliunas, S. L.; Hartmann, L.; Noyes, R. W.; Vaughan, H.;
Preston, G. W.; Frazer, J.; Lanning, H.; Middelkoop, F.; Mihalas, D.
1983ApJ...275..752B Altcode:
For a sample of 47 lower main-sequence stars, including the Sun,
and eight evolved stars, the relative strength of the Ca II H and
K emission cores has been measured daily over a nearly continuous
interval during 1980 July through October at Mount Wilson. From these
time series measurements of chromospheric emission, rotation rates
have been inferred with quantitative estimates of both the reality and
precision of the rotation periods. We find rotation rates easily for
the main-sequence stars with strong emission or those later than about
spectral type K0. With this technique, rotation rates can be measured
precisely for the first time for equatorial velocities as slow as 1 km
s-1 and independently of the aspect of the rotation axis. In
a limited range of spectral type, a small sample of stars indicates that
chromospheric emission decreases smoothly as a function of rotation
period. No conclusion can be drawn on the question of the reality
of a discontinuity in chromospheric emission as a function of time
(the "Vaughan-Preston" gap for stars in the solar neighborhood). In our sample of giant stars, the G2 III star HD 218658 shows a
persistent fluctuation of 4.6 days, a period that is inconsistent with
stellar rotation. The G0 III star HD 6903 is a previously unreported
FK Comae-type star. For a few main-sequence stars, measurements
continued beyond 1980 October suggest the presence of active longitudes
(if not individual active regions) persisting through the observing
season 1981.

---------------------------------------------------------
Title: Combined ultraviolet studies of astronomical sources
Authors: Dupree, A. K.; Giampapa, M. S.; Huchra, J. P.; Noyes,
R. W.; Hartmann, L. W.; Raymond, J. C.; Blair, W. P.; Bothun, G. D.;
Patterson, J. O.; Baliunas, S. L.
1983sao..reptR....D Altcode:
Ultraviolet spectra of non-radiataive shock waves grain destruction and
elemental abundances in interstellar shocks, carbon abundance in M33
and M31 from supernova remnants, determination of the mass function
in the large Magellanic cloud, UV spectra of white dwarf pulsars,
stellar flares, availability of the double quasar Q 0957 + 56' AB,
spectra of late-F dwarfs and their relation to rotation, dynamics of
hot gas surrounding hybrid stars, high resolution study of epsilon
coronae Austriual, active regions on solar-type dwarfs as a function of
rotation rate and age, coordinated chromospheric synoptic observations
of selected late-type stars, the two-component atmosphere of Lambda
Andromedae, and activity in Hyades giants are discussed.

---------------------------------------------------------
Title: Progress in stellar chromospheres observed with the
International Ultraviolet Explorer satellite.
Authors: Baliunas, S. L.
1983PASP...95..532B Altcode:
The historical knowledge gathered over the past two decades of visible
spectrum studies, predominantly at Ca II H and K, combined with
detailed theoretical models and high spectrum-and spatial-resolution
work on the solar atmosphere from space provide the framework for
ultraviolet measurements from IUE for furthering our understanding of
the solar-and-stellar activity connection. Quantitative measurements
of the behavior of stellar chromospheric and coronal emission can be
investigated as a function of stellar parameters such as age, rotation
rate, and mass. Together the visible and ultraviolet spectra probe the
stellar atmospheres as a function of height and reveal the energy budget
in a variety of late-type stars. Atmospheric inhomogeneities such as
stellar active areas, spots, and flares can be profitably studied in
the ultraviolet and visible. At high spectrum resolutions with IUE,
the dynamics of the outer atmospheres, including stellar winds and
mass outflows, yield constraints on global models for mass loss in
late-type stars.

---------------------------------------------------------
Title: Binary Star Evolution in the Old, Open Cluster NGC 188
Authors: Baliunas, S. L.; Guinan, E. F.
1983BAAS...15..924B Altcode:
No abstract at ADS

---------------------------------------------------------
Title: Ca II H and K emission and rotation of the Hyades lower
main sequence.
Authors: Duncan, D. K.; Baliunas, S. L.; Noyes, R. F.; Vaughan, A. H.
1983PASP...95..589D Altcode:
No abstract at ADS

---------------------------------------------------------
Title: Chromospheric and coronal emissions from the giants in
the Hyades.
Authors: Baliunas, S. L.; Hartmann, L.; Dupree, A. K.
1983ApJ...271..672B Altcode:
The visible Ca II K and International Ultraviolet Explorer spectra
from the four K0 III stars (theta-1, gamma, delta, and epsilon Tau)
in the Hyades, along with a field giant of similar spectral type,
beta Gem, have been measured. Among the Hyades giants, the range of
the high-temperature emissions can be a factor of 6 or more for C IV
and an order of magnitude in the X-ray luminosity measured by Stern et
al. (1981). For these presumably coeval cluster giants with similar
macroscopic parameters, such as age, mass, effective temperature,
gravity, and projected rotational velocity, the observed range in
chromospheric and coronal emissions is not easily explained by the
dominant factors thought to control these emissions in cool stars. It
is possible that the emissions are time variable, on a time scale
longer than six months. This would be the first evidence that giants
undergo magnetic activity cycles similar to those of dwarf stars.

---------------------------------------------------------
Title: Observations of the RS CVn Star HD 26337 with the International
Ultraviolet Explorer Satellite
Authors: Baliunas, S. L.; Blair, W. P.; Guinan, E. F.
1983IBVS.2323....1B Altcode:
No abstract at ADS

---------------------------------------------------------
Title: Identification and properties of the M giant/X-ray system HD
154791 =2A 1704+241.
Authors: Garcia, M.; Baliunas, S. L.; Doxsey, R.; Elvis, M.; Fabbiano,
G.; Koenigsberger, G.; Patterson, J.; Schwartz, D.; Swank, J.; Watson,
M. G.
1983ApJ...267..291G Altcode:
The Aerial V X-ray source 2A 1704+241 (= 4U 1700+24 = 3A 1703+241) is
identified with the M3 II star HD 154791. The identification is based on
a precise X-ray position determined by the HEAO 1 scanning modulation
collimator and the Einstein Observatory imaging proportional counter,
together with a spectrum measured by the International Ultraviolet
Explorer. The ultraviolet spectrum shows strong emission of C IV
1550 A, N v 1238 A, and Mg II 2800 A, which is very unusual among M
giants. This is the first X-ray detection of an M giant which has a
completely normal optical spectrum. The X-ray luminosity reaches three
orders of magnitude above the mean upper limit for the coronal X-ray
flux from M giants. Although there is no direct evidence for a binary
system, since radial velocity variations have not been observed, it
is shown that a plausible neutron star binary model can be constructed.

---------------------------------------------------------
Title: Rotation, Convection, and Solar-Stellar Dynamos
Authors: Noyes, R. W.; Baliunas, S. L.; Duncan, D. K.; Hartmann,
L. W.; Vaughan, A. H.
1983BAAS...15Q.698N Altcode:
No abstract at ADS

---------------------------------------------------------
Title: Vertical Structure of the Atmospheres of Active G-Giant Stars
Authors: Baliunas, Sallie L.
1983iue..prop.1409B Altcode:
Two G8 giants in binary systems present a unique opportunity to
measure the vertical scale height of emitting regions through the
extended atmospheres of these stars. For lambda And, geometrically
extended regions will be mapped as an active area which either appears
or disappears over the stellar limb. In FF Aqr, the hot, sdO binary
companion will be used to probe geometrically-extended inhomogeneities
during eclipse through the late-type giant atmosphere. Study of the
similarities and differences between atmospheric inhomogeneities
as a function of temperature and height may reveal separable data
on localized "active" areas, compared to non-localized background
emission. With a comparison of these two stars with ostensibly
similar photospheres but widely different rotation rates we hope to
investigate the interplay of rotation with the coronal structure and
coronal heating rates.

---------------------------------------------------------
Title: Stellar activity and calcium emission variability
Authors: Baliunas, S. L.
1983ASSL..102..195B Altcode: 1983ards.proc..195B; 1983IAUCo..71..195B
Findings on the long-term behavior, intermediate timescale
variations, and short-term variations obtained through time series
analysis of fluctuations of Ca II H and K chromospheric emission are
summarized. Many of the dwarfs in the spectrum type range F-G-K-early M
undergo long-term variations. Forty percent show smooth fluctuations
which appear to be cyclic with periods of 5-10 years or slightly
longer. Forty percent show erratic variations and the remainder show
little observable fluctuations. Rotation in open-cluster dwarfs slows
with decreasing Ca II emission strength, and no good correlation exists
between rotation period and activity cycle period. The success rate
for determining rotation in the chromospherically more active stars
can be over 80 percent. Flarelike events in chromospheric emission
similar to those seen in flare stars and large solar flares have been
observed in HD 22049 and other G-K stars.

---------------------------------------------------------
Title: Stellar activity measured at Ca II H and K.
Authors: Baliunas, S. L.
1982SAOSR.392B..31B Altcode: 1982csss....2...31B
No abstract at ADS

---------------------------------------------------------
Title: Ultraviolet and optical spectrum studies of lambda Andromedae :
evidence for atmospheric inhomogeneities.
Authors: Baliunas, S. L.; Dupree, A. K.
1982ApJ...252..668B Altcode:
To pursue the study of solar phenomena in cool stars, chromospheric
activity in Lambda Andromedae (HD 222107 has been investigated). This
binary, whose primary star is G7-G8 IV-III, shows strong
chromospheric emissions and is related to the RS CVn-type systems. The
first quantitative measurements of chromospheric and solar-type
transition-region emissions as a function of the variable starspot
and active-region phenomena in an RS CVn star are presented. The
presence of optically darker starspots in Lambda And coincides
with the brightening of both Ca II K emission and the ultraviolet
transition-region lines. The ultraviolet and optical spectra show
attributes of starspots, active regions, and mass flow. Analogies to
solar activity are successful in explaining these observations.

---------------------------------------------------------
Title: Stellar Flares
Authors: Baliunas, Sallie L.
1982iue..prop.1057B Altcode:
Flares on dMe stars have been observed In optical continuum radiation
for many years. IUE has made it possible to observe these flares in
ultraviolet emission lines and continuum. We wish to monitor two stars
in both the ultraviolet and optical spectrum regions to study the energy
released by flares and the nature of the continuum radiation. We will
employ density diagnostics and emission measure analysis techniques
developed for solar observations. The He II A 1840 line will be used
to infer the flare luminosity at 56 &lt; hv &lt; 100 eV.

---------------------------------------------------------
Title: Activity in the Hyades Giants
Authors: Baliunas, Sallie L.
1982iue..prop.1063B Altcode:
The giant stars In the Hyades present a well-studied group of stars of
spectral type KO Ill. Their optical properties are quite similar, If
not Identical. All appear to be slow rotators. Yet their chromospherIc
and coronal emission Is different one from the other, by more than a
factor of ten. We conjecture that this disparity results from different
activity cycles - much as Is present In dwarf stars. We propose to
reobserve these giants to search for variability on a three year
time scale.

---------------------------------------------------------
Title: The Two Component Atmosphere of Lambda Andromedae
Authors: Baliunas, Sallie L.
1982iue..prop.1071B Altcode:
From optical and ultraviolet observations, Lambda Andromedae has been
found to show a clear dichotomy In the structure of its atmosphere
which is strikingly similar to that found in the Sun between active
regions and the quiet Sun or coronal holes. We propose to measure at
high resolution the widths, fluxes and asymmetries of ultraviolet lines
formed in the extended atmosphere of the primary to detect the presence
and character of a stellar wind and the change in atmospheric structure
when active regions and/or spots are present. Frequent observations
In the Mg II transition will be made in an attempt to detect the
high chomosphere equivalent of the rapid (~ 5 minutes) fluctuations
discovered in the Ca K emission cores suggesting impulsive events.

---------------------------------------------------------
Title: Stellar rotation in lower main-sequence stars measured from
time variations in H and K emission-line fluxes. I. Initial results.
Authors: Vaughan, A. H.; Baliunas, S. L.; Middelkoop, F.; Hartmann,
L. W.; Mihalas, D.; Noyes, R. W.; Preston, G. W.
1981ApJ...250..276V Altcode:
Fluxes at 1 Å bands at the centers of the H and K lines in 46 lower
main sequence field stars, and in eight selected subgiants and giant
stars, have been measured at nightly intervals in the course of a
nearly continuous 14-week observing run. In 19 stars we have found
clear evidence of rotational modulation, from which values of the
rotational periods can be assigned by inspection. In nine others,
periods have been found by an autocorrelation analysis of the flux
records. The periods obtained imply rotation velocities that are in
good accord with spectroscopically determined values of V sin i in
the literature for 13 of the stars we have observed. Much of
the short term scatter in H-K flux observed by Wilson appears to be
caused by rotational modulation, although variations on other time
scales are also present. As many as 80% of the chromospherically
active (i.e., young) stars display prominent rotational modulation,
and in some cases the phase of the modulation remained unchanged for
the entire observing period, suggesting that markedly asymmetric and
long-lived distributions of active regions are common in such stars. At a given (B - V) &lt; 1.0, the strength of H-K emission is shown
to vary as a function of rate of rotation, suggesting that rotation,
rather than initial conditions or age per se, is the chief parameter
influencing chromospheric output. From data on stellar activity
cycles available at present, it is suggested that periodic cycles
resembling the Sun's are almost exclusively found in stars with
rotation periods in excess of about 20 days; and, except for this
threshold effect, the cycle periods are uncorrelated with rotation rate.

---------------------------------------------------------
Title: Short time-scale variability of chromospheric CaII in
late-type stars.
Authors: Baliunas, S. L.; Hartmann, L.; Vaughan, A. H.; Liller, W.;
Dupree, A. K.
1981ApJ...246..473B Altcode:
The short time-scale variability of singly ionized calcium chromospheric
emission has been investigated in a few late-type stars. Emission-line
variations with time scales of a few minutes to hours are seen
in Alpha Tau (K5 III), Lambda And (G8 III-IV), and Epsilon Eri
(K2 V). The existence of substantial chromospheric flux changes
(10 to the 30th to 10 to the 32nd ergs) over short periods of time
suggests that the calcium emission arises from a few small, coherent
regions. Frequencies present in the data are discussed in the context
of acoustic wave predictions and estimated acoustic cutoff frequencies
for giants and dwarfs.

---------------------------------------------------------
Title: IUE - ultraviolet and optical chromospheric studies of
late-type giants in the Hyades cluster.
Authors: Baliunas, S. L.; Hartmann, L.; Dupree, A. K.
1981NASCP2171..325B Altcode: 1981uviu.nasa..325B; 1980IUE80......325B; 1981NASCP3171..325B
Ultraviolet and optical observations of four bright, late-type giants in
the Hyades cluster detected with IUE are presented in order to study
chromospheric and coronal activity in stars of the same age. Two
of the giants, 77 Tau and gamma Tau, clearly exhibit emission in
the high temperature ions such as N V, C IV, and Si IV at levels
several times larger than the upper limits for the other two giants,
delta Tau and epsilon Tau. Comparison of the Mg II h and k fluxes and
the Ca II K emission strengths shows that 77 Tau and gamma Tau have
larger chromospheric radiative losses than delta Tau, epsilon Tau,
and beta Gem, a field giant which also displays low upper limits to
emission from high temperature ions. Coronal X-ray emission indicates
that the surface flux in X-rays is an order of magnitude brighter in
77 Tau than in delta Tau. The results indicate that a parameter other
than age, temperature, gravity or metallicity determines the amount
of chromospheric and coronal emission in late-type giants.

---------------------------------------------------------
Title: Optical identification of H 0123+07.5 and 4U 1137-65 : hard
X-ray emission from RS CVn systems.
Authors: Garcia, M.; Baliunas, S. L.; Conroy, M.; Johnston, M. D.;
Ralph, E.; Roberts, W.; Schwartz, D. A.; Tonry, J.
1980ApJ...240L.107G Altcode:
No abstract at ADS

---------------------------------------------------------
Title: Ultraviolet and Optical Chromospheric Activity in
Lambda-Andromedae - Evidence for Starspots and Active Regions
Authors: Baliunas, S. L.; Dupree, A. K.
1980SAOSR.389..101B Altcode: 1980csss....1..101B
No abstract at ADS

---------------------------------------------------------
Title: Optical and Ultraviolet Studies of Stellar Chromospheres of
Lambda Andromedae and Other Late-Type Stars.
Authors: Baliunas, S. L.
1980PhDT........10B Altcode:
Chromospheric studies of the outer atmospheres of several late-type
stars are presented along with a comprehensive study of (lamda)
Andromedae, an "active chromosphere" star. Investigations were made
of the chromospheric features of Ca II H and K, Mg II h and k, and
other, high-temperature emissions accessible to the Copernicus and
IUE satellites. Analogues to solar activity are consistent with the
spectral behavior of the chromospheric indicators. The chromospheric
activity and variability in Ca II H and K in (lamda) And are similar
to sunspot and solar flare activity. In addition, a search was begun
for short-timescale (few minutes) fluctuations in the H and K cores
in several late-type stars. Calibrated spectrophotometry for the
Ca II K profiles and additional constraints provided by H(alpha)
and the ultraviolet observations of Mg II and the high-temperature
transition-region emissions were employed in the construction of
semi-empirical chromospheric models of (lamda) And, (alpha) Aur, and
(alpha) Boo. A prescription is given for models of active-chromosphere
stars, which may also be useful for other late-type stars.

---------------------------------------------------------
Title: Silicon lines as spectral diagnostics - The effect of charge
transfer
Authors: Baliunas, S. L.; Butler, S. E.
1980ApJ...235L..45B Altcode:
The paper discusses the importance of charge transfer as an ionization
source in astrophysical plasmas. The effect of the rapid charge
transfer reactions Si(+) + H(+) yields Si(+2) + H - 2.74 eV and SI(2+)
+ He(+) yields Si(+3) + He - 8.88 eV on the ionization equilibrium
of silicon is calculated. The dominant ionization stage of silicon
in a coronal plasma is shown to be Si(+2) for temperatures as low as
20,000 K in contrast to the temperature of 35,000 K determined from
earlier ionization equilibrium calculations. The Si(+3) abundance is
also substantially modified. For the quiet-sun transition region, the
effect of charge transfer upon the emissivity of the Si III lambda 1892
emission line is calculated. The peak emissivity occurs at a temperature
a factor of 2 lower and is an order of magnitude higher than implied
by calculations neglecting the silicon charge-transfer process. The
results have widespread importance for the interpretation of solar,
stellar, interstellar, and extragalactic silicon lines.

---------------------------------------------------------
Title: Optical and ultraviolet studies of stellar chromospheres of
lambda Andromedae and other late-type stars
Authors: Baliunas, Sallie Louise
1980PhDT.......212B Altcode:
No abstract at ADS

---------------------------------------------------------
Title: Optical observations of SS 433.
Authors: Noyes, R.; Liller, W.; Davis, M.; Baliunas, S.; Sternberg,
A.; Tokarz, S.
1979BAAS...11..732N Altcode:
No abstract at ADS

---------------------------------------------------------
Title: Chromospheric Event in alpha Aquarii
Authors: Dupree, A. K.; Baliunas, S.
1979IAUC.3435....1D Altcode: 1979IAUC.3435....0D
A. K. Dupree and S. Baliunas, Center for Astrophysics, report that IUE
observations of alpha Aqr (G2Ib) on Nov. 11 show substantial changes
in the Mg II line profile from measurements 11 months earlier. The
flux in the short-wavelength emission peaks at 279.5 and 280.2 nm
has increased and is accompanied by a broadening of the profile and
an increased absorption by the extended stellar wind. The terminal
wind velocity remained constant. The flux of C II (133.5 nm) and O I
(135.7 nm) increased by a factor of about 2 as compared to the previous
measurements, whereas C IV (155.0 nm) and Si IV (140 nm) increased
by lesser amounts. High-dispersion Ca II K profiles obtained with an
intensified Reticon detector and echelle spectrograph at Mt. Hopkins
Observatory reveal a change in the peak line asymmetry with the blue
emission peak becoming substantially stronger than the red peak between
Nov. 4 and 11. By Dec. 8, the blue emission had weakened again, becoming
comparable to the red emission peak. This is the first quantitative
evidence of chromospheric variability in such a supergiant atmosphere,
and the star should be monitored, for it may be in a phase of activity
resulting from the passage of enhanced flux regions across its disk.

---------------------------------------------------------
Title: Optical Observations of SS 433
Authors: Liller, W.; Noyes, R.; Davis, M.; Baliunas, S.; Sternberg,
A.; Tokarz, S.
1979BAAS...11..732L Altcode:
No abstract at ADS

---------------------------------------------------------
Title: High-pressure transition regions in stellar model
chromospheres.
Authors: Baliunas, S. L.; Avrett, E. H.; Hartmann, L.; Dupree, A. K.
1979ApJ...233L.129B Altcode:
The implications of recent ultraviolet observations of stellar
transition-region lines for calculations of the Ca II and Mg II
resonance lines are investigated. It is found that the adoption of
high transition-region pressures for stars with active chromospheres,
such as Lambda And and Alpha Aur, can be consistent with observed Ca
II fluxes, contrary to the results obtained by Kelch et al. (1978)
for Alpha Aur. Furthermore, the adoption of the high-pressure models
removes a long-standing difficulty in the line profile calculations,
since the deep central absorption present in earlier calculations is
less pronounced or absent, in closer agreement with observations. The
apparent contradiction between these models and the recent density
diagnostic of Doschek et al. (1978) is also discussed.

---------------------------------------------------------
Title: Optical Observations of SS 433.
Authors: Noyes, R.; Liller, W.; Davis, M.; Baliunas, S.; Sternberg,
A.; Tokarz, S.
1979BAAS...11..786N Altcode:
No abstract at ADS

---------------------------------------------------------
Title: SS 433
Authors: Baliunas, S.; Noyes, R.; Liller, W.; Tokarz, S.
1979IAUC.3410....1B Altcode:
S. Baliunas, R. Noyes, W. Liller and S. Tokarz, Harvard-Smithsonian
Center for Astrophysics, report that the central intensity of H-alpha
relative to the continuum in SS 433 showed factor-of-two increases
on Apr. 29 and June 20, each lasting about two days. Observations
over five nights during these times, plus additional observations on
14 other nights throughout the interval Apr. 28 to June 24, showed
all the data to be commensurate with the 13.1-day period reported by
Crampton et al. (IAUC 3388). Comparison with other photometric data
indicates that the ratio increases represent increases of absolute
H-alpha-emission-line intensity. The data were obtained with the
digital spectrograph at the Mount Hopkins 1.5-m telescope.

---------------------------------------------------------
Title: What tides and flares do to RS Canum Venaticorum binaries.
Authors: Decampli, W. M.; Baliunas, S. L.
1979ApJ...230..815D Altcode:
The effects that anisotropic mass should have on the orbital and
spin states of RS Canum Venaticorum binaries are discussed. In the
absence of magnetic fields, orbital period changes reported for
several RS Canum Venaticorum systems require dM/dt of about 0.000001
solar masses/yr. Magnetic braking can lower this required rate if the
surface magnetic fields are not less than 1000 gauss. However, this
requires a method much more powerful than tidal torques to convert
spin angular momentum loss to orbital angular momentum loss. This
possibility is important when interpreting the complicated light
curves of these systems, and may contradict the Hall's 'drifting star
spot' hypothesis. In addition, large mass-loss rates may result in
significant self-absorption of quiescent soft X-rays observed from
several of these binaries.

---------------------------------------------------------
Title: High-Pressure Transition Regions in Stellar Model Chromospheres
Authors: Baliunas, S. L.; Avrett, E. H.; Hartmann, L. W.; Dupree, A. K.
1979BAAS...11..448B Altcode:
No abstract at ADS

---------------------------------------------------------
Title: Ultraviolet and optical spectroscopic studies of lambda
Andromedae: the chromosphere and interstellar medium.
Authors: Baliunas, S. L.; Dupree, A. K.
1979ApJ...227..870B Altcode:
Chromospheric lines of, and interstellar lines toward, the spectroscopic
binary Lambda And (primary component G7-G8 III-IV) have been observed
in the ultraviolet with the spectrometer and telescope on board the
Copernicus satellite. An extensive, high-resolution spectroscopic study
of the Ca II H and K profiles has also been undertaken. Some of these
optical spectra were obtained simultaneously with the ultraviolet
data. The ultraviolet emission lines of Lamba And are compared
to the sun and to stars of similar spectral type. The star Lamba
And resembles the active sun in surface brightness of chromospheric
emissions and in appearance of the Mg II and Ca II profiles. The largest
variations in the integrated calcium emission cores amount to an 80%
increase in the K core and a corresponding 40% increase in the H core
between observations two years apart. Variations in the cores may
show a dependence on spectroscopic phase, and may be contributed to
by circumstellar matter in the binary system. Previously unreported,
transient emission features have also been observed, at a velocity of
-70 km/s with respect to the Ca II emission cores.

---------------------------------------------------------
Title: Photometric and Spectroscopic Varability of Ca II H and K in G-
and K-Type Giants.
Authors: Baliunas, S. L.; Hartmann, L. W.; Liller, W.; Vaughan, A. H.,
Jr.; Avrett, E. H.; Dupree, A. K.
1978BAAS...10..461B Altcode:
No abstract at ADS

---------------------------------------------------------
Title: Detection of [Fe XIV] emission in HD 153919 (3U 1700-37).
Authors: Dupree, A. K.; Baliunas, S. L.; Lester, J. B.
1977ApJ...218L..71D Altcode:
Spectra of HD 153919 show a previously unreported broad emission line
near 5293 A that is present at phases 0.2 and 0.8 and is absent or
weaker at other phases, including the time of eclipse of the X-ray
source. Approximate calculations suggest identification of this feature
with the forbidden Fe XIV transition at 5303 A. This line may arise in
the extended atmosphere of the primary ionized by the compact X-ray
source or may occur in a high-temperature corona. Further monitoring
is needed.

---------------------------------------------------------
Title: Deuterium and hydrogen in the local interstellar medium.
Authors: Dupree, A. K.; Baliunas, S. L.; Shipman, H. L.
1977ApJ...218..361D Altcode:
Densities of neutral hydrogen and deuterium are found from observation
with the Copernicus satellite of the Ly-alpha line toward two nearby
stars. The hydrogen density is 0.03 + or - 0.01 per cu cm toward
Alpha Aur (Capella) and 0.20 + or - 0.05 per cu cm in the direction
of Alpha Cen A, values indicating that the nearby (less than 14 pc)
interstellar medium is inhomogeneous and can be of low density in
certain directions. The ratios of deuterium to hydrogen - 3.9 (+5.7,
-1.7) by 10 to the -5th power and 0.24 (+0.12, -0.07) by 10 to the
-5th power for Alpha Aur and Alpha Cen A, respectively - suggest that
variations in the deuterium abundance may exist.

---------------------------------------------------------
Title: Possible Detection of Fe XIV in the X-Ray Binary HD 153919.
Authors: Baliunas, S. L.; Dupree, A. K.; Lester, J. B.
1977BAAS....9..298B Altcode:
No abstract at ADS

---------------------------------------------------------
Title: Interstellar Density of Deuterium and Hydrogen Towards Alpha
Aurigae.
Authors: Dupree, A. K.; Baliunas, S. L.
1976BAAS....8..551D Altcode:
No abstract at ADS

---------------------------------------------------------
Title: Optical and Ultraviolet Observations of Lambda Andromedae
Authors: Baliunas, S. L.; Dupree, A. K.; Lester, J. B.
1976BAAS....8..353B Altcode:
No abstract at ADS

---------------------------------------------------------
Title: The chromosphere and corona of Capella.
Authors: Dupree, A. K.; Baliunas, S.
1976BAAS....8..397D Altcode:
No abstract at ADS

---------------------------------------------------------
Title: Halpha and Hbeta photoelectric photometry of gamma Cassiopeiae.
Authors: Baliunas, S. L.; Guinan, E. F.
1976PASP...88...10B Altcode:
Photoelectric observations of gamma Cas (B0 IVe) were made using two
pairs of wide- and narrow-band interference filters centered near the
rest wavelengths of the hydrogen Balmer alpha and beta lines. H-alpha
and H-beta indices were obtained on 19 nights from February 1972 to
February 1975. Variations in the H-alpha and H-beta indices were found
with a range of 0.18 and 0.10 min, respectively.

---------------------------------------------------------
Title: Halpha and Hbeta photoelectric photometry of bright Be stars.
Authors: Baliunas, S. L.; Ciccone, M. A.; Guinan, E. F.
1975PASP...87..969B Altcode:
Ha and H photoelectric observations of 33 early-type standard stars
and 23 Be stars were obtained at the Villanova University Observatory
on 27 nights between January 1972 and February 1973. The data permit
separation of the stronger-lined Be stars from the normal stars and
reveal variations in the Be star Cas. When compared with earlier data
obtained by others, the Villanova data show longer-term variations in
five other Be stars as well: w Ori, Tau, K Dra, 23 Tau, and Per. Key
words: Be stars - emission - narrow-band photometry

---------------------------------------------------------
Title: Photoelectric Study of the Bright Be Stars γ Cas, 48 Per,
ψ Per, and φ Per.
Authors: Baliunas, S. D.; Ciccone, M. A.; Guinan, E. F.; Miskinis, P.
1975BAAS....7Q.252B Altcode:
No abstract at ADS

---------------------------------------------------------
Title: Hα and Hβ Photoelectric Photometry of Bright Be Stars.
Authors: Baliunas, S. L.; Ciccone, M.; Guinan, E. F.
1973BAAS....5..317B Altcode:
No abstract at ADS