berdyugina

explanation blue bibcodes open ADS page with paths to full text

Author name code: berdyugina
ADS astronomy entries on 2022-09-14
author:"Berdyugina, Svetlana V."

---------------------------------------------------------
Title: Searching for technosignatures in exoplanetary systems with
current and future missions
Authors: Haqq-Misra, Jacob; Schwieterman, Edward W.; Socas-Navarro,
Hector; Kopparapu, Ravi; Angerhausen, Daniel; Beatty, Thomas G.;
Berdyugina, Svetlana; Felton, Ryan; Sharma, Siddhant; De la Torre,
Gabriel G.; Apai, Dániel; TechnoClimes 2020 workshop participants
2022AcAau.198..194H Altcode: 2022arXiv220600030H
Technosignatures refer to observational manifestations of technology
that could be detected through astronomical means. Most previous
searches for technosignatures have focused on searches for radio
signals, but many current and future observing facilities could also
constrain the prevalence of some non-radio technosignatures. This search
could thus benefit from broader participation by the astronomical
community, as contributions to technosignature science can also take
the form of negative results that provide statistically meaningful
quantitative upper limits on the presence of a signal. This paper
provides a synthesis of the recommendations of the 2020 TechnoClimes
workshop, which was an online event intended to develop a research
agenda to prioritize and guide future theoretical and observational
studies technosignatures. The paper provides a high-level overview
of the use of current and future missions to detect exoplanetary
technosignatures at ultraviolet, optical, or infrared wavelengths,
which specifically focuses on the detectability of atmospheric
technosignatures, artificial surface modifications, optical beacons,
space engineering and megastructures, and interstellar flight. This
overview does not derive any new quantitative detection limits but
is intended to provide additional science justification for the use
of current and planned observing facilities as well as to inspire
astronomers conducting such observations to consider the relevance of
their ongoing observations to technosignature science. This synthesis
also identifies possible technology gaps with the ability of current
and planned missions to search for technosignatures, which suggests
the need to consider technosignature science cases in the design of
future mission concepts.

---------------------------------------------------------
Title: Optical polarization signatures of black hole X-ray binaries
Authors: Kravtsov, Vadim; Berdyugin, Andrei V.; Kosenkov, Ilia A.;
Veledina, Alexandra; Piirola, Vilppu; Qadir, Yasir Abdul; Berdyugina,
Svetlana V.; Sakanoi, Takeshi; Kagitani, Masato; Poutanen, Juri
2022MNRAS.514.2479K Altcode: 2022MNRAS.tmp.1446K; 2022arXiv220512121K
Polarimetry provides an avenue for probing the geometry and physical
mechanisms producing optical radiation in many astrophysical
objects, including stellar binary systems. We present the results of
multiwavelength (BVR) polarimetric studies of a sample of historical
black hole X-ray binaries, observed during their outbursts or in
the quiescent (or near-quiescent) state. We surveyed both long- and
short-period systems, located at different Galactic latitudes. We
performed careful analysis of the interstellar polarization in the
direction on the sources to reliably estimate the intrinsic source
polarization. Intrinsic polarization was found to be small (&lt;0.2
per cent) in sources observed in bright soft states (MAXI J0637-430
and 4U 1957+115). It was found to be significant in the rising hard
state of MAXI J1820+070 at the level of ~0.5 per cent and negligible
in the decaying hard state and during its failed outbursts, while
Swift J1357.2-0933 showed its absence in the rising hard state. Three
(XTE J1118+480 , V4641 Sgr , V404 Cyg) sources observed during
quiescence show no evidence of significant intrinsic polarization,
while MAXI J1820+070 is the only black hole X-ray binary which showed
substantial (&gt;5 per cent) intrinsic quiescent-state polarization
with a blue spectrum. The absence of intrinsic polarization at the
optical wavelengths puts constraints on the potential contribution of
non-stellar (jet, hot flow, accretion disc) components to the total
spectra of black hole X-ray binaries.

---------------------------------------------------------
Title: Observation of a small-scale magnetic vortex associated with
a chromospheric swirl: signatures of a small-scale magnetic tornado
Authors: Milena Diaz Castillo, Saida; Steiner, Oskar; Fischer,
Catherine; Berdyugina, Svetlana; Rezaei, Reza
2022cosp...44.2521M Altcode:
\newcommand{\ion}[2]{#1\,{\textsc{#2}}} High-resolution solar
observations revealed the existence of small-scale swirling vortices
in chromospheric intensity maps and velocity diagnostics. These events
are commonly localized in the quiet sun intergranular space and are
often related to small-scale magnetic flux concentrations at the solar
surface. Frequently, vortices have been observed in the vicinity of
magnetic flux concentrations, indicating a link between swirls and the
evolution of the small-scale magnetic fields. Vortices were also studied
with MHD numerical simulations of the solar atmosphere, revealing
their complexity, dynamics, and magnetic nature. In particular, it
has been suggested that the chromospheric swirling plasma motion is
due to a coherently rotating magnetic field structure, which again
is driven by a photospheric vortex flow at its footpoint. In this
contribution, we present a comprehensive description of the evolution
of an isolated small-scale magnetic element interacting with a vortex
flow, which in turn is related to a chromospheric swirl. We study
observations taken with the CRisp Imaging SpectroPolarimeter (CRISP)
instrument and the CHROMospheric Imaging Spectrometer (CHROMIS) at the
1m Swedish Solar Telescope (SST) in April 2019 as part of a SOLARNET
access program. The data were taken at quiet-Sun disk-center, recording
full Stokes photospheric maps in the \ion{Fe}{i} line at 617\,nm, full
Stokes data in the \ion{Ca}{ii} infrared triplet line at 854\,nm, and
spectroscopic maps in the H$\alpha$ 656\,nm, \ion{Ca}{ii} K 393\,nm,
and \ion{Ca}{ii} H 396\,nm lines. Utilizing the multi-wavelength
data and applying height-dependent Stokes inversion and local
correlation tracking methods, we are able to analyse the magnetic
field dynamics in the presence of vortex structures at photospheric
and chromospheric layers. The temporal evolution of the magnetic
element shows an appreciable increase in the magnetic field strength
during the interaction with the vortex flow, reaching kG values for
a few minutes. We also find a clear evidence of a Rapid Blue-shift
Excursion (RBE) associated with the magnetic field intensification
event propagating along the chromospheric vortex. In addition, we
explore the polarization signatures in the photosphere to reveal the
intrinsic structure of the magnetic element. Marginal but consistent
detection of linear polarization signals in the surroundings of the
magnetic element before intensification suggests a magnetic field
torsion. Our analysis indicates that we have observed a rotating
magnetic object reaching from the photosphere to the chromosphere,
resembling a small-scale magnetic tornado.

---------------------------------------------------------
Title: Polarimetry of M-type asteroids in the context of their
surface composition
Authors: Belskaya, I.; Berdyugin, A.; Krugly, Yu.; Donchev, Z.;
Sergeyev, A.; Gil-Hutton, R.; Mykhailova, S.; Bonev, T.; Piirola,
V.; Berdyugina, S.; Kagitani, M.; Sakanoi, T.
2022A&A...663A.146B Altcode: 2022arXiv220404929B
 Aims: We aim to investigate how polarimetric observations can
improve our understanding of the nature and diversity of M/X-type
asteroids. Methods: Polarimetric observations of the selected
M/X-type asteroids were carried out at the Tohoku 0.6-m telescope
at Haleakala Observatory, Hawaii (simultaneously in BVR filters),
the 2-m telescope of the Bulgarian National Astronomical Observatory
in Rozhen (in R filter), and the 2.15-m telescope of the Complejo
Astronómico El Leoncito (CASLEO), Argentina (in V filter). We analysed
the polarimetric characteristics of M/X-type asteroids along with
the available data obtained by other techniques. Results:
New polarimetric observations of 22 M/X-type asteroids combined with
published observations provide a data set of 41 asteroids for which
the depth of a negative polarisation branch and/or inversion angle
were determined. We found that the depth of the negative polarisation
branch tends to increase with decreasing steepness of the near-infrared
spectra. Asteroids with a deeper negative polarisation branch tend
to have a higher radar circular polarisation ratio. We show that,
based on the relationship of the depth of the negative polarisation
branch and inversion angle, two main sub-types can be distinguished
among M-type asteroids. We suggest that these groups may be related to
different surface compositions similar to (1) irons and stony-irons and
(2) enstatite and iron-rich carbonaceous chondrites.

---------------------------------------------------------
Title: Towards the Identification and Classification of Solar
Granulation Structures Using Semantic Segmentation
Authors: Díaz Castillo, S. M.; Asensio Ramos, A.; Fischer, C. E.;
Berdyugina, S. V.
2022FrASS...9.6632D Altcode:
Solar granulation is the visible signature of convective cells at
the solar surface. The granulation cellular pattern observed in the
continuum intensity images is characterised by diverse structures e.g.,
bright individual granules of hot rising gas or dark intergranular
lanes. Recently, the access to new instrumentation capabilities has
given us the possibility to obtain high-resolution images, which have
revealed the overwhelming complexity of granulation (e.g., exploding
granules and granular lanes). In that sense, any research focused
on understanding solar small-scale phenomena on the solar surface
is sustained on the effective identification and localization of the
different resolved structures. In this work, we present the initial
results of a proposed classification model of solar granulation
structures based on neural semantic segmentation. We inspect the
ability of the U-net architecture, a convolutional neural network
initially proposed for biomedical image segmentation, to be applied to
the dense segmentation of solar granulation. We use continuum intensity
maps of the IMaX instrument onboard the Sunrise I balloon-borne solar
observatory and their corresponding segmented maps as a training
set. The training data have been labeled using the multiple-level
technique (MLT) and also by hand. We performed several tests of the
performance and precision of this approach in order to evaluate
the versatility of the U-net architecture. We found an appealing
potential of the U-net architecture to identify cellular patterns
in solar granulation images reaching an average accuracy above 80%
in the initial training experiments.

---------------------------------------------------------
Title: Making the Most of Transmission Spectra in Light of Stellar
Activity: Needs Identified by ExoPAG's Study Analysis Group 21
Authors: Rackham, Benjamin V.; Espinoza, Néstor; Berdyugina, Svetlana
V.; Korhonen, Heidi; MacDonald, Ryan J.; Montet, Benjamin T.; Morris,
Brett M.; Oshagh, Mahmoudreza; Shapiro, Alexander I.; Unruh, Yvonne
C.; Quintana, Elisa V.; Zellem, Robert T.; SAG 21 Committee
2022BAAS...54e4404R Altcode:
Transmission spectroscopy, a method for studying exoplanetary
atmospheres by measuring the wavelength-dependent radius of a planet as
it transits its star, relies on a precise understanding of the spectrum
of the star being occulted. However, stars are not homogeneous,
constant light sources but have temporally evolving photospheres
and chromospheres with inhomogeneities like spots, faculae, and
plages. Study Analysis Group 21 (SAG21) of NASA's Exoplanet Exploration
Program Analysis Group (ExoPAG) was organized to study the effect
of stellar photospheric heterogeneity on space-based transmission
spectroscopy. This SAG brought together an interdisciplinary team
of more than 100 scientists, with observers and theorists from the
heliophysics, stellar astrophysics, planetary science, and exoplanetary
atmosphere research communities, to study the current needs that can be
addressed in this context to make the most of transit studies from NASA
facilities like HST and JWST. Here we report on the main conclusions
of this analysis, highlighting needs to be addressed and mitigation
efforts underway. The analysis produced 14 findings, which fall into
three Science Themes that encompass (1) how the Sun is used as our best
laboratory to calibrate our understanding of stellar heterogeneities
("The Sun as the Stellar Benchmark"), (2) how stars other than the Sun
extend our knowledge of heterogeneities ("Surface Heterogeneities of
Other Stars"), and (3) how to incorporate information gathered for the
Sun and other stars into transit studies ("Mapping Stellar Knowledge
to Transit Studies"). Addressing the needs identified through this
large community effort will ensure that we can optimally leverage
space-based transmission spectra in light of stellar activity.

---------------------------------------------------------
Title: Polarized X-rays Constrain The Disk-Jet Geometry in a Black
Hole X-ray Binary
Authors: Krawczynski, Henric; Muleri, Fabio; Dovčiak, Michal;
Veledina, Alexandra; Rodriguez Cavero, Nicole; Svoboda, Jiri;
Ingram, Adam; Matt, Giorgio; Garcia, Javier A.; Loktev, Vladislav;
Negro, Michela; Poutanen, Juri; Kitaguchi, Takao; Podgorný, Jakub;
Rankin, John; Zhang, Wenda; Berdyugin, Andrei; Berdyugina, Svetlana
V.; Bianchi, Stefano; Blinov, Dmitry; Capitanio, Fiamma; Di Lalla,
Niccolò; Draghis, Paul; Fabiani, Sergio; Kagitani, Masato; Kravtsov,
Vadim; Kiehlmann, Sebastian; Latronico, Luca; Lutovinov, Alexander
A.; Mandarakas, Nikos; Marin, Frédéric; Marinucci, Andrea; Miller,
Jon; Mizuno, Tsunefumi; Molkov, Sergey V.; Omodei, Nicola; Petrucci,
Pierre-Olivier; Ratheesh, Ajay; Sakanoi, Takeshi; Semena, Andrei N.;
Skalidis, Raphael; Soffitta, Paolo; Tennant, Allyn F.; Thalhammer,
Phillipp; Tombesi, Francesco; Weisskopf, Martin C.; Wilms, Joern;
Zhang, Sixuan; Agudo, Iván; Antonelli, Lucio A.; Bachetti, Matteo;
Baldini, Luca; Baumgartner, Wayne H.; Bellazzini, Ronaldo; Bongiorno,
Stephen D.; Bonino, Raffaella; Brez, Alessandro; Bucciantini, Niccolò;
Castellano, Simone; Cavazzuti, Elisabetta; Ciprini, Stefano; Costa,
Enrico; De Rosa, Alessandra; Del Monte, Ettore; Di Gesu, Laura;
Di Marco, Alessandro; Donnarumma, Immacolata; Doroshenko, Victor;
Ehlert, Steven R.; Enoto, Teruaki; Evangelista, Yuri; Ferrazzoli,
Riccardo; Gunji, Shuichi; Hayashida, Kiyoshi; Heyl, Jeremy; Iwakiri,
Wataru; Jorstad, Svetlana G.; Karas, Vladimir; Kolodziejczak, Jeffery
J.; La Monaca, Fabio; Liodakis, Ioannis; Maldera, Simone; Manfreda,
Alberto; Marscher, Alan P.; Marshall, Herman L.; Massaro, Francesco;
Mitsuishi, Ikuyuki; Ng, C. -Y.; O'Dell, Stephen L.; Oppedisano, Chiara;
Papitto, Alessandro; Pavlov, George G.; Peirson, Abel L.; Perri,
Matteo; Pesce-Rollins, Melissa; Pilia, Maura; Possenti, Andrea;
Puccetti, Simonetta; Ramsey, Brian D.; Romani, Roger W.; Sgrò,
Carmelo; Slane, Patrick; Spandre, Gloria; Tamagawa, Toru; Tavecchio,
Fabrizio; Taverna, Roberto; Tawara, Yuzuru; Thomas, Nicolas E.; Trois,
Alessio; Tsygankov, Sergey; Turolla, Roberto; Vink, Jacco; Wu, Kinwah;
Xie, Fei; Zane, Silvia
2022arXiv220609972K Altcode:
In a black hole X-ray binary (XRB) system, gas accreted from a normal
star onto a black hole glows brightly in X-rays. We report on an
observation of the XRB Cygnus X-1 (Cyg X-1) by the Imaging X-ray
Polarimetry Explorer IXPE) yielding the first highly significant
detection of X-ray polarization from an accreting black hole. The
electric vector polarization angle aligns with the outflowing radio jet,
supporting the hypothesis that the jet is launched from the inner X-ray
emitting region. The higher than expected 2-8 keV polarization degree
of 4.0+-0.2% implies that the accretion disk is viewed more edge-on
than inferred from the orbital parameters. The spectropolarimetric data
reveal that the hot X-ray emitting plasma is extended in the plane of
the accretion disk rather than along the jet axis.

---------------------------------------------------------
Title: Black hole spin–orbit misalignment in the x-ray binary
MAXI J1820+070
Authors: Poutanen, Juri; Veledina, Alexandra; Berdyugin, Andrei V.;
Berdyugina, Svetlana V.; Jermak, Helen; Jonker, Peter G.; Kajava,
Jari J. E.; Kosenkov, Ilia A.; Kravtsov, Vadim; Piirola, Vilppu;
Shrestha, Manisha; Perez Torres, Manuel A.; Tsygankov, Sergey S.
2022Sci...375..874P Altcode: 2021arXiv210907511P
The observational signatures of black holes in x-ray binary systems
depend on their masses, spins, accretion rate, and the misalignment
angle between the black hole spin and the orbital angular momentum. We
present optical polarimetric observations of the black hole x-ray
binary MAXI J1820+070, from which we constrain the position angle of
the binary orbital. Combining this with previous determinations of
the relativistic jet orientation, which traces the black hole spin,
and the inclination of the orbit, we determine a lower limit of 40° on
the spin-orbit misalignment angle. The misalignment must originate from
either the binary evolution or black hole formation stages. If other
x-ray binaries have similarly large misalignments, these would bias
measurements of black hole masses and spins from x-ray observations.

---------------------------------------------------------
Title: Highly sensitive search for magnetic fields in white dwarfs
using broad-band circular polarimetry
Authors: Berdyugin, Andrei V.; Piirola, Vilppu; Bagnulo, Stefano;
Landstreet, John D.; Berdyugina, Svetlana V.
2022A&A...657A.105B Altcode: 2021arXiv211111174B
Circular polarisation measurements of white dwarfs of various ages
and spectral types are useful to understand the origin and evolution
of the magnetic field in degenerate stars. In the latest stages of
white dwarf evolution, when stars are so cool that spectral lines
are no longer formed in the normal H- or He-dominated atmospheres,
magnetic fields can be probed only by means of circular polarimetry
of the continuum. The study of the fields of featureless DC white
dwarfs may reveal whether Ohmic decay acts on magnetic white dwarfs,
or if magnetic fields continue to be generated even several billion
years after white dwarf formation. Compared to spectropolarimetry,
broad-band circular polarisation measurements have the advantage of
reaching a higher accuracy in the continuum, with the potential of
detecting magnetic fields as weak as a fraction of a MG in DC stars,
if the telescope size is adequate for the star's magnitude. Here we
present the results of a first (short) observing campaign with the
DIPol-UF polarimeter, which we have used to measure broad-band circular
polarisation of white dwarfs. Our observing run was in part aimed to
fully characterise the instrument, and in part to study the relationship
between magnetic field strength (when known from spectropolarimetry) and
circular polarisation of the continuum. We also observed a small number
of previously unexplored DC white dwarfs, and we present the discovery
of two new magnetic white dwarfs of spectral class DC, probably the
first discovery of this kind made with broad-band circular polarimetric
techniques since the late 1970s. We also discuss the characteristics of
our instrument, and predict the level of polarimetric accuracy that
may be reached as a function of stellar magnitude, exposure time,
and telescope size.

---------------------------------------------------------
Title: Final Report for SAG 21: The Effect of Stellar Contamination
on Space-based Transmission Spectroscopy
Authors: Rackham, Benjamin V.; Espinoza, Néstor; Berdyugina, Svetlana
V.; Korhonen, Heidi; MacDonald, Ryan J.; Montet, Benjamin T.; Morris,
Brett M.; Oshagh, Mahmoudreza; Shapiro, Alexander I.; Unruh, Yvonne C.;
Quintana, Elisa V.; Zellem, Robert T.; Apai, Dániel; Barclay, Thomas;
Barstow, Joanna K.; Bruno, Giovanni; Carone, Ludmila; Casewell, Sarah
L.; Cegla, Heather M.; Criscuoli, Serena; Fischer, Catherine; Fournier,
Damien; Giampapa, Mark S.; Giles, Helen; Iyer, Aishwarya; Kopp, Greg;
Kostogryz, Nadiia M.; Krivova, Natalie; Mallonn, Matthias; McGruder,
Chima; Molaverdikhani, Karan; Newton, Elisabeth R.; Panja, Mayukh;
Peacock, Sarah; Reardon, Kevin; Roettenbacher, Rachael M.; Scandariato,
Gaetano; Solanki, Sami; Stassun, Keivan G.; Steiner, Oskar; Stevenson,
Kevin B.; Tregloan-Reed, Jeremy; Valio, Adriana; Wedemeyer, Sven;
Welbanks, Luis; Yu, Jie; Alam, Munazza K.; Davenport, James R. A.;
Deming, Drake; Dong, Chuanfei; Ducrot, Elsa; Fisher, Chloe; Gilbert,
Emily; Kostov, Veselin; López-Morales, Mercedes; Line, Mike; Močnik,
Teo; Mullally, Susan; Paudel, Rishi R.; Ribas, Ignasi; Valenti, Jeff A.
2022arXiv220109905R Altcode:
Study Analysis Group 21 (SAG21) of the Exoplanet Exploration Program
Analysis Group (ExoPAG) was organized to study the effect of stellar
contamination on space-based transmission spectroscopy, a method for
studying exoplanetary atmospheres by measuring the wavelength-dependent
radius of a planet as it transits its star. Transmission spectroscopy
relies on a precise understanding of the spectrum of the star being
occulted. However, stars are not homogeneous, constant light sources
but have temporally evolving photospheres and chromospheres with
inhomogeneities like spots, faculae, and plages. This SAG has brought
together an interdisciplinary team of more than 100 scientists, with
observers and theorists from the heliophysics, stellar astrophysics,
planetary science, and exoplanetary atmosphere research communities,
to study the current needs that can be addressed in this context to
make the most of transit studies from current NASA facilities like
HST and JWST. The analysis produced 14 findings, which fall into
three Science Themes encompassing (1) how the Sun is used as our best
laboratory to calibrate our understanding of stellar heterogeneities
("The Sun as the Stellar Benchmark"), (2) how stars other than the Sun
extend our knowledge of heterogeneities ("Surface Heterogeneities of
Other Stars") and (3) how to incorporate information gathered for the
Sun and other stars into transit studies ("Mapping Stellar Knowledge
to Transit Studies").

---------------------------------------------------------
Title: Optical polarimetric observations of the black hole X-ray
binary V4641 Sgr
Authors: Kravtsov, V.; Berdyugin, A.; Veledina, A.; Poutanen, J.;
Piirola, V.; Berdyugina, S.; Sakanoi, T.; Kagitani, M.
2021ATel15023....1K Altcode:
Following the renewed activity of the black hole X-ray binary V4641 Sgr
(ATel #14968, #14971), we performed optical polarimetric observations
of the source.

---------------------------------------------------------
Title: UV Spectropolarimetry with Polstar: Protoplanetary Disks
Authors: Wisniewski, John P.; Berdyugin, Andrei V.; Berdyugina,
Svetlana V.; Danchi, William C.; Dong, Ruobing; Oudmaijer, Rene D.;
Airapetian, Vladimir S.; Brittain, Sean D.; Gayley, Ken; Ignace,
Richard; Langlois, Maud; Lawson, Kellen D.; Lomax, Jamie R.; Tamura,
Motohide; Vink, Jorick S.; Scowen, Paul A.
2021arXiv211106891W Altcode:
Polstar is a proposed NASA MIDEX mission that would feature a high
resolution UV spectropolarimeter capable of measure all four Stokes
parameters onboard a 60cm telescope. The mission would pioneer
the field of time-domain UV spectropolarimetry. Time domain UV
spectropolarimetry offers the best resource to determine the geometry
and physical conditions of protoplanetary disks from the stellar surface
to &lt;5 AU. We detail two key objectives that a dedicated time domain
UV spectropolarimetry survey, such as that enabled by Polstar, could
achieve: 1) Test the hypothesis that magneto-accretion operating in
young planet-forming disks around lower-mass stars transitions to
boundary layer accretion in planet-forming disks around higher mass
stars; and 2) Discriminate whether transient events in the innermost
regions of planet-forming disks of intermediate mass stars are caused
by inner disk mis-alignments or from stellar or disk emissions.

---------------------------------------------------------
Title: Mercury's exospheric He I 58.4 nm emission: Dependence on
the orbital phase
Authors: Yoneda, M.; Dima, G.; Berdyugina, S. V.
2021A&A...654L...7Y Altcode:
 Aims: Emission from helium atoms in Mercury's exosphere at
58.4 nm was observed by the Mariner 10 spacecraft in the 1970s. This
emission is due to resonant scattering of solar radiation. Since
Mercury's orbit is ellipsoidal, solar radiation and wind fluxes on
Mercury vary along its orbit. Furthermore, the flux of the solar He
I 58.4 nm emission observed on Mercury varies with Mercury's radial
velocity with the Sun. Using model simulations, we demonstrate how
Mercury's exospheric He I 58.4 nm emission varies due to the periodic
changes in solar radiation and wind. Methods: The simulation
is based on our Monte-Carlo model that accounts for changes in fluxes
of the solar wind and radiation. Results: The model results
indicate that the He I 58.4 nm brightness varies by between one and
three orders of magnitude along the planet's orbit. These findings are
strongly dependent on the intrinsic line width of the solar He I 58.4
nm emission. Conclusions: Although this variation has never
been observed because Mariner 10 only sampled emission near Mercury's
aphelion, we expect this variation to be observable by new missions,
such as BepiColombo and Hisaki. Our results are also important for
the characterization of exoplanets with ultraviolet space missions.

---------------------------------------------------------
Title: Measuring the Magnetic Origins of Solar Flares, Coronal Mass
Ejections, and Space Weather
Authors: Judge, Philip; Rempel, Matthias; Ezzeddine, Rana; Kleint,
Lucia; Egeland, Ricky; Berdyugina, Svetlana V.; Berger, Thomas; Bryans,
Paul; Burkepile, Joan; Centeno, Rebecca; de Toma, Giuliana; Dikpati,
Mausumi; Fan, Yuhong; Gilbert, Holly; Lacatus, Daniela A.
2021ApJ...917...27J Altcode: 2021arXiv210607786J
We take a broad look at the problem of identifying the magnetic
solar causes of space weather. With the lackluster performance
of extrapolations based upon magnetic field measurements in the
photosphere, we identify a region in the near-UV (NUV) part of the
spectrum as optimal for studying the development of magnetic free energy
over active regions. Using data from SORCE, the Hubble Space Telescope,
and SKYLAB, along with 1D computations of the NUV spectrum and numerical
experiments based on the MURaM radiation-magnetohydrodynamic and
HanleRT radiative transfer codes, we address multiple challenges. These
challenges are best met through a combination of NUV lines of bright Mg
II, and lines of Fe II and Fe I (mostly within the 4s-4p transition
array) which form in the chromosphere up to 2 × 104
K. Both Hanle and Zeeman effects can in principle be used to derive
vector magnetic fields. However, for any given spectral line the τ
= 1 surfaces are generally geometrically corrugated owing to fine
structure such as fibrils and spicules. By using multiple spectral
lines spanning different optical depths, magnetic fields across nearly
horizontal surfaces can be inferred in regions of low plasma β, from
which free energies, magnetic topology, and other quantities can be
derived. Based upon the recently reported successful sub-orbital space
measurements of magnetic fields with the CLASP2 instrument, we argue
that a modest space-borne telescope will be able to make significant
advances in the attempts to predict solar eruptions. Difficulties
associated with blended lines are shown to be minor in an Appendix.

---------------------------------------------------------
Title: Double Image Polarimeter—Ultra Fast: Simultaneous Three-color
(BV R) Polarimeter with Electron-multiplying Charge-coupled Devices
Authors: Piirola, Vilppu; Kosenkov, Ilia A.; Berdyugin, Andrei V.;
Berdyugina, Svetlana V.; Poutanen, Juri
2021AJ....161...20P Altcode:
We describe a new instrument capable of high-precision (10-5)
polarimetric observations simultaneously in three passbands (BVR). The
instrument utilizes electron-multiplying charge-coupled device (EM CCD)
cameras for high efficiency and fast image readout. The key features
of the Double Image Polarimeter—Ultra Fast (DIPol-UF) are: (i)
the optical design with high throughput and inherent stability; (ii)
great versatility, which makes the instrument optimally suitable for
observations of bright and faint targets; and (iii) a control system,
which allows the use of the polarimeter remotely. Examples are given
of the first results obtained from high signal-to-noise observations
of bright nearby stars and of fainter sources such as X-ray binaries
in their quiescent states.

---------------------------------------------------------
Title: High dynamic-range observation using a 1.8-m off-axis telescope
PLANETS: feasibility study and telescope design
Authors: Kagitani, Masato; Sakanoi, Takeshi; Kasaba, Yasumasa;
Hirahara, Yasuhiro; Kurita, Mikio; Kuhn, Jeffrey R.; Berdyugina,
Svetlana V.; Emilio, Marcelo
2020SPIE11445E..43K Altcode:
PLANETS will be a 1.8-m off-axis telescope combined with contrast
enhancement techniques, enabling us to observe faint emissions in
the vicinity of bright objects. This "high dynamic-range" capability
is largely dependent upon precision of telescope optics as well as
atmospheric distortion. We present feasibility study of monitoring
water plumes on Europa, neutral torus close to Enceladus, and
ionosphere on Mars using PLANETS telescope. To test feasibility of
high dynamic-range observation under actual conditions of wavefront
error, we modeled propagation of light though the system based on
Fraunhofer calculation taking into account for wavefront error made by
atmospheric distortion and by primary mirror figure error. Then point
spread function is calculated for several cases of figure errors under
use of adaptive optics. The modeling result predicts that the moderate
or high-precision primary mirror is mandatory to accomplish the high
dynamic-range observation. We also present the latest design of PLANETS,
especially focus on the support structures of primary mirror. We employ
36-point whiffletrees with 33 warping harnesses for axial support, and
24-point Schwesinger support for lateral support. The active support
system is expected to reduce pre-polished RMS error from 1.51 μm
to 0.66 μm corresponding to 70% reduction in total volume of final
polish. The laboratory experiment using one third part of prototype
whiffletrees shows supporting force RMS repeatability &lt; 0.005 kgf,
and drive hysteresis &lt; 0.7% of load range, which are precise enough
to control or to keep the primary mirror figure.

---------------------------------------------------------
Title: Orbital variability of the optical linear polarization of
the γ-ray binary LS I +61° 303 and new constraints on the orbital
parameters
Authors: Kravtsov, Vadim; Berdyugin, Andrei V.; Piirola, Vilppu;
Kosenkov, Ilia A.; Tsygankov, Sergey S.; Chernyakova, Maria; Malyshev,
Denys; Sakanoi, Takeshi; Kagitani, Masato; Berdyugina, Svetlana V.;
Poutanen, Juri
2020A&A...643A.170K Altcode: 2020arXiv201000999K
We studied the variability of the linear polarization and brightness of
the γ-ray binary LS I +61° 303. High-precision BVR photopolarimetric
observations were carried out with the Dipol-2 polarimeter on the
2.2 m remotely controlled UH88 telescope at Mauna Kea Observatory and
the 60 cm Tohoku telescope at Haleakala bservatory (Hawaii) over 140
nights in 2016-2019. We also determined the degree and angle of the
interstellar polarization toward LS I +61° 303 using two out of four
nearby field stars that have Gaia's parallaxes. After subtracting the
interstellar polarization, we determined the position angle of the
intrinsic polarization θ ≃ 11°, which can either be associated
with the projection of the Be star's decretion disk axis on the plane
of sky, or can differ from it by 90°. Using the Lomb-Scargle method,
we performed timing analyses and period searches of our polarimetric
and photometric data. We found statistically significant periodic
variability of the normalized Stokes parameters q and u in all
passbands. The most significant period of variability, PPol
= 13.244 ± 0.012 d, is equal to one half of the orbital period
Porb = 26.496 d. The fits of the polarization variability
curves with Fourier series show a dominant contribution from the second
harmonic which is typical for binary systems with circular orbits and
nearly symmetric distribution of light scattering material with respect
to the orbital plane. The continuous change of polarization with the
orbital phase implies co-planarity of the orbit of the compact object
and the Be star's decretion disk. Using a model of Thomson scattering by
a cloud that orbits the Be star, we obtained constraints on the orbital
parameters, including a small eccentricity e &lt; 0.2 and periastron
phase of ϕp ≈ 0.6, which coincides with the peaks in
the radio, X-ray, and TeV emission. These constraints are independent
of the assumption about the orientation of the decretion disk plane
on the sky. We also extensively discuss the apparent inconsistency
with the previous measurements of the orbital parameters from radial
velocities. By folding the photometry data acquired during a three-year
time span with the orbital period, we found a linear phase shift of the
moments of the brightness maximum, confirming the possible existence
of superorbital variability.

---------------------------------------------------------
Title: DIPol-UF: simultaneous three-color ($BVR$) polarimeter with
EM CCDs
Authors: Piirola, Vilppu; Kosenkov, Ilia A.; Berdyugin, Andrei V.;
Berdyugina, Svetlana V.; Poutanen, Juri
2020arXiv201102129P Altcode:
We describe a new instrument capable of high precision ($10^{-5}$)
polarimetric observations simultaneously in three passbands ($BVR$). The
instrument utilizes electron-multiplied EM CCD cameras for high
efficiency and fast image readout. The key features of DIPol-UF are:
(i) optical design with high throughput and inherent stability; (ii)
great versatility which makes the instrument optimally suitable for
observations of bright and faint targets; (iii) control system which
allows using the polarimeter remotely. Examples are given of the first
results obtained from high signal-to-noise observations of bright
nearby stars and of fainter sources such as X-ray binaries in their
quiescent states

---------------------------------------------------------
Title: GREGOR: Optics redesign and updates from 2018-2020
Authors: Kleint, Lucia; Berkefeld, Thomas; Esteves, Miguel; Sonner,
Thomas; Volkmer, Reiner; Gerber, Karin; Krämer, Felix; Grassin,
Olivier; Berdyugina, Svetlana
2020A&A...641A..27K Altcode: 2020arXiv200611875K
The GREGOR telescope was inaugurated in 2012. In 2018, we began
a complete upgrade, involving optics, alignment, instrumentation,
mechanical upgrades for vibration reduction, updated control systems,
and building enhancements, and in addition, adapted management
and policies. This paper describes all major updates performed
during this time. Since 2012, all powered mirrors except for M1 were
exchanged. Since March 2020, GREGOR observes with diffraction-limited
performance and a new optics and instrument layout.

---------------------------------------------------------
Title: Disc and wind in black hole X-ray binary MAXI J1820+070
observed through polarized light during its 2018 outburst
Authors: Kosenkov, Ilia A.; Veledina, Alexandra; Berdyugin, Andrei V.;
Kravtsov, Vadim; Piirola, Vilppu; Berdyugina, Svetlana V.; Sakanoi,
Takeshi; Kagitani, Masato; Poutanen, Juri
2020MNRAS.496L..96K Altcode: 2020arXiv200509699K; 2020MNRAS.tmpL..91K
We describe the first complete polarimetric data set of the entire
outburst of a low-mass black hole X-ray binary system and discuss the
constraints for geometry and radiative mechanisms it imposes. During
the decaying hard state, when the optical flux is dominated by the
non-thermal component, the observed polarization is consistent with
the interstellar values in all filters. During the soft state, the
intrinsic polarization of the source is small, ∼0.15 per cent in B
and V filters, and is likely produced in the irradiated disc. A much
higher polarization, reaching ∼0.5 per cent in V and R filters, at a
position angle of ∼25○ observed in the rising hard state
coincides in time with the detection of winds in the system. This angle
coincides with the position angle of the jet. The detected optical
polarization is best explained by scattering of the non-thermal (hot
flow or jet base) radiation in an equatorial wind.

---------------------------------------------------------
Title: VizieR Online Data Catalog: Polarization of LMXB MAXI J1820+070
(Kosenkov+, 2020)
Authors: Kosenkov, I. A.; Veledina, A.; Berdyugin, A. V.; Kravtsov, V.;
Piirola, V.; Berdyugina, S. V.; Sakanoi, T.; Kagitani, M.; Poutanen, J.
2020yCat..74969096K Altcode:
Nightly average observed polarisation degrees (PD) and
polarisation angles (PA), obtained during the 2018 outburst of MAXI
J1820+070. Polarimetric measurements were performed using Dipol-2
polarimeter (Piirola et al., 2014, Proc. SPIE Conf. Ser. Vol. 9147,
p. 91478I) mounted on the Tohoku 60cm telescope (T60) at Haleakala
observatory, Hawaii. Dipol - 2 is a remotely operated "double - image"
CCD polarimeter, which is capable of recording images in three(BVR)
filters simultaneously. The innovative design of the polarimeter,
where the two orthogonally polarised images of the sky overlap on
the images of the source, allows to completely eliminate the sky
polarisation at an instrumental stage (even if it is variable), and
to achieve unprecedentedly high, up to 10-5, accuracy of
target polarimetric measurements (Piirola 1973A&amp;A....27..383P,
Berdyugin, 2019, Astrophysics and Space Science Library, Vol. 460,
p. 33). (1 data file).

---------------------------------------------------------
Title: High-precision polarimetry of nearby stars (d &lt; 50
pc). Mapping the interstellar dust and magnetic field inside the
Local Bubble
Authors: Piirola, V.; Berdyugin, A.; Frisch, P. C.; Kagitani, M.;
Sakanoi, T.; Berdyugina, S.; Cole, A. A.; Harlingten, C.; Hill, K.
2020A&A...635A..46P Altcode: 2020arXiv200203682P
Context. We investigate the linear polarization produced by interstellar
dust aligned by the magnetic field in the solar neighborhood (d &lt; 50
pc). We also look for intrinsic effects from circumstellar processes,
specifically in terms of polarization variability and wavelength
dependence. Aims: We aim to detect and map dust clouds which
give rise to statistically significant amounts of polarization
of the starlight passing through the cloud, and to determine the
interstellar magnetic field direction from the position angle of
the observed polarization. Methods: High-precision broad-band
(BV R) polarization observations are made of 361 stars in spectral
classes F to G, with detection sensitivity at the level of or better
than 10-5 (0.001%). The sample consists of 125 stars in the
magnitude range 6-9 observed at the 2.2 m UH88 telescope on Mauna Kea,
205 stars in the magnitude range 3-6 observed at the Japanese (Tohoku)
T60 telescope on Haleakala, and 31 stars in the magnitude range 4-7
observed at the 1.27 m H127 telescope of the Greenhill Observatory,
Tasmania. Identical copies of the Dipol-2 polarimeter are used on
these three sites. Results: Statistically significant (&gt;3σ)
polarization is found in 115 stars, and &gt;2σ detection in 178 stars,
out of the total sample of 361 stars. Polarization maps based on these
data show filament-like patterns of polarization position angles,
which are related to both the heliosphere geometry, the kinematics
of nearby clouds, and the Interstellar Boundary EXplorer ribbon
magnetic field. From long-term multiple observations, a number (~20)
of stars show evidence of intrinsic variability at the 10-5
level. This can be attributed to circumstellar effects (e.g., debris
disks and chromospheric activity). The star HD 101805 shows a peculiar
wavelength dependence, indicating size distribution of scattering
particles different from that of a typical interstellar medium. Our
high signal-to-noise measurements of nearby stars with very low
polarization also provide a useful dataset for calibration purposes. Tables 6 and 7 are only available at the CDS via anonymous ftp to <A
href="http://cdsarc.u-strasbg.fr">http://cdsarc.u-strasbg.fr</A>
(ftp://130.79.128.5) or via <A
href="http://cdsarc.u-strasbg.fr/viz-bin/cat/J/A+A/635/A46">http://cdsarc.u-strasbg.fr/viz-bin/cat/J/A+A/635/A46</A>.

---------------------------------------------------------
Title: VizieR Online Data Catalog: High-precision polarimetry of
nearby stars (Piirola+, 2020)
Authors: Piirola, V.; Berdyugin, A.; Frisch, P. C.; Kagitani, M.;
Sakanoi, T.; Berdyugina, S.; Cole, A. A.; Harlingten, C.; Hill, K.
2020yCat..36350046P Altcode:
We carried out observations in 2014-2019 at three telescopes, the
2.2 m UH88 telescope on Mauna Kea, the Tohoku60 cm telescope (T60) on
Haleakala, and the University of Tasmania (UTAS) 1.27m (H127) telescope
at Greenhill Observatory, Tasmania. Observations were made with the
simultaneous three-color (BV R) polarimeter Dipol-2. Identical
copies of the instrument are used at each of the three sites. At
UH88 and T60 the observations were carried out in remote operation
mode. Some additional data on the stars in our sample were obtained
at the Nordic Optical Telescope (NOT) and William Herschel Telescope
(WHT) at ORM, La Palma. (3 data files).

---------------------------------------------------------
Title: Configuration of the Interstellar Magnetic Field Near the
Heliosphere from Polarized Starlight
Authors: Frisch, P. C.; Piirola, V.; Berdyugin, A.; Magalhaes, A. M.;
Berdyugina, S.; Harlingten, C.; Hill, K.; Cole, A.; Wiktorowicz, S.;
Cotton, D.; Bailey, J.; Kedziora-Chudczer, L.; Marshall, J.; Bott,
K.; McComas, D. J.; Schwadron, N.; Funsten, H. O.; Seriacopi, D.;
Redfield, S.; Heiles, C.; Livadiotis, G.
2019AGUFMSH53A..06F Altcode:
Early measurements of polarized starlight showed that an interstellar
magnetic field (ISMF) extends to the solar vicinity (Piirola 1978,
Tinbergen 1982). IBEX measurements of energetic neutral atoms
(ENAs) revealed a ribbon of enhanced ENA emission upstream of
the heliopause that is ordered by the ISMF around the heliosphere
(Schwadron et al. 2009). The relation between the IBEX ISMF and the
ambient ISMF around the heliosphere can be studied with starlight
that is linearly polarized by magnetically aligned interstellar dust
grains. We are surveying linear polarizations of nearby stars at high
sensitivities in order to relate the ambient ISMF to the ISMF shaping
the heliosphere. New linear polarization data have been acquired
for over 500 nearby stars, utilizing eight observatories in both
hemispheres. Over half of new data have been collected by the DIPOL
instruments. All-sky maps of the polarization position angles show
that the very local ISMF is arranged into distinct magnetic filaments,
some with spatial extents larger than ninety degrees. Sections of some
filaments are aligned with local interstellar cloud boundaries. Large
regions with stars lacking significant polarizations are also found,
which can indicate nearby depolarization screens or regions at the
poles of the magnetic field. These results improve understanding of
the galactic environment of the Sun and are not surprising since since
magnetic filaments pervade interstellar space. These polarization
data support models showing that the IBEX ribbon is formed by the
distortion of the very local interstellar magnetic field around the
heliosphere. Refs: Piirola A&amp;AS v30 1977; Tinbergen A&amp;A v105
1982; Schwadron Sci v326, 966 2009.

---------------------------------------------------------
Title: Surface Imaging of Proxima b and Other Exoplanets: Albedo Maps,
Biosignatures, and Technosignatures
Authors: Berdyugina, S. V.; Kuhn, J. R.
2019AJ....158..246B Altcode:
Seeing oceans, continents, quasi-static weather, and other surface
features on exoplanets may allow for detecting and characterizing life
outside the solar system. The Proxima b exoplanet resides within the
stellar habitable zone, possibly allowing for liquid water on its
surface, as on Earth. However, even the largest planned telescopes
will not be able to resolve its surface features directly. Here we
demonstrate an inversion technique to indirectly image exoplanet
surfaces using observed unresolved reflected light variations
over the course of the exoplanet’s orbital and axial rotation:
ExoPlanet Surface Imaging (EPSI). We show that the reflected light curve
contains enough information to detect both longitudinal and latitudinal
structures and to map exoplanet surface features. We demonstrate this
using examples of solar system planets and moons, as well as simulated
planets with Earth-like life and artificial structures. We also describe
how it is possible to infer the planet and orbit geometry from light
curves. Then, we show how albedo maps of Proxima b can be successfully
reconstructed for tidally locked, resonance, and unlocked axial and
orbital rotation. Such albedo maps obtained in different wavelength
passbands can provide “photographic” views of distant exoplanets. We
estimate the signal-to-noise ratio necessary for successful inversions
and analyze telescope and detector requirements necessary for the first
surface image reconstructions of Proxima b and other nearby exoplanets
using EPSI. This is a significant challenge, but the success of such
measurements depends heavily on large-aperture diffraction-limited
telescope performance—a feat that may be achieved on the ground
before it is in space.

---------------------------------------------------------
Title: Optical polarimetry of the soft-state low-mass X-ray binary
MAXI J0637-430
Authors: Kravtsov, V.; Berdyugin, A.; Veledina, A.; Poutanen, J.;
Piirola, V.; Berdyugina, S.; Sakanoi, T.; Kagitani, M.
2019ATel13291....1K Altcode:
We report optical polarimetric observations of the new soft-state
low-mass X-ray binary MAXI J0637-430 (ATel #13256, #13257, #13270). We
observed the source with the Dipol-2 BVR-polarimeter using the remotely
controlled Tohoku 0.60 m (T60) telescope at Haleakala Observatory,
Hawaii, for 3 nights (UT 2019 Nov 5.6, 7.6 and 9.6).

---------------------------------------------------------
Title: Observations on spatial variations of the Sr I 4607 Å
scattering polarization signals at different limb distances with
ZIMPOL
Authors: Dhara, Sajal Kumar; Capozzi, Emilia; Gisler, Daniel; Bianda,
Michele; Ramelli, Renzo; Berdyugina, Svetlana; Alsina, Ernest;
Belluzzi, Luca
2019A&A...630A..67D Altcode: 2019arXiv190803366D
Context. The Sr I 4607 Å spectral line shows one of the strongest
scattering polarization signals in the visible solar spectrum. The
amplitude of this polarization signal is expected to vary at granular
spatial scales, due to the combined action of the Hanle effect and the
local anisotropy of the radiation field. Observing these variations
would be of great interest because it would provide precious information
on the small-scale activity of the solar photosphere. At present, few
detections of such spatial variations have been reported. This is due
to the difficulty of these measurements, which require combining high
spatial (∼0.1″), spectral (≤20 mÅ), and temporal resolution (&lt;
1 min) with increased polarimetric sensitivity (∼10-4). Aims: We aim to detect spatial variations at granular scales of the
scattering polarization peak of the Sr I 4607 Å line at different
limb distances, and to study the correlation with the continuum
intensity. Methods: Using the Zurich IMaging POLarimeter
(ZIMPOL) system mounted at the GREGOR telescope and spectrograph in
Tenerife, Spain, we carried out spectro-polarimetric measurements
to obtain the four Stokes parameters in the Sr I line at different
limb distances, from μ = 0.2 to μ = 0.8, on the solar disk. 
Results: Spatial variations of the scattering polarization signal in
the Sr I 4607 Å line, with a spatial resolution of about 0.66″, are
clearly observed at every μ. The spatial scale of these variations is
comparable to the granular size. A statistical analysis reveals that
the linear scattering polarization amplitude in this Sr I spectral
line is positively correlated with the intensity in the continuum,
corresponding to the granules, at every μ.

---------------------------------------------------------
Title: Complexity of magnetic fields on red dwarfs
Authors: Afram, N.; Berdyugina, S. V.
2019A&A...629A..83A Altcode: 2019arXiv190800076A
Context. Magnetic fields in cool stars can be investigated by
measuring Zeeman line broadening and polarization in atomic and
molecular lines. Similar to the Sun, these fields are complex and
height-dependent. Many molecular lines dominating M-dwarf spectra (e.g.,
FeH, CaH, MgH, and TiO) are temperature- and Zeeman-sensitive and form
at different atmospheric heights, which makes them excellent probes
of magnetic fields on M dwarfs. Aims: Our goal is to analyze
the complexity of magnetic fields in M dwarfs. We investigate how
magnetic fields vary with the stellar temperature and how "surface"
inhomogeneities are distributed in height - the dimension that
is usually neglected in stellar magnetic studies. Methods:
We have determined effective temperatures of the photosphere and
of magnetic features, magnetic field strengths and filling factors
for nine M dwarfs (M1-M7). Our χ2 analysis is based on a
comparison of observed and synthetic intensity and circular polarization
profiles. Stokes profiles were calculated by solving polarized radiative
transfer equations. Results: Properties of magnetic structures
depend on the analyzed atomic or molecular species and their formation
heights. Two types of magnetic features similar to those on the Sun
have been found: a cooler (starspots) and a hotter (network) one. The
magnetic field strength in both starspots and network is within 3-6 kG,
on average it is 5 kG. These fields occupy a large fraction of M dwarf
atmospheres at all heights, up to 100%. The plasma β is less than one,
implying highly magnetized stars. Conclusions: A combination of
molecular and atomic species and a simultaneous analysis of intensity
and circular polarization spectra have allowed us to better decipher the
complexity of magnetic fields on M dwarfs, including their dependence on
the atmospheric height. This work provides an opportunity to investigate
a larger sample of M dwarfs and L-type brown dwarfs. The spectra
of the stars are also available at the CDS via anonymous ftp to <A
href="http://cdsarc.u-strasbg.fr">http://cdsarc.u-strasbg.fr</A>
(ftp://130.79.128.5) or via <A
href="http://cdsarc.u-strasbg.fr/viz-bin/cat/J/A+A/629/A83">http://cdsarc.u-strasbg.fr/viz-bin/cat/J/A+A/629/A83</A>

---------------------------------------------------------
Title: VizieR Online Data Catalog: Complexity of magnetic fields on
red dwarfs (Afram+, 2019)
Authors: Afram, N.; Berdyugina, S. V.
2019yCat..36290083A Altcode:
Circular polarization and total intensity spectra obtained with
ESPaDOnS at the CFHT for the nine M dwarfs with the spectral class
range M1-M7. The spectra cover the wavelength range from 370nm to
1048nm. All files were taken from the online data archive 'The
Canadian Astronomy Data Centre' www.cadc.hia.nrc.gc.ca/AdvancedSearch/
For the polarimetric case, sets of 4 exposures produce one *p.fits
file. The p.fits files have: COL1 = 'Wavelength' / Normalized
COL2 = 'Intensity' / Normalized COL3 = 'Stokes ' / Normalized COL4 =
'CheckN1 ' / Normalized COL5 = 'CheckN2 ' / Normalized COL6 = 'ErrorBar'
/ Normalized COL7 = 'Wavelength' / UnNormalized COL8 = 'Intensity'
/ UnNormalized COL9 = 'Stokes ' / UnNormalized COL10 = 'CheckN1 ' /
UnNormalized COL11 = 'CheckN2 ' / UnNormalized COL12 = 'ErrorBar' /
UnNormalized COL13 = 'Wavelength' / Normalized, no autowave correction
COL14 = 'Intensity' / Normalized, no autowave correction COL15 =
'Stokes ' / Normalized, no autowave correction COL16 = 'CheckN1 ' /
Normalized, no autowave correction COL17 = 'CheckN2 ' / Normalized,
no autowave correction COL18 = 'ErrorBar' / Normalized, no autowave
correction COL19 = 'Wavelength' / UnNormalized, no autowave correction
COL20 = 'Intensity' / UnNormalized, no autowave correction COL21 =
'Stokes ' / UnNormalized, no autowave correction COL22 = 'CheckN1 ' /
UnNormalized, no autowave correction COL23 = 'CheckN2 ' / UnNormalized,
no autowave correction COL24 = 'ErrorBar' / UnNormalized, no autowave
correction (2 data files).

---------------------------------------------------------
Title: The inner dust shell of Betelgeuse detected by polarimetric
aperture-masking interferometry
Authors: Haubois, X.; Norris, B.; Tuthill, P. G.; Pinte, C.; Kervella,
P.; Girard, J. H.; Kostogryz, N. M.; Berdyugina, S. V.; Perrin, G.;
Lacour, S.; Chiavassa, A.; Ridgway, S. T.
2019A&A...628A.101H Altcode: 2019arXiv190708594H
Context. Theory surrounding the origin of the dust-laden winds
from evolved stars remains mired in controversy. Characterizing the
formation loci and the dust distribution within approximately the
first stellar radius above the surface is crucial for understanding
the physics that underlie the mass-loss phenomenon. Aims:
By exploiting interferometric polarimetry, we derive the fundamental
parameters that govern the dust structure at the wind base of a red
supergiant. Methods: We present near-infrared aperture-masking
observations of Betelgeuse in polarimetric mode obtained with the
NACO/SAMPol instrument. We used both parametric models and radiative
transfer simulations to predict polarimetric differential visibility
data and compared them to SPHERE/ZIMPOL measurements. Results:
Using a thin dust shell model, we report the discovery of a dust halo
that is located at only 0.5 R⋆ above the photosphere
(i.e. an inner radius of the dust halo of 1.5 R⋆). By
fitting the data under the assumption of Mie scattering, we estimate
the grain size and density for various dust species. By extrapolating
to the visible wavelengths using radiative transfer simulations,
we compare our model with SPHERE/ZIMPOL data and find that models
based on dust mixtures that are dominated by forsterite are most
favored. Such a close dusty atmosphere has profound implications for
the dust formation mechanisms around red supergiants. Based on
SAMPol data obtained at the ESO VLT Yepun telescope (090.D-0898(A)).

---------------------------------------------------------
Title: Measurement of the Evolution of the Magnetic Field of the
Quiet Photosphere over a Solar Cycle
Authors: Ramelli, R.; Bianda, M.; Berdyugina, S.; Belluzzi, L.;
Kleint, L.
2019ASPC..526..283R Altcode:
The solar photosphere is filled by magnetic fields tangled at scales
much smaller than the resolution capability of solar telescopes. These
hidden magnetic fields can be investigated via the Hanle effect. In
2007, we started a synoptic program to explore whether the magnetic flux
of the quiet photosphere varies with the solar cycle. For this purpose
we applied a differential Hanle effect technique based on observations
of scattering polarization in C2 molecular lines around
514.0 nm, taken with a cadence of approximately one month. Our results
now span almost one complete solar cycle.

---------------------------------------------------------
Title: Hanle Coronal Magnetometry Using Permitted He I 1083 nm and
Forbidden Si X 1430 nm IR Emission Lines
Authors: Dima, G. I.; Kuhn, J. R.; Berdyugina, S. V.
2019ASPC..526..199D Altcode:
With a model of the coronal Hanle effect, and by measuring the linear
polarization of permitted and forbidden lines, it is possible to
determine the magnetic field in the emission region of the considered
lines. This technique may be applicable in the corona because of the
discovery of faint He I emission, possibly due to a non-equilibrium
population of He I atoms originating on coronal dust grains. He I 1083
nm lies in the unsaturated Hanle regime for field strengths below 8
G, so that the polarization amplitude and orientation are sensitive
to both the orientation and strength of the magnetic field. To break
this degeneracy we can use one of several coronal infrared forbidden
lines, like Fe XIII 1075 nm or Si X 1430 nm. These forbidden lines
are sensitive to different coronal temperature regimes, and provide
additional constraints on the orientation of the magnetic field. We
discuss magnetic field uncertainties inherent to this measurement
technique, and present the first polarized measurements of the Si X
1430 nm line, obtained using the SOLARC telescope on Haleakalā.

---------------------------------------------------------
Title: Center-to-Limb Continuum Polarization in Solar and Stellar
Atmospheres
Authors: Kostogryz, N. M.; Berdyugina, S. V.; Yakobchuk, T. M.;
Milić, I.
2019ASPC..526..139K Altcode:
The center-to-limb variation of the intensity (CLVI) and of the linear
polarization (CLVP) of stellar radiation arise when the scattering
and absorption processes are important in the stellar atmosphere. We
model the CLVI and CLVP of continuum radiation, taking into account
different contributions of scattering and absorption opacity for
a variety of spectral type stars with plane-parallel and spherical
PHOENIX atmosphere models. We show how the polarization depends on
the effective temperature and surface gravity of a star and how the
considered geometry of the stellar atmosphere affects the polarization
signal. For the Sun, we compare existing measurements with our
theoretical predictions for different solar models (FALA, FALC, FALP,
HSRA, and Phoenix). The CLVI and CLVP of stellar atmospheres are also
needed to interpret the light curves of transiting exoplanets. Here we
present the variation of the polarization in exoplanetary systems caused
by transits and grazing transits and discuss how the considered geometry
of stellar atmosphere models affect the transit curves of exoplanets.

---------------------------------------------------------
Title: Spatial variations of the SrI 4607Åscattering polarization
signals at subgranular scale observed with ZIMPOL at GREGOR telescope
Authors: Dhara, Sajal Kumar; Capozzi, Emilia; Gisler, Daniel; Bianda,
Michele; Ramelli, Renzo; Berdyugina, Svetlana; Alsina, Ernest;
Belluzzi, Luca
2019arXiv190403986D Altcode:
Sr I 4607Åspectral line shows one of the strongest scattering
polarization signals in the visible solar spectrum. The amplitudes of
these signals are expected to vary at granular spatial scales. This
variation can be due to changes in the magnetic field intensity
and orientation (Hanle effect) as well as due to spatial and
temporal variations in the plasma properties. Measuring the spatial
variation of such polarization signal would allow us to study the
properties of the magnetic fields at subgranular region. But, the
observations are challenging since both high spatial resolution and
high spectropolarimetric sensitivity are required at the same time. To
the aim of measuring these spatial variations at granular scale, we
carried out a spectro-polarimetric measurement with the Zurich IMaging
POLarimeter (ZIMPOL), at the GREGOR solar telescope at different
limb distances on solar disk. Our results show a spatial variation
of scattering linear polarization signals in Sr I 4607Åline at the
granular scale at every $\mu$, starting from 0.2 to 0.8. The correlation
between the polarization signal amplitude and the continuum intensity
imply statistically that the scattering polarization is higher at the
granular regions than in the intergranular lanes.

---------------------------------------------------------
Title: Evolving optical polarisation of the black hole X-ray binary
MAXI J1820+070
Authors: Veledina, Alexandra; Berdyugin, Andrei V.; Kosenkov, Ilia A.;
Kajava, Jari J. E.; Tsygankov, Sergey S.; Piirola, Vilppu; Berdyugina,
Svetlana V.; Sakanoi, Takeshi; Kagitani, Masato; Kravtsov, Vadim;
Poutanen, Juri
2019A&A...623A..75V Altcode: 2018arXiv180809002V
 Aims: The optical emission of black hole transients increases by
several magnitudes during the X-ray outbursts. Whether the extra light
arises from the X-ray heated outer disc, from the inner hot accretion
flow, or from the jet is currently debated. Optical polarisation
measurements are able to distinguish the relative contributions
of these components. Methods: We present the results of
BVR polarisation measurements of the black hole X-ray binary MAXI
J1820+070 during the period of March-April 2018. Results: We
detect small, ∼0.7%, but statistically significant polarisation,
part of which is of interstellar origin. Depending on the interstellar
polarisation estimate, the intrinsic polarisation degree of the source
is between ∼0.3% and 0.7%, and the polarisation position angle
is between ∼10 ° -30°. We show that the polarisation increases
after MJD 58222 (2018 April 14). The change is of the order of 0.1%
and is most pronounced in the R band. The change of the source Stokes
parameters occurs simultaneously with the drop of the observed V-band
flux and a slow softening of the X-ray spectrum. The Stokes vectors
of intrinsic polarisation before and after the drop are parallel,
at least in the V and R filters. Conclusions: We suggest that
the increased polarisation is due to the decreasing contribution of the
non-polarized component, which we associate with the the hot flow or jet
emission. The low polarisation can result from the tangled geometry of
the magnetic field or from the Faraday rotation in the dense, ionised,
and magnetised medium close to the black hole. The polarized optical
emission is likely produced by the irradiated disc or by scattering
of its radiation in the optically thin outflow.

---------------------------------------------------------
Title: Stochastic entropy production in the quite Sun magnetic fields
Authors: Gorobets, Andriy Y.; Berdyugina, Svetlana V.
2019MNRAS.483L..69G Altcode: 2018arXiv181202561G
The second law of thermodynamics imposes an increase of macroscopic
entropy with time in an isolated system. Microscopically, however,
the entropy production can be negative for a single, microscopic
realization of a thermodynamic process. The so-called fluctuation
theorems provide exact relations between the stochastic entropy
consumption and generation. Here, we analyse pixel-to-pixel fluctuations
in time of small-scale magnetic fields (SSMF) in the quiet Sun observed
with the SDO/HMI instrument. We demonstrate that entropy generated by
SSMF obeys the fluctuation theorems. In particular, the SSMF entropy
consumption probability is exactly exponentially smaller than the SSMF
entropy generation probability. This may have fundamental implications
for the magnetic energy budget of the Sun.

---------------------------------------------------------
Title: Spatial variations of the Sr I 4607 Åscattering polarization
signals at subgranular scale observed with ZIMPOL at the GREGOR
telescope
Authors: Kumar Dhara, Sajal; Capozzi, Emilia; Gisler, Daniel; Bianda,
Michele; Ramelli, Renzo; Berdyugina, Svetlana; Alsina, Ernest;
Belluzzi, Luca
2019NCimC..42....6K Altcode:
Sr I 4607 Åspectral line shows one of the strongest scattering
polarization signals in the visible solar spectrum. The amplitudes of
these signals are expected to vary at granular spatial scales. This
variation can be due to changes in the magnetic field intensity and
orientation (Hanle effect) as well as due to spatial and temporal
variations in the plasma properties. Measuring the spatial variation
of such polarization signal are challenging since both high spatial
resolution and high spectropolarimetric sensitivity are required at
the same time. To the aim of measuring these spatial variations at
granular scale, we carried out a spectro-polarimetric measurement
with the Zurich IMaging POLarimeter (ZIMPOL), at the GREGOR solar
telescope at different limb distances on solar disk. Our results show
a spatial variation of scattering linear polarization signals in Sr
I 4607 Åline at the granular scale at every μ, starting from 0.2
to 0.8. The correlation between the scattering linear polarization
signal amplitude and the continuum intensity imply statistically that
the scattering polarization is higher at the granular regions than in
the intergranular lanes.

---------------------------------------------------------
Title: Exoplanet Terra Incognita
Authors: Berdyugina, Svetlana V.; Kuhn, Jeff R.; Belikov, Ruslan;
Turyshev, Slava G.
2018arXiv180905031B Altcode:
Exoplanet surface imaging, cartography and the search for exolife are
the next frontiers of planetology and astrophysics. Here we present
an over-view of ideas and techniques to resolve albedo features
on exoplanetary surfaces. Albedo maps obtained in various spectral
bands (similar to true-colour images) may reveal exoplanet terrains,
geological history, life colonies, and even artificial structures of
advanced civilizations.

---------------------------------------------------------
Title: High-precision and high-accuracy polarimetry of exoplanets
Authors: Berdyugin, A. V.; Berdyugina, S. V.; Piirola, V.
2018SPIE10702E..4ZB Altcode:
Detecting polarization of the light reflected from an exoplanet requires
extremely high-precision polarimeters and highaccuracy calibration
techniques. The polarimetric precision of a few parts per million (ppm),
approaching the photon noise, was demonstrated for the Sun and bright
distant stars by several groups and instruments. However, the accuracy
of absolute polarimetric calibration strongly depends on the polarimeter
design and observing conditions, which results in largely unknown
systematic errors hindering the exoplanet polarization detection. Here
we discuss some of the crucial aspects of exoplanet polarimetric data
acquisition, e.g., effects of seeing, sky polarization, telescope
polarization, etc. We simulate examples of polarimetric measurements
with various levels of random and systematic errors. They demonstrate
that sparse measurements (ten or less) and unknown systematic errors can
hinder exoplanet signal detection even when the signal is significantly
larger than the polarimetric precision. We discuss various approaches
which help improve random errors (precision) and mitigate systematic
errors (accuracy) caused by various effects. We also discuss the
performance of polarimeters with different designs and indicate their
strengths and weaknesses in terms of precision and accuracy.

---------------------------------------------------------
Title: The Exo-Life Finder Telescope (ELF): design and beam synthesis
concepts
Authors: Kuhn, J. R.; Berdyugina, S. V.; Capsal, J. -F.; Gedig, M.;
Langlois, M.; Moretto, G.; Thetpraphi, K.
2018SPIE10700E..15K Altcode:
Currently planned massively segmented telescopes like the European
Extremely Large Telescope (EELT)1 or the Thirty Meter Telescope (TMT)2,
use "Keck-era" optics. Their mirror subapertures create a dynamically
rigid primary optical surface from 100's of 1m-scale few-cm thick
mirrors. We suggest that a dedicated telescope for distinguishing
reflected exoplanet light from its host star may not follow these
design principles. To reduce moving mass and telescope-scattered
light, a post-Keck era large telescope could use new technologies that
replace this opto-mechanical stiffness with massively parallel active
electro-optics and interferometric concepts. This opens the intriguing
possibility of building a dedicated ground-based exoplanet telescope
with an aperture of 20m at a cost-scale of $100M. This is a compelling
reason for exploring what we call "synthetic aperture" or "hybrid
optical telescopes." Even larger apertures that could be an order of
magnitude less costly per square meter than comparable Keck-like optics
are possible. Here we consider an optical system built from a relatively
"floppy" optical structure and scalable interferometrically phased,
moderate size (5m diameter), subapertures. This ExoLife Finder (ELF)
telescope is sensitive to optical biomarker signals and has the power to
map the surfaces of nearby M-dwarf exoplanets on subcontinental scales.

---------------------------------------------------------
Title: Development of PLANETS telescope and visible-infrared
spectrometer for monitoring of planetary and exoplanetary atmospheres
Authors: Sakanoi, Takeshi; Kuhn, Jeff; Berdyugina, Svetlana; Emilio,
Marcelo; Kagitani, Masato; Hirahara, Yasuhiro; Nakagawa, Hiromu;
Kasaba, Yasumasa; Obara, Takahiro; Okano, Shoichi; Scholl, Isabelle;
Berdyugin, Andrei; Piirola, Vilppu
2018SPIE10700E..4JS Altcode:
We report the current status of small-telescope activities and the 1.8-m
aperture telescope PLANETS project at Haleakala dedicated to planetary
and exoplanetary observations. Continuous monitoring is essential to
understand the planetary atmospheric phenomena, and therefore, own
facilities with even small- and medium sized telescopes and instruments
are important. On the summit of Mt. Haleakala, Hawaii, we are operating
a 40 cm (T40) and 60 cm (T60) telescopes for measuring faint atmospheric
features such as Io torus, Mercury, and so on. It has uniquely provided
long-term Io torus activities for more than ten years. T60 is now
observing planetary atmospheres in visible and infrared ranges. The
polarization imager DIPOL-2 is also installed to measure the weak
polarization of exoplanetary light. In addition, we are carrying
out a 1.8-m off-axis telescope project PLANETS at Haleakala. This
project is managed by the PLANETS Foundation (www.planets.life) is
an international collaboration of several institutes from Japan, USA,
Germany, Brazil, and France. This off-axis optical system enables very
low-stray light contamination and high-contrast in data, i.e., "high
dynamic range". It will achieve unrivaled scientific capabilities on
coronagraphy and polarimetry, aimed at detecting exoplanet reflected
light and tenuous planetary exo-atmospheres in the Solar system. The
main mirror is Clearceram ZHS with a diameter of 1850 mm, which is now
on the final polishing process. We completed the telescope design and
wind analysis of the mechanical support and tracking. The "split-ring"
mount is so stiff that it has a first vibration mode above 50 Hz.

---------------------------------------------------------
Title: The ExoLife Finder (ELF) Telescope: new adaptive optics and
hybrid dynamic live-optical surfaces strategies
Authors: Moretto, Gil; Kuhn, Jeff R.; Capsal, Jean-Fabien; Audigier,
David; Thetpraphi, Kritsadi; Langlois, Maud; Tallon, Michel; Gedig,
Mike; Berdyugina, Svetlana V.; Halliday, David
2018SPIE10700E..4CM Altcode:
The exponential growth in exoplanets studies and related science such
as detecting life and even civilizations on Earth-like planets requires
high angular resolution and high-contrast observations. Such appealing
sciences cases are a powerful reason for developing a dedicated high
contrast telescope concept - The ExoLife Finder (ELF) Telescope. Here
we describe the ELF overall optical concept, its preliminary Adaptive
Optics concept and a novel and revolutionary technology to produce
mirrors making use of force-sensor-actuator elements that are 3D-printed
onto very thin slumped glass-sandwich elements of fire-polished glass -
a very precise aspherical optical surface dedicated to high contrast
measurements.

---------------------------------------------------------
Title: The Exo-Life Finder (ELF) telescope: New strategies for direct
detection of exoplanet biosignatures and technosignatures
Authors: Berdyugina, S. V.; Kuhn, J. R.; Langlois, M.; Moretto, G.;
Krissansen-Totton, J.; Catling, D.; Grenfell, J. L.; Santl-Temkiv,
T.; Finster, K.; Tarter, J.; Marchis, F.; Hargitai, H.; Apai, D.
2018SPIE10700E..4IB Altcode:
The Exo-Life Finder (ELF) will be an optical system with the
resolving power of a &gt;=20m telescope optimized for characterizing
exoplanets and detecting exolife. It will allow for direct detection
of Earth-size planets in commonlyconsidered water-based habitable zones
(WHZ) of nearby stars and for generic exolife studies. Here we discuss
capabilities of the ELF to detect biosignatures and technosignatures in
exoplanetary atmospheres and on their surfaces in the visual and near
infrared. We evaluate sensitivity limits for mid- and low-resolution
spectral, photometric and polarimetric measurements, analyzed using
atmosphere models and light-curve inversions. In particular, we model
and estimate integration times required to detect O2,
O3, CO2, CH4, H2O and
other biosignature gases and habitability markers. Disequilibrium
biosignature pairs such as O2+CH4 or
CO2+CH4-CO are also explored. Photosynthetic and
nonphotosynthetic pigments are other important biosignatures that ELF
will search for in atmospheres and on resolved surfaces of exoplanets,
in the form of bioaerosols and colonies of organisms. Finally, possible
artificial structures on exoplanet surfaces and in near-exoplanet space
can be detected. Practical instrument requirements are formulated
for detecting these spectral and structural biosignatures and
technosignatures. It is imperative that such a study is applied first
to characterize the nearest exoplanet Proxima b, then to search for
exo-Earths in the Alpha Cen A and B system and other near-Sun stars,
and finally to explore larger exoplanets around more distant stars.

---------------------------------------------------------
Title: Simulation of the small-scale magnetism in main-sequence
stellar atmospheres
Authors: Salhab, R. G.; Steiner, O.; Berdyugina, S. V.; Freytag, B.;
Rajaguru, S. P.; Steffen, M.
2018A&A...614A..78S Altcode:
Context. Observations of the Sun tell us that its granular and
subgranular small-scale magnetism has significant consequences for
global quantities such as the total solar irradiance or convective
blueshift of spectral lines. Aims: In this paper, properties
of the small-scale magnetism of four cool stellar atmospheres,
including the Sun, are investigated, and in particular its effects
on the radiative intensity and flux. Methods: We carried out
three-dimensional radiation magnetohydrodynamic simulations with the
CO5BOLD code in two different settings: with and without
a magnetic field. These are thought to represent states of high and
low small-scale magnetic activity of a stellar magnetic cycle. Results: We find that the presence of small-scale magnetism
increases the bolometric intensity and flux in all investigated
models. The surplus in radiative flux of the magnetic over the magnetic
field-free atmosphere increases with increasing effective temperature,
Teff, from 0.47% for spectral type K8V to 1.05% for the solar
model, but decreases for higher effective temperatures than solar. The
degree of evacuation of the magnetic flux concentrations monotonically
increases with Teff as does their depression of the visible
optical surface, that is the Wilson depression. Nevertheless, the
strength of the field concentrations on this surface stays remarkably
unchanged at ≈1560 G throughout the considered range of spectral
types. With respect to the surrounding gas pressure, the field strength
is close to (thermal) equipartition for the Sun and spectral type F5V
but is clearly sub-equipartition for K2V and more so for K8V. The
magnetic flux concentrations appear most conspicuous for model K2V
owing to their high brightness contrast. Conclusions: For mean
magnetic flux densities of approximately 50 G, we expect the small-scale
magnetism of stars in the spectral range from F5V to K8V to produce a
positive contribution to their bolometric luminosity. The modulation
seems to be most effective for early G-type stars.

---------------------------------------------------------
Title: Spatial variations of the Sr I 4607 Å scattering polarization
peak
Authors: Bianda, M.; Berdyugina, S.; Gisler, D.; Ramelli, R.; Belluzzi,
L.; Carlin, E. S.; Stenflo, J. O.; Berkefeld, T.
2018A&A...614A..89B Altcode: 2018arXiv180303531B
Context. The scattering polarization signal observed in the
photospheric Sr I 4607 Å line is expected to vary at granular
spatial scales. This variation can be due to changes in the magnetic
field intensity and orientation (Hanle effect), but also to spatial
and temporal variations in the plasma properties. Measuring the
spatial variation of such polarization signal would allow us to
study the properties of the magnetic fields at subgranular scales,
but observations are challenging since both high spatial resolution
and high spectropolarimetric sensitivity are required. Aims:
We aim to provide observational evidence of the polarization peak
spatial variations, and to analyze the correlation they might have
with granulation. Methods: Observations conjugating high spatial
resolution and high spectropolarimetric precision were performed with
the Zurich IMaging POLarimeter, ZIMPOL, at the GREGOR solar telescope,
taking advantage of the adaptive optics system and the newly installed
image derotator. Results: Spatial variations of the scattering
polarization in the Sr I 4607 Å line are clearly observed. The
spatial scale of these variations is comparable with the granular
size. Small correlations between the polarization signal amplitude
and the continuum intensity indicate that the polarization is higher
at the center of granules than in the intergranular lanes.

---------------------------------------------------------
Title: Scattering linear polarization of late-type active stars
Authors: Yakobchuk, T. M.; Berdyugina, S. V.
2018A&A...613A...7Y Altcode: 2018arXiv180101484Y
Context. Many active stars are covered in spots, much more so than the
Sun, as indicated by spectroscopic and photometric observations. It
has been predicted that star spots induce non-zero intrinsic linear
polarization by breaking the visible stellar disk symmetry. Although
small, this effect might be useful for star spot studies, and it
is particularly significant for a future polarimetric atmosphere
characterization of exoplanets orbiting active host stars. 
Aims: Using models for a center-to-limb variation of the intensity
and polarization in presence of continuum scattering and adopting a
simplified two-temperature photosphere model, we aim to estimate the
intrinsic linear polarization for late-type stars of different gravity,
effective temperature, and spottedness. Methods: We developed
a code that simulates various spot configurations or uses arbitrary
surface maps, performs numerical disk integration, and builds Stokes
parameter phase curves for a star over a rotation period for a selected
wavelength. It allows estimating minimum and maximum polarization
values for a given set of stellar parameters and spot coverages. 
Results: Based on assumptions about photosphere-to-spot temperature
contrasts and spot size distributions, we calculate the linear
polarization for late-type stars with Teff = 3500 K-6000 K,
log g = 1.0-5.0, using the plane-parallel and spherical atmosphere
models. Employing random spot surface distribution, we analyze the
relation between spot coverage and polarization and determine the
influence of different input parameters on results. Furthermore, we
consider spot configurations with polar spots and active latitudes
and longitudes.

---------------------------------------------------------
Title: The First Post-Kepler Brightness Dips of KIC 8462852
Authors: Boyajian, Tabetha. S.; Alonso, Roi; Ammerman, Alex; Armstrong,
David; Asensio Ramos, A.; Barkaoui, K.; Beatty, Thomas G.; Benkhaldoun,
Z.; Benni, Paul; Bentley, Rory O.; Berdyugin, Andrei; Berdyugina,
Svetlana; Bergeron, Serge; Bieryla, Allyson; Blain, Michaela G.;
Capetillo Blanco, Alicia; Bodman, Eva H. L.; Boucher, Anne; Bradley,
Mark; Brincat, Stephen M.; Brink, Thomas G.; Briol, John; Brown,
David J. A.; Budaj, J.; Burdanov, A.; Cale, B.; Aznar Carbo, Miguel;
Castillo García, R.; Clark, Wendy J.; Clayton, Geoffrey C.; Clem,
James L.; Coker, Phillip H.; Cook, Evan M.; Copperwheat, Chris M.;
Curtis, J. L.; Cutri, R. M.; Cseh, B.; Cynamon, C. H.; Daniels, Alex
J.; Davenport, James R. A.; Deeg, Hans J.; De Lorenzo, Roberto; de
Jaeger, Thomas; Desrosiers, Jean-Bruno; Dolan, John; Dowhos, D. J.;
Dubois, Franky; Durkee, R.; Dvorak, Shawn; Easley, Lynn; Edwards, N.;
Ellis, Tyler G.; Erdelyi, Emery; Ertel, Steve; Farfán, Rafael. G.;
Farihi, J.; Filippenko, Alexei V.; Foxell, Emma; Gandolfi, Davide;
Garcia, Faustino; Giddens, F.; Gillon, M.; González-Carballo,
Juan-Luis; González-Fernández, C.; González Hernández, J. I.;
Graham, Keith A.; Greene, Kenton A.; Gregorio, J.; Hallakoun, Na'ama;
Hanyecz, Ottó; Harp, G. R.; Henry, Gregory W.; Herrero, E.; Hildbold,
Caleb F.; Hinzel, D.; Holgado, G.; Ignácz, Bernadett; Ilyin, Ilya;
Ivanov, Valentin D.; Jehin, E.; Jermak, Helen E.; Johnston, Steve;
Kafka, S.; Kalup, Csilla; Kardasis, Emmanuel; Kaspi, Shai; Kennedy,
Grant M.; Kiefer, F.; Kielty, C. L.; Kessler, Dennis; Kiiskinen,
H.; Killestein, T. L.; King, Ronald A.; Kollar, V.; Korhonen, H.;
Kotnik, C.; Könyves-Tóth, Réka; Kriskovics, Levente; Krumm, Nathan;
Krushinsky, Vadim; Kundra, E.; Lachapelle, Francois-Rene; LaCourse,
D.; Lake, P.; Lam, Kristine; Lamb, Gavin P.; Lane, Dave; Lau, Marie
Wingyee; Lewin, Pablo; Lintott, Chris; Lisse, Carey; Logie, Ludwig;
Longeard, Nicolas; Lopez Villanueva, M.; Whit Ludington, E.; Mainzer,
A.; Malo, Lison; Maloney, Chris; Mann, A.; Mantero, A.; Marengo,
Massimo; Marchant, Jon; Martínez González, M. J.; Masiero, Joseph R.;
Mauerhan, Jon C.; McCormac, James; McNeely, Aaron; Meng, Huan Y. A.;
Miller, Mike; Molnar, Lawrence A.; Morales, J. C.; Morris, Brett M.;
Muterspaugh, Matthew W.; Nespral, David; Nugent, C. R.; Nugent,
Katherine M.; Odasso, A.; O'Keeffe, Derek; Oksanen, A.; O'Meara,
John M.; Ordasi, András; Osborn, Hugh; Ott, John J.; Parks, J. R.;
Rodriguez Perez, Diego; Petriew, Vance; Pickard, R.; Pál, András;
Plavchan, P.; Pollacco, Don; Pozo Nuñez, F.; Pozuelos, F. J.; Rau,
Steve; Redfield, Seth; Relles, Howard; Ribas, Ignasi; Richards, Jon;
Saario, Joonas L. O.; Safron, Emily J.; Sallai, J. Martin; Sárneczky,
Krisztián; Schaefer, Bradley E.; Schumer, Clea F.; Schwartzendruber,
Madison; Siegel, Michael H.; Siemion, Andrew P. V.; Simmons, Brooke D.;
Simon, Joshua D.; Simón-Díaz, S.; Sitko, Michael L.; Socas-Navarro,
Hector; Sódor, Á.; Starkey, Donn; Steele, Iain A.; Stone, Geoff;
Strassmeier, Klaus G.; Street, R. A.; Sullivan, Tricia; Suomela, J.;
Swift, J. J.; Szabó, Gyula M.; Szabó, Róbert; Szakáts, Róbert;
Szalai, Tamás; Tanner, Angelle M.; Toledo-Padrón, B.; Tordai, Tamás;
Triaud, Amaury H. M. J.; Turner, Jake D.; Ulowetz, Joseph H.; Urbanik,
Marian; Vanaverbeke, Siegfried; Vanderburg, Andrew; Vida, Krisztián;
Vietje, Brad P.; Vinkó, József; von Braun, K.; Waagen, Elizabeth
O.; Walsh, Dan; Watson, Christopher A.; Weir, R. C.; Wenzel, Klaus;
Westendorp Plaza, C.; Williamson, Michael W.; Wright, Jason T.; Wyatt,
M. C.; Zheng, WeiKang; Zsidi, Gabriella
2018ApJ...853L...8B Altcode: 2018arXiv180100732B
We present a photometric detection of the first brightness dips of
the unique variable star KIC 8462852 since the end of the Kepler space
mission in 2013 May. Our regular photometric surveillance started in
2015 October, and a sequence of dipping began in 2017 May continuing
on through the end of 2017, when the star was no longer visible from
Earth. We distinguish four main 1%-2.5% dips, named “Elsie,”
“Celeste,” “Skara Brae,” and “Angkor,” which persist
on timescales from several days to weeks. Our main results so far
are as follows: (i) there are no apparent changes of the stellar
spectrum or polarization during the dips and (ii) the multiband
photometry of the dips shows differential reddening favoring non-gray
extinction. Therefore, our data are inconsistent with dip models that
invoke optically thick material, but rather they are in-line with
predictions for an occulter consisting primarily of ordinary dust,
where much of the material must be optically thin with a size scale
≪1 μm, and may also be consistent with models invoking variations
intrinsic to the stellar photosphere. Notably, our data do not place
constraints on the color of the longer-term “secular” dimming,
which may be caused by independent processes, or probe different
regimes of a single process.

---------------------------------------------------------
Title: Constraining Line-of-sight Confusion in the Corona Using
Linearly Polarized Observations of the Infrared FeXIII 1075nm and
SiX 1430nm Emission Lines
Authors: Dima, G. I.; Kuhn, J. R.; Berdyugina, S.
2017AGUFMSH54A..03D Altcode:
Measurements of the coronal magnetic field are difficult because
of the intrinsically faint emission of coronal plasma and the large
spurious background due to the bright solar disk. This work addresses
the problem of resolving the confusion of the line-of-sight (LOS)
integration through the optically-thin corona being observed. Work on
developing new measuring techniques based on single-point inversions
using the Hanle effect has already been described (Dima et al. 2016). It
is important to develop a technique to assess when the LOS confusion
makes comparing models and observations problematic. Using forward
integration of synthetic emission through magnetohydrodynamic (MHD)
models together with simultaneous linearly polarized observations of
the FeXIII 1075nm and SiX 1430nm emission lines allows us to assess
LOS confusion. Since the lines are both in the Hanle saturated regime
their polarization angles are expected to be aligned as long as the
gas is sampling the same magnetic field. If significant contributions
to the emission is taking place from different regions along the LOS
due to the additive nature of the polarized brightness the measured
linear polarization between the two lines will be offset. The size
of the resolution element is important for this determination since
observing larger coronal regions will confuse the variation along the
LOS with that in the plane-of-sky. We also present comparisons between
synthetic linearly polarized emission through a global MHD model and
observations of the same regions obtained using the 0.5m Scatter-free
Observatory for Limb Active Regions and Coronae (SOLARC) telescope
located on Haleakala, Maui. This work is being done in preparation
for the type of observations that will become possible when the next
generation 4m DKIST telescope comes online in 2020.

---------------------------------------------------------
Title: The Maximum Entropy Limit of Small-scale Magnetic Field
Fluctuations in the Quiet Sun
Authors: Gorobets, A. Y.; Berdyugina, S. V.; Riethmüller, T. L.;
Blanco Rodríguez, J.; Solanki, S. K.; Barthol, P.; Gandorfer, A.;
Gizon, L.; Hirzberger, J.; van Noort, M.; Del Toro Iniesta, J. C.;
Orozco Suárez, D.; Schmidt, W.; Martínez Pillet, V.; Knölker, M.
2017ApJS..233....5G Altcode: 2017arXiv171008361G
The observed magnetic field on the solar surface is characterized by a
very complex spatial and temporal behavior. Although feature-tracking
algorithms have allowed us to deepen our understanding of this behavior,
subjectivity plays an important role in the identification and tracking
of such features. In this paper, we continue studies of the temporal
stochasticity of the magnetic field on the solar surface without relying
either on the concept of magnetic features or on subjective assumptions
about their identification and interaction. We propose a data analysis
method to quantify fluctuations of the line-of-sight magnetic field by
means of reducing the temporal field’s evolution to the regular Markov
process. We build a representative model of fluctuations converging to
the unique stationary (equilibrium) distribution in the long time limit
with maximum entropy. We obtained different rates of convergence to the
equilibrium at fixed noise cutoff for two sets of data. This indicates
a strong influence of the data spatial resolution and mixing-polarity
fluctuations on the relaxation process. The analysis is applied to
observations of magnetic fields of the relatively quiet areas around an
active region carried out during the second flight of the Sunrise/IMaX
and quiet Sun areas at the disk center from the Helioseismic and
Magnetic Imager on board the Solar Dynamics Observatory satellite.

---------------------------------------------------------
Title: Surface Imaging of Proxima b and Other Exoplanets: Topography,
Biosignatures, and Artificial Mega-Structures
Authors: Berdyugina, Svetlana V.; Kuhn, Jeff R.
2017arXiv171100185B Altcode:
Seeing oceans, continents, quasi-static weather, and other surface
features on exoplanets may allow us to detect and characterize life
outside the solar system. The Proxima b planet resides within the
stellar habitable zone allowing for liquid water on its surface, and
it may be Earth-like. However, even the largest planned telescopes
will not be able to resolve its surface features directly. Here,
we demonstrate an inversion technique to image indirectly exoplanet
surfaces using observed unresolved reflected light variations over the
course of the exoplanets orbital and axial rotation: ExoPlanet Surface
Imaging (EPSI). We show that the reflected light curve contains enough
information to detect both longitudinal and latitudinal structures and
to map exoplanet surface features. We demonstrate this using examples
of Solar system planets and moons as well as simulated planets with
Earth-like life and artificial megastructures. We also describe how it
is possible to infer the planet and orbit geometry from light curves. In
particular, we show how albedo maps of Proxima b can be successfully
reconstructed for tidally locked, resonance, and unlocked axial and
orbital rotation. Such albedo maps obtained in different wavelength
passbands can provide "photographic" views of distant exoplanets. We
estimate the signal-to-noise ratio necessary for successful inversions
and analyse telescope and detector requirements necessary for the
first surface images of Proxima b and other nearby exoplanets.

---------------------------------------------------------
Title: Space Weathering of Super-Earths: Model Simulations of
Exospheric Sodium Escape from 61 Virgo b
Authors: Yoneda, M.; Berdyugina, S.; Kuhn, J.
2017AJ....154..139Y Altcode:
Rocky exoplanets are expected to be eroded by space weather in a
similar way as in the solar system. In particular, Mercury is one of the
dramatically eroded planets whose material continuously escapes into its
exosphere and further into space. This escape is well traced by sodium
atoms scattering sunlight. Due to solar wind impact, micrometeorite
impacts, photo-stimulated desorption and thermal desorption, sodium
atoms are released from surface regolith. Some of these released sodium
atoms are escaping from Mercury’s gravitational-sphere. They are
dragged anti-Sun-ward and form a tail structure. We expect similar
phenomena on exoplanets. The hot super-Earth 61 Vir b orbiting a
G3V star at only 0.05 au may show a similar structure. Because of
its small separation from the star, the sodium release mechanisms
may be working more efficiently on hot super-Earths than on Mercury,
although the strong gravitational force of Earth-sized or even more
massive planets may be keeping sodium atoms from escaping from the
planet. Here, we performed model simulations for Mercury (to verify
our model) and 61 Vir b as a representative super-Earth. We have found
that sodium atoms can escape from this exoplanet due to stellar wind
sputtering and micrometeorite impacts, to form a sodium tail. However,
in contrast to Mercury, the tail on this hot super-Earth is strongly
aligned with the anti-starward direction because of higher light
pressure. Our model suggests that 61 Vir b seems to have an exo-base
atmosphere like that of Mercury.

---------------------------------------------------------
Title: First Spectropolarimetric Measurement of a Brown Dwarf Magnetic
Field in Molecular Bands
Authors: Kuzmychov, Oleksii; Berdyugina, Svetlana V.; Harrington,
David M.
2017ApJ...847...60K Altcode: 2017arXiv170501590K
We present the first measurements of the surface magnetic field
of a late-M dwarf, LSR J1835+3259, with the help of the full-Stokes
spectropolarimetry in the bands of diatomic molecules. Our measurements
at different rotational phases of a dwarf yielded one 5σ and two 3σ
magnetic field detections. The observational data have been obtained
with the LRISp polarimeter at the Keck observatory on 2012 August 22
and 23. These data have been compared against synthetic full-Stokes
spectra in the bands of the molecules CrH, FeH, and TiO, which have
been calculated for a range of the stellar parameters and magnetic
field strengths. Making use of χ 2-minimization and maximum
likelihood estimation, we determine the net magnetic field strength B
(and not flux Bf) of LSR J1835+3259 to ∼5 kG with the help of the
Paschen-Back effect in the CrH lines. Our measurements at different
rotational phases suggest that the dwarf’s surface might be covered
with strong small-scale magnetic fields. In addition, recent findings
of the dwarf’s hydrogen emission and the Stokes V signal from the
lower chromosphere indicate that its surface magnetic field might be
changing rapidly giving rise to flare activity, similar to young dMe
dwarfs. We substantiate the substellar origin of LSR J1835+3259 by
making use of our own data as well as the photometric data from the
all-sky surveys 2MASS and WISE.

---------------------------------------------------------
Title: First Detection of a Strong Magnetic Field on a Bursty Brown
Dwarf: Puzzle Solved
Authors: Berdyugina, S. V.; Harrington, D. M.; Kuzmychov, O.; Kuhn,
J. R.; Hallinan, G.; Kowalski, A. F.; Hawley, S. L.
2017ApJ...847...61B Altcode: 2017arXiv170902861B
We report the first direct detection of a strong, 5 kG magnetic field on
the surface of an active brown dwarf. LSR J1835+3259 is an M8.5 dwarf
exhibiting transient radio and optical emission bursts modulated by
fast rotation. We have detected the surface magnetic field as circularly
polarized signatures in the 819 nm sodium lines when an active emission
region faced the Earth. Modeling Stokes profiles of these lines reveals
the effective temperature of 2800 K and log gravity acceleration of
4.5. These parameters place LSR J1835+3259 on evolutionary tracks as
a young brown dwarf with the mass of 55+/- 4{M}{{J}} and
age of 22 ± 4 Myr. Its magnetic field is at least 5.1 kG and covers
at least 11% of the visible hemisphere. The active region topology
recovered using line profile inversions comprises hot plasma loops with
a vertical stratification of optical and radio emission sources. These
loops rotate with the dwarf in and out of view causing periodic emission
bursts. The magnetic field is detected at the base of the loops. This
is the first time that we can quantitatively associate brown dwarf
non-thermal bursts with a strong, 5 kG surface magnetic field and
solve the puzzle of their driving mechanism. This is also the coolest
known dwarf with such a strong surface magnetic field. The young age
of LSR J1835+3259 implies that it may still maintain a disk, which may
facilitate bursts via magnetospheric accretion, like in higher-mass
T Tau-type stars. Our results pave a path toward magnetic studies of
brown dwarfs and hot Jupiters.

---------------------------------------------------------
Title: Inactive Comets from the Oort Cloud: Manxes are Tracing the
History of Solar System Formation
Authors: Hainaut, O. R.; Meech, K. J.; Yang, B.; Berdyugina, S.;
Keane, J. V.; Micheli, M.; Morbidelli, A.; Wainscoat, R. J.
2017EPSC...11..582H Altcode:
Manx comets are nearly tailless objects on long-period comet
orbits. They may early inner solar system remnants, ejected to the
Oort cloud at the time of planet formation. The fraction of rocky
objects on these orbits sets strong constraints on the dynamical models
attempting to reproduce our current solar system. We present our program
to observe Manx comets and the implications on the early solar system.

---------------------------------------------------------
Title: Measurement of the evolution of the magnetic field of the
quiet photosphere during a solar cycle
Authors: Ramelli, Renzo; Bianda, Michele; Berdyugina, Svetlana;
Belluzzi, Luca; Kleint, Lucia
2017arXiv170803287R Altcode:
The solar photosphere is filled by a magnetic field which is tangled
on scales much smaller than the resolution capability of solar
telescopes. This hidden magnetic field can be investigated via the
Hanle effect. In 2007 we started a synoptic program to explore if the
magnetic flux of the quiet photosphere varies with the solar cycle. For
this purpose we applied a differential Hanle effect technique based
on observations of scattering polarization in C$_2$ molecular lines
around 514.0 nm, taken generally every month. Our results now span
almost one complete solar cycle.

---------------------------------------------------------
Title: Polarimetry of transiting planets: Differences between
plane-parallel and spherical host star atmosphere models
Authors: Kostogryz, N. M.; Yakobchuk, T. M.; Berdyugina, S. V.;
Milic, I.
2017A&A...601A...6K Altcode:
Context. To properly interpret photometric and polarimetric observations
of exoplanetary transits, accurate calculations of center-to-limb
variations of intensity and linear polarization of the host star are
needed. These variations, in turn, depend on the choice of geometry of
stellar atmosphere. Aims: We want to understand the dependence
of the flux and the polarization curves during a transit on the choice
of the applied approximation for the stellar atmosphere: spherical
and plane-parallel. We examine whether simpler plane-parallel models
of stellar atmospheres are good enough to interpret the flux and the
polarization light curves during planetary transits, or whether more
complicated spherical models should be used. Methods: Linear
polarization during a transit appears because a planet eclipses
a stellar disk and thus breaks left-right symmetry. We calculate
the flux and the polarization variations during a transit with given
center-to-limb variations of intensity and polarization. Results:
We calculate the flux and the polarization variations during transit for
a sample of 405 extrasolar systems. Most of them show higher transit
polarization for the spherical stellar atmosphere. Our calculations
reveal a group of exoplanetary systems that demonstrates lower maximum
polarization during the transits with spherical model atmospheres of
host stars with effective temperatures of Teff = 4400-5400
K and surface gravity of log g = 4.45-4.65 than that obtained with
plane-parallel atmospheres. Moreover, we have found two trends of the
transit polarization. The first trend is a decrease in the polarization
calculated with spherical model atmosphere of host stars with effective
temperatures Teff = 3500-5100 K, and the second shows an
increase in the polarization for host stars with Teff =
5100-7000 K. These trends can be explained by the relative variation
of temperature and pressure dependences in the plane-parallel and
spherical model atmospheres. Conclusions: For most cases of
known transiting systems the plane-parallel approximation of stellar
model atmospheres may be safely used for calculation of the flux and
the polarization curves because the difference between two models
is tiny. However, there are some examples where the spherical model
atmospheres are necessary to get proper results, such as the systems
with grazing transits, with Earth-size planets, or for the hot host
stars with effective temperatures higher than 6000 K.

---------------------------------------------------------
Title: Detecting magnetic fields on brown dwarfs and exoplanets
Authors: Berdyugina, Svetlana
2017reph.conf20003B Altcode:
There is growing evidence that brown dwarfs may possess rather strong
magnetic fields, similar to active, early M-type red dwarf stars. Strong
clues come from extremely energetic flares detected in UV, X-ray and
optical line emission as well as quiescent and transient radio emission
and bursts. Our recent spectropolarimetric study of one such active
brown dwarf has revealed a 5 kG magnetic spot on its surface. The
emitting region topology recovered using spectral line profile
inversions indicates the presence of a hot plasma large-scale loop of
at least 7000 K with a vertical stratification of the sources producing
both optical and radio emission. This loop rotates with the dwarf in
and out of view causing the emission bursts. The 5 kG magnetic field is
detected at the base of the loop. This result provides the first direct
observational constraint for a magnetically driven non-thermal emission
mechanism and for generation of magnetic fields in fully convective
brown dwarfs. It also paves a path towards magnetic studies of hot
Jupiters of similar temperatures. We model relevant atomic lines and
molecular bands in order to predict spectropolarimetric signals due
to magnetic fields on brown dwarfs, hot Jupiters and other types of
exoplanets. This exercise helps to determine instrumental requirements
for magnetic surveys of brown dwarfs and exoplanets.

---------------------------------------------------------
Title: Haze and cloud distribution in Uranus' atmosphere based on
high-contrast spatially resolved polarization measurements
Authors: Kostogryz, Nadiia; Berdyugina, Svetlana; Gisler, Daniel;
Berkefeld, Thomas
2017EGUGA..1918092K Altcode:
In planetary atmospheres, main sources of opacity are molecular
absorption and scattering on molecules, hazes and aerosols. Hence,
light reflected from a planetary atmosphere can be linearly
polarized. Polarization study of inner solar system planets and
exoplanets is a powerful method to characterize their atmospheres,
because of a wide range of observable phase angles. For outer solar
system planets, observable phase angles are very limited. For instance,
Uranus can only be observed up to 3.2 degrees away from conjunctions,
and its disk-integrated polarization is close to zero due to the
back-scattering geometry. However, resolving the disk of Uranus and
measuring the center-to-limb polarization can help constraining the
vertical atmospheric structure and the nature of scattering aerosols and
particles. In October 2016, we carried out polarization measurements
of Uranus in narrow-band filters centered at methane bands and the
adjacent continuum using the GREGOR Planet Polarimeter (GPP). The GPP is
a high-precision polarimeter and is mounted at the 1.5-m GREGOR solar
telescope, which is suitable for observing at night. In order to reach
a high spatial resolution, the instrument uses an adaptive-optics system
of the telescope. To interpret our measurements, we solve the polarized
radiative transfer problem taking into account different scattering
and absorption opacities. We calculate the center-to-limb variation of
polarization of Uranus' disk in the continuum spectrum and in methane
bands. By varying the vertical distribution of haze and cloud layers,
we derive the vertical structure of the best-fit Uranus atmosphere.

---------------------------------------------------------
Title: Partially filled aperture interferometric telescopes: achieving
large aperture and coronagraphic performance
Authors: Moretto, Gil; Kuhn, Jeff R.; Berdyugina, Svetlana V.;
Langlois, Maud; Tallon, Michel; Thiébaut, Eric; Halliday, David
2016SPIE.9906E..2BM Altcode:
The exponential growth in exoplanet studies and science cases requiring
high contrast observations is a powerful reason for developing very
large optical systems optimized for narrow-field science. Concepts
which cross the boundary between fixed aperture telescopes and
interferometers, combined with technologies that decrease the system
moving mass, can violate the cost and mass scaling laws that make
conventional large-aperture telescopes relatively expensive. Here we
describe concepts of large, filled-aperture (Colossus) and partially
filled aperture (ParFAIT) interferometric optical/IR telescope systems
which break this scaling relation. These systems are dedicated to high
dynamic range science such as detecting life and even civilizations
on Earth-like planets.

---------------------------------------------------------
Title: Markov Properties of the Magnetic Field in the Quiet Solar
Photosphere
Authors: Gorobets, A. Y.; Borrero, J. M.; Berdyugina, S.
2016ApJ...825L..18G Altcode: 2016arXiv160500074G
The observed magnetic field on the solar surface is characterized by a
very complex spatial and temporal behavior. Although feature-tracking
algorithms have allowed us to deepen our understanding of this behavior,
subjectivity plays an important role in the identification and tracking
of such features. In this paper, we study the temporal stochasticity of
the magnetic field on the solar surface without relying on either the
concept of magnetic feature or on the subjective assumptions about their
identification and interaction. The analysis is applied to observations
of the magnetic field of the quiet solar photosphere carried out with
the Imaging Magnetograph eXperiment (IMaX) instrument on board the
stratospheric balloon, Sunrise. We show that the joint probability
distribution functions of the longitudinal ({B}\parallel )
and transverse ({B}\perp ) components of the magnetic field,
as well as of the magnetic pressure ({B}2={B}\perp
2+{B}\parallel 2), verify the
necessary and sufficient condition for the Markov chains. Therefore,
we establish that the magnetic field as seen by IMaX with a resolution
of 0.″15-0.″18 and 33 s cadence, which can be considered as a
memoryless temporal fluctuating quantity.

---------------------------------------------------------
Title: Polarized Scattering and Biosignatures in Exoplanetary
Atmospheres
Authors: Berdyugina, S. V.
2016arXiv160706874B Altcode:
Polarized scattering in planetary atmospheres is computed in the context
of exoplanets. The problem of polarized radiative transfer is solved
for a general case of absorption and scattering, while Rayleigh and Mie
polarized scattering are considered as most relevant examples. We show
that (1) relative contributions of single and multiple scattering depend
on the stellar irradiation and opacities in the planetary atmosphere;
(2) cloud (particle) physical parameters can be deduced from the
wavelength-dependent measurements of the continuum polarization and from
a differential analysis of molecular band absorption; (3) polarized
scattering in molecular bands increases the reliability of their
detections in exoplanets; (4) photosynthetic life can be detected on
other planets in visible polarized spectra with high sensitivity. These
examples demonstrate the power of spectropolarimetry for exoplanetary
research and for searching for life in the universe.

---------------------------------------------------------
Title: Planet imaging polarimetry with the solar telescope GREGOR
Authors: Gisler, Daniel; Berkefeld, Thomas; Berdyugina, Svetlana
2016SPIE.9906E..5EG Altcode:
Polarimetry of planets and planetary systems provide unique information
on physics and chemistry of planetary atmospheres. We have built a
new instrument, GREGOR Planet Polarimeter (GPP), which includes fast
polarimetric modulation, high-rate readout CCD, and adaptive optics. It
operates at the solar telescope GREGOR on Tenerife, Canary Islands,
and it benefits from the possibility to calibrate the entire optical
train after the secondary mirror. Here we present the instrument design,
performance tests, and first scientific data. This research is supported
by the ERC Advanced Grant HotMol.

---------------------------------------------------------
Title: Alpha Virginis: line-profile variations and orbital elements
Authors: Harrington, David; Koenigsberger, Gloria; Olguín, Enrique;
Ilyin, Ilya; Berdyugina, Svetlana V.; Lara, Bruno; Moreno, Edmundo
2016A&A...590A..54H Altcode: 2016arXiv160402057H
Context. Alpha Virginis (Spica) is a B-type binary system whose
proximity and brightness allow detailed investigations of the
internal structure and evolution of stars undergoing time-variable
tidal interactions. Previous studies have led to the conclusion
that the internal structure of Spica's primary star may be more
centrally condensed than predicted by theoretical models of single
stars, raising the possibility that the interactions could lead
to effects that are currently neglected in structure and evolution
calculations. The key parameters in confirming this result are the
values of the orbital eccentricity e, the apsidal period U, and the
primary star's radius, R1. Aims: The aim of this
paper is to analyze the impact that Spica's line profile variability
has on the derivation of its orbital elements and to explore the use
of the variability for constraining R1. Methods:
We use high signal-to-noise and high spectral resolution observations
obtained in 2000, 2008, and 2013 to derive the orbital elements
from fits to the radial velocity curves. We produce synthetic line
profiles using an ab initio tidal interaction model. Results:
The general variations in the line profiles can be understood in terms
of the tidal flows, whose large-scale structure is relatively fixed
in the rotating binary system reference frame. Fits to the radial
velocity curves yield e = 0.108 ± 0.014. However, the analogous RV
curves from theoretical line profiles indicate that the distortion
in the lines causes the fitted value of e to depend on the argument
of periastron; I.e., on the epoch of observation. As a result, the
actual value of e may be as high as 0.125. We find that U = 117.9
± 1.8, which is in agreement with previous determinations. Using
the value R1 = 6.8 R⊙ derived by Palate et
al. (2013) the value of the observational internal structure constant
k2,obs is consistent with theory. We confirm the presence of
variability in the line profiles of the secondary star. RV Table
for the NOT data is only available at the CDS via anonymous ftp to
<A href="http://cdsarc.u-strasbg.fr">http://cdsarc.u-strasbg.fr</A>
(<A href="http://130.79.128.5">http://130.79.128.5</A>) or via <A
href="http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/590/A54">http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/590/A54</A>

---------------------------------------------------------
Title: Infrared Dual-line Hanle diagnostic of the Coronal Vector
Magnetic Field
Authors: Dima, Gabriel; Kuhn, Jeffrey; Berdyugina, Svetlana
2016FrASS...3...13D Altcode:
Measuring the coronal vector magnetic field is still a major challenge
in solar physics. This is due to the intrinsic weakness of the field
(e.g. ~4G at a height of 0.1Rsun above an active region) and the
large thermal broadening of coronal emission lines. We propose using
concurrent linear polarization measurements of near-infrared forbidden
and permitted lines together with Hanle effect models to calculate
the coronal vector magnetic field. In the unsaturated Hanle regime
both the direction and strength of the magnetic field affect the
linear polarization, while in the saturated regime the polarization
is insensitive to the strength of the field. The relatively long
radiative lifetimes of coronal forbidden atomic transitions implies
that the emission lines are formed in the saturated Hanle regime
and the linear polarization is insensitive to the strength of the
field. By combining measurements of both forbidden and permitted lines,
the direction and strength of the field can be obtained. For example,
the SiX 1.4301 um line shows strong linear polarization and has been
observed in emission over a large field-of-view (out to elongations
of 0.5 Rsun. Here we describe an algorithm that combines linear
polarization measurements of the SiX 1.4301 um forbidden line with
linear polarization observations of the HeI 1.0830 um permitted coronal
line to obtain the vector magnetic field. To illustrate the concept we
assume the emitting gas for both atomic transitions is located in the
plane of the sky. The further development of this method and associated
tools will be a critical step towards interpreting the high spectral,
spatial and temporal infrared spectro-polarimetric measurements that
will be possible when the Daniel K. Inouye Solar Telescope (DKIST)
is completed in 2019.

---------------------------------------------------------
Title: Inner solar system material discovered in the Oort cloud
Authors: Meech, Karen J.; Yang, Bin; Kleyna, Jan; Hainaut, Olivier R.;
Berdyugina, Svetlana; Keane, Jacqueline V.; Micheli, Marco; Morbidelli,
Alessandro; Wainscoat, Richard J.
2016SciA....2E0038M Altcode: 2016SciA....200038M
We have observed C/2014 S3 (PANSTARRS), a recently discovered object on
a cometary orbit coming from the Oort cloud that is physically similar
to an inner main belt rocky S-type asteroid. Recent dynamical models
successfully reproduce the key characteristics of our current solar
system; some of these models require significant migration of the
giant planets, whereas others do not. These models provide different
predictions on the presence of rocky material expelled from the inner
solar system in the Oort cloud. C/2014 S3 could be the key to verifying
these predictions of the migration-based dynamical models. Furthermore,
this object displays a very faint, weak level of comet-like activity,
five to six orders of magnitude less than that of typical ice-rich
comets on similar Orbits coming from the Oort cloud. For the nearly
tailless appearance, we are calling C/2014 S3 a Manx object. Various
arguments convince us that this activity is produced by sublimation of
volatile ice, that is, normal cometary activity. The activity implies
that C/2014 S3 has retained a tiny fraction of the water that is
expected to be present at its formation distance in the inner solar
system. We may be looking at fresh inner solar system Earth-forming
material that was ejected from the inner solar system and preserved
for billions of years in the Oort cloud.

---------------------------------------------------------
Title: VizieR Online Data Catalog: alpha Vir RV and EW variations
(Harrington+, 2016)
Authors: Harrington, D.; Koenigsberger, G.; Olguin, E.; Berdyugina,
S. V.; Lara, B.; Moreno, E.
2016yCat..35900054H Altcode:
We use high signal-to-noise and high spectral resolution observations
obtained in 2000, 2008, and 2013 to derive the orbital elements from
fits to the radial velocity curves. We produce synthetic line profiles
using an ab initio tidal interaction model. (1 data file).

---------------------------------------------------------
Title: Center-to-limb variation of intensity and polarization in
continuum spectra of FGK stars for spherical atmospheres
Authors: Kostogryz, N. M.; Milic, I.; Berdyugina, S. V.; Hauschildt,
P. H.
2016A&A...586A..87K Altcode: 2015arXiv151107213K
 Aims: One of the necessary parameters needed for the
interpretation of the light curves of transiting exoplanets or
eclipsing binary stars (as well as interferometric measurements of a
star or microlensing events) is how the intensity and polarization
of light changes from the center to the limb of a star. Scattering
and absorption processes in the stellar atmosphere affect both the
center-to-limb variation of intensity (CLVI) and polarization (CLVP). In
this paper, we present a study of the CLVI and CLVP in continuum
spectra, taking into consideration the different contributions of
scattering and absorption opacity for a variety of spectral type stars
with spherical atmospheres. Methods: We solve the radiative
transfer equation for polarized light in the presence of a continuum
scattering, taking into consideration the spherical model of a stellar
atmosphere. To cross-check our results, we developed two independent
codes that are based on Feautrier and short characteristics methods,
respectively, Results: We calculate the center-to-limb variation
of intensity (CLVI) and polarization (CLVP) in continuum for the
Phoenix grid of spherical stellar model atmospheres for a range of
effective temperatures (4000-7000 K), gravities (log g = 1.0-5.5), and
wavelengths (4000-7000 Å), which are tabulated and available at the
CDS. In addition, we present several tests of our codes and compare our
calculations for the solar atmosphere with published photometric and
polarimetric measurements. We also show that our two codes provide
similar results in all considered cases. Conclusions: For
sub-giant and dwarf stars (log g = 3.0-4.5), the lower gravity and
lower effective temperature of a star lead to higher limb polarization
of the star. For giant and supergiant stars (log g = 1.0-2.5), the
highest effective temperature yields the largest polarization. By
decreasing the effective temperature of a star down to 4500-5500 K
(depending on log g), the limb polarization decreases and reaches a
local minimum. It increases again with a corresponding decrease in
temperature down to 4000 K. For the most compact dwarf stars (log g =
5.0-5.5), the limb polarization degree shows a maximum for models with
effective temperatures in the range 4200-4600 K (depending on log g) and
decreases toward higher and lower temperatures. The intensity and
polarization profiles are only available at the CDS via anonymous ftp to
<A href="http://cdsarc.u-strasbg.fr">http://cdsarc.u-strasbg.fr</A>
(ftp://130.79.128.5) or via <A
href="http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/586/A87">http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/586/A87</A>

---------------------------------------------------------
Title: Remote sensing of life: polarimetric signatures of
photosynthetic pigments as sensitive biomarkers
Authors: Berdyugina, Svetlana V.; Kuhn, Jeff R.; Harrington, David M.;
Šantl-Temkiv, Tina; Messersmith, E. John
2016IJAsB..15...45B Altcode:
We develop a polarimetry-based remote-sensing method for detecting
and identifying life forms in distant worlds and distinguishing them
from non-biological species. To achieve this we have designed and
built a bio-polarimetric laboratory experiment BioPol for measuring
optical polarized spectra of various biological and non-biological
samples. Here we focus on biological pigments, which are common in
plants and bacteria that employ them either for photosynthesis or
for protection against reactive oxygen species. Photosynthesis, which
provides organisms with the ability to use light as a source of energy,
emerged early in the evolution of life on Earth. The ability to harvest
such a significant energy resource could likely also develop on habited
exoplanets. Thus, we investigate the detectability of biomolecules
that can capture photons of particular wavelengths and contribute to
storing their energy in chemical bonds. We have carried out laboratory
spectropolarimetric measurements of a representative sample of plants
containing various amounts of pigments such as chlorophyll, carotenoids
and others. We have also measured a variety of non-biological samples
(sands, rocks). Using our lab measurements, we have modelled intensity
and polarized spectra of Earth-like planets having different surface
coverage by photosynthetic organisms, deserted land and ocean,
as well as clouds. Our results demonstrate that linearly polarized
spectra provide very sensitive and rather unambiguous detection of
photosynthetic pigments of various kinds. Our work paves the path
towards analogous measurements of microorganisms and remote sensing of
microbial ecology on the Earth and of extraterrestrial life on other
planets and moons.

---------------------------------------------------------
Title: VizieR Online Data Catalog: Center-to-limb polarization of
FGK stars (Kostogryz+, 2016)
Authors: Kostogryz, N. M.; Milic, I.; Berdyugina, S. V.; Hauschildt,
P. H.
2016yCat..35860087K Altcode:
Calculated center-to-limb variations of intensity (limb darkening)
for different stellar parameters with spherical atmosphere model
approximation. All intensities are normalized to the intensity in
the center of stellar disks, therefore, in the centre of the disks
(mu=1.0), I(mu)/I(1.0)=1.0. The parameters of spherical Phoenix
stellar model atmospheres we considered here are the following:
effective temperature is in the range of 4000K-7000K with the step of
100K and for logg=1.0-5.5 with the step of 0.5. All calculations are
made for such wavelengths: 4000Å, 4500Å, 5000Å, 6000Å, 7000Å. We
also present the position of the stellar limb and calculated stellar
radius. Calculated center-to-limb variations of polarization
(CLVP) for different stellar parameters with spherical atmosphere model
approximation. All intensities are normalized to the intensity in the
center of stellar disks, therefore, in the centre of the disks (mu=1.0),
I(mu)/I(1.0)=1.0. The parameters of spherical Phoenix model atmosphere
we considered here are the following: effective temperature is in
the range of 4000K-7000 K with the step of 100K and for logg=1.0-5.5
with the step of 0.5. All calculations are made for such wavelengths:
4000Å, 4500Å, 5000Å, 6000Å, 7000Å. We also present the position
of the stellar limb. (2 data files).

---------------------------------------------------------
Title: Early Solar System Leftovers: Testing Solar System Formation
Models
Authors: Meech, Karen Jean; Yang, Bin; Kleyna, Jan; Hainaut, Olivier
R.; Keane, Jacqueline V.; Micheli, Marco; Berdyugina, Svetlana;
Bhatt, Bhuwan; Sahu, Devendra; Hsieh, Henry; Veres, Peter; Wainscoat,
Richard J.; Riesen, Timm-Emanuel; Kaluna, Heather
2015DPS....4750704M Altcode:
One of the most intriguing predictions of the Grand Tack model is
the presence of volatile poor objects in the Oort cloud that were
swept from the region where the terrestrial planets formed. This
volatile-poor material is represented today by ordinary chondrites,
enstatite chondrites and differentiated planetesimals. These are the
main constituents of the S-type asteroids that reside in the inner
Solar system. According to the Grand Tack model, the fraction of
S-type material in cometary orbits should be around 0.1-0.2%. Recent
Pan-STARRS 1 discoveries of objects on long-period comet orbits that
are minimally active while at small perihelia have suggested the
intriguing possibility that these could potentially represent inner
solar system material that was ejected into the outer solar system
during planet migration, that is now making its way back in. The first
object discovered, C/2013 P2 has a spectrum redder than D-type objects,
but exhibits low-level activity throughout its perihelion passage. The
second one, C/2014 S3, appears to have an S-type asteroid spectrum, and
likewise exhibits low-level activity.Nearly 100 of these objects have
now been identified, approximately half of which are still observable,
and more are being discovered. We will report on observations made for
a selection of these objects with several facilities including Gemini
N 8 m, VLT 8 m, Canada-France-Hawaii 3.6 m, PS1 2 m, UH2.2 m, HCT 2 m,
and the Lowell 1.8 m telescopes. We will discuss the implications of
seeing volatile activity in these objects.

---------------------------------------------------------
Title: New Cophasing and AO strategies for an extremely large
telescope dedicated to extremely high contrast: The Colossus Project
Authors: Moretto, Gilles; Kuhn, Jeff R.; Langlois, Maud; Tallon,
Michel; Thiebaut, Eric; Berdyugina, Svetlana; Halliday, David
2015aoel.confE..78M Altcode:
No abstract at ADS

---------------------------------------------------------
Title: Synoptic program to measure the evolution of the photospheric
magnetic field during a solar cycle
Authors: Ramelli, Renzo; Bianda, Michele; Berdyugina, Svetlana;
Stenflo, Jan Olof; Belluzzi, Luca
2015IAUGA..2257074R Altcode:
The solar photosphere is seething with a vast amount of magnetic flux
tangled on scales much smaller than the resolution scale of solar
telescopes that can be investigated by considering the Hanle effect. In
2007, near a minimum of the solar cycle, we started a synoptic program
to explore possible variations of such hidden magnetic flux with
the solar cycle, through the application of a differential Hanle
effect technique on observations of scattering polarization in C2
molecular lines in the region around 514.0 nm. The observing program
is still ongoing generally with the cadence of about one month. The
observations obtained up to now, which include the recent maximum
of the solar activity, don't show large variations of the turbulent
unresolved magnetic field. If the apparent constancy is confirmed
through the current cycle, than it will have important implications,
since it provides hints on the existence of a local dynamo effect at
granular and sub-granular scale, uncorrelated with the global magnetic
field varying with the solar cycle.

---------------------------------------------------------
Title: Correcting Systematic Polarization Effects in Keck LRISp
Spectropolarimetry to &lt; 0.05%
Authors: Harrington, David M.; Berdyugina, Svetlana V.; Kuzmychov,
Oleksii; Kuhn, Jeffrey R.
2015PASP..127..757H Altcode: 2015arXiv150503916H
Spectropolarimetric measurements at moderate spectral resolutions
are effective tracers of stellar magnetic fields and circumstellar
environments when signal to noise ratios (SNRs) above 2000 can be
achieved. The LRISp spectropolarimeter is capable of achieving these
SNRs on faint targets with the 10m aperture of the Keck telescope,
provided several instrumental artifacts can be suppressed. We describe
here several methods to overcome instrumental error sources that
are required to achieve these high SNRs on LRISp. We explore high SNR
techniques such as defocusing and slit-stepping during integration with
high spectral and spatial oversampling. We find that the instrument
flexure and interference fringes introduced by the achromatic retarders
create artificial signals at 0.5\% levels in the red channel which mimic
real stellar signals and limit the sensitivity and calibration stability
of LRISp. Careful spectral extraction and data filtering algorithms
can remove these error sources. For faint targets and long exposures,
cosmic ray hits are frequent and present a major limitation to the
upgraded deep depletion red-channel CCD. These must be corrected to
the same high SNR levels, requiring careful spectral extraction using
iterative filtering algorithms. We demonstrate here characterization
of these sources of instrumental polarization artifacts and present
several methods used to successfully overcome these limitations. We
have measured the linear to circular cross-talk and find it to be
roughly 5\%, consistent with the known instrument limitations. We show
spectropolarimetric signals on brown dwarfs are clearly detectable
at 0.2\% amplitudes with sensitivities better than 0.05\% at full
spectral sampling in atomic and molecular bands. Future LRISp users
can perform high sensitivity observations with high quality calibration
when following the described algorithms.

---------------------------------------------------------
Title: Molecules in Magnetic Fields
Authors: Berdyugina, Svetlana
2015IAUGA..2257732B Altcode:
Molecules probe cool matter in the Universe and various astrophysical
objects. Their ability to sense magnetic fields provides new insights
into magnetic properties of these objects. During the past fifteen
years we have carried out a theoretical study of molecular magnetic
effects such as the Zeeman, Paschen-Back and Hanle effects and
their applications for inferring magnetic structures and spatial
inhomogeneities on the Sun, cool stars, brown dwarfs, and exoplanets
from molecular spectro-polarimetry (e.g., Berdyugina 2011). Here,
we present an overview of this study and compare our theoretical
predictions with recent laboratory measurements of magnetic properties
of some molecules. We present also a new web-based tool to compute
molecular magnetic effects and polarized spectra which is supported
by the ERC Advanced Grant HotMol.

---------------------------------------------------------
Title: Exoplanets as Probes of Stellar Activity
Authors: Berdyugina, Svetlana
2015IAUGA..2257835B Altcode:
Continuous light curves provided by the Kepler and CoRoT missions
contain immense information on both stellar variability and
exoplanets. We have developed a new technique to infer distribution of
active regions in both longitude and latitude on the stellar surface
(stellar images) from continuous light curves. This allows us to
constrain stellar differential rotation, obtain butterfly diagrams,
and investigate activity cycles. We further increase the spatial
resolution of inferred stellar images by utilizing transit curves of
exoplanets when they occult active regions (if available). We show
also that exoplanets help to "see" active regions even when they are
outside the planet transit path.

---------------------------------------------------------
Title: 3D Magnetic Structure of Active Regions on Flaring Red and
Brown Dwarfs: From the Photosphere to the Chromosphere
Authors: Berdyugina, Svetlana
2015IAUGA..2257651B Altcode:
Magnetic activity is a fundamental feature of stars with outer
convection envelopes and fully convective red and brown dwarfs. It is
detected directly through the Zeeman effect and indirectly through
brightness variability due to spots and flares. Recently we have
demonstrated a technique capable of recovering 3D topology of active
regions on cool stars (temperature and magnetic field) using inversions
of atomic and molecular lines forming at different heights in the
atmosphere (Berdyugina 2011). Here we extend this technique to the
chromosphere by including an inversion of chromospheric emission during
active states (e.g., flares). We apply this technique to several very
active red and brown dwarfs and recover 3D magnetic structures in the
photosphere and chromosphere. We compare the recovered loop structure
and properties with those observed in solar active regions.

---------------------------------------------------------
Title: Global warming as a detectable thermodynamic marker of
Earth-like extrasolar civilizations: the case for a telescope like
Colossus
Authors: Kuhn, Jeff R.; Berdyugina, Svetlana V.
2015IJAsB..14..401K Altcode:
Earth-like civilizations generate heat from the energy that they
utilize. The thermal radiation from this heat can be a thermodynamic
marker for civilizations. Here we model such planetary radiation on
Earth-like planets and propose a strategy for detecting such an alien
unintentional thermodynamic electromagnetic biomarker. We show that
astronomical infrared (IR) civilization biomarkers may be detected
within an interestingly large cosmic volume using a 70 m-class or
larger telescope. In particular, the Colossus telescope with achievable
coronagraphic and adaptive optics performance may reveal Earth-like
civilizations from visible and IR photometry timeseries' taken during
an exoplanetary orbit period. The detection of an alien heat signature
will have far-ranging implications, but even a null result, given 70
m aperture sensitivity, could also have broad social implications.

---------------------------------------------------------
Title: Magnetospherically driven optical and radio aurorae at the
end of the stellar main sequence
Authors: Hallinan, G.; Littlefair, S. P.; Cotter, G.; Bourke, S.;
Harding, L. K.; Pineda, J. S.; Butler, R. P.; Golden, A.; Basri, G.;
Doyle, J. G.; Kao, M. M.; Berdyugina, S. V.; Kuznetsov, A.; Rupen,
M. P.; Antonova, A.
2015Natur.523..568H Altcode: 2015arXiv150708739H
Aurorae are detected from all the magnetized planets in our Solar
System, including Earth. They are powered by magnetospheric current
systems that lead to the precipitation of energetic electrons into
the high-latitude regions of the upper atmosphere. In the case of the
gas-giant planets, these aurorae include highly polarized radio emission
at kilohertz and megahertz frequencies produced by the precipitating
electrons, as well as continuum and line emission in the infrared,
optical, ultraviolet and X-ray parts of the spectrum, associated
with the collisional excitation and heating of the hydrogen-dominated
atmosphere. Here we report simultaneous radio and optical spectroscopic
observations of an object at the end of the stellar main sequence,
located right at the boundary between stars and brown dwarfs, from which
we have detected radio and optical auroral emissions both powered by
magnetospheric currents. Whereas the magnetic activity of stars like
our Sun is powered by processes that occur in their lower atmospheres,
these aurorae are powered by processes originating much further out in
the magnetosphere of the dwarf star that couple energy into the lower
atmosphere. The dissipated power is at least four orders of magnitude
larger than what is produced in the Jovian magnetosphere, revealing
aurorae to be a potentially ubiquitous signature of large-scale
magnetospheres that can scale to luminosities far greater than those
observed in our Solar System. These magnetospheric current systems may
also play a part in powering some of the weather phenomena reported
on brown dwarfs.

---------------------------------------------------------
Title: Polarization in Exoplanetary Systems Caused by Transits,
Grazing Transits, and Starspots
Authors: Kostogryz, N. M.; Yakobchuk, T. M.; Berdyugina, S. V.
2015ApJ...806...97K Altcode: 2015arXiv150402943K
We present results of numerical simulations of flux and linear
polarization variations in transiting exoplanetary systems, caused by
host star disk symmetry breaking. We consider different configurations
of planetary transits depending on orbital parameters. The starspot
contribution to the polarized signal is also estimated. Applying the
method to known systems and simulating observational conditions, a
number of targets is selected where transit polarization effects could
be detected. We investigate several principal benefits of the transit
polarimetry, particularly for determining orbital spatial orientation
and distinguishing between grazing and near-grazing planets. Simulations
show that polarization parameters are also sensitive to starspots,
and they can be used to determine spot positions and sizes.

---------------------------------------------------------
Title: Molecules as magnetic probes of starspots
Authors: Afram, N.; Berdyugina, S. V.
2015A&A...576A..34A Altcode: 2015arXiv150107875A
Context. Stellar dynamo processes can be explored by measuring
the magnetic field. This is usually obtained using the atomic and
molecular Zeeman effect in spectral lines. While the atomic Zeeman
effect can only access warmer regions, the use of molecular lines
is of advantage for studying cool objects. The molecules MgH, TiO,
CaH, and FeH are suited to probe stellar magnetic fields, each one
for a different range of spectral types, by considering the signal
that is obtained from modeling various spectral types. Aims:
We have analyzed the usefulness of different molecules (MgH, TiO,
CaH, and FeH) as diagnostic tools for studying stellar magnetism on
active G-K-M dwarfs. We investigate the temperature range in which the
selected molecules can serve as indicators for magnetic fields on highly
active cool stars and present synthetic Stokes profiles for the modeled
spectral type. Methods: We modeled a star with a spot size of
10% of the stellar disk and a spot comprising either only longitudinal
or only transverse magnetic fields and estimated the strengths of the
polarization Stokes V and Q signals for the molecules MgH, TiO, CaH,
and FeH. We combined various photosphere and spot models according to
realistic scenarios. Results: In G dwarfs, the molecules MgH and
FeH show overall the strongest Stokes V and Q signals from the starspot,
whereas FeH has a stronger Stokes V signal in all G dwarfs with a
spot temperature of 3800 K. In K dwarfs, CaH signals are generally
stronger, and the TiO signature is most prominent in M dwarfs. 
Conclusions: Modeling synthetic polarization signals from starspots
for a range of G-K-M dwarfs leads to differences in the prominence of
various molecular signatures in different wavelength regions, which
helps to efficiently select targets and exposure times for observations.

---------------------------------------------------------
Title: Center-to-limb polarization in continuum spectra of F, G,
K stars
Authors: Kostogryz, N. M.; Berdyugina, S. V.
2015A&A...575A..89K Altcode: 2014arXiv1408.5019K
Context. Scattering and absorption processes in stellar atmosphere
affect the center-to-limb variations of the intensity (CLVI) and the
linear polarization (CLVP) of stellar radiation. Aims: There are
several theoretical and observational studies of CLVI using different
stellar models, however, most studies of CLVP have concentrated on the
solar atmosphere and have not considered the CLVP in cooler non-gray
stellar atmospheres at all. In this paper, we present a theoretical
study of the CLV of the intensity and the linear polarization in
continuum spectra of different spectral type stars. Methods: We
solve the radiative transfer equations for polarized light iteratively
assuming no magnetic field and considering a plane-parallel model
atmospheres and various opacities. Results: We calculate the
CLVI and the CLVP for Phoenix stellar model atmospheres for the range
of effective temperatures (4500 K-6900 K), gravities (log g = 3.0-5.0),
and wavelengths (4000-7000 Å), which are tabulated and available at
the CDS. In addition, we present several tests of our code and compare
our results with measurements and calculations of CLVI and the CLVP
for the Sun. The resulting CLVI are fitted with polynomials and their
coefficients are presented in this paper. Conclusions: For the
stellar model atmospheres with lower gravity and effective temperature
the CLVP is larger. Full Tables 1 and 2, and coefficients of
polynomials are only available at the CDS via anonymous ftp to <A
href="http://cdsarc.u-strasbg.fr">http://cdsarc.u-strasbg.fr</A>
(ftp://130.79.128.5) or via <A
href="http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/575/A89">http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/575/A89</A>

---------------------------------------------------------
Title: Serendipitous Discovery of a Dwarf Nova in the Kepler Field
Near the G Dwarf KIC 5438845
Authors: Brown, Alexander; Neff, James E.; Ayres, Thomas R.; Kowalski,
Adam; Hawley, Suzanne; Berdyugina, Svetlana; Harper, Graham M.;
Korhonen, Heidi; Piskunov, Nikolai; Saar, Steven; Walkowicz, Lucianne;
Wells, Mark A.
2015AJ....149...67B Altcode:
The Kepler satellite provides a unique window into stellar temporal
variability by observing a wide variety of stars with multi-year,
near-continuous, high precision, optical photometric time series. While
most Kepler targets are faint stars with poorly known physical
properties, many unexpected discoveries should result from a long
photometric survey of such a large area of sky. During our Kepler
Guest Observer programs that monitored late-type stars for starspot and
flaring variability, we discovered a previously unknown dwarf nova that
lies within a few arcseconds of the mid-G dwarf star KIC 5438845. This
dwarf nova underwent nine outbursts over a 4 year time span. The two
largest outbursts lasted ∼17-18 days and show strong modulations with
a 110.8 minute period and a declining amplitude during the outburst
decay phase. These properties are characteristic of an SU UMa-type
cataclysmic variable. By analogy with other dwarf nova light curves,
we associate the 110.8 minute (1.847 hr) period with the superhump
period, close to but slightly longer than the orbital period of the
binary. No precursor outbursts are seen before the super-outbursts
and the overall super-outburst morphology corresponds to Osaki &amp;
Meyer “Case B” outbursts, which are initiated when the outer edge
of the disk reaches the tidal truncation radius. “Case B” outbursts
are rare within the Kepler light curves of dwarf novae. The dwarf nova
is undergoing relatively slow mass transfer, as evidenced by the long
intervals between outbursts, but the mass transfer rate appears to
be steady, because the smaller “normal” outbursts show a strong
correlation between the integrated outburst energy and the elapsed time
since the previous outburst. At super-outburst maximum the system was
at V ∼ 18, but in quiescence it is fainter than V ∼ 22, which will
make any detailed quiescent follow-up of this system difficult.

---------------------------------------------------------
Title: Doppler images and the underlying dynamo. The case of AF
Leporis
Authors: Järvinen, S. P.; Arlt, R.; Hackman, T.; Marsden, S. C.;
Küker, M.; Ilyin, I. V.; Berdyugina, S. V.; Strassmeier, K. G.;
Waite, I. A.
2015A&A...574A..25J Altcode: 2014arXiv1412.2892J
Context. The (Zeeman-)Doppler imaging studies of solar-type stars very
often reveal large high-latitude spots. This also includes F stars that
possess relatively shallow convection zones, indicating that the dynamo
operating in these stars differs from the solar dynamo. Aims:
We aim to determine whether mean-field dynamo models of late-F type
dwarf stars can reproduce the surface features recovered in Doppler
maps. In particular, we wish to test whether the models can reproduce
the high-latitude spots observed on some F dwarfs. Methods:
The photometric inversions and the surface temperature maps of AF Lep
were obtained using the Occamian-approach inversion technique. Low
signal-to-noise spectroscopic data were improved by applying the
least-squares deconvolution method. The locations of strong magnetic
flux in the stellar tachocline as well as the surface fields obtained
from mean-field dynamo solutions were compared with the observed
surface temperature maps. Results: The photometric record of
AF Lep reveals both long- and short-term variability. However, the
current data set is too short for cycle-length estimates. From the
photometry, we have determined the rotation period of the star to be
0.9660 ± 0.0023 days. The surface temperature maps show a dominant,
but evolving, high-latitude (around +65°) spot. Detailed study of
the photometry reveals that sometimes the spot coverage varies only
marginally over a long time, and at other times it varies rapidly. Of
a suite of dynamo models, the model with a radiative interior rotating
as fast as the convection zone at the equator delivered the highest
compatibility with the obtained Doppler images. Partially
based on observations made with the Nordic Optical Telescope,
operated by the Nordic Optical Telescope Scientific Association at
the Observatorio del Roque de los Muchachos, La Palma, Spain, of
the Instituto de Astrofísica de Canarias.Based partly on STELLA SES
data.Tables 1-3 and Figs. 7-14 are available in electronic form at <A
href="http://www.aanda.org/10.1051/0004-6361/201424229/olm">http://www.aanda.org</A>

---------------------------------------------------------
Title: VizieR Online Data Catalog: Center-to-limb polarization of
FGK stars (Kostogryz+, 2015)
Authors: Kostogryz, N. M.; Berdyugina, S. V.
2015yCat..35750089K Altcode: 2015yCat..35759089K
The stellar parameters we considered here are the following: effective
temperature is in the range of 4500K-6900K with the step of 100K and
for logg=3.0, 3.5, 4.0, 4.5, 5.0. All calculations are made for such
wavelengths: 4000Å, 4500Å, 5000Å, 6000Å, 7000Å. table1.dat:
Calculated center-to-limb variations of intensity (limb darkening)
for different stellar parameters with plane-parallel atmosphere model
approximation. All intensities are normalized to the intensity in the
center of stellar disks, therefore, in the centre of the disks (mu=1.0),
I(mu)/I(1.0)=1.0. table2.dat: Calculated center-to-limb variations
of linear polarization (Stokes parameter Q/I) for different stellar
parameters with plane-parallel atmosphere model approximation. The
radiation coming from the centre of the stellar disk is nonpolarized,
so all values of Q/I(1.0)=0.0. table3.dat: Calculated polynomial
coefficients of center-to-limb variations of intensity (limb darkening)
fits for different stellar parameters with plane-parallel atmosphere
model approximation. (3 data files).

---------------------------------------------------------
Title: Transit Polarimetry of Exoplanetary System HD 189733
Authors: Kostogryz, N. M.; Berdyugina, S. V.; Yakobchuk, T. M.
2015csss...18..773K Altcode: 2014arXiv1408.5023K
We present and discuss a polarimetric effect caused by a planet
transiting the stellar disk thus breaking the symmetry of the light
distribution and resulting in linear polarization of the partially
eclipsed star. Estimates of this effect for transiting planets have
been made only recently. In particular, we demonstrate that the maximum
polarization during transits depends strongly on the centre-to-limb
variation of the linear polarization of the host star. However,
observational and theoretical studies of the limb polarization
have largely concentrated on the Sun. Here we solve the radiative
transfer problem for polarized light and calculate the centre-to-limb
polarization for one of the brightest transiting planet host HD 189733
taking into account various opacities. Using that we simulate the
transit effect and estimate the variations of the flux and the linear
polarization for HD 189733 during the event. As the spots on the stellar
disk also break the limb polarization symmetry we simulate the flux
and polarization variation due to the spots on the stellar disk.

---------------------------------------------------------
Title: Magnetic Field on Brown Dwarf LSR J18353790+3259545
Authors: Kuzmychov, O.; Berdyugina, S. V.; Harrington, D.
2015csss...18..441K Altcode: 2015arXiv150306964K
We model the full Stokes spectrum of the brown dwarf LSR
J18353790+3259545 in the bands of the diatomic molecules CrH, TiO,
and FeH in order to infer its magnetic properties. The models are then
compared to the observational data obtained with the low resolution
polarimeter LRIS at Keck observatory. Our preliminary analysis shows
that the brown dwarf considered possesses a magnetic field of the
order of 2-3 kG.

---------------------------------------------------------
Title: InnoPOL: an EMCCD imaging polarimeter and 85-element curvature
AO system on the 3.6-m AEOS telescope for cost effective polarimetric
speckle suppression
Authors: Harrington, David; Berdyugina, Svetlana; Chun, Mark; Ftaclas,
Christ; Gisler, Daniel; Kuhn, Jeff
2014SPIE.9147E..7CH Altcode: 2016arXiv160402738H
The Hokupa'a-85 curvature adaptive optics system components have been
adapted to create a new AO-corrected coudé instrument at the 3.67m
Advanced Electro-Optical System (AEOS) telescope. This new AO-corrected
optical path is designed to deliver an f/40 diffraction-limited focus
at wavelengths longer than 800nm. A new EMCCD-based dual-beam imaging
polarimeter called InnoPOL has been designed and is presently being
installed behind this corrected f/40 beam. The InnoPOL system is
a flexible platform for optimizing polarimetric performance using
commercial solutions and for testing modulation strategies. The
system is designed as a technology test and demonstration platform
as the coudé path is built using off-the-shelf components wherever
possible. Models of the polarimetric performance after AO correction
show that polarization modulation at rates as slow as 200Hz can
cause speckle correlations in brightness and focal plane location
sufficient enough to change the speckle suppression behavior of the
modulators. These models are also verified by initial EMCCD scoring
camera data at AEOS. Substantial instrument trades and development
efforts are explored between instrument performance parameters and
various polarimetric noise sources.

---------------------------------------------------------
Title: Comparison of solar photospheric bright points between Sunrise
observations and MHD simulations
Authors: Riethmüller, T. L.; Solanki, S. K.; Berdyugina, S. V.;
Schüssler, M.; Martínez Pillet, V.; Feller, A.; Gandorfer, A.;
Hirzberger, J.
2014A&A...568A..13R Altcode: 2014arXiv1406.1387R
Bright points (BPs) in the solar photosphere are thought to be the
radiative signatures (small-scale brightness enhancements) of magnetic
elements described by slender flux tubes or sheets located in the darker
intergranular lanes in the solar photosphere. They contribute to the
ultraviolet (UV) flux variations over the solar cycle and hence may
play a role in influencing the Earth's climate. Here we aim to obtain
a better insight into their properties by combining high-resolution
UV and spectro-polarimetric observations of BPs by the Sunrise
Observatory with 3D compressible radiation magnetohydrodynamical
(MHD) simulations. To this end, full spectral line syntheses are
performed with the MHD data and a careful degradation is applied
to take into account all relevant instrumental effects of the
observations. In a first step it is demonstrated that the selected
MHD simulations reproduce the measured distributions of intensity at
multiple wavelengths, line-of-sight velocity, spectral line width,
and polarization degree rather well. The simulated line width also
displays the correct mean, but a scatter that is too small. In
the second step, the properties of observed BPs are compared with
synthetic ones. Again, these are found to match relatively well,
except that the observations display a tail of large BPs with strong
polarization signals (most likely network elements) not found in the
simulations, possibly due to the small size of the simulation box. The
higher spatial resolution of the simulations has a significant effect,
leading to smaller and more numerous BPs. The observation that most BPs
are weakly polarized is explained mainly by the spatial degradation,
the stray light contamination, and the temperature sensitivity of the Fe
i line at 5250.2 Å. Finally, given that the MHD simulations are highly
consistent with the observations, we used the simulations to explore
the properties of BPs further. The Stokes V asymmetries increase with
the distance to the center of the mean BP in both observations and
simulations, consistent with the classical picture of a production
of the asymmetry in the canopy. This is the first time that this has
been found also in the internetwork. More or less vertical kilogauss
magnetic fields are found for 98% of the synthetic BPs underlining
that basically every BP is associated with kilogauss fields. At the
continuum formation height, the simulated BPs are on average 190 K
hotter than the mean quiet Sun, the mean BP field strength is found to
be 1750 G, and the mean inclination is 17°, supporting the physical
flux-tube paradigm to describe BPs. On average, the synthetic BPs
harbor downflows increasing with depth. The origin of these downflows
is not yet understood very well and needs further investigation.

---------------------------------------------------------
Title: DIPOL-2: a double image high precision polarimeter
Authors: Piirola, V.; Berdyugin, A.; Berdyugina, Svetlana
2014SPIE.9147E..8IP Altcode:
We have built a new broad-band polarimeter (DIPOL-2), capable of
measuring polarization with the precision at the 10-5
level. Two dichroic beam-splitters are used to split light into three
passbands (BVR), simultaneously recorded with three CCDs. A rotatable
superachromatic λ/2 (or λ/4) plate is used as the polarization
modulator and a plane parallel calcite plate as the polarization
analyzer. Simple yet effective design with small number of optical
elements and moving mechanical parts makes DIPOL-2 a highly versatile
and reliable instrument with negligible instrumental polarization,
very well suitable for observations with remotely controlled
telescopes. Current and planned observing programs are briefly
described.

---------------------------------------------------------
Title: Looking beyond 30m-class telescopes: the Colossus project
Authors: Kuhn, J. R.; Berdyugina, S. V.; Langlois, M.; Moretto, G.;
Thiébaut, E.; Harlingten, C.; Halliday, D.
2014SPIE.9145E..1GK Altcode:
The exponential growth in exoplanet studies is a powerful reason for
developing very large optical systems optimized for narrow-field
science. Concepts which cross the boundary between fixed aperture
telescopes and interferometers, combined with technologies that decrease
the system moving mass, can violate the cost and mass scaling laws that
make conventional large-aperture telescopes relatively expensive. Here
we describe a concept which breaks this scaling relation in a large
optical/IR system called "Colossus"1.

---------------------------------------------------------
Title: First successful deployment of the ZIMPOL-3 system at the
GREGOR telescope
Authors: Ramelli, Renzo; Gisler, Daniel; Bianda, Michele; Bello
González, Nazaret; Berdyugina, Svetlana; Soltau, Dirk
2014SPIE.9147E..3GR Altcode:
Since several years the Zurich Imaging polarimeter (ZIMPOL)
system is successfully used as a high sensitivity polarimeter. The
polarimeter system, which is mainly based on a fast modulator and a
special demodulating camera with a masked CCD, has been continuously
improved. The third version of the system (ZIMPOL-3) is routinely used
at IRSOL, Locarno. The fast modulation allows to "freeze" intensity
variations due to seeing, and to achieve a polarimetric sensitivity
below 10-5 if the photon statistics is large enough. In
October 2013 the ZIMPOL system has been brought and installed for the
first time at the GREGOR telescope in Tenerife for a spectropolarimetric
observing campaign. There, the system configuration took advantage
from the calibration unit installed at the primary focus of the GREGOR
telescope, while the analyzer was inserted in the optical path just
before the spectrograph slit after several folding mirrors. This
setup has been tested successfully by the authors for the first time
in this occasion.

---------------------------------------------------------
Title: New strategies for an extremely large telescope dedicated to
extremely high contrast: the Colossus project
Authors: Moretto, Gil; Kuhn, Jeff R.; Thiébaut, Eric; Langlois,
Maud; Berdyugina, Svetlana V.; Harlingten, Caisey; Halliday, David
2014SPIE.9145E..1LM Altcode:
Detecting an exoplanetary life signal is extremely challenging
with current technology because it requires a sensitive telescope
and instrument that can measure the planet's reflected optical and
infrared light, while distinguishing this from the star's scattered
light and the terrestrial thermal noise background. This requires
highly accurate adaptive optics, a coronagraph system, and a specially
designed and aligned giant telescope. We present here new strategies for
building such a telescope with large circular segments using adaptive
optics correction independently for each of these segments prior to
cophasing the segments. The foreseen cophasing technique uses focal
plane images that allow piston measurements and correction between
all the segments. In this context we propose to derive the segment
phase error using the inverse approach knowing the segment positions
and the single aperture Airy function.

---------------------------------------------------------
Title: Enabling Technologies for Detecting Life in the Universe:
The Colossus Project
Authors: Kuhn, J.; Berdyugina, S.; Halliday, D.; Harlingten, C.;
Langlois, M.; Moretto, G.
2014ebi..conf.4.19K Altcode:
An international consortium of scientists, engineers, and private
interests formed two in 2012 to develope a large telescope with
the capability of detecting life signatures, and potentially even
Earth-like civilizations, on hundreds of nearby exoplanets. This
"Colossus Telescope" departs from all currently planned large optical
telescope designs in order to achieve the required coronagraphic
performance, angular resolution, and flux sensitivity. As a nearly
filled-aperture, highly redundant-baseline optical and IR imaging
instrument, it has several advantages for studying exoplanets. This
presentation introduces the instrument concept and some strategies
for finding life within about 25pc of the Sun.

---------------------------------------------------------
Title: Detecting extraterrestrial life with the Colossus telescope
using photosynthetic biosignatures
Authors: Berdyugina, S.; Kuhn, J.; Harrington, D.; Moretto, G.;
Langlois, M.; Halliday, D.; Harlingten, C.
2014ebi..confP4.89B Altcode:
We propose to search for life on Earth-like planets in habitable
zones using photosynthesis biosignatures. Many life forms on Earth
process the solar light and utilize it to support their own activity
and to provide a valuable energy source for other life forms. We expect
therefore that photosynthesis is very likely to arise on another planet
and can produce conspicuous biosignatures. We have recently identified
biological polarization effects, e.g., selective light absorption or
scattering by photosynthetic molecules which can be used for remote
detection of extraterrestrial life. Here we present synthetic spectra
and polarization of Earth-like planets with photosynthetic life and
evaluate the sensitivity of the Colossus telescope for their remote
detection in the solar neighborhood.

---------------------------------------------------------
Title: Brightness fluctuations of the Sun and p-mode oscillations:
The inverse problem and nonadiabatic waves in the photosphere
Authors: Prokhorov, A.; Zhugzhda, Y. D.; Berdyugina, S.
2014AN....335..150P Altcode:
Using photometric observations of the Sun as a star (DIFOS, SoHO) we
were able to solve the inverse heloiseismic problem and determine the
global time-dependent relative temperature fluctuations as functions of
the geometric height. This was done under the adiabatic assumption. A
mathematical tool was developed to solve the inverse problem, which
is ill-posed. The calculations were done using the numerical software
Matlab 7. The adiabatic solution shows signs of temperature waves
in the lower photosphere, which agrees with calculations done by
\citet{Hidalgo} and Stodilka (2011).

---------------------------------------------------------
Title: Polarimetry of Hot Inflated Jupiters Reveals Their Albedo
and Color (Invited)
Authors: Berdyugina, S.; Berdyugin, A.; Piirola, V.
2013AGUFM.P42B..08B Altcode:
Polarimetry is a powerful technique for detecting directly
exoplanetary atmospheres and probing their geometry, chemistry, and
thermodynamics. We carry out a polarimetric survey of nearby planetary
systems with hot Jupiters closely orbiting their host stars. Here we
will present new polarimetric measurements, discuss our results, and
compare them with recent albedo estimates using the secondary eclipses
in transiting systems. Finally, we will discuss implications for the
composition of planetary atmospheres.

---------------------------------------------------------
Title: Paschen-Back effect in the CrH molecule and its application for
magnetic field measurements on stars, brown dwarfs, and hot exoplanets
Authors: Kuzmychov, O.; Berdyugina, S. V.
2013A&A...558A.120K Altcode: 2013arXiv1309.5240K
 Aims: We investigated the Paschen-Back effect in the (0,0)
band of the A6Σ+ - X6Σ+
system of the CrH molecule, and we examined its potential for
estimating magnetic fields on stars and substellar objects, such
as brown dwarfs and hot exoplanets. Methods: We carried out
quantum mechanical calculations to obtain the energy level structure
of the electronic-vibrational-rotational states considered both in
the absence and in the presence of a magnetic field. Level mixing
due to magnetic field perturbation (the Paschen-Back effect) was
consistently taken into account. Then, we calculated frequencies
and strengths of transitions between magnetic sublevels. Employing
these results and solving numerically a set of the radiative transfer
equations for polarized radiation, we calculated Stokes parameters
for both the individual lines and the (0,0) band depending on the
strength and orientation of the magnetic field. Results: We
demonstrate that magnetic splitting of the individual CrH lines shows
a significant asymmetry due to the Paschen-Back effect already at 1 G
field. This leads to a considerable signal in both circular and linear
polarization, up to 30% at the magnetic field strength of ≥3 kG in
early L dwarfs. The polarization does not cancel out completely even at
very low spectral resolution and is seen as broad-band polarization of
a few percent. Since the line asymmetry depends only on the magnetic
field strength and not on the filling factor, CrH lines provide a
very sensitive tool for direct measurement of the stellar magnetic
fields on faint cool objects, such as brown dwarfs and hot Jupiters,
observed with low spectral resolution.

---------------------------------------------------------
Title: Spectropolarimetric observations of cool DQ white dwarfs
Authors: Vornanen, T.; Berdyugina, S. V.; Berdyugin, A.
2013A&A...557A..38V Altcode: 2013arXiv1308.4505V
 Aims: Following our recent discovery of a new magnetic DQ
white dwarf (WD) with CH molecular features, we report the results for
the rest of the DQ WDs from our survey. Methods: We use high
signal-to-noise spectropolarimetric data to search for magnetic fields
in a sample of 11 objects. Results: One object in our sample,
WD1235+422, shows the signs of continuum circular polarization that is
similar to some peculiar DQs with unidentified molecular absorption
bands, but the low signal-to-noise ratio and spectral resolution of
these data make more observations necessary to reveal the true nature
of this object.

---------------------------------------------------------
Title: CrH molecule: New diagnostic tool for measuring magnetic
fields of cool dwarfs
Authors: Kuzmychov, Oleksii; Berdyugina, Svetlana V.
2013IAUS..294..477K Altcode:
The quantum mechanical calculations for the A6Σ+
- X6Σ+ system of the CrH molecule were done in
order to obtain its energy level structure and transition strenghts
both in the absence and in the presence of a magnetic field. Employing
this results and solving a set of the radiative transfer equations,
we calculated the Stokes profiles for the entire 0-0 band for different
magnetic field strengths and orientations. We show that the CrH lines
produce a considerable polarization signal (up to 20%) at 0.5 - 10
kG. Furthermore, the polarization signal shows a significant asymmetry
(broad-band polarization) that arises from the Paschen-Back effect
in the individual CrH lines. An example of the signal, as it can be
observed, is provided.

---------------------------------------------------------
Title: Chemical composition of photospheres in RS CVn stars
Authors: Tautvaišienė, G.; Barisevičius, G.; Berdyugina, S.; Ilyin,
I.; Chorniy, Y.
2013IAUS..294..207T Altcode:
In order to investigate how magnetic activity influences a stellar
evolution, we undertake a detailed study of photospheric abundances
in a sample of RS CVn stars. Using the Nordic Optical Telescope we
investigate abundances of more than 20 chemical elements, including
carbon isotopes, nitrogen and other mixing-sensitive species. In
this presentation we report on current results of the analysis, among
which there are first evidences that extra-mixing processes may start
acting in low-mass chromospherically active stars below a bump of the
luminosity function of red giants.

---------------------------------------------------------
Title: Coronal Permitted Line Magnetometry: A New Approach to
Measuring Coronal Magnetic Fields
Authors: Berdyugina, Svetlana; Dima, Gabriel; Kuhn, Jeff; Swindle, Ryan
2013shin.confE..62B Altcode:
Solar magnetic field is a driving force of space weather, and the solar
corona supplies the heliosphere with its magnetic field, coronal mass
ejections and the solar wind. However, measurements of the coronal
magnetic field are, so far, seldom possible. The discovery of cool
Helium far into the hot corona offers new opportunities for learning
about the coronal field strength and direction. Currently only either
its direction or strength but not both at the same time have been
rarely inferred. In the absence of reliable measurements, various
extrapolations of the photospheric magnetic fields into the corona and
beyond are being attempted, but uncertainties of these extrapolations
are unknown and can be very large. Here we propose a new approach
to measuring coronal magnetic fields which employes simultaneously
(i) the unsaturated Hanle effect in the permitted He I 1083 nm line,
constraining the direction and strength of the coronal magnetic field,
(ii) the saturated Hanle effect in the forbidden Fe XIII 1074.7
nm line, constraining the direction of the coronal magnetic field,
(iii) the Zeeman effect in the brighter Fe XIII lines, constraining the
strength and direction of the coronal magnetic field. These combined and
observed (quasi-)simultaneously can provide an unambiguous measurement
of the magnetic vector in the corona. We investigate the sensitivity of
our new approach and corresponding requirements for observations. We
simulate possible observing scenarios using potential and nonlinear
force field extrapolations from photospheric magnetic fields. This
poster introduces and explores how this technique may open a new window
onto coronal magnetometry.

---------------------------------------------------------
Title: Observations and Modeling of DQ White Dwarfs
Authors: Vornanen, T.; Berdyugina, S.; Berdyugin, A.
2013ASPC..469..205V Altcode: 2012arXiv1210.0707V
We present spectropolarimetric observations and modeling of 12 DQ
white dwarfs. Modeling is based on the method presented in Berdyugina
et al. (2005). We use the model to fit the C2 absorption bands to get
atmospheric parameters in different configurations, including stellar
spots and stratified atmospheres, searching for the best possible
fit. We still have problem to solve before we can give temperature
estimates based on the Swan bands alone.

---------------------------------------------------------
Title: The project of installing a ZIMPOL_3 polarimeter at GREGOR
in Tenerife
Authors: Bianda, M.; Ramelli, R.; Stenflo, J.; Berdyugina, S.; Gisler,
D.; Defilippis, I.; Bello González, N.
2013MmSAI..84..413B Altcode:
A project of collaboration between Kiepenheuer Institut für
Sonnenphysik, KIS, and Istituto Ricerche Solari Locarno, IRSOL,
includes the installation of a ZIMPOL_3 high resolution polarimeter at
the 1.5 meter aperture solar telescope GREGOR in Tenerife. Important
scientific topics are expected to be investigated, in particular in the
case of events showing faint amplitude polarization signatures like
scattering polarization effects, and the Hanle effect. This project
has also a technical importance, this combination can be used as test
bench for future polarimeters to be installed on the new generation
solar telescopes.

---------------------------------------------------------
Title: A Large Sample of Magnetically-Active Stars Observed With
Kepler
Authors: Wells, Mark; Neff, J. E.; Brown, A.; Ayres, T. R.; Basri,
G. S.; Berdyugina, S.; Harper, G.; Hawley, S. L.; Korhonen, H.;
Kowalski, A.; Micela, G.; Piskunov, N. E.; Ramsey, L. W.; Saar, S. H.;
Walkowicz, L. M.
2013AAS...22135415W Altcode:
We have observed about 325 stars in our Kepler Guest Observer
programs (Cycles 1 through 4). For most of these targets, we are
analyzing extremely high-precision light curves that have been
continuously sampled every 30 minutes for up to 3 years. Our sample
of candidate magnetically-active stars was selected primarily using
GALEX colors. Starspots, pulsations, and variations due to eclipsing
and contact binaries combine to produce a rich variety of light
curves. We have developed semi-automated procedures to characterize
this variability and thus to classify the targets and identify the
physical mechanisms that dominate their Kepler light curves. We will
describe these procedures and discuss the range of physical properties
covered by our final classification scheme. We are using this Kepler
database of variability over timescales of minutes to years to provide
diagnostics of flares, starspot formation, evolution, migration, and
ultimately of stellar cycles in general. This work contains results
obtained using the NASA Kepler satellite and from the Apache Point
Observatory, the MMT (using NOAO community access time), and the
Hobby-Eberly Telescope. Funding is provided by NASA Kepler grants
NNX10AC51G, NNX11AC79G, and NNX12AC85G to the University of Colorado,
by NSF grant AST-1109695 to the College of Charleston, and by a grant
from the South Carolina Space Grant consortium.

---------------------------------------------------------
Title: Investigating the magnetism of brown dwarfs
Authors: Kuzmychov, O.; Berdyugina, S. V.; Harrington, D.; Kuhn, J.
2013MmSAI..84.1127K Altcode: 2013arXiv1309.4617K
We model the spectra of two brown dwarfs observed with the low
resolution spectropolarimeter LRIS (R ∼ 3000, Keck observatory)
during several rotational phases in order to infer their magnetic
properties. The spectra modeled include the intensity signal (Stokes
I/I_c) as well as the polarimetric signals (Stokes Q/I_c, U/I_c and
V/I_c), all coming from the 0-0 vibrational band of the CrH molecule
at ≈ 8610 Å. In order to model the Stokes profiles, we solve a
set of the radiative transfer equations for the CrH transitions in
the presence of an external magnetic field. We present here the upper
limits for the magnetic field strengths for the objects observed, based
on the modeling of the intensity signal I/I_c and the signal-to-noise
information only. The proper modeling of the polarimetric signals,
that requires more careful data reduction, is underway. Nevertheless,
our preliminary results show a hint for kG magnetic fields for both
brown dwarfs, that is in a good agreement with the result obtained
from the simultaneous radio, Halpha and X-Ray observations of one
another radio pulsating brown dwarf.

---------------------------------------------------------
Title: Young Star Populations in the Kepler Field
Authors: Brown, Alexander; Neff, J. E.; Wells, M.; Saar, S.; Furesz,
G.; Walkowicz, L. M.; Ayres, T. R.; Basri, G. S.; Berdyugina, S.;
Harper, G.; Hawley, S. L.; Korhonen, H.; Kowalski, A.; Micela, G.;
Piskunov, N. E.; Ramsey, L. W.
2013AAS...22135414B Altcode:
The Kepler satellite is providing spectacular optical photometric
light-curves of unprecedented precision and duration that routinely
allow detailed studies of stellar magnetic activity on late-type stars
that were difficult previously. Kepler provides multi-year duration
light-curves that allow investigation of how activity phenomena --
such as the growth, migration, and decay of star-spots, differential
rotation, activity cycles, and flaring -- operate on a wide variety of
single and binary stars. The 105 square degree Kepler Field contains
tens of thousands of late-type stars showing rotational modulation due
to star-spots with periods ranging from one day to a “solar-like”
month. Short rotation periods and high levels of magnetic activity are
strongly correlated. However, there are only two basic reasons why stars
with rotation periods of a few days possess such high angular momentum
--- either they are close binaries or they are young stars. During
Kepler GO Cycles 1 through 4 we have been studying the Long-cadence
(30 minute sampling) photometry of hundreds of active late-type stars
and as an absolutely essential complement we have been obtaining high
resolution optical spectra to understand the physical properties of
these stars. We present results from a spectroscopic survey using the
MMT Hectochelle multi-object echelle of 4 square degrees of the Kepler
Field. We have discovered a significant population of young stars with
Li I absorption indicating ages of ~100 Myr or less at a spatial density
of at least 20 stars per square degree. Our detected young star sample
comprises at least 80 stars and represents a dramatic advance compared
to the previously known sample over the full Kepler Field of three
stars in this age range. Roughly one sixth of the stars observed are
young and a similar number short-period binaries based on 2-4 radial
velocities. We show how the rotational properties of the stars and their
physical properties are related. This work is based on data obtained
with the NASA Kepler satellite and the MMT Hectochelle spectrograph
using NOAO community access time. Support by NASA Kepler grants to the
University of Colorado and by NSF grant to the College of Charleston.

---------------------------------------------------------
Title: Gregor@night: The future high-resolution stellar spectrograph
for the GREGOR solar telescope
Authors: Strassmeier, K. G.; Ilyin, I. V.; Woche, M.; Granzer,
T.; Weber, M.; Weingrill, J.; Bauer, S. -M.; Popow, E.; Denker, C.;
Schmidt, W.; von der Lühe, O.; Berdyugina, S.; Collados, M.; Koubsky,
P.; Hackman, T.; Mantere, M. J.
2012AN....333..901S Altcode:
We describe the future night-time spectrograph for the GREGOR solar
telescope and present its science core projects. The spectrograph
provides a 3-pixel resolution of up to R=87 000 in 45 échelle orders
covering the wavelength range 390-900 nm with three grating settings. An
iodine cell can be used for high-precision radial velocity work in the
500-630 nm range. The operation of the spectrograph and the telescope
will be fully automated without the presence of humans during night-time
and will be based on the successful STELLA control system. Future
upgrades include a second optical camera for even higher spectral
resolution, a Stokes-V polarimeter and a link to the laser-frequency
comb at the Vacuum Tower Telescope. The night-time core projects are a
study of the angular-momentum evolution of “The Sun in Time” and a
continuation of our long-term Doppler imaging of active stars.

---------------------------------------------------------
Title: Revealing the nature of radio-pulsating brown dwarfs
Authors: Berdyugina, Svetlana
2012koa..prop..159B Altcode:
No abstract at ADS

---------------------------------------------------------
Title: CrH molecule: A new diagnostic tool for measuring magnetic
fields of ultra-cool dwarfs
Authors: Kuzmychov, O.; Berdyugina, S. V.
2012AIPC.1429...94K Altcode:
This paper investigates the Paschen-Back effect in the 0 - 0 band
of the A6Σ+ - X6Σ+ system of the CrH molecule and demonstrates a
possibility to measure magnetic fields on cool dwarfs. The quantum
mechanical calculations were done in order to obtain the energy level
structure of the CrH molecule both in the absence and in the presence
of the magnetic field. In addition, we calculated the frequencies of
the transitions between the magnetic levels according to the selection
rules and their strengths (Hönl-London factors). Employing these
results and the analytical solution of the transport equation for
polarized radiative transfer in a stellar atmosphere, based on the
Milne-Eddington approximation, we calculated the four Stokes parameters
and estimated the polarization signal in dependence of the strength
and orientation of the magnetic field. We show that net polarisation
is produced in CrH bands due to the Paschen-Back effect.

---------------------------------------------------------
Title: Detection of a weak magnetic field on arcturus using the
Zeeman component decomposition technique
Authors: Sennhauser, C.; Berdyugina, S. V.
2012AIPC.1429...75S Altcode:
Stellar dynamos are believed to be driven by convection and differential
rotation. In the recent past the search for magnetic activity in
evolved stars to test both local and global dynamo theories at the
extremes of parameter space has gained more and more attention. We
discuss the first direct detections of a weak sub-Gauss magnetic
field on the red giant Arcturus, endorsing an intraseasonal activity
variability [1]. We applied our new Zeeman component decomposition (ZCD)
technique to recover an intrinsic line profile and the mean longitudinal
magnetic field component &lt;Blon&gt; from Stokes I and V spectra. The
performance of the multi-line analysis method ZCD enables us to detect
very weak stellar magnetic fields, and makes ZCD a powerful tool for
studies of active MS stars, early and late-type giants.

---------------------------------------------------------
Title: Probing cool DQ white dwarf atmospheres with polarized
molecular bands
Authors: Vornanen, Tommi; Berdyugin, Andrei; Berdyugina, Svetlana
2012AIPC.1429..200V Altcode:
We have carried out a spectropolarimetric survey of cool DQ white dwarfs
to search for magnetic fields. Among 12 objects one new magnetic DQ
WD, GJ841B has been found. It is an analog of the only previously
known magnetic cool DQ WD with CH molecular bands in the spectrum,
G99-37. Modelling the circular polarization features as well as
intensity spectrum revealed a magnetic field strength of 1.3 MG and
a temperature of 6100 K. Other objects are unpolarized. Modelling
the intensity spectra of these stars with many C2 bands is still
challenging. We also searched for photometric variability of some DQ
WDs and found no variations larger than 15 mmag.

---------------------------------------------------------
Title: Albedo of exoplanets constrained by polarimetry
Authors: Berdyugina, S. V.; Berdyugin, A. V.; Piirola, V.
2012AIPC.1429...29B Altcode:
Polarimetry is a novel and powerful technique for detecting directly
starlight scattered in a planetary atmosphere and inferring information
on its geometry, chemistry, and thermodynamics. Recently, we have
started a polarimetric survey of nearby planetary systems with hot
Jupiters closely orbiting their host stars. We have demonstrated
how polarized scattered light reveals reflecting properties of
exoplanets and provides direct probes of their atmospheres. We find
good consistency of our results with photometric, spectroscopic,
and other polarimetric measurements. Altogether they indicate the
dominance of Rayleigh scattering in the optical and high albedos in
the blue for some hot Jupiters.

---------------------------------------------------------
Title: Using Kepler Data to Characterize the Flare Properties of
GK Stars
Authors: Kowalski, Adam F.; Deitrick, Russell J.; Brown, Alex;
Davenport, Jim R. A.; Hawley, Suzanne L.; Hilton, Eric J.; Ayres,
Thomas R.; Berdyugina, Svetlana V.; Harper, Graham M.; Korhonen,
Heidi; Walkowicz, Lucianne M.
2012decs.confE.120K Altcode:
Due to their high occurrence rate and large contrast against the
background stellar emission, white-light flares on a handful of
very active low-mass M stars have been the primary source for our
understanding of optical flare emission. Kepler's high-precision, long
baseline light curves have opened up the characterization of white-light
emission to new domains of stars, including active G dwarfs. We present
the properties of white-light flares on GALEX-selected solar-type stars
from GO data in Q1-Q7. The flares are discussed in relation to intrinsic
stellar properties, which are constrained by a vast amount of follow-up
characterization of the sample. We compare the flare properties to
large white-light flares observed on the Sun. These high-precision
state-of-the-art observations will provide important constraints for
models of internal magnetic dynamos and NLTE radiative-hydrodynamic
simulations of energy deposition in the lower atmospheric layers.

---------------------------------------------------------
Title: Magnetic Field Detection on Late-type Giants from Zeeman
Component Decomposition
Authors: Sennhauser, C.; Berdyugina, S. V.
2011ASPC..448.1255S Altcode: 2011csss...16.1255S
We have recently developed a new method called Zeeman Component
Decomposition (ZCD) for recovering an intrinsic line profile and
the magnetic field vector from polarized spectra (Sennhauser
&amp; Berdyungina 2010b). ZCD can be deployed to various
stellar spectropolarimetric data with minor prior information
on the stellar parameters by fitting each atomic/molecular line
depth independently. The ZCD combines advantages of inversion
procedures with multi-line techniques (MLT), which is a standard
tool in stellar astronomy for increasing the signal-to-noise ratio
(SNR) of spectropolarimetric measurements. We present results for
the line-of-sight component BLOS from applying ZCD to
spectropolarimetric (Stokes IV) observations of three evolved late-type
(super-)giants obtained at the CFHT/Espadons. These results demonstrate
the functionality of the ZCD on one hand, while on the other hand
disclosing several differences to other multi-line techniques. In
particular, we report on the first detection of a weak, probably
varying magnetic field on Arcturus.

---------------------------------------------------------
Title: Solar turbulent magnetic fields: Non-LTE modeling of the
Hanle effect in the C2 molecule
Authors: Kleint, L.; Shapiro, A. I.; Berdyugina, S. V.; Bianda, M.
2011A&A...536A..47K Altcode:
Context. Scattering polarization measurements contain a wealth of
information that needs a thorough interpretation. This often requires
accounting for the non-local origin of photons with different
frequencies and at different limb positions. Currently, modeling
scattering polarization in several molecular C2 lines
simultaneously is only successful for lines with similar quantum
numbers. More sophisticated models are needed to understand the
dependence on quantum numbers and to reliably derive the strength of
the turbulent magnetic fields using the differential Hanle effect. Aims: We have developed a non-LTE analyzing technique for the
C2 lines to determine the strength of turbulent magnetic
fields and have applied it to observations obtained during our synoptic
program at the Istituto Ricerche SOlari Locarno (IRSOL). Methods:
The influence of magnetic fields on scattering polarization can be
interpreted differentially, i.e., by comparing several spectral lines
within one spectral region. Through the application of the differential
Hanle effect and non-LTE 1D radiative transfer, we are able to infer
a magnetic field strength from the photospheric C2 lines
around 5141 Å. Compared to previous models we include the effect
of collisions and investigate their dependence on the total angular
momentum number J. Results: We carry out a detailed parameter
study to investigate the influence of model parameters on the resulting
scattering polarization. A good fit can now be obtained for spectral
lines from different C2 triplets. For the 78 measurements
obtained during the solar minimum in 2007-2009 we infer a mean magnetic
field strength of 7.41 G with a standard deviation of 0.76 G.

---------------------------------------------------------
Title: Chemical composition of AY Ceti: A flaring, spotted star with
a white dwarf companion
Authors: Tautvaišienė, G.; Barisevičius, G.; Berdyugina, S.; Ilyin,
I.; Chorniy, Y.
2011AN....332..925T Altcode: 2012arXiv1201.4699T
The detailed chemical composition of the atmosphere AY Cet (HD 7672)
is determined from a high-resolution spectrum in the optical region. The
main atmospheric parameters and the abundances of 22 chemical elements,
including key species such as 12C, 13C, N, and O,
are determined. A differential line analysis gives T_eff=5080 K, log
g=3.0, [Fe/H]=-0.33, [C/Fe]=-0.17, [N/Fe]=0.17, [O/Fe]=0.05, C/N=1.58,
and 12C/13C=21. Despite the high chromospheric
activity, the optical spectrum of AY Cet provides a chemical composition
typical for first ascent giants after the first dredge-up.

---------------------------------------------------------
Title: Exoplanets as blue as Neptune
Authors: Berdyugina, S.; Berdyugin, A.; Piirola, V.
2011AGUFM.P11F1634B Altcode:
Polarimetry is a powerful technique for detecting directly
exoplanetary atmospheres and exploring its geometry, chemistry,
and thermodynamics. In addition, observed polarization variability
exhibits the orbital period of the planet and reveal the inclination,
eccentricity, and orientation of the orbit. Recently, we have
started a polarimetric survey of nearby planetary systems with hot
Jupiters closely orbiting their host stars. Here we will demonstrate
how polarized scattered light reveals the presence of exoplanets
in unresolved planetary systems and provides direct probes of their
atmospheres. We identify a small group of inflated and highly reflective
hot Jupiters, with albedo defined by Rayleigh scattering on, most
probably, condensates in high altitude haze or clouds. The scattering
results in the blue shine of these planets similar to Neptune.

---------------------------------------------------------
Title: Aspects of Multi-Dimensional Modelling of Substellar
Atmospheres
Authors: Helling, Ch.; Pedretti, E.; Berdyugina, S.; Vidotto, A. A.;
Beeck, B.; Baron, E.; Showman, A. P.; Agol, E.; Homeier, D.
2011ASPC..448..403H Altcode: 2010arXiv1012.3013H; 2011csss...16..403H
Theoretical arguments and observations suggest that the atmospheres
of Brown Dwarfs and planets are very dynamic on chemical and on
physical time scales. The modelling of such substellar atmospheres
has, hence, been much more demanding than initially anticipated. This
Splinter1 has combined new developments in atmosphere
modelling, with novel observational techniques, and new challenges
arising from planetary and space weather observations.

---------------------------------------------------------
Title: Polarimetry of Extrasolar Planets
Authors: Berdyugin, A.; Berdyugina, S.; Fluri, D.; Piirola, V.
2011ASPC..449..389B Altcode:
Polarimetry is a powerful technique for detecting directly the starlight
that is scattered in a planetary atmosphere and, thus, possesses
information on its geometry, chemistry, and thermodynamics. Recently,
we have started a polarimetric survey of nearby planetary systems
with hot Jupiters closely orbiting their host stars using the DiPol
polarimeter at the KVA telescope and the TurPol polarimeter at the
Nordic Optical Telescope, La Palma. Here we present our first results
and discuss orbital parameters of the HD 189733 system and scattering
properties of its planet.

---------------------------------------------------------
Title: Polarimetry of Hot Inflated Jupiters Reveals Their Neptune-like
Blue Appearance
Authors: Berdyugina, Svetlana; Berdyugin, A.; Piirola, V.
2011ESS.....2.1407B Altcode:
Polarimetry is a powerful technique for detecting directly
exoplanetary atmospheres and probing their geometry, chemistry,
and thermodynamics. The light scattered in the planetary atmosphere
is linearly polarized perpendicular to the scattering plane. In
general, when the planet revolves around the parent star, the
scattering angle changes and the Stokes parameters vary. Therefore,
the observed polarization variability exhibits the orbital period of
the planet and reveal the inclination, eccentricity, and orientation
of the orbit as well as the nature of scattering particles in the
planetary atmosphere. Recently, we have started a polarimetric survey
of nearby planetary systems with hot Jupiters closely orbiting their
host stars. Here we will present first polarimetric detection
of Upsilon And b which identifies this planet to have low density
(0.36 g/cm3) and relatively high average geometrical albedo (0.35)
with the maximum in the blue. Together with HD189733b and Kepler-7b,
these constitute a small group of inflated and highly reflective hot
Jupiters, with albedo defined by Rayleigh scattering on, most probably,
condensates in high altitude haze or clouds. The scattering results
in the blue shine similar to Neptune. Some other planet parameters
determined from polarimetry agree well with those which could be
previously evaluated from spectroscopy. We will also present
upper limits on polarimetric detections of HD209458b, 51 Peg b, and
Tau Boo b. Spurious polarization effects, e.g. due to starspots
or limb polarization, will be evaluated.

---------------------------------------------------------
Title: Upsilon Andromedae b in polarized light: New constraints on
the planet size, density and albedo
Authors: Berdyugina, S. V.; Berdyugin, A. V.; Piirola, V.
2011arXiv1109.3116B Altcode:
Polarimetry is a novel tool to detect and characterize exoplanets and
their atmospheres. Polarized scattered light from the non-transiting
hot Jupiter $\upsilon$~And~b is measured to further constrain its
orbit, mass, density, and geometrical albedo. We obtained polarimetric
measurements in the $UBV$ bands over the orbital period and deduce
an average peak-to-peak amplitude of $(49 \pm 5)\times10^{-6}$
in both Stokes $q$ and $u$. From our data we evaluate the orbit
inclination $i=111\degr\pm11\degr$, longitude of the ascending
node $\Omega=236\degr\pm12\degr$ (or equivalently 56\degr), the
effective size of the scattering atmosphere in the optical blue
of $1.36\pm0.20$\,$R_{\rm J}$. These combined with spectroscopic
measurements result in the planet mass $0.74\pm0.07$\,$M_{\rm J}$,
mean density $0.36\pm0.08$\,g\,cm$^{-3}$, and surface gravity
$\sim10^3$\,cm\,s$^{-2}$, which favor a close similarity of
$\upsilon$~And~b to other inflated hot Jupiters. We also significantly
improved the periastron epoch $T_{\rm p}={\rm JD}2,450,032.451$,
interior conjunction epoch $T_{\rm t}={\rm JD}2,450,034.668$, and
periastron longitude $\omega=279\degr\pm14\degr$. The latter indicates
that the apsidal resonance known for planets c and d includes also
planet b. Obtained limits on the wavelength dependent geometrical albedo
(average 0.35) indicate its similarity to Neptune with peak reflectivity
in the blue. Combining all available measurements at various passbands,
we construct a unified wavelength dependent albedo of an average
hot Jupiter. It appears to be largely shaped by Rayleigh scattering
in the blue and atomic and molecular absorption in the optical and
near infrared. Our findings demonstrate the power of polarimetry for
studying non-transiting exoplanets.

---------------------------------------------------------
Title: Starspot variability and evolution from modeling Kepler
photometry of active late-type stars
Authors: Brown, Alexander; Korhonen, Heidi; Berdyugina, Svetlana;
Tofany, Barton; Ayres, Thomas R.; Kowalski, Adam; Hawley, Suzanne;
Harper, Graham; Piskunov, Nikolai
2011IAUS..273...78B Altcode:
The Kepler satellite provides a unique opportunity to study the detailed
optical photometric variability of late-type stars with unprecedentedly
long (several year) continuous monitoring and sensitivity to very
small-scale variations. We are studying a sample of over two hundred
cool (mid-A - late-K spectral type) stars using Kepler long-cadence
(30 minute sampling) observations. These stars show a remarkable
range of photometric variability, but in this paper we concentrate on
rotational modulation due to starspots and flaring. Modulation at the
0.1% level is readily discernable. We highlight the rapid timescales
of starspot evolution seen on solar-like stars with rotational periods
between 2 and 7 days.

---------------------------------------------------------
Title: NLTE modeling of Stokes vector center-to-limb variations in
the CN violet system
Authors: Shapiro, A. I.; Fluri, D. M.; Berdyugina, S. V.; Bianda,
M.; Ramelli, R.
2011A&A...529A.139S Altcode: 2011arXiv1103.2524S
Context. The solar surface magnetic field is connected with and even
controls most of the solar activity phenomena. Zeeman effect diagnostics
allow for measuring only a small fraction of the fractal-like
structured magnetic field. The remaining hidden magnetic fields can
only be accessed with the Hanle effect. Aims: Molecular lines
are very convenient for applying the Hanle effect diagnostics thanks
to the broad range of magnetic sensitivities in a narrow spectral
region. With the UV version of the Zurich Imaging Polarimeter ZIMPOL II
installed at the 45 cm telescope of the Istituto Ricerche Solari Locarno
(IRSOL), we simultaneously observed intensity and linear polarization
center-to-limb variations in two spectral regions containing the (0,
0) and (1, 1) bandheads of the CN B2Σ - X2Σ
system. Here we present an analysis of these observations. 
Methods: We have implemented coherent scattering in molecular lines into
an NLTE radiative transfer code. A two-step approach was used. First,
we separately solved the statistical equilibrium equations and compute
opacities and intensity while neglecting polarization. Then we used
these quantities as input for calculating scattering polarization and
the Hanle effect. Results: We have found that it is impossible
to fit the intensity and polarization simultaneously at different
limb angles in the framework of standard 1D modeling. The atmosphere
models that provide correct intensity center-to-limb variations fail
to fit linear polarization center-to-limb variations due to lacking
radiation-field anisotropy. We had to increase the anisotropy by
means of a specially introduced free parameter. This allows us to
successfully interpret our observations. We discuss possible reasons
for underestimating the anisotropy in the 1D modeling.

---------------------------------------------------------
Title: Kepler Observations of Starspot Evolution, Differential
Rotation, and Flares on Late-Type Stars
Authors: Brown, Alexander; Korhonen, H.; Berdyugina, S.; Walkowicz,
L.; Kowalski, A.; Hawley, S.; Neff, J.; Ramsey, L.; Redman, S.; Saar,
S.; Furesz, G.; Piskunov, N.; Harper, G.; Ayres, T.; Tofany, B.
2011AAS...21820502B Altcode: 2011BAAS..43G20502B
The Kepler satellite is providing spectacular optical photometric
light-curves of unprecedented precision and duration that
routinely allow detailed studies of stellar magnetic activity on
late-type stars that were difficult, if not impossible, to attempt
previously. Rotational modulation due to starspots is commonly seen
in the Kepler light-curves of late-type stars, allowing detailed
study of the surface distribution of their photospheric magnetic
activity. Kepler is providing multi-year duration light-curves that
allow us to investigate how activity phenomena -- such as the growth,
migration, and decay of starspots, differential rotation, activity
cycles, and flaring -- operate on single and binary stars with a
wide range of mass and convection zone depth. We present the
first results from detailed starspot modeling using newly-developed
light-curve inversion codes for a range of GALEX-selected stars with
typical rotation periods of a few days, that we have observed as part of
our 200 target Kepler Cycle 1/2 Guest Observer programs. The physical
properties of the stars have been measured using high resolution
optical spectroscopy, which allows the Kepler results to be placed
within the existing framework of knowledge regarding stellar magnetic
activity. These results demonstrate the powerful diagnostic capability
provided by tracking starspot evolution essentially continuously for
more than 16 months. The starspots are clearly sampling the stellar
rotation rate at different latitudes, enabling us to measure the
differential rotation and starspot lifetimes. As would be expected,
stars with few day rotation show frequent flaring that is easily seen
as "white-light" flares in Kepler light-curves. We compare the observed
flare rates and occurrence with the starspot properties. This work
contains results obtained using the NASA Kepler satellite and from the
Apache Point Observatory, the MMT (using NOAO community access time),
and the Hobby-Eberly Telescope. Funding is provided by NASA Kepler
grants NNX10AC51G and NNX11AC79G.

---------------------------------------------------------
Title: First detection of a weak magnetic field on the giant Arcturus:
remnants of a solar dynamo?
Authors: Sennhauser, C.; Berdyugina, S. V.
2011A&A...529A.100S Altcode:
Context. Arcturus is the second closest K giant and among the brightest
stars in the sky. It has not been found to have a magnetic field,
even though Ca ii H&amp;K lines as activity indicators imply that
Arcturus is magnetically active. Aims: We measure the mean
longitudinal magnetic field strengths and interpret them in terms of
an intraseasonal activity modulation. Methods: We apply our
new Zeeman component decomposition (ZCD) technique to three single
sets of Stokes I and V spectra to measure the longitudinal component
of the magnetic field responsible for tiny Zeeman signatures detected
in spectral line profiles. Results: For two of the spectra, we
report the detection of the Zeeman signature of a weak longitudinal
magnetic field of 0.65 ± 0.26 G and 0.43 ± 0.16 G. The third
measurement is less significant, but all the measurements closely
reproduce a rotationally modulated activity cycle with four active
longitudes. Conclusions: For the first time, a magnetic field
on Arcturus is directly detected. This field can be attributed to a
diminishing solar-type αΩ-dynamo acting in the deepening convection
zone of Arcturus. We demonstrate that our new method ZCD lowers the
detection limit of very weak magnetic fields from spectropolarimetric
measurements.

---------------------------------------------------------
Title: Zeeman Component Decomposition (ZCD): Common Line Profile
and Magnetic Field Reconstruction from Polarized Spectra
Authors: Sennhauser, C.; Berdyugina, S. V.
2011ASPC..437..173S Altcode:
We present our new method Zeeman Component Decomposition (ZCD) for
recovering an intrinsic line profile and the magnetic field vector
from polarized spectra (Sennhauser &amp; Berdyugina 2010b). The ZCD
combines advantages of inversion procedures with multi-line techniques
(MLT), which is a standard tool in stellar astronomy for increasing the
signal-to-noise ratio (SNR) of spectropolarimetric measurements. In
addition to accounting for the nonlinearity in blended profiles
(cf. NDD, Sennhauser et al. 2009), ZCD is not restricted by the weak
line approximation (WLA), and is independent of pre-calculated line
lists. Furthermore, the ZCD overcomes a common disadvantage of MLTs
where the weak field approximation (WFA) is widely used. Therefore,
the ZCD permits us to analyze many lines with arbitrary Zeeman splitting
and to simultaneously deploy Stokes IQUV spectra to determine a common
line profile. With all these abilities, ZCD has significantly increased
the interpretability of common absorption line profiles, and has at the
same time lowered the detection limit for weak magnetic fields. This
enabled us for the first time to directly detect a weak longitudinal
magnetic field on the surface of the red giant Arcturus.

---------------------------------------------------------
Title: Polarimetry of Cool Atmospheres: From the Sun to Exoplanets
Authors: Berdyugina, S. V.
2011ASPC..437..219B Altcode: 2010arXiv1011.0751B
This is a review of a decades-long effort to develop novel tools for
exploring magnetism in cold astrophysical media and to establish
a new field of molecular spectropolarimetry since Berdyugina et
al. (2000). It is most directly applicable to the Sun, cool stars,
substellar objects, planets and other minor bodies as well as
interstellar and circumstellar matter. It is close to being a mature
field with developed theoretical tools poised to uncover new insights
into the magnetic structures in cooler environments. Here I attempt a
broad description of the literature and present some recent exciting
results. In particular, following my programmatic review at SPW3,
I discuss advances in molecular magnetic diagnostics which are based
on the modeling of about a dozen diatomic molecules with various
electronic transitions and states, including the most challenging -
FeH. The applications stretch from sunspots to starspots, small-scale
and turbulent solar magnetic fields, red and white dwarfs, and spin-offs
such as polarimetry of protoplanetary disks and exoplanets.

---------------------------------------------------------
Title: Solar Polarization Workshop 6
Authors: Kuhn, J. R.; Harrington, D. M.; Lin, H.; Berdyugina, S. V.;
Trujillo-Bueno, J.; Keil, S. L.; Rimmele, T.
2011ASPC..437.....K Altcode:
No abstract at ADS

---------------------------------------------------------
Title: Polarized Reflected Light from the Exoplanet HD189733b:
First Multicolor Observations and Confirmation of Detection
Authors: Berdyugina, S. V.; Berdyugin, A. V.; Fluri, D. M.; Piirola, V.
2011ApJ...728L...6B Altcode: 2011arXiv1101.0059B
We report the first multicolor polarimetric measurements (UBV bands)
for the hot Jupiter HD189733b and confirm our previously reported
detection of polarization in the B band. The wavelength dependence of
polarization indicates the dominance of Rayleigh scattering with a peak
in the blue B and U bands of ~10-4 ± 10-5 and
at least a factor of two lower signal in the V band. The Rayleigh-like
wavelength dependence, also detected in the transmitted light during
transits, implies a rapid decrease of the polarization signal toward
longer wavelengths. Therefore, the nondetection by Wiktorowicz,
based on a measurement integrated within a broad passband covering
the V band and partly covering the B and R bands, is inconclusive and
consistent with our detection in B. We discuss possible sources of the
polarization and demonstrate that effects of incomplete cancellation of
stellar limb polarization due to starspots or tidal perturbations are
negligible as compared with scattering polarization in the planetary
atmosphere. We compare the observations with a Rayleigh-Lambert model
and determine effective radii and geometrical albedos for different
wavelengths. We find a close similarity of the wavelength-dependent
geometrical albedo with that of the Neptune atmosphere, which is known
to be strongly influenced by Rayleigh and Raman scattering. Our result
establishes polarimetry as a reliable means for directly studying
exoplanetary atmospheres.

---------------------------------------------------------
Title: Chemical Composition of the RS CVn-type Star 33 Piscium
Authors: Barisevičius, G.; Tautvaišienė, G.; Berdyugina, S.;
Chorniy, Y.; Ilyin, I.
2011BaltA..20...53B Altcode: 2011arXiv1105.5650B; 2011OAst...20...53B
Abundances of 22 chemical elements, including the key elements
and isotopes such as 12C, 13C, N and O, are
investigated in the spectrum of 33 Psc, a single-lined RS CVn-type
binary of low magnetic activity. The high resolution spectra were
observed on the Nordic Optical Telescope and analyzed with the MARCS
model atmospheres. The following main parameters have been determined:
T eff = 4750 K, log g = 2.8, [Fe/H] = -0.09, [C/Fe] = -0.04,
[N/Fe] = 0.23, [O/Fe] = 0.05, C/N = 2.14, 12C/13C
= 30, which show the first-dredge-up mixing signatures and no
extra-mixing.

---------------------------------------------------------
Title: Solar turbulent magnetic fields: surprisingly homogeneous
distribution during the solar minimum
Authors: Kleint, L.; Berdyugina, S. V.; Shapiro, A. I.; Bianda, M.
2010A&A...524A..37K Altcode:
Context. Small-scale, weak magnetic fields are ubiquitous in the
quiet solar atmosphere. Yet their properties and temporal and spatial
variations are not well known. Aims: We have initiated a
synoptic program, carried out at the Istituto Ricerche Solari Locarno
(IRSOL), to investigate both turbulent, mixed-polarity magnetic
fields and nearly horizontal, directed fields and their variation
with the solar cycle. Methods: Through spectropolarimetric
observations we monitor linear and circular polarization at the solar
limb (5” on the disk) at five positional angles (N, NW, S, SW, W)
with the sensitivity of ~10-5. In addition, we analyzed
measurements taken at different limb distances. We measure signatures
in the 5141 Å region including two C2 triplets and three
Fe i lines. Linear polarization in these lines arises from scattering
and can be modified via the Hanle effect in the presence of turbulent
magnetic fields. Through the application of the differential Hanle
effect to the C2 R-triplet line ratios and the use of a
simplified line formation model, we are able to infer a strength of
turbulent magnetic fields while using the P-triplet to further restrict
it. A Zeeman analysis of Fe i Stokes V/I is used to evaluate flux
densities of horizontally directed fields. Results: We conclude
that weak fields were evenly distributed over the Sun during this solar
minimum. The turbulent field strength was at least 4.7 ± 0.2 G, and it
did not vary during the last two years. This result was complemented
with earlier, mainly unpublished measurements in the same region,
which extend our set to nearly one decade. A statistical analysis of
these all data suggests that there could be a very small variation of
the turbulent field strength (3σ-limit) since the solar maximum in
2000. The Zeeman analysis of Fe i Stokes V/I reveals weak horizontal
flux densities of 3-8 G. Conclusions: Our results demonstrate
the potential of long-term observations of small-scale magnetic fields,
which may vary with the solar cycle in both mean strength and spatial
distribution. This provides important constraints on the energy budget
of the solar cycle. Extending this synoptic program to many spectral
lines would provide a sample of heights in the solar atmosphere.

---------------------------------------------------------
Title: Zeeman component decomposition for recovering common profiles
and magnetic fields
Authors: Sennhauser, C.; Berdyugina, S. V.
2010A&A...522A..57S Altcode:
Context. High resolution spectropolarimetric data contain information
about the region where atomic and/or molecular lines form. Existing
multi-line techniques assuming similarities in shapes of line profiles
can extract generalized Stokes signatures from noisy spectra. However,
the interpretability of these signatures is limited by the commonly
employed weak-field and weak-line approximations. On the other hand,
inversion techniques based on realistic polarized radiative transfer
can interpret complicated individual line profiles but still unable
to handle the informative wealth of broad-band spectra. Aims:
We present a new method, Zeeman component decomposition (ZCD), which
combines the versatility of an unconstrained line profile resulting from
a multi-line analysis with the radiative transfer physics implying that
one profile constitutes all Stokes parameters. We show that the ZCD is
capable of inferring a common Zeeman component profile as well as a
reliable magnetic field vector from noisy broad-band spectra. 
Methods: We employ an analytic polarized radiative transfer solution
describing formation of polarized line profiles in a Milne-Eddington
atmosphere. The ZCD is built as a nonlinear inversion procedure with
a number of free parameters, namely an unconstrained line profile,
the line central depths, and the magnetic field parameters |B|, γ and
χ. The procedure is applied to all Stokes parameters simultaneously. We
carefully analyse blending of line profiles and Zeeman components and
obtain practical analytical expressions. By comparing the anomalous
Zeeman splitting with the commonly used triplet approximation, we obtain
an estimate of the error, helping us to identify the cases where the
simplification is not applicable. Results: We demonstrate the
capabilities of the ZCD by applying it to simulated Stokes I, V, and
full I, Q, U, V spectra. The first test shows that the ZCD outperforms
standard multi-line techniques in finding common line profiles for
noisy polarization spectra and, in addition, consistently recovers the
line-of-sight magnetic field. Trials with I, Q, U, V spectra demonstrate
the ability of the ZCD to work with noisy linear polarization spectra
and recover the magnetic field parameters in realistic scenarios.

---------------------------------------------------------
Title: Quiet-sun Intensity Contrasts in the Near-ultraviolet as
Measured from SUNRISE
Authors: Hirzberger, J.; Feller, A.; Riethmüller, T. L.; Schüssler,
M.; Borrero, J. M.; Afram, N.; Unruh, Y. C.; Berdyugina, S. V.;
Gandorfer, A.; Solanki, S. K.; Barthol, P.; Bonet, J. A.; Martínez
Pillet, V.; Berkefeld, T.; Knölker, M.; Schmidt, W.; Title, A. M.
2010ApJ...723L.154H Altcode:
We present high-resolution images of the Sun in the near-ultraviolet
spectral range between 214 nm and 397 nm as obtained from the first
science flight of the 1 m SUNRISE balloon-borne solar telescope. The
quiet-Sun rms intensity contrasts found in this wavelength range are
among the highest values ever obtained for quiet-Sun solar surface
structures—up to 32.8% at a wavelength of 214 nm. We compare the
rms contrasts obtained from the observational data with theoretical
intensity contrasts obtained from numerical magnetohydrodynamic
simulations. For 388 nm and 312 nm the observations agree well with
the numerical simulations whereas at shorter wavelengths discrepancies
between observed and simulated contrasts remain.

---------------------------------------------------------
Title: Imaging of stellar surfaces with the Occamian approach and
the least-squares deconvolution technique
Authors: Järvinen, S. P.; Berdyugina, S. V.
2010A&A...521A..86J Altcode:
Context. We present in this paper a new technique for the indirect
imaging of stellar surfaces (Doppler imaging, DI), when low
signal-to-noise spectral data have been improved by the least-squares
deconvolution (LSD) method and inverted into temperature maps with the
Occamian approach. We apply this technique to both simulated and real
data and investigate its applicability for different stellar rotation
rates and noise levels in data. Aims: Our goal is to boost the
signal of spots in spectral lines and to reduce the effect of photon
noise without loosing the temperature information in the lines. Methods: We simulated data from a test star, to which we added
different amounts of noise, and employed the inversion technique based
on the Occamian approach with and without LSD. In order to be able to
infer a temperature map from LSD profiles, we applied the LSD technique
for the first time to both the simulated observations and theoretical
local line profiles, which remain dependent on temperature and limb
angles. We also investigated how the excitation energy of individual
lines effects the obtained solution by using three submasks that have
lines with low, medium, and high excitation energy levels. 
Results: We show that our novel approach enables us to overcome
the limitations of the two-temperature approximation, which was
previously employed for LSD profiles, and to obtain true temperature
maps with stellar atmosphere models. The resulting maps agree well
with those obtained using the inversion code without LSD, provided
the data are noiseless. However, using LSD is only advisable for poor
signal-to-noise data. Further, we show that the Occamian technique, both
with and without LSD, approaches the surface temperature distribution
reasonably well for an adequate spatial resolution. Thus, the stellar
rotation rate has a great influence on the result. For instance, in
a slowly rotating star, closely situated spots are usually recovered
blurred and unresolved, which affects the obtained temperature range
of the map. This limitation is critical for small unresolved cool
spots and is common for all DI techniques. Finally the LSD method was
carried out for high signal-to-noise observations of the young active
star V889 Her: the maps obtained with and without LSD are found to be
consistent. Conclusions: Our new technique provides meaningful
information on the temperature distribution on the stellar surfaces,
which was previously inaccessible in DI with LSD. Our approach can be
easily adopted for any other multi-line techniques.

---------------------------------------------------------
Title: GJ 841B—the Second DQ White Dwarf With Polarized CH
Molecular Bands
Authors: Vornanen, T.; Berdyugina, S. V.; Berdyugin, A. V.; Piirola, V.
2010ApJ...720L..52V Altcode: 2010arXiv1008.3903V
We report a discovery of the circularly polarized CH A 2Δ-X
2Π and B 2Σ--X 2Π
molecular bands in the spectrum of the DQ white dwarf (WD) GJ 841B. This
is only the second such object since the discovery of G99-37 in the
1970s. GJ 841B is also the first WD to unambiguously show polarization
in the C2 Swan bands. By modeling the intensity and circular
polarization in the CH bands, we determine the longitudinal magnetic
field strength of 1.3 ± 0.5 MG and the temperature of 6100 ± 200 K
in the absorbing region. We also present new observations of G99-37
and obtain estimates of the magnetic field strength 7.3 ± 0.3 MG and
temperature 6200 ± 200 K, in good agreement with previous results.

---------------------------------------------------------
Title: Quiet-Sun intensity contrasts in the near ultraviolet
Authors: Hirzberger, Johann; Feller, Alex; Riethmüller, Tino L.;
Schüssler, Manfred; Borrero, Juan M.; Afram, Nadine; Unruh, Yvonne C.;
Berdyugina, Svetlana V.; Gandorfer, Achim; Solanki, Sami K.; Barthol,
Peter; Bonet, Jose A.; Martínez Pillet, Valentin; Berkefeld, Thomas;
Knölker, Michael; Schmidt, Wolfgang; Title, Alan M.
2010arXiv1009.1050H Altcode:
We present high-resolution images of the Sun in the near ultraviolet
spectral range between 214 nm and 397 nm as obtained from the first
science flight of the 1-m Sunrise balloon-borne solar telescope. The
quiet-Sun rms intensity contrasts found in this wavelength range
are among the highest values ever obtained for quiet-Sun solar
surface structures - up to 32.8% at a wavelength of 214 nm. We
compare with theoretical intensity contrasts obtained from numerical
magneto-hydrodynamic simulations. For 388 nm and 312 nm the observations
agree well with the numerical simulations whereas at shorter wavelengths
discrepancies between observed and simulated contrasts remain.

---------------------------------------------------------
Title: Sunspot Umbra Atmosphere from Full Stokes Inversion
Authors: Wenzel, R.; Berdyugina, S. V.; Fluri, D. M.; Arnaud, J.;
Sainz-Dalda, A.
2010ASPC..428..117W Altcode: 2010arXiv1003.5114W
Sunspots are prominent manifestations of the solar cycle and provide
key constraints for understanding its operation. Also, knowing
the internal structure of sunspots allows us to gain insights on
the energy transport in strong magnetic fields and, thus, on the
processes inside the convection zone, where solar magnetic fields
are generated and amplified before emerging at the surface on various
scales, even during solar minima. In this paper, we present results
of a spectropolarimetric analysis of a sunspot observed during the
declining phase of solar cycle 23. By inversion of the full Stokes
spectra, observed in several spectral regions in the optical at the
THEMIS facility, we infer the height dependence of physical quantities
such as the temperature and the magnetic field strength for different
sunspot regions. The simultaneous use of atomic (Fe I 5250.2 and 5250.6
Å) and highly temperature-sensitive molecular (TiO 7055 Å and MgH
5200 Å) lines allows us to improve a model of the sunspot umbra.

---------------------------------------------------------
Title: Zeeman Component Decomposition (ZCD) of Polarized Spectra:
Application for the Quiet Sun Internetwork Magnetic Field
Authors: Sennhauser, C.; Berdyugina, S. V.
2010ASPC..428..113S Altcode: 2010arXiv1003.5112S
Multiline techniques assuming similar line profiles have become a
standard tool in stellar astronomy for increasing the signal-to-noise
ratio (SNR) of spectropolarimetric measurements. However, due to the
widely-used weak field approximation, their benefits could not so far
be used for solar observations, where a large variety of Stokes profiles
emerge from local magnetic fields and measuring weak fields in the quiet
Sun remains a challenge. The method presented here permits us to analyze
many lines, with arbitrary Zeeman splitting, and to simultaneously
deploy Stokes IQUV spectra to determine a common line profile
with the SNR increased by orders of magnitude. The latter provides
a valuable constraint for determining separate field strengths for
each contributing absorber. This method represents an extension of our
recently developed technique of Nonlinear Deconvolution with Deblending
(NDD; Sennhauser et al. 2009), which accounts for the nonlinearity in
blended profiles. Equipped with all those abilities, Zeeman Component
Decomposition (ZCD) is the perfect tool to further increase the
informative value of high-precision polarimetric observations.

---------------------------------------------------------
Title: A synoptic program for large solar telescopes: Cyclic variation
of turbulent magnetic fields
Authors: Kleint, L.; Berdyugina, S. V.; Gisler, D.; Shapiro, A. I.;
Bianda, M.
2010AN....331..644K Altcode:
Upcoming large solar telescopes will offer the possibility of
unprecedented high resolution observations. However, during periods
of non-ideal seeing such measurements are impossible and alternative
programs should be considered to best use the available observing
time. We present a synoptic program, currently carried out at
the Istituto Ricerche Solari Locarno (IRSOL), to monitor turbulent
magnetic fields employing the differential Hanle effect in atomic and
molecular lines. This program can be easily adapted for the use at large
telescopes exploring new science goals, nowadays impossible to achieve
with smaller telescopes. The current, interesting scientific results
prove that such programs are worthwhile to be continued and expanded in
the future. We calculate the approximately achievable spatial resolution
at a large telescope like ATST for polarimetric measurements with a
noise level below 5 × 10-5 and a temporal resolution which
is sufficient to explore variations on the granular scale. We show
that it would be important to optimize the system for maximal photon
throughput and to install a high-speed camera system to be able to
study turbulent magnetic fields with unprecedented accuracy.

---------------------------------------------------------
Title: Turbulent Magnetic Fields in the Quiet Sun: A Search for
Cyclic Variations
Authors: Kleint, L.; Berdyugina, S. V.; Shapiro, A. I.; Bianda, M.
2010ASPC..428..103K Altcode: 2010arXiv1003.4103K
Turbulent magnetic fields fill most of the volume of the solar
atmosphere. However, their spatial and temporal variations are
still unknown. Since 2007, during the current solar minimum, we
are periodically monitoring several wavelength regions in the solar
spectrum to search for variations of the turbulent magnetic field in
the quiet Sun. These fields, which are below the resolution limit,
can be detected via the Hanle effect which influences the scattering
polarization signatures (Q/I) in the presence of magnetic fields. We
present a description of our program and first results showing that
such a synoptic program is complementary to the daily SOHO magnetograms
for monitoring small-scale magnetic fields.

---------------------------------------------------------
Title: Commission 36: Theory of Stellar Atmospheres
Authors: Asplund, Martin; Puls, Joachim; Landstreet, John; Allende
Prieto, Carlos; Ayres, Thomas; Berdyugina, Svetlana; Gustafsson,
Bengt; Hubeny, Ivan; Ludwig, Hans Günter; Mashonkina, Lyudmila;
Randich, Sofia
2010IAUTB..27..197A Altcode:
The members of the Commission 36 Organizing Committee attending the IAU
General Assembly in Rio de Janeiro met for a business session on August
7. Both members from the previous (2006-2009) and the new (2009-2012)
Organizing Committee partook in the discussions. Past president John
Landstreet described the work he had done over the past three years
in terms of supporting proposed conferences on the topic. He has
also spent significant amount of time establishing an updated mailing
list of all &gt;350 members of the commission, which is unfortunately
not provided automatically by the IAU. Such a list is critical for a
rapid dissemination of information to the commission members and for
a correct and smooth running of elections of IAU officials. Everyone
present thanked John effusively for all of his hard work over the past
three years to stimulate a high level of activity within the discipline.

---------------------------------------------------------
Title: Orbital parameters of extrasolar planets derived from
polarimetry
Authors: Fluri, D. M.; Berdyugina, S. V.
2010A&A...512A..59F Altcode: 2010arXiv1001.3091F
Context. Polarimetry of extrasolar planets becomes a new tool for their
investigation, which requires the development of diagnostic techniques
and parameter case studies. Aims: Our goal is to develop a
theoretical model which can be applied to interpret polarimetric
observations of extrasolar planets. Here we present a theoretical
parameter study that shows the influence of the various involved
parameters on the polarization curves. Furthermore, we investigate
the robustness of the fitting procedure. We focus on the diagnostics
of orbital parameters and the estimation of the scattering radius
of the planet. Methods: We employ the physics of Rayleigh
scattering to obtain polarization curves of an unresolved extrasolar
planet. Calculations are made for two cases: (i) assuming an angular
distribution for the intensity of the scattered light as from a Lambert
sphere and for polarization as from a Rayleigh-type scatterer; and
(ii) assuming that both the intensity and polarization of the scattered
light are distributed according to the Rayleigh law. We show that the
difference between these two cases is negligible for the shapes of the
polarization curves. In addition, we take the size of the host star into
account, which is relevant for hot Jupiters orbiting giant stars. 
Results: We discuss the influence of the inclination of the planetary
orbit, the position angle of the ascending node, and the eccentricity
on the linearly polarized light curves both in Stokes Q/I and U/I. We
also analyze errors that arise from the assumption of a point-like
star in numerical modeling of polarization as compared to consistent
calculations accounting for the finite size of the host star. We find
that errors due to the point-like star approximation are reduced with
the size of the orbit, but still amount to about 5% for known hot
Jupiters. Recovering orbital parameters from simulated data is shown
to be very robust even for very noisy data because the polarization
curves react sensitively to changes in the shape and orientation of the
orbit. Conclusions: The proposed model successfully diagnoses
orbital parameters of extrasolar planets and can also be applied to
predict polarization curves of known exoplanets. Polarization curves of
extrasolar planets thus provide an ideal tool to determine parameters
that are difficult to obtain with other methods, namely inclination
and position angle of the ascending node of orbits as well as true
masses of extrasolar planets.

---------------------------------------------------------
Title: Chemical Composition of the RS CVn-type Star Lambda Andromedae
Authors: Tautvaišienė, G.; Barisevičius, G.; Berdyugina, S.;
Chorniy, Y.; Ilyin, I.
2010BaltA..19...95T Altcode: 2010OAst...19...95T; 2010arXiv1009.0903T
Photospheric parameters and chemical composition are determined
for the single-lined chromospherically active RS CVn-type star
λ And (HD 222107). From the high resolution spectra obtained on
the Nordic Optical Telescope, abundances of 22 chemical elements
and isotopes, including such key elements as 12C,
13C, N and O, were investigated. The differential line
analysis with the MARCS model atmospheres gives T
eff=4830 K, log g=2.8, [Fe/H]=-0.53, [C/Fe]=0.09, [N/Fe]=0.35,
[O/Fe]=0.45, C/N=2.21, 12C/13C = 14. The value
of 12C/13C ratio for a star of the RS CVn-type
is determined for the first time, and its low value gives a hint that
extra-mixing processes may start acting in low-mass chromospherically
active stars below the bump of the luminosity function of red giants.

---------------------------------------------------------
Title: Chemical Composition of the RS CVn-type Star 29 Draconis
Authors: Barisevičius, G.; Tautvaišienė, G.; Berdyugina, S.;
Chorniy, Y.; Ilyin, I.
2010BaltA..19..157B Altcode: 2011arXiv1105.0947B; 2010OAst...19..157B
Photospheric parameters and chemical composition are determined
for the single-lined chromospherically active RS CVn-type star 29
Draconis (HD 160538). From the high resolution spectra obtained on
the Nordic Optical Telescope, abundances of 22 chemical elements,
including the key elements such as 12C, 13C,
N and O, were investigated. The differential line analysis with the
MARCS model atmospheres gives T eff = 4720 K, log g = 2.5,
[Fe/H] = --0.20, [C/Fe] = --0.14, [N/Fe] = 0.08, [O/Fe] = --0.04,
C/N = 2.40, 12C/13C = 16. The low value of the
12C/13C ratio gives a hint that extra mixing
processes in low-mass chromospherically active stars may start earlier
than the theory of stellar evolution predicts.

---------------------------------------------------------
Title: Nonlinear deconvolution with deblending: a new analyzing
technique for spectroscopy
Authors: Sennhauser, C.; Berdyugina, S. V.; Fluri, D. M.
2009A&A...507.1711S Altcode:
Context: Spectroscopy data in general often deals with an entanglement
of spectral line properties, especially in the case of blended line
profiles, independently of how high the quality of the data may be. In
stellar spectroscopy and spectropolarimetry, where atomic transition
parameters are usually known, the use of multi-line techniques to
increase the signal-to-noise ratio of observations has become common
practice. These methods extract an average line profile by means
of either least squares deconvolution (LSD) or principle component
analysis (PCA). However, only a few methods account for the blending
of line profiles, and when they do, they assume that line profiles
add linearly. Aims: We abandon the simplification of linear
line-adding for Stokes I and present a novel approach that accounts for
the nonlinearity in blended profiles, also illuminating the process
of a reasonable deconvolution of a spectrum. Only the combination of
those two enables us to treat spectral line variables independently,
constituting our method of nonlinear deconvolution with deblending
(NDD). The improved interpretation of a common line profile achieved
compensates for the additional expense in calculation time, especially
when it comes to the application to (Zeeman) doppler imaging (ZDI). Methods: By examining how absorption lines of different depths
blend with each other and describing the effects of line-adding in a
mathematically simple, yet physically meaningful way, we discover how
it is possible to express a total line depth in terms of a (nonlinear)
combination of contributing individual components. Thus, we disentangle
blended line profiles and underlying parameters in a truthful manner
and strongly increase the reliability of the common line patterns
retrieved. Results: By comparing different versions of LSD with
our NDD technique applied to simulated atomic and molecular intensity
spectra, we are able to illustrate the improvements provided by our
method to the interpretation of the recovered mean line profiles. As a
consequence, it is possible for the first time to retrieve an intrinsic
line pattern from a molecular band, offering the opportunity to fully
include them in a NDD-based ZDI. However, we also show that strong
line broadening deters the existence of a unique solution for heavily
blended lines such as in molecular bandheads.

---------------------------------------------------------
Title: New Solar System Researches expected by a New Telescope
Project at Mt. Haleakala, Hawaii
Authors: Kagitani, Masato; Okano, S.; Kasaba, Y.; Kuhn, J.;
Berdyugina, S.
2009DPS....41.4509K Altcode:
We Tohoku University starts the project for the new ground-based
telescope dedicated to planets and exoplanets, in collaboration
with the Institute for Astronomy of University of Hawaii(IfA/UH)
and ETH Zurich. The summit of Mt. Haleakala in Maui, Hawaii is
one of the best sites with clear skies, good seeing, and low humidity
conditions as well as good accessibility despite its high altitude
(elv. 3,000m). Haleakala High Altitude Observatory is operated by
IfA/UH, and we have been making observation of planets there since
2000. Currently, our observation facility consists of a 40cm
telescope. We have been making observations of faint atmospheric and
plasma features around bright planets, Io plasma torus, Mercury and
Lunar sodium tail, and so on. Atmospheric escapes from Mars and Venus,
the exoplanets close to mother stars are also possible future important
topics. When we try to observe those faint emissions surrounding the
bright objects, intense scattered light causes a serious problem. The
new telescope shall avoid the diffraction due to a spider structure
that holds a secondary mirror and to minimize the scattered light
from mirror surfaces as far as possible. Such telescope with a wide
dynamic range dedicated to planetary and exoplanetary sciences does
not exist yet. The project, called PLANETS (Poralized Light
from Atmospheres of Nearby Extra Terrestrial Planets), develops a new
telescope (tentatively named as JHET; Japan Hawaii Europe Telescope)
which consists of an off-axis primary mirror with a diameter of
1.8m, and Gregorian optics on an equatorial mount. State-of-art
adaptive optics and masking technologies will also be adopted to
eliminate the scattering light. This telescope will enables us to do
spectro-polarimetric observations and faint plasma and atmospheres
around the bright bodies. We will introduce the progress of our
ground-based observations and the future plan involving the wide area
of the international communities.

---------------------------------------------------------
Title: Spot evolution and active longitudes on FK Com: more than a
decade of detailed surface mapping
Authors: Korhonen, H.; Berdyugina, S. V.; Ilyin, I. V.; Strassmeier,
K. G.; Hackman, T.
2009RMxAC..36..323K Altcode:
Stellar surface maps can be obtained from high resolution, high
signal-to-noise spectra using Doppler imaging techniques. In this
work we present new surface temperature maps of the giant FK Com for
2004-2007, and combine them with our earlier maps. The detailed images
of the stellar surface span now almost 15 years. Together with the
photometric observations this unique time series is used to study
the spot evolution, spot life times, and possible permanent active
longitudes on FK Com.

---------------------------------------------------------
Title: Zeeman-Doppler Imaging of Stellar Magnetic Fields with Atomic
and Molecular Lines
Authors: Sennhauser, C.; Berdyugina, S. V.; Fluri, D. M.
2009ASPC..405..543S Altcode:
We have developed a new code for Zeeman-Doppler Imaging (ZDI)
of stellar magnetic fields using the Occamian approach for solving
inverse problems. The inversions are applied to Stokes I and V parameter
sets obtained by solving the full set of polarized radiative transfer
equations for both atomic and molecular lines. For the first time we
demonstrate that molecular polarization strongly constrains the ZDI maps
and is crucial for obtaining a realistic solution from Stokes I and V
only observed at a few stellar rotational phases. We also present an
enhanced LSD technique, which allows analytic separation of blended line
profiles. The resulting LSD profiles are free from systematic effects
induced by blends, which are typical for other multi-line techniques.

---------------------------------------------------------
Title: Magnetic Fields on M Dwarfs Measured with FeH
Authors: Afram, N.; Reiners, A.; Berdyugina, S. V.
2009ASPC..405..527A Altcode:
Measurements of magnetic fields on cool M dwarfs provide important
information on stellar dynamo models, however direct measurements
are very difficult to obtain. Most of our knowledge about magnetic
fields on cool stars is based on Zeeman broadened measurements of
atomic and molecular lines observed in their spectra. The FeH molecule
is an excellent diagnostic for M dwarfs with many Zeeman sensitive
lines persisting to very cool temperatures. Previous usage of FeH
transitions for measuring magnetic fields was based on a comparison of
Zeeman sensitive and insensitive lines observed in active and inactive
stars, thus, introducing an unknown bias to uncertainties in stellar
temperatures, rotational and thermal broadening, etc. Thanks to the
recent progress in our theoretical understanding of FeH we compared
synthetic Stokes profiles with observations and determined mean
magnetic field for a number of M dwarfs, independently of the thermal
uncertainties. Also, we investigated the limits of determining magnetic
fields by using intensity spectra only. This provides an opportunity
to apply the method for cooler objects, including brown dwarfs.

---------------------------------------------------------
Title: Solar Polarization 5: In Honor of Jan Stenflo
Authors: Berdyugina, S. V.; Nagendra, K. N.; Ramelli, R.
2009ASPC..405.....B Altcode:
No abstract at ADS

---------------------------------------------------------
Title: Solar Magnetic Field Diagnostics with the Molecular Hanle
Effect
Authors: Shapiro, A. I.; Fluri, D. M.; Berdyugina, S. V.
2009ASPC..405..343S Altcode:
Weak entangled magnetic fields with mixed polarity occupy the main part
of the quiet solar photosphere. While the Zeeman effect diagnostics
fail to measure such fields due to cancellation in polarization, the
Hanle effect, accessible through the second solar spectrum, provides
us with a very sensitive tool for studying the distribution of weak
magnetic fields on the Sun. Molecular lines are valuable for magnetic
field diagnostics thanks to their broad range of magnetic sensitivities
within narrow spectral regions, so that the differential Hanle effect
can be employed, which greatly reduces the model dependence of deduced
magnetic field strengths. Here we present our recent results on the
diagnostic of solar turbulent magnetic fields with the help of CN
transitions in the violet system. In addition, we have implemented
modeling of coherent scattering in molecular lines into a non-LTE
radiative transfer code. Together with the Hanle effect theory this
provides us with a realistic model for studying turbulent magnetic
fields.

---------------------------------------------------------
Title: FeH -- A Valuable Magnetic Diagnostic Tool
Authors: Afram, N.; Berdyugina, S. V.; Fluri, D. M.
2009ASPC..405..349A Altcode:
Transitions of the FeH molecule are dominating features in the
near-infrared spectra of sunspots, starspots and red and brown
dwarfs. Their remarkable magnetic sensitivity provides an excellent
opportunity to study magnetic fields in these cool objects. However,
the absence of an adequate theoretical model of the molecule capable
to reproduce its observed magnetic properties limits the usage of these
transitions in solar and stellar magnetic studies. Here we present the
first successful semi-empirical model of the FeH F4Δ --
X4Δ system based on the Hamiltonian for the intermediate
Hund's case (a-b) and a perturbation from a nearby electronic state,
resulting in modification of the spin-orbit and spin-spin coupling. Our
model is able to reproduce the broadening of FeH lines due to the
Zeeman effect and their polarization signatures detected in sunspots
and starspots and, for the first time, provides reliable Landé
factors. This opens a door for developing further applications for
red and brown dwarfs.

---------------------------------------------------------
Title: First measurement of the magnetic field on FK Com and its
relation to the contemporaneous star-spot locations
Authors: Korhonen, H.; Hubrig, S.; Berdyugina, S. V.; Granzer, Th.;
Hackman, T.; Schöller, M.; Strassmeier, K. G.; Weber, M.
2009MNRAS.395..282K Altcode: 2008arXiv0812.0603K; 2009MNRAS.tmp..407K
In this study, we present simultaneous low-resolution longitudinal
magnetic field measurements and high-resolution spectroscopic
observations of the cool single giant FK Com. The variation of the
magnetic field over the rotational period of 2.4d is compared with the
star-spot location obtained using Doppler imaging techniques, V-band
photometry and V - I colours. The chromospheric activity is studied
simultaneously with the photospheric activity using high-resolution
observations of the Hα, Hβ and Hγ line profiles. Both the maximum
(272 +/- 24G) and minimum (60 +/- 17G) in the mean longitudinal
magnetic field, &lt;Bz&gt;, are detected close to the
phases where cool spots appear on the stellar surface. A possible
explanation for such a behaviour is that the active regions at the
two longitudes separated by 0.2 in phase have opposite polarities. *
Based on the observations collected at the European Southern
Observatory, Chile (Prg. 280.D-5075); at the automatic STELLar Activity
(STELLA) observatory at Tenerife, Spain; and with the Vienna automatic
photometric telescopes Wolfgang and Amadeus, Arizona, USA. E-mail:
hkorhonen@eso.org

---------------------------------------------------------
Title: Stellar magnetic fields across the H-R diagram: observational
evidence
Authors: Berdyugina, Svetlana V.
2009IAUS..259..323B Altcode:
This review presents most recent measurements of magnetic fields in
various types of stars and substellar objects across the H-R diagram
with the emphasis on measurement methods, observational and modeling
biases, and the role of magnetic fields in stellar evolution.

---------------------------------------------------------
Title: LSD-a nonlinear approach
Authors: Sennhauser, C.; Berdyugina, S. V.; Fluri, D. M.
2009AIPC.1094..732S Altcode: 2009csss...15..732S
Stellar spectra usually are very limited in the signal-to-noise ratio
(SNR) that can be obtained. In order to increase their informative
value, different techniques have been developed in the past ten
years which combine multiple spectral lines by cutting out individual
line profiles and analysing them by means of least-squares errors or
PCA. They usually neglect that the bulk of lines are blended, resulting
in artificial broadening of the retrieved common line pattern, while
those that care to disentangle blended profiles assume linear line
adding. Based on the well-known least-squares deconvolution (LSD)
method, we developed a new technique, which truly accounts for blended
profiles and deconvolves them in a physically meaningful way by taking
into account the nonlinearity when abandoning the regime of optically
thin lines. The so-called interpolation formula by M. Minnaert is
a unique tool to describe a line profile both in the optically thin
and the optically thick regime. It enables us to write a total line
depth in terms of a (nonlinear) combination of contributing individual
components. Applying different versions of LSD, among them our
nonlinear (NL-) LSD, to simulated atomic and molecular intensity
spectra shows the unrivaled functionality of our new method in terms
of interpretability of the retrieved common line pattern. For the
first time it is possible to recover an intrinsic line pattern from
a molecular band.

---------------------------------------------------------
Title: Correlating the starspot distributions and the photometric
activity cycles on two young solar analogues
Authors: Järvinen, S. P.; Korhonen, H.; Berdyugina, S. V.; Ilyin, I.
2009AIPC.1094..660J Altcode: 2009csss...15..660J
V889 Herculis and EK Draconis are both young active dwarfs that
can be considered as young solar analogues. Earlier Doppler imaging
studies of these stars have shown that they have quite different spot
distributions. Despite of that, latitudinal spot distribution seems
to have a connection to the photometrically determined activity
cycle. However, especially for EK Dra there have not been many
Doppler images available for a detailed study. Here we present new
surface temperature maps for both stars, and discuss further possible
connections to the activity cycles and compare the results with the
solar case.

---------------------------------------------------------
Title: FeH and its capability to measure magnetic fields on M dwarfs
Authors: Afram, N.; Reiners, A.; Berdyugina, S. V.
2009AIPC.1094..704A Altcode: 2009csss...15..704A
Iron hydride (FeH) bands are the most sensitive indicators of magnetic
fields in cool atmospheres, where atomic lines lose their utility. In
the first part of our work, we established the theoretical foundations
for the analysis of the astrophysically important Wing-Ford FeH
F4Δ-X4Δ system around 1 μm. We calculated
the molecular Zeeman effect, computed the Landé factors of the
energy levels and transitions, and calibrated molecular constants to
account for unknown perturbations by comparing observed and modeled
sunspot spectra. In the second part we illustrate the applicability
of the FeH lines to diagnose stellar magnetic fields. We modeled
highly magnetically sensitive FeH line profiles employing our novel
quantum-mechanical treatment of the Zeeman effect in the FeH molecule
and compared them with observed M dwarf spectra to infer magnetic
field strengths. Measurements of magnetic fields on cool M dwarfs
provide important information on stellar dynamo processes, since
the transformation between the solar type to a turbulent dynamo takes
place roughly at a spectral type M3 to M4 and the dynamo mechanism that
generates and amplifies magnetic fields in fully convective stars is
still unknown.

---------------------------------------------------------
Title: Commission 36: Theory of Stellar Atmospheres
Authors: Landstreet, John D.; Asplund, Martin; Spite, Monique;
Balachandran, Suchitra B.; Berdyugina, Svetlana V.; Hauschildt, Peter
H.; Ludwig, Hans G.; Mashonkina, Lyudmila I.; Nagendra, K. N.; Puls,
Joachim; Randich, M. Sofia; Tautvaisiene, Grazina
2009IAUTA..27..222L Altcode:
Commission 36 covers the whole field of the physics of stellar
atmospheres. The scientific activity in this large subject has been very
intense during the last triennium and led to the publication of a large
number of papers, which makes a complete report quite impractical. We
have therefore decided to keep the format of the preceding report:
first a list of areas of current research, then Web links for obtaining
further information.

---------------------------------------------------------
Title: Synoptic program - Variations of the Turbulent magnetic field
Authors: Kleint, L.; Berdyugina, S.; Bianda, M.
2008ESPM...12.2.71K Altcode:
We have initiated a synoptic program at the Istituto Ricerche Solari
Locarno (IRSOL) to observe variations of the turbulent magnetic field
with the solar cycle. Our main target are C2 molecular lines at 5141
A which are excellent for employing the differential Hanle effect to
determine the strength of the turbulent magnetic field (see Berdyugina
&amp; Fluri 2004). These lines are monitored about twice per month
at five position angles around the solar limb (N, NW, W, SW, S) at
mu=0.1. Several other lines, for example the Cr I triplet at 5206 A,
have also been chosen for our observations. This is the first systematic
study of temporal variations of the second solar spectrum, and we have
already noticed significant differences between single measurements
taken at the solar maximum and minimum. We present a description of
the synoptic program and first observations.

---------------------------------------------------------
Title: Magnetic activity on V889 Herculis. Combining photometry
and spectroscopy
Authors: Järvinen, S. P.; Korhonen, H.; Berdyugina, S. V.; Ilyin,
I.; Strassmeier, K. G.; Weber, M.; Savanov, I.; Tuominen, I.
2008A&A...488.1047J Altcode:
Aims: In this paper we analyse photometric and spectroscopic
observations of the young active dwarf V889 Her. We present new surface
temperature maps, and compare them to earlier published Doppler maps,
as well as to the results obtained from long-term photometry. Methods: The light curve inversions and surface temperature maps
were obtained using the Occamian approach inversion technique. Results: The 12 years of photometric records on V889 Her suggest
a possible photometric cycle of approximately 9 years. Variability
on this time scale is detected in the maximum, minimum, and mean
photometric magnitudes. The spots prefer to concentrate on two
active longitudes that are approximately 180° apart. Furthermore,
one flip-flop event, i.e., a sudden change of the dominant active
longitude by 180°, is detected at the time of the global maximum
activity. The wings of the Ca II 8662 Å indicate that the quiet
photosphere of the V889 Her is similar to the one of the present
Sun supporting earlier determined atmospheric parameters, while the
chromosphere of V889 Her shows signs of much stronger activity. The
temperature maps reveal that the polar regions are covered by spots,
which are about 1500 K cooler than the quiet photosphere. The mean
spot latitude varies slightly with time. It appears that the spot
latitudes from our Doppler images and the spot migration rates
revealed by photometry indicate a weaker differential rotation than
reported earlier, but in the same (solar-like) direction. Based
on observations made with the Nordic Optical Telescope, operated on
the island of La Palma jointly by Denmark, Finland, Iceland, Norway,
and Sweden, in the Spanish Observatorio del Roque de los Muchachos
of the Instituto de Astrofisica de Canarias. Table [see full textsee
full textsee full text] and Figs. [see full textsee full textsee full
text]-[see full textsee full textsee full text] are only available in
electronic form at http://www.aanda.org

---------------------------------------------------------
Title: The FeH F4Δ-X4Δ system. Creating a
valuable diagnostic tool to explore solar and stellar magnetic fields
Authors: Afram, N.; Berdyugina, S. V.; Fluri, D. M.; Solanki, S. K.;
Lagg, A.
2008A&A...482..387A Altcode:
Context: Lines of diatomic molecules are ideal tools for studying
cool stellar atmospheres and the internal structure of sunspots
and starspots, given their temperature and pressure sensitivities,
which are typically higher than in atomic lines. The Wing-Ford FeH
F4Δ-X4Δ system represents such a diatomic
molecule that is, in addition, highly sensitive to magnetic fields. The
current theoretical description of those transitions that include the
involved molecular constants, however, are only based on intensity
measurements because polarimetric observations have not been available
until now, which limits their diagnostic value. Furthermore, the theory
has so far been optimized to reproduce energy levels and line strengths
without taking magnetic sensitivities into account. Aims: The
FeH F4Δ-X4Δ system is produced by transitions
between two electronic states with the coupling of the angular momenta
that is intermediate between limiting Hund's cases (a) and (b). Our goal
is to investigate the diagnostic capabilities of the current theoretical
description of the molecule FeH. Methods: Using the most precise
available Hamiltonian, we carried out the perturbation calculation
of the molecular Zeeman effect for this transition and computed the
Landé factors of the energy levels and of transitions. We extracted
Landé factors from a comparison of observed and calculated Stokes
I and V profiles. Certain spectral lines, most frequently with high
magnetic sensitivity, exhibited discrepancies between the theory and
observations. We extended the theoretical model with a semi-empirical
approach to obtain a diagnostic tool that is able to reproduce many
of the interesting spectral lines. Results: We find that the
current theory successfully reproduces the magnetic properties of
a large number of lines in the FeH F4Δ-X4Δ
system and that the modified Hamiltonian allows us to synthesize
and successfully reproduce the most sensitive lines. Thus, our
observations have provided valuable constraints for determining
empirical molecular constants and Landé factors. Conclusions:
The FeH F4Δ-X4Δ system is found to be a very
sensitive magnetic diagnostic tool. Polarimetric data of these lines,
in contrast to intensity measurements, provide us with more direct
and detailed information to study the coolest parts of sunspot and
starspot umbrae, as well as cool active dwarfs.

---------------------------------------------------------
Title: Searching for links between magnetic fields and stellar
evolution. III. Measurement of magnetic fields in open cluster Ap
stars with ESPaDOnS
Authors: Landstreet, J. D.; Silaj, J.; Andretta, V.; Bagnulo, S.;
Berdyugina, S. V.; Donati, J. -F.; Fossati, L.; Petit, P.; Silvester,
J.; Wade, G. A.
2008A&A...481..465L Altcode: 2008arXiv0803.0877L
Context: A small fraction of upper main sequence stars have strong,
highly structured magnetic fields. The origin and evolution
of these fields are not adequately understood. Aims: We
are carrying out a survey of magnetic fields in Ap stars in open
clusters in order to obtain the first sample of magnetic upper main
sequence stars with precisely known ages. These data will constrain
theories of field evolution in these stars. Methods: A survey
of candidate open cluster magnetic Ap stars was carried out using
the new ESPaDOnS spectropolarimeter at the CFHT. This instrument
provides an alternative to the FORS1 spectropolarimeter used up to
now for this survey. Results: We have obtained 44 measurements
of the mean longitudinal fields &lt; Bz &gt; of 23 B6-A2
stars that have been identified as possible Ap stars and that are
possible members of open clusters, with a median uncertainty of about
45 G. Of these stars, 10 have definite field detections. Nine stars of
our sample are found not to be magnetic Ap stars. These observations
significantly increase the information available about low-mass stars
near the TAMS compared to our previous sample. Conclusions:
We find that ESPaDOnS provides field measurements comparable to those
that we have previously obtained with FORS1, and that these data also
contain a large amount of useful information not readily obtained from
lower resolution spectropolarimetry. With the new data we are able to
expand the available data on low-mass, relatively evolved Ap stars,
and identify more robustly which observed stars are actually magnetic
Ap stars and cluster members. Re-analysis of the enlarged data set
of cluster Ap stars indicates that such stars with masses in the
range of 2-5 {M_⊙} show rms fields larger than about 1 kG only when
they are near the ZAMS. The time scale on which these large fields
disappear varies strongly with mass, ranging from about 250 Myr for
stars of 2-3 {M_⊙} to 15 Myr for stars of 4-5 {M_⊙}. Our data are
consistent either with emergent flux conservation for most (but not
all) Ap stars, or with modest decline in flux with age. Based
on observations made with the Canada-France-Hawaii Telescope,
operated by the National Research Council of Canada, the Centre
National de Recherche Scientifique of France, and the University
of Hawaii, under programme 05A-C19.

---------------------------------------------------------
Title: First Direct Detection of Magnetic Fields in Starspots and
Stellar Chromospheres
Authors: Berdyugina, S. V.; Fluri, D. M.; Afram, N.; Suwald, F.;
Petit, P.; Arnaud, J.; Harrington, D. M.; Kuhn, J. R.
2008ASPC..384..175B Altcode: 2008csss...14..175B; 2007astro.ph..3559B
Here we report on the first detection of circular polarization in
molecular lines formed in cool magnetic regions (starspots) and in
chromospheric emission lines formed in hot plages on the surfaces
of active stars. Our survey of G-K-M stars included young
main-sequence dwarfs and RS~CVn-type giants and subgiants. All
stars were found to possess surface magnetic fields producing
Stokes V LSD signals in atomic lines of 0.05% to 0.5%. Several stars
clearly showed circular polarization in molecular lines of 0.1% to
1%. The molecular Stokes V signal is reminiscent of that observed in
sunspots. Chromospheric magnetic fields were detected on most active
targets in Stokes~V profiles of emission lines with peak polarization
up to 2%. The observed molecular circular polarization on M dwarfs
indicates single-polarity magnetic fields covering at least 10% of
the stellar disk. Smaller signals on K stars imply that their magnetic
fields are apparently weaker, more entangled than on M dwarfs, or more
diluted by the bright photosphere.

---------------------------------------------------------
Title: First Detection of Polarized Scattered Light from an
Exoplanetary Atmosphere
Authors: Berdyugina, S. V.; Berdyugin, A. V.; Fluri, D. M.; Piirola, V.
2008ApJ...673L..83B Altcode: 2007arXiv0712.0193B
We report the first direct detection of an exoplanet in the visible
polarized light. The transiting planet HD 189733b is one of the
very hot Jupiters with shortest periods and, thus, smallest orbits,
which makes them ideal candidates for polarimetric detections. We
obtained polarimetric measurements of HD 189733 in the B band well
distributed over the orbital period and detected two polarization
maxima near planetary elongations with a peak amplitude of ~2 ×
10-4. Assuming Rayleigh scattering, we estimated the
effective size of the scattering atmosphere (Lambert sphere) to be
1.5 ± 0.2 RJ, which is 30% larger than the radius of the
opaque body previously inferred from transits. If the scattering matter
fills the planetary Roche lobe, the lower limit of the geometrical
albedo can be estimated as 0.14. The phase dependence of polarization
indicates that the planetary orbit is oriented almost in a north-south
direction with a longitude of ascending node Ω = (16° or 196°)
± 8°. We obtain independent estimates of the orbit inclination i =
98° ± 8° and eccentricity e = 0.0 (with an uncertainty of 0.05),
which are in excellent agreement with values determined previously from
transits and radial velocities. Our findings clearly demonstrate the
power of polarimetry and open a new dimension in exploring exoplanetary
atmospheres even for systems without transits.

---------------------------------------------------------
Title: Starspots and relativity: Applied Doppler imaging for the
Gravity Probe B mission
Authors: Marsden, S. C.; Berdyugina, S. V.; Donati, J. -F.; Eaton,
J. A.; Williamson, M. H.
2007AN....328.1047M Altcode:
We present Doppler images and surface differential rotation measurements
for the primary of the RS CVn binary IM Pegasi, the guide star for
the Gravity Probe B experiment. The data used is a subset of that
taken during optical support of the mission and was obtained almost
nightly over a near three year period from the Automatic Spectroscopic
Telescope operated by Tennessee State University. Using the technique
of least-squares deconvolution to increase the signal-to-noise ratio
of the data, we have reconstructed 31 maximum entropy Doppler images of
the star. The images show that the spot features are relatively stable
for over a year (and possibly longer) with both a polar spot and lower
latitude features. The most intense features are located on the side
facing the secondary. In addition, we have incorporated a solar-like
differential rotation law into the imaging process to determine the
level of surface differential rotation for IM Peg for 22 epochs. A
weighted least-squares average of the measurements gives a surface
shear of 0.0142 ± 0.0007 rad/d, meaning that the equator takes ∼440
± 20 days to lap the poles. Although the level of surface differential
rotation was shown to vary over the period of the observations, this
may indicate an underestimate in the errors of the method rather than
any temporal evolution in the differential rotation. Movies are
available via http://www.aip.de/AN/movies

---------------------------------------------------------
Title: Study of FK Comae Berenices. V. Spot evolution and detection
of surface differential rotation
Authors: Korhonen, H.; Berdyugina, S. V.; Hackman, T.; Ilyin, I. V.;
Strassmeier, K. G.; Tuominen, I.
2007A&A...476..881K Altcode:
Aims:We investigate the spot evolution and the surface differential
rotation of the single late-type giant FK Com. Methods: A total
of 18 new surface temperature maps of FK Com are calculated with
the Doppler imaging technique for the years 1993-2003. Photometric
observations from 2002-2004 are also given. The new and previously
published spectroscopic and photometric observations are used to
study the spot locations and lifetimes, and to estimate the value of
the surface differential rotation. Results: The phases of the
active regions determined from the Doppler images follow closely the
active longitudes determined earlier from the long-term photometric
observations. One active longitude can remain active for several
years, but the exact spot configuration within the active longitude
changes on much shorter time scales, indicating that the spot
lifetime is months instead of years. There are periods during which
the spot configuration changes even within days. Measurements using
spot latitudes from the Doppler images and spot rotation periods
from the photometric observations yield a surface differential
rotation law of Ω=(151.30°/day ± 0.09°/day)-(1.78°/day ±
0.12°/{day})sin2ψ and the relative differential rotation
coefficient α=0.012± 0.002 for FK Comae. Based on observations
obtained at the Nordic Optical Telescope, Observatorio Roque de los
Muchachos, La Palma, Canary Islands, Spain; the Kitt Peak National
Observatory, USA; the National Astronomical Observatory, Rozhen,
Bulgaria; Automatic Photometric Telescopes Phoenix 10, Wolfgang and
Amadeus, Arizona, USA. Tables 2a-c are only available in electronic
form at the CDS via anonymous ftp to cdsarc.u-strasbg.fr (130.79.128.5)
or via http://cdsweb.u-strasbg.fr/cgi-bin/qcat?J/A+A/476/881 Figures
2 and 3 are only available in electronic form at http://www.aanda.org

---------------------------------------------------------
Title: Hanle effect in the CN violet system with LTE modeling
Authors: Shapiro, A. I.; Berdyugina, S. V.; Fluri, D. M.; Stenflo,
J. O.
2007A&A...475..349S Altcode: 2007arXiv0709.2515S
Context: Weak entangled magnetic fields with mixed polarity occupy
the main part of the quiet Sun. The Zeeman effect diagnostics
fails to measure such fields because of cancellation in circular
polarization. However, the Hanle effect diagnostics, accessible through
the second solar spectrum, provides us with a very sensitive tool for
studying the distribution of weak magnetic fields on the Sun. Aims: Molecular lines are very strong and even dominate in some
regions of the second solar spectrum. The CN B {}2 Σ -
X {}2 Σ system is one of the richest and most promising
systems for molecular diagnostics and well suited for the application
of the differential Hanle effect method. The aim is to interpret
observations of the CN B {}2 Σ - X {}2 Σ system
using the Hanle effect and to obtain an estimation of the magnetic
field strength. Methods: We assume that the CN molecular layer
is situated above the region where the continuum radiation is formed
and employ the single-scattering approximation. Together with the
Hanle effect theory this provides us with a model that can diagnose
turbulent magnetic fields. Results: We have succeeded in fitting
modeled CN lines in several regions of the second solar spectrum to
observations and obtained a magnetic field strength in the range from
10-30 G in the upper solar photosphere depending on the considered
lines. Tables [see full textsee full textsee full textsee full
text]-[see full textsee full textsee full textsee full text] are only
available in electronic form at http://www.aanda.org

---------------------------------------------------------
Title: VizieR Online Data Catalog: Differential photometry of FK Com
(Korhonen+, 2007)
Authors: Korhonen, H.; Berdyugina, S. V.; Hackman, T.; Ilyin, I. V.;
Strassmeier, K. G.; Tuominen, I.
2007yCat..34760881K Altcode:
In the present work we publish new photometric observations of
the very active single giant, FK Com for the time period between
the 1st of January 2002 and the 8th of July 2004. The observations
have been carried out with three different automatic photometric
telescopes: Phoenix 10, Wolfgang and Amadeus, all located in Arizona,
USA. Observations contain measurements at the following bands: Johnson
U, B and V, Cousins I and Stroemgren b and y. The observations are
differential photometry in respect to the primary comparison star HD
117567. (3 data files).

---------------------------------------------------------
Title: A New Mechanism for Polarizing Light from Obscured Stars
Authors: Kuhn, J. R.; Berdyugina, S. V.; Fluri, D. M.; Harrington,
D. M.; Stenflo, J. O.
2007ApJ...668L..63K Altcode: 2007arXiv0708.0599K
Recent spectropolarimetric observations of Herbig Ae/Be stellar systems
show linear polarization variability with wavelength and epoch near
their obscured Hα emission. Surprisingly, this polarization is
not coincident with the Hα emission peak but is variable near the
absorptive part of the line profile. With a new and novel model, we
show here that this is evidence of optical pumping-anisotropy of the
incident radiation that leads to a linear polarization-dependent optical
depth within the intervening hydrogen wind or disk cloud. This effect
can yield a larger polarization signal than scattering polarization
in these systems.

---------------------------------------------------------
Title: First polarimetric observations and modeling of the FeH
F4Δ-X4Δ system
Authors: Afram, N.; Berdyugina, S. V.; Fluri, D. M.; Semel, M.;
Bianda, M.; Ramelli, R.
2007A&A...473L...1A Altcode: 2007arXiv0708.0298A
Context: Lines of diatomic molecules are typically much more
temperature and pressure sensitive than atomic lines, which makes
them ideal, complementary tools for studying cool stellar atmospheres
as well as the internal structure of sunspots and starspots. The
FeH F^4Δ-X^4Δ system represents such an example that exhibits in
addition a large magnetic field sensitivity. However, the current
theoretical descriptions of these transitions including the molecular
constants involved are only based on intensity measurements because
polarimetric observations have not been available so far, which limits
their diagnostic value. Furthermore, the theory was optimized to
reproduce energy levels and line strengths without taking the magnetic
sensitivities into account. Aims: We present for the first
time spectropolarimetric observations of the FeH F^4Δ-X^4Δ system
measured in sunspots to investigate their diagnostic capabilities for
probing solar and stellar magnetic fields. In particular, we investigate
whether the current theoretical model of FeH can reproduce the observed
Stokes profiles including their magnetic properties. Methods: The
polarimetric observations of the FeH F^4Δ-X^4Δ system in Stokes I and
V are compared with synthetic Stokes profiles modeled with radiative
transfer calculations. This allows us to infer the temperature and
the magnetic field strength of the observed sunspots. Results:
We find that the current theory successfully reproduces the magnetic
properties of a large number of lines in the FeH F^4Δ-X^4Δ
system. In a few cases the observations indicate a larger Zeeman
splitting than predicted by the theory. There, our observations have
provided additional constraints, which allowed us to determine empirical
molecular constants. Conclusions: The FeH F^4Δ-X^4Δ system is
found to be a very sensitive magnetic diagnostic tool. Polarimetric
data of these lines, in contrast to intensity measurements, provide us
with more direct and detailed information to study the coolest parts
of sunspot and starspot umbrae, and cool active dwarfs.

---------------------------------------------------------
Title: EK Draconis. Magnetic activity in the photosphere and
chromosphere
Authors: Järvinen, S. P.; Berdyugina, S. V.; Korhonen, H.; Ilyin,
I.; Tuominen, I.
2007A&A...472..887J Altcode:
Context: As a young solar analogue, EK Draconis provides an opportunity
to study the magnetic activity of the infant Sun. Aims: We present
three new surface temperature maps of EK Draconis and compare them
with previous results obtained from long-term photometry. Furthermore,
we determined a set of stellar parameters and compared the determined
values with the corresponding solar values. Methods: Atmospheric
parameters were determined by comparing observed and synthetic spectra
calculated with stellar atmosphere models. Surface temperature maps
were obtained using the Occamian approach inversion technique. The
differential rotation of EK Dra was estimated using two different
methods. Results: A detailed model atmosphere analysis of high
resolution spectra of EK Dra has yielded a self-consistent set of
atmospheric parameters: T_eff = 5750 K, log g = 4.5, [M/H] = 0.0,
ξt = 1.6 km s-1. The evolutionary models imply
that the star is slightly more massive than the Sun and has an age
between 30-50 Myr, which agrees with the determined lithium abundance
of log N(Li) = 3.02. Moreover, the atmospheric parameters, as well
as the wings of the Ca ii 8662 Å, indicate that the photosphere of
EK Dra is very similar to the one of the present Sun, while their
chromospheres differ. There also seems to be a correlation between
magnetic features seen in the photosphere and chromosphere. The
temperature images reveal spots of only 500 K cooler than the quiet
photosphere. The mean spot latitude varies with time. The obtained
differential rotation is very small, but the sign of it supports solar
type differential rotation on EK Dra. Based on observations made
with the Nordic Optical Telescope, operated on the island of La Palma
jointly by Denmark, Finland, Iceland, Norway, and Sweden, in the Spanish
Observatorio del Roque de los Muchachos of the Instituto de Astrofisica
de Canarias. Table [see full text] and Figs. [see full text] and [see
full text] are only available in electronic form at http://www.aanda.org

---------------------------------------------------------
Title: Broad-Band Molecular Polarization in White Dwarfs
Authors: Berdyugina, S. V.; Berdyugin, A. V.; Piirola, V.; Shapiro, A.
2007ASPC..372..177B Altcode:
We present novel calculations of broad-band polarization due to the
molecular Paschen--Back effect in a strong magnetic field. Based
on that, we analyze new spectropolarimetric observations of the
cool magnetic helium-rich white dwarf G 99-37 which shows strongly
polarized molecular bands in its spectrum. Combining the polarimetric
observations with our model calculations for the CH bands at 4300 Å,
we deduce a magnetic field of 8 MG on this unique magnetic white dwarf.

---------------------------------------------------------
Title: Molecular Magnetic Dichroism in Spectra of White Dwarfs
Authors: Berdyugina, S. V.; Berdyugin, A. V.; Piirola, V.
2007PhRvL..99i1101B Altcode: 2007PhRvL..9991101B
We present novel calculations of the magnetic dichroism appearing in
molecular bands in the presence of a strong magnetic field, which
perturbs the internal structure of the molecule and results in net
polarization due to the Paschen-Back effect. Based on that, we analyze
new spectropolarimetric observations of the cool magnetic helium-rich
white dwarf G99-37, which shows strongly polarized molecular bands in
its spectrum. In addition to previously known molecular bands of the
C2 Swan and CH A-X systems, we find a firm evidence for the
violet CH B-X bands at 390 nm and C2 Deslandres-d’Azambuja
bands at 360 nm. Combining the polarimetric observations with our
model calculations, we deduce a dipole magnetic field of 7.5±0.5MG
with the positive pole pointing towards the Earth. We conclude that
the developed technique is an excellent tool for studying magnetic
fields on cool magnetic stars.

---------------------------------------------------------
Title: Flip-flop cycles in solar and stellar activity
Authors: Berdyugina, Svetlana V.
2007HiA....14..275B Altcode:
We discuss flip-flop cycles in solar and stellar activity.

---------------------------------------------------------
Title: Butterfly Diagram and Activity Cycles in HR 1099
Authors: Berdyugina, Svetlana V.; Henry, Gregory W.
2007ApJ...659L.157B Altcode: 2007astro.ph..3530B
We analyze photometric data of the active RS CVn-type star HR 1099 for
the years 1975-2006 with an inversion technique and reveal the nature
of two activity cycles of 15-16 yr and 5.3+/-0.1 yr duration. The 16 yr
cycle is related to variations of the total spot area and is coupled
with the differential rotation, while the 5.3 yr cycle is caused by
the symmetric redistribution of the spotted area between the opposite
stellar hemispheres (flip-flop cycle). We recover long-lived active
regions comprising two active longitudes that migrate in the orbital
reference frame with a variable rate because of the differential
rotation along with changes in the mean spot latitudes. The migration
pattern is periodic with the 16 yr cycle. Combining the longitudinal
migration of the active regions with a previously measured differential
rotation law, we recover the first stellar butterfly diagram without
an assumption about spot shapes. We find that mean latitudes of active
regions at opposite longitudes change antisymmetrically in the course
of the 16 yr cycle: while one active region migrates to the pole,
the other approaches the equator. This suggests a precession of the
global magnetic field with respect to the stellar rotational axis.

---------------------------------------------------------
Title: (1) Preferred longitudes in sunspot activity (2) Preferred
sunspot longitudes: non-axisymmetry and differential rotation
Authors: Usoskin, I. G.; Berdyugina, S. V.; Poutanen, J.
2007A&A...464..761U Altcode:
No abstract at ADS

---------------------------------------------------------
Title: Long-term persistence of solar active longitudes and its
implications for the solar dynamo theory
Authors: Usoskin, I. G.; Berdyugina, S. V.; Moss, D.; Sokoloff, D. D.
2007AdSpR..40..951U Altcode:
We present an overview of the observational results related to the
existence of long-lived sunspot active longitudes. These are affected
by the solar differential rotation. The existence of such migrating
active longitudes imposes an important constraint on the dynamo
theory. We review different approaches to model non-axisymmetry in
solar dynamo models and find that, in principle, plausible mechanisms
exist to reproduce the observed non-axisymmetry. The most favorable
interpretation is suggested by the 'stroboscopic effect', where
a quasi-rigidly rotating non-axisymmetric mean field can produce
seemingly migrating active longitudes in sunspots. Other scenarios
are less favorable but cannot yet be excluded.

---------------------------------------------------------
Title: Molecular Hanle effect in the Paschen-Back regime
Authors: Shapiro, A. I.; Fluri, D. M.; Berdyugina, S. V.; Stenflo,
J. O.
2007A&A...461..339S Altcode:
Context: The second solar spectrum resulting from coherent scattering
is a main tool for diagnostics of turbulent magnetic fields on the
Sun. Scattering on diatomic molecules plays an important role in
forming this spectrum and even dominates in some spectral regions. Aims: In a magnetic field electronic states of a molecule are often
perturbed via the Paschen-Back effect. Sometimes this perturbation
can completely change the spectrum, not only quantitatively, but
even qualitatively. Here we calculate molecular scattering properties
taking into account the Paschen-Back effect. Methods: Starting
with the Hund's case (a) wave functions as a basis we obtain with the
perturbation theory wave functions of the intermediate Hund's case
(a-b) in a magnetic field. Using new, perturbed values of the Landé
factors and transition amplitudes we calculate the Mueller matrix
for coherent scattering at diatomic molecules in the intermediate
Hund's case (a-b) and look for the effects that can be caused by
the Paschen-Back effect. Results: We have found a considerable
deviation from the Zeeman regime and discuss here the quantitative
and qualitative effects on observed polarization signals for the CN
B {}2 Σ - X {}2 Σ and MgH B' {}2
Σ - X {}2 Σ systems as examples.

---------------------------------------------------------
Title: Molecular Hanle effect in the Paschen-Back regime: theory
and application
Authors: Shapiro, A. I.; Berdyugina, S. V.; Fluri, D. M.; Stenflo,
J. O.
2007msfa.conf..317S Altcode:
The second solar spectrum resulting from coherent scattering is a main
tool for diagnostics of turbulent magnetic fields on the Sun. Scattering
on diatomic molecules plays an important role in forming this spectrum
and even dominates in some spectral regions. In a magnetic field
electronic states of a molecule are often perturbed via the Paschen-Back
effect. Sometimes this perturbation can completely change the spectrum,
not only quantitatively, but even qualitatively. Here we calculate
molecular scattering properties taking into account the Paschen-Back
effect. We calculate the Mueller matrix for coherent scattering at
diatomic molecules in the intermediate Hund's case (a-b) and look for
the effects that can be caused by the Paschen-Back effect. We have
found a considerable deviation from the Zeeman regime and discuss
here the quantitative and qualitative effects on observed polarization
signals for the CN B 2 [Sigma] - X 2 [Sigma] system as an example. We
show an application of the Hanle effect for the interpretation of
observations of

---------------------------------------------------------
Title: Spectro-polarimetry of a sunspot simultaneously in atomic
and molecular lines.
Authors: Arnaud, J.; Berdyugina, S. V.; Fluri, D. M.; Afram, N.
2007MmSAI..78...89A Altcode:
We performed with THEMIS spectro-polarimetric observations
simultaneously in various atomic and molecular lines. We present the
observations and discuss an important aspect of spectro-polarimetric
data reduction: the recentering of the frames in the spectral
direction needed before substracting spectra to extract polarized
Stokes parameters. We conclude that THEMIS has the unique capability,
among present time large solar telescope, of providing polarization
data almost free from instrumental effects.

---------------------------------------------------------
Title: Preferred longitudes in solar and stellar activity
Authors: Berdyugina, S. V.
2007MmSAI..78..242B Altcode:
An analysis of the distribution of starspots on the surfaces of very
active stars, such as RS CVn- FK Com-type stars as well as young solar
analogs, reveals preferred longitudes of spot formation and their
quasi-periodic oscillations, i.e. flip-flop cycles. A non-linear
migration of the preferred longitudes suggests the presence of the
differential rotation and variations of mean spot latitudes. It enables
recovering stellar butterfly diagrams. Such phenomena are found to
persist in the sunspot activity as well. A comparison of the observed
properties of preferred longitudes on the Sun with those detected on
more active stars leads to the conclusion that we can learn fine details
of the stellar dynamo by studying the Sun, while its global parameters
on the evolutionary time scale are provided by a sample of active stars.

---------------------------------------------------------
Title: Applied Doppler Imaging: Can Magnetic Activity of IM Pegasi
Affect the Gravity Probe B Mission?
Authors: Berdyugina, S. V.; Marsden, S. C.
2006ASPC..358..385B Altcode:
IM Peg is a single-lined, spectroscopic RS CVn binary, with a rapidly
rotating (v sin i=27 km/s), early K-type, giant primary. Magnetic
activity of the primary is indicated by dark spots covering &gt;
15% of the surface. The system is bright in both optical and radio,
and was chosen as a guide star for the Gravity Probe B (GP-B)
satellite mission. The goal of GP-B is to verify two predictions of
Einstein's theory of general relativity (geodetic effect and “frame
dragging”), based on measurements of mean gyroscopic drift with
respect to the optical centroid of IM Peg. The requested precision
of 0.5×10-3 arcsec/yr implies that even small shifts of
the optical centroid of IM Peg due to surface magnetic activity must
be determined. In support of the GP-B mission, we are undertaking an
intensive Doppler imaging survey of the primary component of IM Peg,
to determine the effect of spot features on its optical centroid. We
present an overview of our work for GP-B, and report initial results
from this support project, including the first magnetic maps of the
IM~Peg primary, created using Least-Squares Deconvolution and Zeeman
Doppler Imaging.

---------------------------------------------------------
Title: Spectro-Polarimetry of a Sunspot in Atomic and Molecular
Lines with THEMIS
Authors: Arnaud, J.; Berdyugina, S. V.; Fluri, D. M.; Afram, N.;
Solanki, S. K.; Raouafi, N. -E.
2006ASPC..358..319A Altcode:
We present spectro-polarimetric observations of a sunspot, which were
recorded simultaneously with THEMIS in various atomic and molecular
lines. These observations include the first full Stokes measurements
of the band-head of TiO around 7055 Å.

---------------------------------------------------------
Title: Molecular Diagnostics of the Internal Structure of Starspots
and Sunspots
Authors: Afram, N.; Berdyugina, S. V.; Fluri, D. M.; Solanki, S. K.;
Lagg, A.; Petit, P.; Arnaud, J.
2006ASPC..358..375A Altcode:
We have analyzed the usefulness of molecules as a diagnostic tool for
studying solar and stellar magnetism with the molecular Zeeman and
Paschen-Back effects. In the first part we concentrate on molecules
that are observed in sunspots such as MgH and TiO. We present calculated
molecular line profiles obtained by assuming magnetic fields of 2-3 kG
and compare these synthetic Stokes profiles with spectro-polarimetric
observations in sunspots. The good agreement between the theory and
observations allows us to turn our attention in the second part to
starspots to gain insight into their internal structure. We investigate
the temperature range in which the selected molecules can serve as
indicators for magnetic fields on highly active cool stars and compare
synthetic Stokes profiles with our recent observations.

---------------------------------------------------------
Title: The Molecular Paschen-Back Effect
Authors: Berdyugina, S. V.; Fluri, D. M.; Solanki, S. K.
2006ASPC..358..329B Altcode:
The molecular Paschen-Back effect (PBE) lacks a detailed description
since the problem was first addressed by Hill in 1929. However,
many diatomic molecules exhibit the PBE at field strengths typical of
sunspots and active cool stars. Recently we have presented a complete
theoretical description of the molecular PBE in Hund's cases (a), (b),
and all intermediate cases. This description allows us to compute the
splitting of levels of any multiplicity and the transitions between
them. We find that in the partial PBE regime strongly asymmetric
Stokes profiles are produced, whose strengths and asymmetries depend
sensitively on the magnetic field. Also, the strength of the forbidden
and satellite transitions increases rapidly with field strength,
while the strength of the main branch transitions decreases. These
signatures hold promise to form the basis of new diagnostics of solar
and stellar magnetic fields.

---------------------------------------------------------
Title: Detection of the Molecular Zeeman Effect in Circular
Polarization on Cool Active Stars
Authors: Berdyugina, S. V.; Petit, P.; Fluri, D. M.; Afram, N.;
Arnaud, J.
2006ASPC..358..381B Altcode: 2007astro.ph..3560B
We report on the first ever detection of circular polarization
in molecular lines forming in magnetic regions on the surfaces
of active stars. The new observations were obtained with the
high-resolution spectro-polarimeter ESPaDOnS recently installed at the
Canada-France-Hawaii Telescope. In July 2005 we carried out a survey
of 17 G-K-M stars including active main-sequence dwarfs and RS CVn-type
giants and subgiants. All stars were found to possess surface magnetic
fields producing average atomic Stokes-V signals of 0.05% to 0.5%. Three
stars clearly showed circular polarization in molecular lines of 0.5%
to 1%. The molecular Stokes-V signal is reminiscent of that observed
in sunspots.

---------------------------------------------------------
Title: Hanle Effect in the Paschen-Back Regime
Authors: Shapiro, A. I.; Fluri, D. M.; Berdyugina, S. V.; Stenflo,
J. O.
2006ASPC..358..311S Altcode:
The second solar spectrum resulting from coherent scattering is an
important tool for the diagnostics of turbulent magnetic fields on
the Sun. Molecular scattering plays an important role in forming this
spectrum, and even dominates in some spectral regions. We present
a theory that allows us to calculate the Mueller matrix for coherent
scattering from diatomic molecules in Hund's intermediate coupling case
(a-b) for arbitrary molecular transitions. We performed the calculation
of the molecular Hanle effect in the Paschen-Back regime. We found
significant differences from the Zeeman regime, and as an example we
discuss here, both qualitatively and quantitatively, the effects on
observed polarization signals for the CN violet system.

---------------------------------------------------------
Title: The Search for Polarization Variability in IM Pegasi
Authors: Berdyugin, A. V.; Berdyugina, S. V.; Piirola, V.; Butkevich,
A. G.
2006ApJ...651..475B Altcode:
We have studied linear polarization in the RS CVn binary IM Pegasi
in order to check the possibility that this star has variable
polarization. For this purpose, accurate polarization measurements
in the B, V, and R passbands with the new CCD polarimeter on the
remotely operated KVA telescope at La Palma were carried out in 2005
August-November. Our observations have yielded accurate determination
of the polarization in IM Peg: PB=0.064%+/-0.004%,
θB=97deg+/-2deg
PV=0.102%+/-0.006%,
θV=91deg+/-3deg
and PR=0.078%+/-0.005%,
θR=95deg+/-4deg. Analysis of the
data indicates no significant polarization variability in IM Peg. The
upper limit for the amplitude of possible variability is &lt;=0.03%
in all passbands. In contrast to the previously published results,
the linear polarization in this star is most likely nonvariable and
interstellar in origin.

---------------------------------------------------------
Title: First Polarimetric Measurements and Modeling of the
Paschen-Back Effect in CaH Transitions
Authors: Berdyugina, S. V.; Fluri, D. M.; Ramelli, R.; Bianda, M.;
Gisler, D.; Stenflo, J. O.
2006ApJ...649L..49B Altcode: 2006astro.ph.10588B
We report the first spectropolarimetric observations and modeling of CaH
transitions in sunspots. We have detected strong polarization signals in
many CaH lines from the A-X system, and we provide the first successful
fit to the observed Stokes profiles using the previously developed
theory of the Paschen-Back effect in arbitrary electronic states of
diatomic molecules and polarized radiative transfer in molecular lines
in stellar atmospheres. We analyze the CaH Stokes profiles together
with quasi-simultaneous observations in TiO bands and conclude that
CaH provides a valuable diagnostic of magnetic fields in sunspots,
starspots, cool stars, and brown dwarfs.

---------------------------------------------------------
Title: Flip-flop cycles in solar and stellar activity
Authors: Berdyugina, S. V.
2006IAUJD...8E..64B Altcode:
Doppler images and long time series of photometric observations of cool
active stars reveal permanent active longitudes on their surfaces. They
are found to alternate their dominant activity quasi-periodically which
indicates a new type of the activity cycles, flip-flop cycles. In this
talk I will review properties of active longitudes and flip-flop cycles
on different types of active stars including the Sun.

---------------------------------------------------------
Title: Applied Doppler Imaging: Can The Magnetic Activity Of IM
Pegasi Affect The Gravity Probe B Mission?
Authors: Marsden, S. C.; Berdyugina, S. V.
2006IAUJD...8E..51M Altcode:
IM Pegasi is a single-lined spectroscopic RS CVn binary, with
the primary being a rapidly-rotating (vsini = 27 km/s) early-K
giant. Magnetic activity of the primary is evident as dark spot
features covering 15% or more of the stellar surface. Since the system
is bright in both optical and radio bands, IM Pegasi was chosen as
a guide star for the Gravity Probe B (GP-B) satellite mission. The
mission is designed to verify two predictions of Einstein's theory
of general relativity, the geodetic effect and "frame-dragging",
based on measurements of mean gyroscope drift with respect to the
optical centroid of IM Pegasi. The requested standard error of 0.5
milliarcseconds/year implies that even small contributions to the shift
of the optical centroid of IM Pegasi due to surface magnetic activity
must be determined. In support of the GP-B mission we are undertaking an
intensive Doppler imaging survey of the primary component of IM Pegasi
to determine the effect of spot features on the optical centroid of IM
Pegasi. We present an overview of our role in GP-B and report initial
results from this support project, including the first magnetic maps
of the IM Pegasi primary, created using Least-Squares Deconvolution
and Zeeman Doppler Imaging.

---------------------------------------------------------
Title: Doppler Imaging of EK Dra
Authors: Järvinen, S. P.; Berdyugina, S. V.; Korhonen, H.; Ilyin,
I.; Tuominen, I.
2006IAUJD...8E..48J Altcode:
We present three Doppler images, spanning slightly more than a year,
of a young solar analogue EK Draconis. The spot locations obtained
from these temperature maps are compared to the phases of the spots
determined using long-term photometry. The Doppler images show both
high and low latitude spots, which are at most 800 K cooler than the
unspotted photosphere (5800 K). From the Doppler images we calculate
light curves, which are inverted to spot phase probability maps as we
have done earlier for real photometric observations. The phases of
the spots in probability maps correspond to the phases of spots, or
sometimes rather to the mean phase of a group of spots, seen in Doppler
images. Moreover, the determined phases of the spots from calculated
light curves are well in agreement with the phases determined from
the real observations. This supports the idea that, although light
curve inversions are not that sofisticated way to study the surface
structures of the stars, i.e., star spots, the cyclic behaviour of the
spot phases determined from the photometric inversions is indeed real.

---------------------------------------------------------
Title: Active longitudes, nonaxisymmetric dynamos and phase mixing
Authors: Berdyugina, S. V.; Moss, D.; Sokoloff, D.; Usoskin, I. G.
2006A&A...445..703B Altcode:
We discuss the problem of solar active longitudes from the viewpoint
of dynamo theory. We start from a recent observational analysis of the
problem undertaken by Berdyugina &amp; Usoskin (2003, A&amp;A, 405,
1121) and Usoskin et al. (2005, A&amp;A, 441, 347) who demonstrated
from a study of sunspot data that solar active longitudes rotate
differentially, with a small but significant asynchrony between
northern and southern hemispheres. We suggest two concepts by which the
underlying magnetic structure could lead to the observed phenomenology -
the true differential rotation of a nonaxisymmetric magnetic structure
and a stroboscopic effect. In the latter case, a solid body rotation of
nonaxisymmetric magnetic structure is illuminated by an activity wave
propagating from middle latitudes to the solar equator, and so mimics a
differential rotation. We then discuss several mechanisms which could in
principle lead to the excitation of active longitudes. In particular,
we consider dynamo excitation of nonaxisymmetric magnetic modes,
nonaxisymmetric structures as a manifestation of a relic magnetic
field in the solar core, nonaxisymmetric solar hydrodynamics and
nonlinear instabilities that lack axial symmetry. We conclude that
these mechanisms all provide ways to explain the phenomenology,
provided the stroboscopic interpretation is accepted. Of course, a
quantitative explanation in the framework of any scenario requires
ultimately a detailed numerical simulation. The interpretation of
the available observations as a true differential rotation appears to
provide a much more severe challenge for theorists. We are unable to
suggest a plausible mechanism of this kind; however we can not exclude
in principle such an explanation. We relate the phenomenon of solar
active longitudes to the information available concerning stellar
active longitudes, and also consider evidence from other tracers of
solar activity.

---------------------------------------------------------
Title: Large-scale Non-axisymmetric Magnetic Fields on the Sun and
Cool Stars
Authors: Berdyugina, S. V.
2005ASPC..346..159B Altcode:
The magnetic activity of the Sun is known to be asymmetric in both
North--South (N--S) and East--West (E--W) directions. While the
existence of the N--S asymmetry was largely accepted and confirmed
by numerous studies of various features of solar activity, the E--W
asymmetry was not so obvious on longer time scales. The modulation of
the activity with nearly the solar rotation period suggests however
for the existence of long-lived complexes of activity at preferred
longitudes. For instance, two preferred active longitudes in both
Southern and Northern hemispheres were found to be persistent at the
century time scale. The pattern and behaviour of the active longitudes
on the Sun was found to be similar to that on cool, rapidly rotating
stars with outer convective envelopes. This suggests that the magnetic
dynamo processes are similar in such stars. Also, this allows us to
overview the phenomenon of stellar magnetic activity and to study it
in detail on the Sun.

---------------------------------------------------------
Title: The molecular Zeeman effect and diagnostics of solar and
stellar magnetic fields. III. Theoretical spectral patterns in the
Paschen-Back regime
Authors: Berdyugina, S. V.; Braun, P. A.; Fluri, D. M.; Solanki, S. K.
2005A&A...444..947B Altcode:
Many diatomic molecules present in the atmospheres of the Sun and cool
stars exhibit the Paschen-Back effect at field strengths typical of
sunspots and active cool stars. Here we present a complete theoretical
description of the molecular Paschen-Back efect in Hund's cases (a),
(b) and all cases intermediate to them. This description allows
us to compute the splitting of levels of any multiplicity and the
transitions between them. We also introduce a generalized description
of the effective magnetic Landé factor applicable not just in the
Zeeman regime, but also in the Paschen-Back regime. We find that in
the regime of the partial Paschen-Back effect strongly asymmetric
Stokes profiles are produced, whose strengths and asymmetries depend
sensitively on the magnetic field. In the regime of the complete
Paschen-Back effect the profiles become symmetric again (although
they may be strongly shifted). The strength of the forbidden and
satellite transitions increases rapidly with field strength in the
partial Paschen-Back regime, while the strength of the main branch
transitions decreases. These signatures hold promise to form the basis
of new diagnostics of solar and stellar magnetic fields.

---------------------------------------------------------
Title: Starspots: A Key to the Stellar Dynamo
Authors: Berdyugina, Svetlana V.
2005LRSP....2....8B Altcode:
Magnetic activity similar to that of the Sun is observed on a variety
of cool stars with external convection envelopes. Stellar rotation
coupled with convective motions generate strong magnetic fields in
the stellar interior and produce a multitude of magnetic phenomena
including starspots in the photosphere, chromospheric plages,
coronal loops, UV, X-ray, and radio emission and flares. Here I
review the phenomenon of starspots on different types of cool stars,
observational tools and diagnostic techniques for studying starspots
as well as starspot properties including their temperatures, areas,
magnetic field strengths, lifetimes, active latitudes and longitudes,
etc. Evolution of starspots on various time scales allows us to
investigate stellar differential rotation, activity cycles, and
global magnetic fields. Together these constitute the basis for
our understanding of stellar and solar dynamos and provide valuable
constraints for theoretical models.

---------------------------------------------------------
Title: A Sun in the Spectroscopic Binary IM Pegasi, the Guide Star
for the Gravity Probe B Mission
Authors: Marsden, S. C.; Berdyugina, S. V.; Donati, J. -F.; Eaton,
J. A.; Williamson, M. H.; Ilyin, I.; Fischer, D. A.; Muñoz, M.;
Isaacson, H.; Ratner, M. I.; Semel, M.; Petit, P.; Carter, B. D.
2005ApJ...634L.173M Altcode:
We present the first detection of the secondary of the spectroscopic
binary system IM Pegasi (HR 8703), the guide star for the NASA-Stanford
relativity gyroscope mission Gravity Probe B. In support of this
mission, high-resolution echelle spectra of IM Peg have been obtained
on an almost nightly basis. Applying the technique of least-squares
deconvolution, we achieve very high signal-to-noise ratio line profiles
and detect the orbit of the secondary of the system. Combining almost
700 new radial velocity measurements of both the primary and secondary
of the system with previous measurements, we derive improved orbital
parameters of the IM Peg system. Using these estimates along with
the previously determined range of orbital inclination angles for
the system, we find that the primary of IM Peg is a giant of mass
1.8+/-0.2 Msolar, while the secondary is a dwarf of mass
1.0+/-0.1 Msolar.

---------------------------------------------------------
Title: Interpretation of Solar and Stellar Activity in terms of
Dynamo Modes
Authors: Fluri, D. M.; Berdyugina, S. V.
2005ASPC..346..167F Altcode:
The magnetic activity on active, cool stars and on the Sun is spatially
organized on large scales and exhibits cyclic behavior on various
time scales. In particular, the biggest active regions tend to appear
mainly at two preferred longitudes on opposite sides. Therefore,
a physical mechanism has to exist that breaks the axial symmetry
of the global magnetic field. This implies that in addition to the
axisymmetric dipole a non-axisymmetric dynamo mode should be excited
in the Sun. We discuss possible dynamo mode configurations that can
explain the patterns observed both on stars and the Sun.

---------------------------------------------------------
Title: Preferred sunspot longitudes: non-axisymmetry and differential
rotation
Authors: Usoskin, I. G.; Berdyugina, S. V.; Poutanen, J.
2005A&A...441..347U Altcode: 2005astro.ph..8422U
As recently found, the distribution of sunspots is non-axisymmetric
and spot group formation implies the existence of two persistent
active longitudes separated by 180°. Here we quantitatively study the
non-axisymmetry of sunspot occurrence. In a dynamic reference frame
inferred from the differential rotation law, the raw sunspot data
show a clear clustering around the persistent active longitudes. The
differential rotation describing the dynamic frame is quantified
in terms of the equatorial angular velocity and the differential
rotation rate, which appear to be significantly different from those
for individual sunspots. This implies that the active longitudes are
not linked to the depth of sunspot anchoring. In order to quantify
the observed effect, we introduce a measure of the non-axisymmetry of
the sunspot distribution. The non-axisymmetric component is found to
be highly significant, and the ratio of its strength to that of the
axisymmetric one is roughly 1:10. This provides additional constraints
for solar dynamo models.

---------------------------------------------------------
Title: Spots on EK Draconis. Active longitudes and cycles from
long-term photometry
Authors: Järvinen, S. P.; Berdyugina, S. V.; Strassmeier, K. G.
2005A&A...440..735J Altcode:
We analyse photometric observations of the young active star EK Dra,
altogether about 21 years. Similar to the ZAMS stars LQ Hya and AB
Dor, EK Dra shows long-lived, non-axisymmetric spot distribution with
active longitudes on opposite hemispheres. At least two activity
cycle can be found from the data. The first cycle originates from
repeated switches of the activity between two active longitudes in
about (2-2.25)-year intervals, resulting in a cycle of about (4-4.5)
years. The second cycle is of the order of 10.5 years and comes from
migration of the active longitudes. Our data cover two consecutive
cycles. The periodicity is also present in the maximum, the mean and
the minimum stellar brightness. Additionally, there is a long-term
trend. If we combine our data with the Sonneberg plate measurements, we
can conclude that the overall brightness of EK Dra has been continuously
decreasing at least for the last 45 years. A comparison with current
sunspot activity reveals many similarities between the Sun and EK Dra.

---------------------------------------------------------
Title: Evolution and rotation of large-scale photospheric magnetic
fields of the Sun during cycles 21-23. Periodicities, north-south
asymmetries and r-mode signatures
Authors: Knaack, R.; Stenflo, J. O.; Berdyugina, S. V.
2005A&A...438.1067K Altcode:
We present the results of an extensive time series analysis of
longitudinally-averaged synoptic maps, recorded at the National Solar
Observatory (NSO/Kitt Peak) from 1975 to 2003, and provide evidence
for a multitude of quasi-periodic oscillations in the photospheric
magnetic field of the Sun. In the low frequency range, we have located
the sources of the 3.6~yr, 1.8~yr, and 1.5~yr periodicities that
were previously detected in the north-south asymmetry of the unsigned
photospheric flux (Knaack et al. 2004, A&amp;A, 418, L17). In addition,
quasi-periodicities around 2.6~yr and 1.3~yr have been found. The
1.3~yr period is most likely related to large-scale magnetic surges
toward the poles and appeared in both hemispheres at intermediate
latitudes ~30°-55° during the maxima of all three cycles 21-23,
being particularly pronounced during cycle 22. Periods near 1.3~yr
have recently been reported in the rotation rate at the base of
the convection zone (Howe et al. 2000, Science, 287, 2456), in the
interplanetary magnetic field and geomagnetic activity (Lockwood 2001,
J. Geophys. Res., 106, 16021) and in sunspot data (Krivova &amp; Solanki
2002, A&amp;A, 394, 701). In the intermediate frequency range, we have
found a series of quasi-periodicities of 349-307~d, 282±4~d, 249-232~d,
222-209~d, 177±2~d, 158-151~d, 129-124~d and 103-100~d, which are in
good agreement with period estimates for Rossby-type waves and occurred
predominantly in the southern hemisphere. We provide evidence that
the best known of these periodicities, the Rieger period around 155~d,
appeared in the magnetic flux not only during cycle 21 but also during
cycle 22, likely even during cycle 23. The high frequency range, which
covers the solar rotation periods, shows a dominant (synodic) 28.1±
0.1~d periodicity in the southern hemisphere during cycles 21 and 22. A
periodicity around 25.0-25.5~d occurred in the south during all three
cycles. The large-scale magnetic field of the northern hemisphere
showed dominant rotation periods at 26.9±0.1~d during cycle 21,
at 28.3-29.0~d during cycle 22 and at 26.4±0.1~d during cycle 23.

---------------------------------------------------------
Title: VizieR Online Data Catalog: V light curves of EK Dra
(Jaervinen+, 2005)
Authors: Jaervinen, S. P.; Berdyugina, S. V.; Strassmeier, K. G.
2005yCat..34400735J Altcode:
We analyse photometric observations of the young active dwarf EK Dra,
spanning altogether 21 years, and including previously unpublished
data. The data in Table 2 was observed at the Fairbourn Observatory
in southern Arizona using Amadeus, a 0.75m automatic photoelectric
telescope (APT) of the University of Vienna. Amadeus is optimised
for red wavelengths with an EMI-9828 tube and Johnson-Cousins
V(RI)C filters. Differential V magnitudes are variable
(EK Dra) - comparison (HD 129390) and check (HD 129798) - comparison
(HD 129390). HD 129390 Vmag=7.567 (1 data file).

---------------------------------------------------------
Title: Spot activity cycles and flip-flops on young solar analogs
Authors: Berdyugina, S. V.; Järvinen, S. P.
2005AN....326..283B Altcode:
We discuss activity phenomena observed in the spot distribution on
young single solar-type stars LQ Hya, AB Dor and EK Dra. These include
cyclic variations of the mean activity level, differential rotation,
persistent active longitudes separated by 180 ° and flip-flop cycles. A
comparison with the sunspot activity reveals many similarities between
the Sun and the young solar analogs. Our results confirm the presence
of cyclic activity in very young dwarfs and allow for studying evolution
of the stellar magnetic activity during the main-sequence stage.

---------------------------------------------------------
Title: Surface differential rotation on FK Com
Authors: Korhonen, H.; Berdyugina, S. V.; Tuominen, I.
2005ESASP.560..719K Altcode: 2005csss...13..719K
No abstract at ADS

---------------------------------------------------------
Title: Magnetic activity in the young solar analog AB Dor. Active
longitudes and cycles from long-term photometry.
Authors: Järvinen, S. P.; Berdyugina, S. V.; Tuominen, I.; Cutispoto,
G.; Bos, M.
2005A&A...432..657J Altcode:
We analyse photometric observations of the young active dwarf AB Dor,
spanning more than 20 years. Similar to the young solar analog LQ
Hya, AB Dor shows long-lived, nonaxisymmetric spot distribution-
active longitudes in opposite hemispheres. The active longitudes
migrate nonlinearly in the fixed reference frame, because of the
differential rotation and changes of the mean spot latitudes. At least
two activity cycles are found in the data. One cycle originates from
repeating switches of the activity between the two active longitudes
in about (2-3)-year intervals. This results in the flip-flop cycle of
about 5.5 years, which includes two consecutive switches. The 5.5-yr
cycle also modulates variations of the minimum stellar brightness and
the peak-to-peak amplitude, that suggests a periodic redistribution
of the spot area between the opposite longitudes and supports the
reality of the flip-flop cycle. The other cycle is clearly seen
in variations of the mean and maximum stellar brightness on the
time-scale of 20 years and is reminiscent of the 11-year sunspot
cycle. Tables 2 and 3 are only available in electronic form at
the CDS via anonymous ftp to cdsarc.u-strasbg.fr (130.79.128.5) or
via http://cdsweb.u-strasbg.fr/cgi-bin/qcat?J/A+A/432/657

---------------------------------------------------------
Title: G-band spectral synthesis and diagnostics of simulated solar
magneto-convection
Authors: Shelyag, S.; Schüssler, M.; Solanki, S. K.; Berdyugina,
S. V.; Vögler, A.
2004A&A...427..335S Altcode:
Realistic simulations of radiative magneto-convection in the solar
(sub)photosphere are used for a spectral synthesis of Fraunhofer's G
band, which is dominated by spectral lines from the CH molecule. It
is found that the spatial pattern of integrated G-band brightness
closely matches the spatial structure of magnetic flux concentrations
in the convective downflow regions. The brightness contrast is mainly
caused by the weakening of CH lines due to the reduced CH abundance
and the resulting shift of the optical depth scale in the hot and
tenuous magnetic flux concentrations. Various properties of the
synthetic brightness images agree well with G-band observations. These
results lends credit to the observational usage of G-band bright
features as proxies for magnetic flux concentrations in the solar
photosphere. However, the converse is only correct in a limited sense:
only a fraction of the magnetic flux concentrations turn out to be
bright in the G band.

---------------------------------------------------------
Title: VizieR Online Data Catalog: UBV(RI)c photometry of AB Dor
(Jaervinen+, 2005)
Authors: Jaervinen, S. P.; Berdyugina, S. V.; Tuominen, I.; Cutispoto,
G.; Bos, M.
2004yCat..34320657J Altcode:
We analyse photometric observations of the young active dwarf
AB Dor, spanning more than 20 years, and including previously
unpublished data. The data in table2.dat was observed at Molehill
Astronomical Observatory (Auckland, New Zealand) by M. Bos using a
200mm f10 Schmidt-Cassegrain Telescope with standard Johnson B and V
filters. The data in table3.dat was observed by G. Cutispoto using the
0.5m telescope at the European Southern Observatory (ESO, La Silla,
Chile) and the 0.5~m SAAO telescope (Sutherland, South Africa) with
UBV(RI)c filters. (2 data files).

---------------------------------------------------------
Title: Flip-Flops as Observational Signatures of Different Dynamo
Modes in Cool Stars
Authors: Fluri, D. M.; Berdyugina, S. V.
2004SoPh..224..153F Altcode: 2005SoPh..224..153F
Cool, rapidly rotating stars exhibit enhanced magnetic activity
with cyclic behavior on various time scales. In particular, the
longitude of the dominant activity region switches quasi-periodically
by 180∘, which is known as the "flip-flop" phenomenon. In
the present paper we introduce a new approach for the interpretation of
stellar cycles based on light curve modeling with dipole and quadrupole
dynamo modes. We discuss the observational signatures of different
combinations of the dynamo modes. The proposed simple model is able
to reproduce the basic properties of long-term photometric behavior
of active stars and allows us to study different mechanisms resulting
in flip-flops.

---------------------------------------------------------
Title: Non-Axisymmetric Magnetic Fields and Flip-Flops on the Sun
and Cool Stars
Authors: Berdyugina, S. V.
2004SoPh..224..123B Altcode: 2005SoPh..224..123B
The modulation of solar activity closely follows the solar rotation
period suggesting the existence of long-lived active regions at
preferred longitudes. For instance, two preferred active longitudes
in both southern and northern hemispheres are found to be persistent
at the century time scale. These regions migrate with differential
rotation and periodically alternate their activity levels showing
a flip-flop cycle. The pattern and behaviour of active longitudes
on the Sun is similar to that on cool, rapidly rotating stars with
outer convective envelopes. This suggests that the magnetic dynamo,
including non-axisymmetric magnetic fields and flip-flop cycles, is
also similar in these stars. This allows us to overview the phenomenon
of stellar magnetic activity and to study it in detail on the Sun.

---------------------------------------------------------
Title: Thermal-magnetic relation in a sunspot and a map of its
Wilson depression
Authors: Mathew, S. K.; Solanki, S. K.; Lagg, A.; Collados, M.;
Borrero, J. M.; Berdyugina, S.
2004A&A...422..693M Altcode:
We present relations between thermal and magnetic quantities in a
simple, isolated sunspot, as deduced from the inversion of 1.56 μm
spectropolarimetric data. We used a combination of two infrared Fe I
lines at 15 648.5 Å and 15 652.8 Å/ in the inversions. Due to the
high Zeeman sensitivity of these lines, we can study this relationship
in the entire sunspot. The relevant parameters were derived both as a
function of location within the sunspot and of height in the atmosphere
using an inversion technique based on response functions. In this paper
we relate the magnetic vector with temperature. We find a non-linear
relationship between the various components of the magnetic vector and
temperature, which confirm the results from earlier investigations. We
also computed the Wilson depression and the plasma β for the observed
sunspot and compare our results with earlier findings.

---------------------------------------------------------
Title: Mapping non-radial pulsation using surface imaging techniques
Authors: Berdyugina, S. V.; Korhonen, H.; Telting, J. H.; Schrijvers,
C.
2004CoAst.145...40B Altcode: 2004CoAst.145...38B
We apply stellar surface imaging techniques for studying non-radial
pulsations. Stellar surface imaging is based on inversions of time
series of variable spectral line profiles without making assumptions
on the specific shape of the pulsations. The inversion results in an
image of the stellar surface in which the sectoral and tesseral modes
can in many cases be distinguished, and the pulsational degree l and
the azimuthal order |m| can be determined.

---------------------------------------------------------
Title: Spots on FK Com: active longitudes and "flip-flops"
Authors: Korhonen, H.; Berdyugina, S. V.; Tuominen, I.
2004AN....325..402K Altcode:
We have earlier investigated the surface structures of a late-type,
single, giant FK Com for the years 1994-1998 using Doppler
imaging. These surface temperature maps revealed long-lived active
regions at high latitudes. Long-term photometric observations also
show that these active regions tend to occur at two permanent active
longitudes which are 180 degrees apart from each other, and that
the activity switches the longitude with an average period of about
3 years (the "flip-flop" phenomenon). In this work we present new
Doppler maps of FK Com obtained 1998-2003 and light-curve maps obtained
2002-2003. These new maps are investigated together with the earlier
temperature maps and light-curve maps, with an aim of further studying
the active longitudes, "flip-flop" phenomenon and surface differential
rotation on FK Com.

---------------------------------------------------------
Title: Magnetic cycles and rotation in active late-type stars
Authors: Tuominen, I.; Berdyugina, S. V.; Korpi, M. J.
2004IAUS..215..289T Altcode:
No abstract at ADS

---------------------------------------------------------
Title: Evidence for the Hanle effect in molecular lines
Authors: Berdyugina, S. V.; Fluri, D. M.
2004A&A...417..775B Altcode:
In many wavelength regions molecular lines dominate the second solar
spectrum that results from coherent scattering. Scattering polarization
is modified by magnetic fields via the Hanle effect. This allows us to
explore the magnetic field regime with weak field strengths and mixed
polarities, which is not seen with the Zeeman effect and thus contains
complementary information. Molecular lines are particularly well
suited to diagnose such turbulent fields because they exhibit a broad
range of magnetic sensitivities within narrow spectral regions. Thus,
it is possible to employ the technique of the differential Hanle
effect, i.e. to obtain field strengths by observing polarization
ratios in various lines. We have identified one R- and one P-triplet
of C2 at 5140 Å and 5141 Å, respectively, that satisfy
all conditions to be used in the differential Hanle effect. Based
on these lines we have developed a model that can diagnose turbulent
magnetic fields using the Hanle effect. The tool is sensitive over a
broad range of magnetic field strengths from a few Gauss up to several
hundred Gauss. This tool has allowed us to find a significant Hanle
depolarization of C2 lines in quiet Sun observations,
which corresponds to a magnetic field strength of 15±3 G.

---------------------------------------------------------
Title: Periodic oscillations in the north-south asymmetry of the
solar magnetic field
Authors: Knaack, R.; Stenflo, J. O.; Berdyugina, S. V.
2004A&A...418L..17K Altcode:
We report on significant periodic variations of the magnetic activity
between the north and south hemisphere of the Sun. For this purpose,
we have investigated the north-south asymmetry of two solar data
sets, namely the Kitt Peak synoptic Carrington rotation maps of the
photospheric magnetic field (1975-2003) and monthly averaged sunspot
areas (1874-2003). Using Fourier and wavelet analysis, we have found
a regular pattern of pronounced oscillations with periods of 1.50
± 0.04 yr, 1.79 ± 0.06 yr and 3.6 ± 0.3 yr in the magnetic flux
asymmetry. The former two periods are related to a process which leads
to a gradual shift in the excess magnetic flux from north to south or
vice versa. Additional periods of 43.4 ± 7.1 yr (twice the magnetic
cycle) and 320-329 days were detected in the sunspot asymmetry.

---------------------------------------------------------
Title: Tomography of stellar non-radial pulsations
Authors: Berdyugina, S. V.
2004AN....325..237B Altcode:
The stellar surface imaging technique is used for studying stellar
non-radial pulsations on the basis of inversions of time series of
variable line profiles without making assumptions on the specific shape
of the pulsations. The inversion results in an image of the stellar
surface in which sectoral and tesseral modes can be distinguished in
many cases and the pulsational degree and the azimuthal order can be
determined. The capability of the technique is studied with simulated
data. Then, the surface imaging technique is applied to high-resolution
spectra of the rapidly rotating Beta Cep-type star ω1 Sco,
which shows strong line-profile variations. Stellar surface imaging
is concluded to be a useful technique for pulsation-mode identification.

---------------------------------------------------------
Title: Persistent active longitudes in the surface magnetic activity
on the Sun
Authors: Berdyugina, S.; Usoskin, I. G.
2004cosp...35.1722B Altcode: 2004cosp.meet.1722B
A novel analysis of sunspot data for the past 120 years reveals
that sunspots in both northern and southern hemispheres are formed
preferably in two persistent active longitudes separated by 180°. In
the Carrington reference frame, the active longitudes continuously
migrate in phase with respect to the Carrington meridian. The
migration of the active longitudes is determined by changes of the mean
latitude of sunspots and the surface differential rotation. The two
active longitudes periodically alternate being the dominant region,
similar to the 'flip-flop' phenomenon known in starspot activity. The
period of the oscillations is about 3.8 and 3.65 years in the northern
and southern hemispheres, respectively. The difference between the
periods is significant and can be related to the known north-south
asymmetry in the solar magnetic activity. Similar results are obtained
from the analysis of large-scale surface magnetic fields using solar
magnetic synoptic maps, for the cycles 20 to 23. The persistent active
longitudes 180° apart, which migrate with the surface differential
rotation and alternate their activity level with the 3.7-yr cycle, are
found separately in positive and negative polarity fields. Our results
provide new observational constraints for current solar dynamo models
and strengthen the solar paradigm for magnetic activity on cool stars.

---------------------------------------------------------
Title: First Evidence for the Hanle Effect in Molecular Lines
Authors: Fluri, D. M.; Berdyugina, S. V.
2004IAUS..219..674F Altcode: 2003IAUS..219E.189F
Magnetic fields influence and drive the activity in stellar
atmospheres. In the optical they can be measured via Zeeman and Hanle
effect which are relevant in different magnetic field regimes and
thus complement each other. The Zeeman effect is sensitive to the net
magnetic flux in the resolution element whereas the Hanle effect allows
to detect weak directed or entangled magnetic fields. On the Sun Hanle
effect is observed in prominences in strong chromospheric lines as well
as in many photospheric lines. Especially in the photosphere Hanle
effect observations have led to a new paradigm of the magnetic field
structure. There 99 percent of the volume are filled by relatively weak
entangled fields of the order of a few Gauss to which Zeeman effect
observations are pracitcally blind but which are clearly detected
by the Hanle effect. We find that molecular lines are particularly
well suited for magnetic field diagnostics with the Hanle effect. In
molecular bands closeby lines with different sensitivities to the
magnetic field form under very similar conditions and can be observed
in a single image. Therefore many potential instrumental and physical
sources of errors can be eliminated.

---------------------------------------------------------
Title: Active Longitudes and Magnetic Cycles on AB Dor
Authors: Berdyugina, S. V.; Järvinen, S. P.; Tuominen, I.
2004IAUS..219..848B Altcode: 2003IAUS..219E.186B
We analyze photometric observations of the young active dwarf AB Dor
spanning almost 20 years. Similar to the young solar analogue LQ Hya
and the Sun AB Dor shows long-lived non-axisymmetric spot distribution
- active longitudes in opposite hemispheres. We find indications of
two activity cycles. One cycle originates from repeating switches of
the activity between the two active longitudes in about (2.5-3.5)-year
intervals. This results in the ""flip-flop"" cycle of 5-7 years which
includes two consecutive switches. The second cycle is seen in mean
brightness variations of the star on the time-scale 19-22 years and is
accompanied by migration of the active longitudes due to differential
rotation.

---------------------------------------------------------
Title: Magnetic Activity Cycles on the Sun and Stars
Authors: Usoskin, I. G.; Berdyugina, S.
2004cosp...35.1721U Altcode: 2004cosp.meet.1721U
Cycles of magnetic activity on the Sun and stars are manifestations
of a magnetic dynamo, which is one of the most interesting processes
in solar/stellar astrophysics. Evolution of solar magnetic cycles is
studied for several centuries including the nearly spotless Maunder
minimum and recent super-active cycles, thanks to tremendous work
of R. Wolf and his successors and later D. Hoyt and K. Schatten who
complied sunspot record series. Magnetic cycles in stars are studied
during few decades but they provide a large ensemble statistics
due to a large number of studied stars. Here we review most recent
achievements and findings in studies of solar/stellar magnetic cycles,
such as determinism and chaos in the cyclicity, cycles during active
phases and great minima, active longitudes and 'flip-flop' cycles,
occurrence of great minima and super-active periods.

---------------------------------------------------------
Title: The molecular Zeeman effect and diagnostics of solar and
stellar magnetic fields. II. Synthetic Stokes profiles in the
Zeeman regime
Authors: Berdyugina, S. V.; Solanki, S. K.; Frutiger, C.
2003A&A...412..513B Altcode:
Recent advances in the computation of the Zeeman splitting of
molecular lines have paved the way for their use as diagnostics
of solar and stellar magnetic fields. A systematic study of their
diagnostic capabilities had not been carried out so far, however. Here
we investigate how molecular lines can be used to deduce the magnetic
and thermal structure of sunspots, starspots and cool stars. First, we
briefly describe the Stokes radiative transfer of Zeeman-split molecular
lines. Then, we compute Stokes spectra of TiO, OH, CH and FeH lines and
investigate their diagnostic capabilities. We also compare the synthetic
profiles with observations. Spectra of TiO, OH and FeH are found to be
interesting diagnostics of sunspot magnetic fields. This is also true
for cool stars, where, however, the OH Stokes V profiles may require
very high S/N data to be reliably employed. Finally we investigate
the potential of various molecular bands for high-contrast imaging
of the solar surface. The violet CN and CH bands turn out to be most
promising for imaging the photosphere, the TiO bands are excellent for
imaging sunspot umbrae, while the UV OH band can be used for imaging
both the photosphere and sunspots.

---------------------------------------------------------
Title: Why Solar Magnetic Flux Concentrations Are Bright in Molecular
Bands
Authors: Schüssler, M.; Shelyag, S.; Berdyugina, S.; Vögler, A.;
Solanki, S. K.
2003ApJ...597L.173S Altcode:
Using realistic ab initio simulations of radiative magnetoconvection,
we show that the bright structures in images taken in the “G band,”
a spectral band dominated by lines of the CH molecule, precisely
outline small-scale concentrations of strong magnetic fields on the
visible solar surface. The brightening is caused by a depletion of CH
molecules in the hot and tenuous magnetic structures, thus confirming
the model of radiatively heated magnetic flux concentrations. These
results provide a firm basis for observational studies of the evolution
and dynamics of the small-scale solar magnetic field derived through
“proxy magnetometry” with G-band images.

---------------------------------------------------------
Title: Three dimensional structure of a regular sunspot from the
inversion of IR Stokes profiles
Authors: Mathew, S. K.; Lagg, A.; Solanki, S. K.; Collados, M.;
Borrero, J. M.; Berdyugina, S.; Krupp, N.; Woch, J.; Frutiger, C.
2003A&A...410..695M Altcode:
The magnetic, thermal and velocity structure of a regular sunspot,
observed close to solar disk center is presented. Spectropolarimetric
data obtained with the Tenerife Infrared Polarimeter (TIP) in two
infrared FeI lines at 15 648.5 Å and 15 652.8 Å are inverted
employing a technique based on response functions to retrieve the
atmospheric stratification at every point in the sunspot. In order
to improve the results for the umbra, profiles of Zeeman split OH
lines blending the FeI 15 652.8 Å are also consistently fit. Thus
we obtain maps of temperature, line-of-sight velocity, magnetic
field strength, inclination, and azimuth, as a function of both
location within the sunspot and height in the atmosphere. We present
these maps for an optical depth range between log tau5 =
0 and log tau5 = -1.5, where these lines provide accurate
results. We find decreasing magnetic field strength with increasing
height all over the sunspot, with a particularly large vertical field
gradient of ~ -4 G km-1 in the umbra. We also observe the
so called “spine” structures in the penumbra, i.e. extended radial
features with a stronger and more vertical magnetic field than the
surroundings. Also we found that the magnetic field zenith angle
increases with height. From the velocity map it is clear that the
Evershed flow avoids the spines and mostly concentrates in the more
inclined intervening field. The field inclination at a few locations
in the outer penumbra in lower layers goes beyond 90o. These
locations coincide with the strongest flows in the velocity map.

---------------------------------------------------------
Title: Molecular Lines as Diagnostics of Solar and Stellar Magnetic
Fields
Authors: Berdyugina, S. V.; Solanki, S. K.; Lagg, A.
2003csss...12..210B Altcode:
Thanks to recent advances in theory we can now calculate molecular
line profiles in the presence of magnetic fields with high accuracy,
both in the Zeeman and Paschen-Back regimes (Berdyugina et al. 2000;
Berdyugina &amp; Solanki 2001a). The synthetic Stokes profiles of
various molecular species (e.g. TiO, OH, MgH, CN, FeH) have been
compared with profiles observed in sunspots. The agreement between
the theory and observations is remarkable. For example, the mutually
opposite polarities of different OH lines are reproduced without
invoking any free parameters, except the magnetic field strength and
sunspot temperature. Introducing molecular lines into the inversion
of sunspot spectra leads to significant improvements in the deduced
magnetic field vector. Here we investigate how molecular lines can be
used to deduce magnetic parameters of cool stars. We find that such
lines are of great interest for measuring magnetic fields on cooler
stars and in starspots.

---------------------------------------------------------
Title: Surface imaging of stellar non-radial pulsations. I. Inversions
of simulated data
Authors: Berdyugina, S. V.; Telting, J. H.; Korhonen, H.
2003A&A...406..273B Altcode:
We investigate capability of the stellar surface imaging technique
for studying stellar non-radial pulsations on the basis of inversions
of time series of variable line profiles without making assumptions
on the specific shape of the pulsations. The inversion results in
an image of the stellar surface in which sectoral and tesseral modes
can be distinguished in many cases, and the pulsational degree l and
the azimuthal order |m| can be determined. We find that sectoral and
tesseral modes with l-|m|=2 (or any even number) can be successfully
restored under various conditions (different inclinations of the
rotational axis, surface temperature or velocity fluctuations due to
pulsations). Tesseral modes with l-|m|=1 (or any odd number) do not
show significant line profile variations at higher inclinations of
the rotational axis, and, thus, no information can be recovered from
line profiles. At lower inclinations, only the azimuthal order |m| of
such modes can be recovered. We conclude that stellar surface imaging
is a useful technique for pulsation-mode identification.

---------------------------------------------------------
Title: Surface imaging of stellar non-radial pulsations. II. The β
Cephei star ω1 Sco
Authors: Berdyugina, S. V.; Telting, J. H.; Korhonen, H.; Schrijvers,
C.
2003A&A...406..281B Altcode:
We apply the surface imaging technique to high-resolution spectra of
the rapidly rotating beta Cep-type star omega 1 Sco which
shows strong line-profile variations in the Si Iii lambda 4552, 4567,
4574 Å triplet. These variations have been interpreted in terms of
non-radial pulsations by Telting &amp; Schrijvers (1998). Their analysis
of the spectral time series with traditional Fourier transforms resulted
in one significant frequency, suggesting that the profile variations
are due to only one dominant pulsation mode. Here we apply a spectral
inversion technique to the same time series of the profiles. Assuming
only temperature fluctuations due to pulsations, we obtain an image of
the dominant pulsation mode. We estimate the pulsation degree from the
image, put constraints on the azimuthal number of the mode, and study
the latitudinal distribution of the pulsation pattern. In addition to
the known dominant mode we find traces of a second pulsation mode. Based on observations collected at ESO, La Silla.

---------------------------------------------------------
Title: Active longitudes in sunspot activity: Century scale
persistence
Authors: Berdyugina, S. V.; Usoskin, I. G.
2003A&A...405.1121B Altcode:
A novel analysis of sunspot group data for the past 120 years reveals
that sunspots in both northern and southern hemispheres are formed
preferably in two persistent active longitudes separated by 180°. In
the Carrington reference frame, the active longitudes continuously
migrate in phase with respect to the Carrington meridian with a variable
rate. They remain however a quasi-rigid structure. We find that the
migration of the active longitudes is determined by changes of the mean
latitude of sunspots and the differential rotation. The differential
rotation rate calculated from the migration is in agreement with
SOHO/MDI measurements. The two active longitude periodically alternate
being the dominant region, similar to the “flip-flop” phenomenon
known in starspot activity. The period of the oscillations is 3.8
and 3.65 years in the north and south, respectively. The difference
between the periods is significant and can be related to the known
north-south asymmetry in the solar magnetic activity. Our results
provide new observational constraints for current solar dynamo models
and strengthen the solar paradigm for magnetic activity on cool stars.

---------------------------------------------------------
Title: The Observation of Sunspot Light-Bridge Structure and Dynamics
Authors: Berger, T. E.; Berdyugina, S. V.
2003ApJ...589L.117B Altcode:
We present very high resolution multiwavelength images of a sunspot
light bridge in NOAA Active Region 10132 taken at the Swedish 1
m Solar Telescope on La Palma on 2002 September 25. The adaptive
optics-corrected images resolve 100 km scale bright grains on either
side of an approximately 380 km dark lane in the center of the
bridge. Movies of the data show the grains in a steady unidirectional
flow with an average speed of 900 m s-1 along the entire
length of the bridge. Overturning motions are seen in the larger grains,
suggesting a convective origin for these structures. Simultaneous 160
nm ultraviolet images from the Transition Region and Coronal Explorer
(TRACE) satellite show a constant brightness enhancement over the light
bridge, implying a steady chromospheric heat source. TRACE 160 nm movies
do not resolve the unidirectional flow; instead, they suggest that a
horizontal oscillatory motion exists in the chromosphere of the light
bridge. A C2.0 flare at 16:00 UT, one ribbon of which occurs directly
along the light bridge, indicates a high level of magnetic stress
and impulsive dissipation associated with the observed light-bridge
dynamics.

---------------------------------------------------------
Title: New Molecular Indicators of Sunspot Magnetic Fields: Infrared
OH Lines
Authors: Berdyugina, S. V.; Solanki, S. K.; Lagg, A.
2003ASPC..286..299B Altcode: 2003ctmf.conf..299B
No abstract at ADS

---------------------------------------------------------
Title: Structure of a simple sunspot from the inversion of IR
spectral data
Authors: Mathew, S. K.; Solanki, S. K.; Lagg, A.; Collados, M.;
Berdyugina, S. V.; Frutiger, C.; Krupp, N.; Woch, J.
2003AN....324..388M Altcode:
Analysis of spectral data of two neighboring infrared lines, Fe i
15648.5 Å (g = 3) and Fe i 15652.9 Å (g_eff = 1.53) are carried out
for a simple sunspot when it was near the solar disk center (mu = 0.92),
to understand the basic structure of sunspot magnetic field. Inversions
of Stokes profiles are carried out to derive different atmospheric
parameters both as a function of location within the sunspot and height
in the atmosphere. As a result of the inversion we have obtained maps
of magnetic field strength, temperature, line-of-sight velocity, field
inclination and azimuth for different optical depth layers between log
(tau_ {5}) = 0 and log (tau_ {5}) = -2.0 . In this paper we present
few results from our inversion for a layer averaged between log (tau_
{5}) from 0.0 to -0.5.

---------------------------------------------------------
Title: On the Longitudinal Spot Distribution on FK Com in 1998
Authors: Korhonen, H.; Berdyugina, S. V.; Tuominen, I.
2003IAUS..210P.D23K Altcode:
No abstract at ADS

---------------------------------------------------------
Title: Molecules as Diagnostics of Solar and Stellar Magnetic Fields
Authors: Berdyugina, S. V.; Solanki, S. K.; Stenflo, J. O.
2003ASPC..307..181B Altcode:
No abstract at ADS

---------------------------------------------------------
Title: Tomography of Stellar Non-Radial Pulsations
Authors: Berdyugina, Svetlana V.
2003IAUJD...9E..29B Altcode:
The stellar surface imaging technique is used for studying stellar
non-radial pulsations on the basis of inversions of time series of
variable line profiles without making assumptions on the specific shape
of the pulsations. The inversion results in an image of the stellar
surface in which sectoral and tesseral modes can be distinguished in
many cases and the pulsational degree and the azimuthal order can be
determined. The capability of the technique is studied with simulated
data.Then the surface imaging technique is applied to high-resolution
spectra of the rapidly rotating Beta Cep-type star omega1 Sco
which shows strong line-profile variations. Assuming only temperature
fluctuations due to pulsations we obtain an image of the dominant
pulsation mode. We estimate the pulsation degree from the image
put constraints on the azimuthal number of the mode and study the
latitudinal distribution of the pulsation pattern. In addition to the
known dominant mode we find traces of a second pulsation mode. We
conclude that stellar surface imaging is a useful technique for
pulsation-mode identification.

---------------------------------------------------------
Title: VizieR Online Data Catalog: UBV photometry of LQ Hya
(Berdyugina+, 2002)
Authors: Berdyugina, S. V.; Pelt, J.; Tuominen, I.
2002yCat..33940505B Altcode:
Photometric observations of LQ Hya (HD 82558) obtained in 1995-2001
with the Phoenix 10 robotic telescope (Arizona) in the UBV bands with
HD 82447 as the comparison star. (1 data file).

---------------------------------------------------------
Title: Magnetic activity in the young solar analog LQ
Hydrae. I. Active longitudes and cycles
Authors: Berdyugina, S. V.; Pelt, J.; Tuominen, I.
2002A&A...394..505B Altcode:
We present the first evidence that a single active dwarf of solar
type can show a long-lived, nonaxisymmetric spot distribution -
active longitudes on opposite hemispheres, similar to evolved,
rapidly rotating RS CVn-type binary stars. We analyse new as well as
published photometric observations of the young active dwarf LQ Hya,
spanning almost 20 years. We find that activity of the star has three
activity cycles: a 5.2-yr “flip-flop” cycle, a 7.7-yr period in
the amplitude modulation of the brightness and an approximately 15-yr
period in variations of the mean brightness. The two shorter cycles
are related to the alternating active longitudes and are similar
to cycles observed in RS CVn-type stars. The 15-yr cycle reflects
periodic changes of the mean spottedness of the star and resembles
the solar 11-year cycle. The spot rotation period (about 1.6 days)
changes during the 15-yr cycle, indicating the presence of small
differential rotation. The lengths of the three cycles are related
as 3:2:1, with the repetition of the spot configuration after 15
years. We discuss the possibility that the observed spot cycles
represent two different magnetic dynamo modes operating in LQ Hya:
an axisymmetric mode, as in the Sun, and a nonaxisymmetric higher
order mode with two cycles in spot patterns. Our results suggest that
young stars exhibit their cycles in spot distribution, as seen in LQ
Hya. This is in contrast to the conclusion based on the analysis of
Ca Ii H&amp;K emission from plages. The results suggest also that the
Vaughan-Preston gap represents a transition from a multiple-mode dynamo
to a single-mode dynamo. Table 2 is only available in electronic form
at the CDS via anonymous ftp to cdsarc.u-strasbg.fr (130.79.128.5)
or via http://cdsweb.u-strasbg.fr/cgi-bin/qcat?J/A+A/394/505

---------------------------------------------------------
Title: Thermal-magnetic relation of a sunspot as inferred from the
inversion of 1.5 μm spectral data
Authors: Mathew, S. K.; Solanki, S. K.; Lagg, A.; Krupp, N.; Woch,
J.; Collados, M.; Berdyugina, S.; Frutiger, C.
2002ESASP.505..501M Altcode: 2002IAUCo.188..501M; 2002solm.conf..501M
We present the thermal-magnetic relation in a simple, isolated sunspot
deduced from the inversion of 1.56 μm spectropolarimetric data. Due to
the high Zeeman sensitivity of the g = 3, Fe I 1.5648 μm line, we can
study this relationship in the entire sunspot. An inversion technique
based on response functions is used to derive various parameters,
both as a function of location within the sunspot and of height in the
atmosphere. In this paper we attempt to relate field strength, vertical
and radial field components and the field inclination with temperature.

---------------------------------------------------------
Title: VizieR Online Data Catalog: Study of FK Comae
Berenices. IV. (Korhonen+ 2002)
Authors: Korhonen, H.; Berdyugina, S. V.; Tuominen, I.
2002yCat..33900179K Altcode:
Doppler imaging techniques have earlier been used to study the starspots
and their evolution over a four year period in a single, late-type star
FK Com. In the present work we publish new photometric observations of
FK Com for the year 2001 and analyse them together with the previously
published photometry obtained since 1966. The observations for 2001
have been carried out at the Phoenix 10 automatic photometric telescope
in Arizona, USA. Observations contain measurements at the Johnson U,
B and V bands. The observations are differential photometry in respect
to the primary comparison star HD 117567. In table1, 99.000 means that
no observations were available at that time at that band or that the
error in the magnitude was larger than 0.02. (1 data file).

---------------------------------------------------------
Title: Starspot cycles from Doppler imaging and photometric time
series as nonlinear dynamo
Authors: Tuominen, I.; Berdyugina, S. V.; Korpi, M. J.
2002AN....323..367T Altcode:
In this paper we present evidence of strongly nonaxisymmetric spot
distributions in magnetically very active late-type stars, with a
special cyclic behaviour (the "flip-flop" effect), which is basically
different from the cycles in solar-like older and less active stars. The
analysis is based both on high-resolution spectroscopy with Doppler
imaging methods and on long photometric time series. Theoretical
implications of these results are discussed from the point of view of
nonlinear mean-field dynamo theory.

---------------------------------------------------------
Title: Sunspot and starspot interiors as seen from molecular lines
Authors: Berdyugina, S. V.
2002AN....323..192B Altcode:
Molecular lines represent powerful diagnostics of stellar and solar
magnetic fields. They are currently successfully used for studying the
thermal and magnetic structure of sunspots. The present calculations
show how molecular lines can been used for testing stellar surface
images and measuring magnetic fields inside spatially unresolved
starspots. Particularly, observational capabilities for the registration
of the Stokes V signal from starspots in the TiO band at 7055Å are
estimated.

---------------------------------------------------------
Title: Study of FK Comae Berenices. IV. Active longitudes and the
“flip-flop” phenomenon
Authors: Korhonen, H.; Berdyugina, S. V.; Tuominen, I.
2002A&A...390..179K Altcode:
Doppler imaging techniques have earlier been used to study the starspots
and their evolution over a four year period in a single, late-type star
FK Com. In the present work we publish new photometric observations of
FK Com for the year 2001 and analyse them together with the previously
published photometry obtained since 1966. These observations enable
us to study the spot configuration on the stellar surface over much
longer time period than the Doppler imaging alone permits, and so to
look for possible activity cycles. The longitudinal spot configuration
is recovered from the spot filling factor maps obtained with light
curve inversion method. From the maps it is clear that the shape
of the light curve is usually caused by one active region, which is
often extended, and only occasionally by two regions. The spots tend
to occur at two active longitudes which are 180 degr apart. These
active longitudes are periodically active, i.e. the dominant part
of the spot activity abruptly changes the longitude after about
3 years, indicating the “flip-flop” event. The full activity
cycle is estimated to be 6.4 years. There is also clear evidence
for migration of the active longitudes with at least three different
rates. These rates correspond to the rotational periods of 2fd40038 +/-
0fd00009 (for the years 1979-1993), 2fd4030 +/- 0fd0003 (1994-1997)
and 2fd3960 +/- 0fd0004 (1997-2001). These periods are confirmed by
using a more traditional time series analysis. The different migration
rates of the active longitudes can be explained by weak solar-type
differential rotation. Based on the observations obtained at Phoenix
10, Arizona, USA; Wolfgang and Amadeus, Arizona, USA; Mount Maidanak
Observatory, Uzbekistan; La Palma KVA 0.6 m Cassegrain telescope,
La Palma, Spain. Table 1 is only available in electronic form at the
CDS via anonymous ftp to cdsarc.u-strasbg.fr (130.79.128.5) or via
http://cdsweb-u-strasbg.fr/cgi-bin/qcat?J/A+A/390/179

---------------------------------------------------------
Title: Molecular line scattering and magnetic field effects:
Resolution of an enigma
Authors: Berdyugina, S. V.; Stenflo, J. O.; Gandorfer, A.
2002A&A...388.1062B Altcode:
The linearly polarized solar spectrum that is produced by coherent
scattering processes (also called “the second solar spectrum”) is full
of polarizing features due to molecular transitions, in particular from
MgH and C2. Their greatly different behavior in comparison
with the observed polarization from atomic transitions has presented
us with a new enigma: While the scattering polarization in atomic lines
is very sensitive to magnetic fields via the Hanle effect and therefore
exhibits polarization signatures that vary both spatially and with the
solar cycle, the molecular polarization appears to be immune to the
influence of magnetic fields. To clarify these issues we here develop
a theoretical foundation for polarized molecular scattering, which
can serve as a general tool for interpretations of the structures in
the second solar spectrum. Intrinsic polarizabilities, line strengths,
and effective Landé factors for the different transitions of the P,
Q, and R branches of MgH and C2 are calculated. While the
intrinsic polarizabilities remain significant, the effective Landé
factors are close to zero for the majority of the lines, in contrast
to the behavior of atomic lines. This resolves the enigma and indicates
how the molecular lines may serve as immutable reference lines against
which the atomic lines can be gauged when trying to determine long-term,
solar-cycle variations of the magnetic fields via the Hanle effect.

---------------------------------------------------------
Title: Detection of the mercapto radical SH in the solar atmosphere
Authors: Berdyugina, S. V.; Livingston, W. C.
2002A&A...387L...6B Altcode:
We analyze new high-resolution UV observations of the solar photosphere
in the disk center and the limb and report the first detection of SH
lines in the solar atmosphere. We perform a synthesis of the solar
spectrum including many atomic and molecular lines and find a few
relatively unblended SH lines from which we determine the (0, 0) band
oscillator strength f00=2.2*E-3. We conclude
that these lines are excellent indicators of the sulfur abundance and
isotope ratio in G and K stars.

---------------------------------------------------------
Title: The molecular Zeeman effect and diagnostics of solar and
stellar magnetic fields. I. Theoretical spectral patterns in the
Zeeman regime
Authors: Berdyugina, S. V.; Solanki, S. K.
2002A&A...385..701B Altcode:
An overview of the theory of the Zeeman effect in diatomic molecules
for the limiting Hund's cases (a) and (b) is given and a numerical
approach for the intermediate coupling case (a-b) is developed. In
contrast to earlier derivations, which were limited to doublets, this
approach is valid for terms of any multiplicity. General properties
of the Zeeman effect for the various cases are deduced. Finally,
calculated Landé factors for prominent molecular bands in sunspot
and cool-star spectra are employed to predict the general behaviour of
these bands in the presence of a magnetic field below the Paschen-Back
limit. The limiting field strength is calculated and listed.

---------------------------------------------------------
Title: Persistent active longitudes in sunspot activity
Authors: Berdyugina, S.; Usoskin, I.
2002cosp...34E.864B Altcode: 2002cosp.meetE.864B
It has been recently shown that spot activity of cool stars
including solar analogues, is grouped in two clearly distinguished
active longitudes which are persistent within at least one starspot
cycle. Solar data including positional information of individual
sunspots / groups extends back for about 130 years covering 12 solar
cycles. Here we present the results of our research of longitudinal
distribution of sunspot activity using an analysis similar to
that applied to the stars. First, we synthesized, from the actual
sunspot data, the sun's light curve as if it was defined only by
spots. Then solar images were calculated from this light curve, giving
a natural smoothing of the spot pattern. For each Carrington rotation,
longitudinal position of these smoothed spot regions was calculated. The
analysis reveals the following main features: - Sunspot activity
is grouped in two active longitudes (with the differential rotation
taken into account) 180o apart from each other which are persistent
through the entire studied period of 12 cycles, similarly to stars. -
The longitude migration is determined by changing the mean latitude of
sunspot activity (the Maunder butterfly) and differential rotation. -
The two longitudes periodically alternate the dominant activity with
about 3.7 year period implying for the existence of the Sflip-flopT
phenomenon known in - starspot activity.

---------------------------------------------------------
Title: Zeeman-split opposite-polarity OH lines in sunspot spectra:
Resolution of a puzzle
Authors: Berdyugina, S. V.; Solanki, S. K.
2001A&A...380L...5B Altcode:
We present the first synthetic Zeeman-split Stokes I and V profiles
of OH lines. They explain the puzzling observations reported by Harvey
(\cite{har85}) of two pairs of lines from the infrared (2, 0) band with
Stokes V profiles exhibiting opposite polarities. Our new perturbation
calculations of the Zeeman effect in diatomic molecules, which allow
states of any multiplicity to be treated, resolve the puzzle. They
reveal that the unusual behaviour of these lines stems from the fact
that the two pairs have effective Landé factors of similar magnitude,
but of opposite signs.

---------------------------------------------------------
Title: The first close-up of the “flip-flop” phenomenon in a
single star
Authors: Korhonen, H.; Berdyugina, S. V.; Strassmeier, K. G.;
Tuominen, I.
2001A&A...379L..30K Altcode: 2001astro.ph.10517K
We present temperature maps of the active late-type giant FK Com which
exhibit the first imagining record of the “flip-flop” phenomenon
in a single star. The phenomenon, in which the main part of the spot
activity shifts 180° in longitude, discovered a decade ago in FK Com,
was reported later also in a number of RS CVn binaries and a single
young dwarf. With the surface images obtained right before and after
the “flip-flop”, we clearly show that the “flip-flop” phenomenon in
FK Com is caused by changing the relative strengths of the spot groups
at the two active longitudes, with no actual spot movements across the
stellar surface, i.e. exactly as it happens in other active stars. Based
on the observations obtained at the Kitt Peak National Observatory,
USA; the Automatic Photometric Telescope, Phoenix 10, Arizona, USA;
the Nordic Optical Telescope, Observatorio Roque de los Muchachos,
La Palma, Canary Islands, Spain.

---------------------------------------------------------
Title: Study of FK Comae Berenices. III. Photometry for the years
1993-2001
Authors: Korhonen, H.; Berdyugina, S. V.; Tuominen, I.; Andersen,
M. I.; Piironen, J.; Strassmeier, K. G.; Grankin, K. N.; Kaasalainen,
S.; Karttunen, H.; Mel'nikov, S. Yu.; Shevchenko, V. S.; Trisoglio,
M.; Virtanen, J.
2001A&A...374.1049K Altcode:
We present 8 years of previously unpublished photometric observations
of FK Com together with the determination of the stability of the
primary comparison star HD 117567. The observations have been carried
out between 1993 and 2001 at four different observatories and they
consist of 5157 data points in total: U(903), B(994), V(1643), R(166),
I_c(573), b(461) and y(417). We also analyse this new data together with
the previously published photometric observations. The V magnitude shows
variations with dominant periods of about 3, 6, 12, 14 and 31 years. The
short-term light curve variations appear to be caused by rearrangement
of approximately constant amount of cool spots. From the values
for different colours obtained during the brightest season observed,
corresponding to the supposedly unspotted surface, the spectral type of
FK Com is determined to be G7 III. Based on the observations obtained
at Phoenix 10, Arizona, USA; Wolfgang and Amadeus, Arizona, USA;
Mount Maidanak Observatory, Uzbekistan; La Palma KVA 0.6 m Cassegrain
telescope, La Palma, Spain. Tables 2a-e are only available in electronic
form at the CDS via anonymous ftp to cdsarc.u-strasbg.fr (130.79.128.5)
or via http:/ /cdsweb.u-strasbg.fr/cgi-bin/qcat?J/A+A/374/1049

---------------------------------------------------------
Title: VizieR Online Data Catalog: Photometry of FK Com for 1993-2001
(Korhonen+, 2001)
Authors: Korhonen, H.; Berdyugina, S. V.; Tuominen, I.; Andersen,
M. I.; Piironen, J.; Strassmeier, K. G.; Grankin, K. N.; Kaasalainen,
S.; Karttunen, H.; Mel'Nikov, S. Yu.; Shevchenko, V. S.; Trisoglio,
M.; Virtanen, J.
2001yCat..33741049K Altcode:
We report 8 years of previously unpublished photometric observations
of FK Com. The observations have been carried out between 1993 and
2001 with six different telescopes: 60 cm at Mt. Maidanak (Tashkent,
Uzbekistan), Phoenix 10, Wolfgang and Amadeus located in Arizona,
USA, and 20cm and 60 cm KVA on La Palma, Spain. Observations contain
measurements at the following bands: Johnson U, B, V and R, Bessel R,
Cousins I and Stromgren b and y. The observations are differential
photometry in respect to the primary comparison star HD 117567. NOTE:
Table 1 in the paper contains some small misprints in the Julian
dates. Also for Wolfgang and Amadeus the number of observations given
in Table1 at each band is slightly less than actually given in Table2c
and Table2d. This is caused by accidentally using a limiting error
of 0.01 in magnitudes when creating Table 1. In Table 2 the limiting
error for Wolfgang and Amadeus is 0.02 mag, as mentioned in the paper
itself. In Table2a-e 99.0000 means that no observations were available
at that time at that band or that the error in the magnitude was larger
than 0.02. (5 data files).

---------------------------------------------------------
Title: VizieR Online Data Catalog: Abundances in eta Psc (Antipova+,
1995)
Authors: Antipova, L. I.; Berdyugina, S. V.; Savanov, I. S.
2001yCat..80720855A Altcode:
CCD observations are used to analyse the atmosphere of the G7 IIIa
giant Eta Piscium. The following atmospheric parameters were obtained:
T(eff)=4930K, logg=2.1, and microturbulence v(t)=1.7km/s. The abundances
of 21 elements in the atmosphere of eta Psc were determined. (1
data file).

---------------------------------------------------------
Title: II Peg: Spot Activity Cycle (CD-ROM Directory:
contribs/berdyu1)
Authors: Berdyugina, S. V.; Berdyugin, A. V.; Ilyin, I.; Tuominen, I.
2001ASPC..223.1195B Altcode: 2001csss...11.1195B
No abstract at ADS

---------------------------------------------------------
Title: Magnetic Activity in FK Com
Authors: Korhonen, H.; Berdyugina, S. V.; Tuominen, I.
2001ASPC..248..239K Altcode: 2001mfah.conf..239K
No abstract at ADS

---------------------------------------------------------
Title: Umbral Spectra in the Ultraviolet via Molecular V-Stokes
Authors: Livingston, W.; Berdyugina, S. V.
2001ASPC..236..559L Altcode: 2001aspt.conf..559L
No abstract at ADS

---------------------------------------------------------
Title: Magnetic Cycles in Binaries and Single Stars
Authors: Berdyugina, S. V.; Korhonen, H.; Tuominen, I.
2001ASPC..248..243B Altcode: 2001mfah.conf..243B
No abstract at ADS

---------------------------------------------------------
Title: Magnetic Splitting of Molecular Lines in Sunspot
Authors: Berdyugina, S. V.; Frutiger, C.; Solanki, S. K.
2001IAUS..203..254B Altcode:
A study of molecular lines in sunspots is of particular interest
because of their high temperature and pressure sensitivity. Many of
them are also magnetically sensitive, but this was not yet widely
investigated. With high-resolution, high signal-to-noise Fourier
spectroscopy in four Stokes parameters now available, the use of
molecular lines for studying the structure of sunspots brings real
gains. One is the extension of spot models, including magnetic field,
up to layers, where atomic lines suffer from NLTE effects but molecules
can still be treated in the LTE approximation. Equally important is the
fact that since molecular lines are extremely temperature sensitive
they can be used to probe the thermal and magnetic structure of the
coolest parts of sunspots. We present calculations of splitting and
the Stokes parameters for a number of molecular lines in the visible
and near-infrared regions. Our first selections are the green system of
MgH A2Π-X2σ and the TiO triplet α, γ' and γ
systems as the most studied band systems in the sunspot spectrum. The
calculations involve different regimes of the molecular Zeeman effect,
up to the complete Paschen-Back effect for individual lines. We look
for molecular lines which can be used along with atomic lines to derive
magnetic, thermal and dynamic properties of the umbra.

---------------------------------------------------------
Title: The Molecular Zeeman Effect and Solar Magnetic Fields
Authors: Berdyugina, S. V.; Frutiger, C.; Solanki, S. K.; Livingston,
W.
2001ASPC..236..551B Altcode: 2001aspt.conf..551B
No abstract at ADS

---------------------------------------------------------
Title: Solar and Stellar Magnetic Fields: the Molecular Zeeman Effect
as a Probe
Authors: Berdyugina, S. V.; Solanki, S. K.; Frutiger, C.
2001ASPC..248...99B Altcode: 2001mfah.conf...99B
No abstract at ADS

---------------------------------------------------------
Title: LQ Hya: Surface Images for 1993-1999 (CD-ROM Directory:
contribs/berdyu3)
Authors: Berdyugina, S. V.; Ilyin, I.; Tuominen, I.
2001ASPC..223.1207B Altcode: 2001csss...11.1207B
No abstract at ADS

---------------------------------------------------------
Title: IM Peg: First Surface Images (CD-ROM Directory:
contribs/berdyu2)
Authors: Berdyugina, S. V.; Berdyugin, A. V.; Ilyin, I.; Tuominen, I.
2001ASPC..223.1201B Altcode: 2001csss...11.1201B
No abstract at ADS

---------------------------------------------------------
Title: Spot Evolution in FK Com (CD-ROM Directory: contribs/korhonen)
Authors: Korhonen, H.; Berdyugina, S. V.; Tuominen, I.; Hackman, T.
2001ASPC..223.1257K Altcode: 2001csss...11.1257K
No abstract at ADS

---------------------------------------------------------
Title: Successful spectral synthesis of Zeeman-split molecular bands
in sunspot spectra
Authors: Berdyugina, S. V.; Frutiger, C.; Solanki, S. K.; Livingstone,
W.
2000A&A...364L.101B Altcode:
We present the first spectral synthesis of Zeeman-split Stokes profiles
of the MgH A2Pi -X2BLAigma green system and
TiO gamma -system. The calculations involve different regimes of the
molecular Zeeman effect, up to the complete Paschen-Back effect for
individual lines. The synthetic spectra are compared with observations
of Stokes I and V in sunspot umbrae. We find that although the Stokes
I spectra are reasonably reproduced, some lines are obviously still
missing from the employed line lists. The Stokes V spectra turn
out to be much cleaner since the missing lines do not appear to
be Zeeman-split. We thus provide the first good fit to Zeeman-split
molecular lines, including profiles with unconventional Stokes V shapes,
determined by the Paschen-Back effect. Based on observations from
the Canada-France-Hawaii Telescope operated by the National Research
Council of Canada, the Centre National de la Recherche Scientifique
de France and the University of Hawaii

---------------------------------------------------------
Title: The long-period RS CVn binary IM Pegasi --- II. First surface
images
Authors: Berdyugina, S. V.; Berdyugin, A. V.; Ilyin, I.; Tuominen, I.
2000A&A...360..272B Altcode:
New high-resolution, high signal-to-noise ratio spectroscopic
observations and UBV photometry carried out in 1996-1999 were analysed
with the surface imaging technique. A total of 8 images of IM Peg was
obtained for the first time. A huge high-latitude active region was
found to dominate the stellar surface and decreased in area during
the period of the observations. At the same time, on the opposite
hemisphere (in longitudes), smaller spots were developing. The spots
were migrating in the orbital reference frame, the period of spot
rotation being of 24.d73∓0.d02. The spots constitute two active
longitudes on opposite stellar hemispheres, similar to other RS CVn
stars. The evolution of the spot areas within the active longitudes
indicates a stellar activity cycle, during which one active longitude
dominates the stellar activity, to be about 6.5 years. Then, a total
cycle, comprising two consecutive periods of activity of both active
longitudes, is about 13 years. In 1999, the activity switched to the
other active longitude. This declared the beginning of a new (half-)
cycle. based on observations collected at the Nordic Optical Telescope
(NOT), La Palma, Spain; the 2.6 m and 1.25 m telescopes of the Crimean
Astrophysical Observatory, Ukraine; the 2m telescope of the National
Astronomical Observatory, Rozhen, Bulgaria.

---------------------------------------------------------
Title: Study of FK Comae Berenices --- II. Spot evolution from 1994
to 1997
Authors: Korhonen, H.; Berdyugina, S. V.; Hackman, T.; Strassmeier,
K. G.; Tuominen, I.
2000A&A...360.1067K Altcode: 2000astro.ph..7088K
We present new surface (Doppler) images of the late-type single giant
FK Com for June-July 1996, July-August 1996, April 1997 and June
1997. These images are compared with the previously published images
from 1994 and 1995. The consecutive maps are cross- correlated to see
the possible migration of the spots and the effects of differential
rotation. The cross-correlation confirms an average longitudinal
spot migration of 0.22 ± 0.03 in phase within a year. This movement
is probably an artifact caused by a difference between the accepted
rotation period and the real photometric period for these years. If
this is true, then the photometric rotation period for these years
is 2.d4037 ± 0.0005. Measurements from these four years and six maps
limit the surface differential rotation to α = 0.0001 ± 0.0002, where
α is the difference between polar and equatorial angular velocities
relative to the equatorial angular velocity. Based on the observations
obtained at the Nordic Optical Telescope, Observatorio Roque de los
Muchachos, La Palma, Canary Islands, Spain; the National Astronomical
Observatory, Rozhen, Bulgaria; the Kitt Peak National Observatory,
USA; the Automatic Photometric Telescope, Phoenix 10, Arizona, USA.

---------------------------------------------------------
Title: Mapping the Non-Radial Pulsations
Authors: Berdyugina, S. V.; Korhonen, H.; Schrijvers, C.; Telting,
J. H.
2000ASPC..214..268B Altcode: 2000bpet.conf..268B; 2000IAUCo.175..268B
No abstract at ADS

---------------------------------------------------------
Title: The active RS Canum Venaticorum binary II Pegasi. IV. The
SPOT activity cycle
Authors: Berdyugina, S. V.; Berdyugin, A. V.; Ilyin, I.; Tuominen, I.
1999A&A...350..626B Altcode:
A total of 6 new surface images of II Peg obtained for the years 1997
and 1998 confirms the recently revealed permanent active longitude
structure. The lower limit of the active longitudes' lifetime
is now extended up to 25 years. A new “flip-flop” phenomenon,
redefined as a switch of the activity between the active longitudes,
has started in summer of 1998. It coincides reasonably well with the
moment predicted from the activity cycle of the star. This confirms
definitely the cyclic behaviour of the activity of II Peg we recently
discovered. Therefore, we assign numbers to the cycles of 4.65 yr
since the earliest photoelectric observations of II Peg and define
the active longitudes as “odd” and “even” corresponding to odd and
even numbers of cycles. With such a definition, in late 1998 the 7th
cycle began and the “odd” active longitude became more active. From
the analysis of the spot area evolution within the active longitudes
we conclude that the activity cycle is developed as a rearrangement
of the nearly constant amount of the spot area between the active
longitudes. We discuss the “flip-flop” phenomenon as a tracer of
stellar activity and the role of the unseen secondary in establishing
the cycle. Based on observations collected at the Nordic Optical
Telescope (NOT), La Palma, Spain; the 1.25m telescope of the Crimean
Astrophysical Observatory, Ukraine; the Phoenix 10 robotic telescope,
APT Observatory, Arizona, USA.}

---------------------------------------------------------
Title: The active RS Canum Venaticorum binary II
Pegasi. III. Chromospheric emission and flares in 1994-1996
Authors: Berdyugina, S. V.; Ilyin, I.; Tuominen, I.
1999A&A...349..863B Altcode:
We analyse observations of the very active RS CVn-type star II
Peg carried out simultaneously in chromospheric and photospheric
lines in 1994-1996. We describe the correlation of the strength of
the He i D3, Ca ii,K and Ca ii 8498 Ä emissions with
the spot position on the stellar disk. A two-component structure is
suggested in the chromosphere of II Peg, similar to that in the corona:
nonvariable component (cool plages) with constant contribution to the
line emission and variable, active one (hot plages) showing a growth of
its activity during 1994-1996. The active component is related to the
spots seen in the photosphere. Two subsequent flares on July 19-23,
1995 were observed in the He i D3 and Ca ii,K and 8498 Ä
lines showing strong narrow red-shifted emissions. The development
of the flares took a few hours and decay lasted several days. At
the maximum of the flaring, in addition to the narrow components,
broad blue-shifted emissions appeared in He i and Ca ii,K and in
the cores of many strong absorption lines. The broad components are
attributed to the process of the explosive evaporation from the low
chromosphere. The amount of energy released in different lines is
determined. From the radial velocity curve of the He i emission the
location of the radiating matter is deduced. It appears to be related
to the largest active region which is seen in the stellar image. The
flare occurred concurrently with the break of the extended group on two
well separated spots. On October 26, 1996 another flare was observed
in three spectra, as narrow emissions in the He i and Ca ii,8498 Ä
lines but without development in other lines. It probably was a late
stage of the flare decay. Based on observations collected at the Nordic
Optical Telescope (NOT), La Palma, Spain.

---------------------------------------------------------
Title: The long-period RS Canum Venaticorum binary IM
Pegasi. I. Orbital and stellar parameters
Authors: Berdyugina, S. V.; Ilyin, I.; Tuominen, I.
1999A&A...347..932B Altcode:
New high-resolution and high signal-to-noise ratio spectroscopic
observations carried out in 1996-1997 are analysed. A total of 85 new
high quality radial velocity measurements are used for determining
the new orbital parameters: T_conj=HJD2450342.883+24.64880E, e=0.0,
gamma =-14.09 {km s(-1) }, K1=34.39 {km s(-1) }. A model
atmosphere analysis of the averaged spectrum of the star has yielded a
self-consistent set of fundamental parameters of the primary component:
{T_eff}=4450 K, {log g=2.4, [M/H]=0.0, {xi_t }=1.6 {km s(-1) }, {v
sini=26.5 {km s(-1) }. The primary is found to be a typical K2 III
giant with the mass of about 1.5 M_⊙ which has undergone the first
convective mixing on the Red Giant Branch ([C/H]=-0.32, [N/H]=0.30,
C/N=1.15). The unspotted V magnitude of the star of 5fm 55 is estimated
from the observed variations of the TiO band and quasi-simultaneous
photometry. Combining all parameters, the radius and inclination of
the primary as well as a probable spectral class of the secondary are
estimated. based on observations collected at the 2.6\,m telescope of
the Crimean Astrophysical Observatory, Ukraine and the Nordic Optical
Telescope (NOT), La Palma, Spain

---------------------------------------------------------
Title: Study of FK Comae Berenices. I. Surface images for 1994
and 1995
Authors: Korhonen, H.; Berdyugina, S. V.; Hackman, T.; Duemmler, R.;
Ilyin, I. V.; Tuominen, I.
1999A&A...346..101K Altcode:
We present new surface images of FK Com for August 1994 and July
1995. For the 1995 images two different inversion methods, Tikhonov
regularization and the Occamian approach, are used to check the
dependence on the formal assumptions. The images are found to be very
similar when the same local line profiles, models, stellar parameters
and observations are used as inputs for both methods. The validity of
the maps and their temperature scales are independently checked with
photometric observations. The maps for both years show active regions
of very similar substructures and latitudes. It seems that the same
spot group has survived on the surface of FK Com for the 11 months
between the observations; however, during that time it has moved
about 0.2 in phase. The movement and evolution of the spot groups
seem to cause the photometrically observed “flip-flop” phenomenon,
which is noticed to be repeated with an average period of 6.5 years,
similar to some RS CVn-stars. Based on the observations obtained at
the Nordic Optical Telescope, Observatorio Roque de los Muchachos,
La Palma, Canary Islands, Spain.

---------------------------------------------------------
Title: Investigation of the spot distribution and surface differential
rotation on x
Authors: Aarum, Vidar; Engvold, Oddbjorn; Berdyugina, Svetlana;
Dummler, Rudolf
1999noao.prop...68A Altcode:
The purpose of the programme is to determine the starspot distribution
on the primary component of x using Doppler imaging. Special attention
is given to the possible existence of a polar spot and a technique
to separate the spectra of the individual components. Studying the
system over several years provides information on the star's surface
differential rotation.

---------------------------------------------------------
Title: Stellar surface structures and their evolution
Authors: Berdyugina, S. V.
1999anot.conf..206B Altcode:
No abstract at ADS

---------------------------------------------------------
Title: Doppler imaging of UX Ari (poster)
Authors: Aarum, V.; Berdyugina, S. V.; Ilyin, I. V.
1999anot.conf..222A Altcode:
No abstract at ADS

---------------------------------------------------------
Title: Nonaxisymmetric Stellar Dynamos
Authors: Tuominen, I.; Berdyugina, S. V.; Korpi, M. J.; Rönty, T.
1999ASPC..178..195T Altcode: 1999sdnc.conf..195T
No abstract at ADS

---------------------------------------------------------
Title: Surface imaging of FK Comae Berenices (poster)
Authors: Korhonen, H.; Berdyugina, S. V.; Duemmler, R.; Hackman, T.;
Ilyin, I. V.; Tuominen, I.
1999anot.conf..234K Altcode:
No abstract at ADS

---------------------------------------------------------
Title: The active RS Canum Venaticorum binary II Pegasi. II. Surface
images for 1992-1996
Authors: Berdyugina, S. V.; Berdyugin, A. V.; Ilyin, I.; Tuominen, I.
1998A&A...340..437B Altcode:
Using new high-resolution and high signal-to-noise ratio spectroscopic
observations carried out in 1992-1996, nine surface images of II
Peg are obtained. The inversion technique applied is the recently
developed Occamian approach, which does not put any artificial
constraints on the solution and provides an error analysis of the
solution. The surface imaging is applied to Ca{ i, Fe{ i, and Ni{ i
lines simultaneously, a number of blending atomic and molecular lines
being included into the line list. Two high-latitude active regions
are found to dominate in all seasons, which determine the spectroscopic
and photometric variability. No cool polar cap is seen. The positions
of the spots are constantly migrating to earlier orbital phases with
approximately the same rate. This motion of the spot configuration means
a shorter rotational period, which is just about the mean photometric
period. The mean longitude separation between the active regions
is about 180°. This is considered as two active longitudes. The
largest of the two spots seems to be close to the central meridian,
i.e. tends to be faced toward the secondary. In 1994 it changed its
position from one active longitude to another, showing the effect of
switching the activity between the longitudes. based on observations
collected at the Nordic Optical Telescope (NOT), La Palma, Spain; the
McMath telescope of the National Solar Observatory, USA; the 2.6 m and
1.25 m telescopes of the Crimean Astrophysical Observatory, Ukraine;
the 2m telescope of the National Astronomical Observatory, Rozhen,
Bulgaria; the 2m telescope of the Pic du Midi Observatory, France

---------------------------------------------------------
Title: Surface imaging by the Occamian approach. Basic principles,
simulations, and tests
Authors: Berdyugina, Svetlana V.
1998A&A...338...97B Altcode:
The recently developed Occamian approach for solving inverse problems
was applied to surface imaging of cool stars. With a set of tests
the effects of data noise and uncertainties of the stellar parameters
on the solution have been investigated. The spot locations and spot
configuration are found to be well determined in most cases. The spot
contrast can be successfully restored in case of adequate atmospheric
models and line profile calculations. A formal error analysis of
the solution is applied for the first time to the surface imaging
problem. It is suggested that the pole-to-equator gradient of the
temperature is a consequence of the information distribution on the
stellar surface, which is determined by the available observational
data. &gt;From the analysis of the error distribution on the stellar
surface under different conditions two practical advices have been
formulated for successful surface imaging. First, a total number points
of data ought to be a few times the number of unknown parameters,
since only in such a case most of the stellar surface can be restored
realiably. Second, the S/N ratio should be as large as possible,
since its value affects proportionally the size of the area of the
stellar surface with an acceptable level of the errors.

---------------------------------------------------------
Title: Permanent active longitudes and activity cycles on RS CVn stars
Authors: Berdyugina, Svetlana V.; Tuominen, Ilkka
1998A&A...336L..25B Altcode:
A new analysis of the published long-term photometric observations has
revealed permanent active-longitude structures in four RS CVn stars:
EI Eri, II Peg, sigma Gem, and HR 7275. Two active longitudes separated
by half of the period are found to dominate on the surface during all
available seasons. The positions of the longitudes on three stars (EI
Eri, II Peg, HR 7275) are migrating in the orbital reference frame, and
there is no preferred orientation with respect to the line of centres
in the binaries. The rate of migration is approximately constant. In
case of sigma Gem the active longitude migration is synchronized with
the orbital motion in the direction of the line of centres in the
binary. The active region lifetimes can be longer than the time span
of the observations (&gt;=15 yr). The periods of the active longitude
rotation are determined: for EI Eri 1fd 9510, for II Peg 6fd 7066,
for sigma Gem 19fd 604, for HR 7275 28fd 263. Long-term activity
cycles of the stars are discovered from the analysis of the relative
contribution of the two longitudes to the photometric variability. One
longitude is found to be usually more active than the other at a given
moment, and the change of the activity level between the longitudes
is cyclic with periods of years. The switch of the activity takes a
much shorter time, about a few months, similar to the “flip-flop”
phenomenon found for FK Com stars. Moments of switching are regarded as
new tracers of the activity, and total cycles, which return activity
to the same longitude, are found to be for EI Eri 9.0 yr, for II Peg
9.3 yr, for sigma Gem 14.9 yr, for HR 7275 17.5 yr.

---------------------------------------------------------
Title: The active RS Canum Venaticorum binary II Pegasi. I. Stellar
and orbital parameters
Authors: Berdyugina, S. V.; Jankov, S.; Ilyin, I.; Tuominen, I.;
Fekel, F. C.
1998A&A...334..863B Altcode:
A detailed model atmosphere analysis of high-resolution and high S/N
CCD spectra of II Peg has yielded for the first time a self-consistent
set of fundamental parameters of the primary component: {T_eff}=4600
K, {log g=3.2, [M/H]=-0.4, {xi_t }=2.0 {km s(-1) }. In addition, 121
new high quality radial velocity measurements allowed us to determine
improved orbital parameters, resulting in a new orbital ephemeris of
T_conj=2449582.9268+6.724333E. The position of the primary of II Peg
in the HR diagram with the new parameters corresponds to a K2 IV star
with mass ~0.8 M_⊙. The evolved character of the star is confirmed
by the C/N ratio, which is reduced significantly relative to the solar
value. The unspotted V magnitude of the star of 6fm 9 is estimated
from the observed variations of the TiO bands and quasi-simultaneous
photometry. The blend of Li{ i 6707 Angstroms is suspected to vary in
equivalent width due to spot modulation. The lithium abundance for
the unspotted star, Li/H=1.0±m0.1, is found to be consistent with
other post-main sequence chromospherically active stars. Combining
all parameters, the radius R ~ 3.4 R_⊙ and the inclination i ~ 60°
of the primary are estimated with the assumption that its rotational
axis is perpendicular to the orbital plane. The secondary is probably a
M0-M3 V star with a mass of about 0.4 M_⊙. Based on observations
collected at the Nordic Optical Telescope (NOT), La Palma, Spain; the
2.6 m telescope of the Crimean Astrophysical Observatory, Ukraine;
the 2.7 m and 2.1 m telescopes of the McDonald Observatory, USA;
the coudé feed telescope of the Kitt Peak National Observatory,
USA Table 2 is also available in electronic form at the CDS
via anonymous ftp to cdsarc.u-strasbg.fr (130.79.128.5) or via
http://cdsweb.u-strasbg.fr/Abstract.html.

---------------------------------------------------------
Title: New photometric and polarimetric observations of the massive
interacting binary KX And
Authors: Berdyugin, A. V.; Berdyugina, S. V.; Tarasov, A. E.
1998AstL...24..309B Altcode: 1998PAZh...24..367B
New UBVRI photometry and polarimetry of the interacting binary KX And
are presented. The shape of its light curve in the 1992-1994 season
provides evidence for a shift of the time of minimum light from the
phase of main elongation, which can be determined from spectroscopic
observations. This previously unobserved effect suggests that the
orbital position of the cloud of gas that obscures the hot component
can change in longitude. The binary exhibits a variable (with orbital
phase) linear polarization. The variable polarization is dominated by
the first harmonic of the orbital period. This polarization is shown to
arise from the scattering of light in the upper layers of the optically
thick shell around the hot component with a thickening at its front
edge. An analysis of the polarimetric data has yielded estimates of the
orbital inclination, i 50, and the spatial orientation of the orbit,
Omega = 100+/-30deg.

---------------------------------------------------------
Title: The massive interacting binary KX And: The orbit and physical
parameters of the secondary component
Authors: Tarasov, A. E.; Berdyugina, S. V.; Berdyugin, A. V.
1998AstL...24..316T Altcode: 1998PAZh...24..375T
High-resolution spectra with large signal-to-noise ratios are used to
study the variability of the line profiles for the interacting binary
Be star KX And. Lines of the secondary component were found to be
present in the red spectral region. These lines are used to determine
its physical and kinematic parameters. The orbit of the secondary
component is shown to be circular, with the system's center-of-mass
velocity being 10 +/- 2 km s^-1 and K_2 = 86.2 +/- 0.8 km s^-1;
consequently, the orbital eccentricity inferred from observed lines
of the primary component is false. An analysis of the lines of the
secondary component yields an estimate of its spectral type close to
G8 II, with T_eff = 5000 +/- 400 K, log g = 2.0 +/- 0.5, and V sin i =
25 +/- 5 km s^-1. The detection of a considerable strengthening of ZrI
and BaII lines points to an overabundance of these elements relative to
iron as compared to the solar values, which suggests that the secondary
component is an AGB star.

---------------------------------------------------------
Title: VizieR Online Data Catalog: II Peg radial velocities
(Berdyugina+ 1998)
Authors: Berdyugina, S. V.; Jankov, S.; Ilyin, I.; Tuominen, I.;
Fekel, F. C.
1998yCat..33340863B Altcode:
A detailed model atmosphere analysis of high-resolution and high S/N CCD
spectra of IIPeg has yielded for the first time a self-consistent set of
fundamental parameters of the primary component: Teff=4600K,
logg=3.2, [M/H]=-0.4, ξt=2.0km/s. In addition, 121 new
high quality radial velocity measurements allowed us to determine
improved orbital parameters, resulting in a new orbital ephemeris of
Tconj=2449582.9268+6.724333E. The position of the primary
of II Peg in the HR diagram with the new parameters corresponds to a
K2 IV star with mass =~0.8M⊙. The evolved character of
the star is confirmed by the C/N ratio, which is reduced significantly
relative to the solar value. The unspotted V magnitude of the star of
6.9mag is estimated from the observed variations of the TiO bands and
quasi-simultaneous photometry. The blend of LiI 6707Å is suspected to
vary in equivalent width due to spot modulation. The lithium abundance
for the unspotted star, Li/H=1.0+/-0.1, is found to be consistent with
other post-main sequence chromospherically active stars. Combining all
parameters, the radius R=~3.4R⊙ and the inclination i=~60°
of the primary are estimated with the assumption that its rotational
axis is perpendicular to the orbital plane. The secondary is probably
a M0-M3 V star with a mass of about 0.4M⊙. (1 data file).

---------------------------------------------------------
Title: Coordinated Observations of the Red Dwarf Flare Star EV LAC
in 1994 and 1995
Authors: Abranin, E. P.; Alekseev, I. Yu.; Avgoloupis, S.; Bazelyan,
L. L.; Berdyugina, S. V.; Cutispoto, G.; Gershberg, R. E.; Larionov,
V. M.; Leto, G.; Lisachenko, V. N.; Marino, G.; Mavridis, L. N.;
Messina, S.; Mel'Nik, V. N.; Pagano, I.; Pustil'Nik, S. V.; Rodonò,
M.; Roizman, G. Sh.; Seiradakis, J. H.; Sigal, G. P.; Shakhovskaya,
N. I.; Shakhovskoy, D. N.; Shcherbakov, V. A.
1998A&AT...17..221A Altcode:
The results of photometric, spectral and radio studies of the flare star
EV Lac we obtained during the course of cooperative observations in 1994
and 1995 are presented. A quantitative analysis of the radiation emitted
by two powerful flares using the colour-colour diagram confirms the
previous conclusion on the essential heterogeneity of matter radiating
in optical flares. From simultaneous observations of the star in
UBVRI, K and H bands no significant brightness variations in IR were
found in coincidence with observed small-amplitude optical flares,
except a gradual decrease in the K-band following a 1.0 mag flare in
the U-band. A differential spottedness of bright and dark hemispheres
of EV Lac is estimated using observations in separate seasons and the
total stellar spottedness is determined within the framework of the
zonal spottedness model. Spectra of quiet and active states of the
star in the blue-green region in 1994 and in the red region in 1995
are described: the characteristics of the quiet chromosphere in the H,
H, H lines, their widening during flares, the strengthening of neutral
helium lines and the appearance of emission lines of He II and metals
are presented. The monitoring of EV Lac in decametric wavelengths with
the largest radio telescope UTR-2 led to the detection of 18 radio
bursts, one of which satisfies the majority of criteria of signals of
non-terrestrial origin and coincides in time with an optical flare.

---------------------------------------------------------
Title: II Peg: Quiescent Cromospheric Emission and Flares in 1994-1996
Authors: Berdyugina, S.; Ilyin, I.; Tuominen, I.
1998ASPC..154.1477B Altcode: 1998csss...10.1477B
Simultaneous observations of Ca 2 K, Ca 2 8498 AA, He 1 D3,
and photospheric lines in 1994-1996 with the high-resolution
spectrograph SOFIN at the Nordic Optical Telescope have revealed
correlation of the strength of the He 1 D3 line and the Ca
2 emission with the spot position on the stellar disk. A two-component
structure is seen in the quiescent chromosphere of II Peg, as it is seen
in the corona, and a filament visible in the corona seems to be based
on the largest spot visible in the surface images of the star. Also,
two flares were serendipitously observed. The first one, which started
on July 19, 1995, was noticed in the He 1 D3 line which
appeared as a nonsymmetric, red-shifted, narrow (FWHM ~50 km {s}^{-1})
emission, while other lines kept their quiescent shapes. The emission
in the He 1 line was seen until the end of the observing run (July 23,
1995) and reached the maximum on July 22, 1995, when in addition to
the narrow component, a broad (FWHM ~100 km {s}^{-1}) blue-shifted one
was seen in both the He 1 line and the Ca 2 K line. At that moment, the
two-component emission was observed in cores of many other absorption
lines as well. The amount of energy released in different lines at the
maximum of the flare is estimated. From the radial velocity curve of
the He 1 emission the location of the radiating matter is deduced. It
appears to be close to the largest spot (or group of spots) which is
seen from the surface imaging. The second flare was noticed on Oct. 26,
1996, in three spectra, again as a narrow emission in the He 1 line,
but without susequent development in other lines.

---------------------------------------------------------
Title: II Peg: Stellar and Orbital Parameters
Authors: Berdyugina, S.; Ilyin, I.; Tuominen, I.
1998ASPC..154.1384B Altcode: 1998csss...10.1384B
A detailed model atmosphere analysis of high-resolution and high S/N
CCD spectra of II Peg has yielded a self-consistent set of fundamental
parameters of the primary component for the first time. In addition,
new orbital parameters have been determined. The position of the primary
of II Peg in the HR diagram with these new parameters is compatible
with the modern evolutionary models for hydrogen-shell-burning stars
of mass ~0.9 Msun with low metallicity (Z = 0.008), and
corresponds to K2 IV. Combining all parameters, the radius R ~4.5
Rsun and the inclination i ~45 deg of the primary can be
estimated under the assumption that its rotational axis is perpendicular
to the orbital plane. Also, the nature of the secondary can be deduced
from these parameters. It might be a K5 V star with a mass of about
0.7 Msun.

---------------------------------------------------------
Title: II Peg: New Surface Images for 1992-1996
Authors: Berdyugina, S.; Ilyin, I.; Tuominen, I.
1998ASPC..154.1952B Altcode: 1998csss...10.1952B
Using new high-resolution and high signal-to-noise ratio spectroscopic
observations carried out in 1992-1996, nine new surface images of
II Peg have been obtained. The technique employed was the recently
developed Occamian approach, which does not use any prior smoothness
assumption, but the resulting solution is nevertheless stable with
respect to measurement errors and uncertainties in the adopted stellar
parameters. The surface imaging was applied to Fe 1 and Ni 1 lines
simultaneously, and a number of blending atomic and molecular lines
were included into the line list. Two high latitude spots were found
to dominate in all seasons, and no polar cap was seen. The positions
of the spots were constantly migrating to larger longitudes with
approximately the same rate. Since phases were computed from the
orbital period, this longitudinal motion of the spot configuration
means the spots have a shorter rotational period, which is just about
the mean photometric one. The longitude separation between the spots
was approximately constant and equal to about 180 degrees. They can
be considered as two long living active longitudes.

---------------------------------------------------------
Title: Modeling the observed chemical anomalies in metallic-line
stars: Effects of spottedness
Authors: Savanov, I. S.; Berdyugina, S. V.
1996ARep...40..690S Altcode:
No abstract at ADS

---------------------------------------------------------
Title: On the chemical composition of the G7 IIIa red giant eta
Piscium.
Authors: Antipova, L. I.; Berdyugina, S. V.; Savanov, I. S.
1995AZh....72..855A Altcode:
CCD observations are used to analyze the atmosphere of the G7IIIa giant
Eta Psc by the method of model atmospheres. The following atmospheric
parameters were obtained: Teff = 4930 K, log g = 2.1, and microturbulent
velocity of 1.7 km/s. The abundances of 21 elements in the atmosphere
of Eta Psc were determined. The conclusion about a high Li abundance
and a high isotopic ratio of C-12/C-13 is validated. A slight excess of
Na is reported. The assumption that Eta Psc may belong to a subgroup
of mild barium stars is discussed. It is inferred from an analysis of
the derived abundances that Eta Psc is a normal red giant.

---------------------------------------------------------
Title: On the chemical composition of the G7 IIIa red giant η Piscium
Authors: Antipova, L. I.; Berdyugina, S. V.; Savanov, I. S.
1995ARep...39..761A Altcode:
No abstract at ADS

---------------------------------------------------------
Title: Li-rich giants: evidence for convection mixing.
Authors: Berdyugina, S. V.; Savanov, I. S.
1995MmSAI..66..425B Altcode:
No abstract at ADS

---------------------------------------------------------
Title: Modeling of chemical anomalies of Am-star
Authors: Savanov, I. S.; Berdyugina, S. V.
1995IAUS..176P.145S Altcode:
No abstract at ADS

---------------------------------------------------------
Title: Doppler imaging by the Mean Information Principle
Authors: Berdyugina, S. V.
1995IAUS..176P..12B Altcode:
No abstract at ADS

---------------------------------------------------------
Title: Long-slit spectroscopy of comet Shoemaker-Levy 9 impact sites.
Authors: Korsun, P. P.; Sizonenko, Yu. V.; Berdyugina, S. V.; Sergeev,
S. G.
1995ESOC...52..219K Altcode: 1995esl9.conf..219K; 1995eslj.work..219K
Long-slit CCD spectra of the impact sites of comet Shoemaker-Levy 9
were obtained at the Nasmyth and coudé focuses of the 2.6 m telescope
ZTSh of Crimean Astrophysical Observatory. The Nasmyth spectra covered
4600 - 10,240 Å at a resolution of 4.5 Å. The coudé spectra were
made at the CH4 and Na absorptions with resolution 0.85 -
1.7 Å. All the Nasmyth spectra were obtained along the crash latitude
of Jupiter. Combined investigations of the extracted spectra along
the impact parallel as well as spatial profiles at different spectral
regions show that the impact sites have some spectral peculiarities. In
addition to the well seen absorption in the impact sites over the
observed wavelength region and a decreasing of the CH4
absorptions near 8900 Å and 1 μm, moderate weakening of the
CH4 band at 7200 Å and NH3 band at 7900 Å was
detected in some observed spots as well. The coudé spectra showed
weakening of the CH4 features, but lack of any variations
in the Na lines.

---------------------------------------------------------
Title: Shoemaker-Levy 9 impact with Jupiter: Spectral peculiarities
of the impact sites H, K, L, N, and D + G + S + R group
Authors: Korsun, P. P.; Sizonenko, Yu. V.; Sergeev, S. G.; Berdyugina,
S. V.
1995EM&P...69...87K Altcode:
Long-slit CCD spectra of the impact parallel of Jupiter were obtained
on July 20 21, 1994. Observations were made at Nasmith focus of the 2.6
m Shajn telescope of the Crimean Astrophysical Observatory. Observed
spectra covered 4600 10,250 Å at a resolution of 4.5 Å. Combined
investigations of the Nasmith spectra, both the spatial profiles for
different spectral regions and extracted spectra for different sites
of the crash latitude, show that the impact spots have some spectral
peculiarities. Detectable absorption in the observed wavelength region
is the general peculiarity of the observed impact sites, except for
CH4 bands at 8900 Å and 1 μm, where methane absorption was
weakened. Also, our analysis evidenced that there are two types of the
spectral peculiarities. One of them, related to the great spots D +
G + R + S, K, and L, shows that the absorption in the impact sites
is increasing gradually to the blue with respect to the unaffected
sites. The other, related to the medium-sized spots, H and N, shows
no obvious changes in the gradient of the spots' spectra over a wide
wavelength region, except that for the green region, where absorption
is slightly weakened.

---------------------------------------------------------
Title: New surface-gravity calibration for G-K giants and subgiants
Authors: Berdyugina, S. V.; Savanov, I. S.
1994AstL...20..755B Altcode: 1994PAZh...20..864B
No abstract at ADS

---------------------------------------------------------
Title: CNO and s-element abundances in the atmospheres of the binaries
AY Cet and RD Dra with active chromospheres: Testing the hypothesis
on the formation of barium stars
Authors: Berdyugina, S. V.
1994AstL...20..796B Altcode: 1994PAZh...20..910B
No abstract at ADS

---------------------------------------------------------
Title: Photometric and spectroscopic observations of the spotted T
Tauri star V410 Tauri.
Authors: Petrov, P. P.; Shcherbakov, V. A.; Berdyugina, S. V.;
Shevchenko, V. S.; Grankin, K. N.; Melnikov, S. Y.
1994A&AS..107....9P Altcode:
V410 Tau is a fast rotating weak line T Tau star with a large cool
spot or spotted area on its surface, which has been observed through
the periodic (P=1.872d) light variations during several years. We
present here UBVR photometric monitoring data for the star for 7
years since 1986 to 1992. The data permit us to derive the spot
parameters and search for their annual variations. In 1992/93 the
photometric monitoring was carried out along with low resolution high
signal-to-noise spectroscopy of V410 Tau in the spectral region of
the TiO bands near λ7100, Li Iλ6707 and Hα. We found a relationship
between the TiO bands strength and stellar brightness in favor of the
cool spot hypothesis. Parameters of the spotted region were derived,
and an integrated spectrum of the spotted star was calculated using
synthetic spectra of stellar atmospheres. The Hα emission was found
to vary in a more complex way, with two flux maxima at the phases of
axial rotation when the spot is near the stellar limb. High resolution
Hα profiles were obtained for all phases of the rotational period.

---------------------------------------------------------
Title: Li and CNO abundances in the atmospheres of stars evolving
to the red-giant branch
Authors: Berdyugina, S. V.
1994AstL...20..631B Altcode: 1994PAZh...20..731B
No abstract at ADS

---------------------------------------------------------
Title: CNO abundances and 12C/13C ratios in
the atmospheres of lithium-rich giants
Authors: Berdyugina, S. V.; Savanov, I. S.
1994AstL...20..639B Altcode: 1994PAZh...20..740B
No abstract at ADS

---------------------------------------------------------
Title: The chemical composition of the atmosphere of the active
giant λ And
Authors: Savanov, I. S.; Berdyugina, S. V.
1994AstL...20..227S Altcode: 1994PAZh...20..279S
No abstract at ADS

---------------------------------------------------------
Title: MgH as a surface gravity criterion for red giants
Authors: Berdyugina, S. V.; Savanov, I. S.
1994msep.conf...12B Altcode: 1994IAUCo.146P..12B
No abstract at ADS

---------------------------------------------------------
Title: Variability of TiO bands in spectrum of the spotted T Tauri
star V410 Tauri
Authors: Berdyugina, S. V.; Petrov, P. P.; Sherbakov, V. A.
1994msep.conf...16B Altcode: 1994IAUCo.146P..16B
No abstract at ADS

---------------------------------------------------------
Title: The abundances of the CNO elements in the atmospheres of
normal and mildly barium-enriched G8 to K3 giants
Authors: Berdyugina, S. V.
1993AstL...19..378B Altcode: 1993PAZh...19..933B
No abstract at ADS

---------------------------------------------------------
Title: Numerical model of interaction of strong spherical shocks in
intergalactic gas
Authors: Berdyugina, S. V.; Petrov, P. P.; Shcherbakov, V. A.
1992SvAL...18..449B Altcode: 1992PAZh...18.1095B
A dynamic picture of interaction of intergalactic shocks of the
same intensity, generated by the explosions of massive stars, is
described by quantitative estimates. A complex set of hydrodynamical
discontinuities develops in the interaction area, including the unstable
vortex list. Decay of this vortex list gives rise to a vortex cell
on the scale of the characteristic size of spiral galaxies. Results
of numerical models for the shock-shock interaction, which improve
sufficiently our preliminary rough estimates, are presented.

---------------------------------------------------------
Title: A search for variability of TiO bands in the spectrum of the
T Tauri star V410 Tau.
Authors: Berdyugina, S. V.; Petrov, P. P.; Shcherbakov, V. A.
1992SvAL...18..443B Altcode: 1992PAZh...18.1080B
Low resolution, high signal-to-noise ratio CCD-spectroscopy of the T Tau
star V410 Tau in the region of TiO bands near 7100 Å was carried out
in 1991/92. Relationship between V-magnitude of the star and intensity
of the TiO bands was found, in favour of the hypothesis of cool spots
on the star's surface. The relationship is modelled using synthetic
spectra of the photosphere and the cool spot.

---------------------------------------------------------
Title: Determination of the Parameters of the Atmospheres of Red
Giants - MGH as a Luminosity Criterion
Authors: Berdyugina, S. V.; Savanov, I. S.
1992SvA....36..425B Altcode:
No abstract at ADS

---------------------------------------------------------
Title: The determination of the parameters of red giants
atmospheres. MgH as a luminosity criterion.
Authors: Berdyugina, S. V.; Savanov, I. S.
1992AZh....69..829B Altcode:
The possibility of using MgH lines as a gravity criterion for red giant
atmospheres is considered. The effective temperatures of 12 K0-K3 giants
are determined from (V-K) colors, and the gravities are obtained from a
comparison of observed and calculated equivalent widths of MgH features
with wavelengths of 5134.6, 5138.7, and 5140.2 AA. The results of an
investigation of the influence of some parameters (microturbulence,
macroturbulence, metallicity, and abundance of Mg) on the calculated
MgH line profiles are discussed. Calibration diagrams for determining
the gravities of red giants with effective temperatures from 4000 to
5000 K from the equivalent widths and the central intensities of MgH
lines are proposed.

---------------------------------------------------------
Title: The investigation of the atmosphere of the K2 III star
alpha Ari.
Authors: Berdyugina, S. V.; Boyarchuk, M. E.; Pavlenko, Ya. V.;
Savanov, I. S.; Shavrina, A. V.
1991AZh....68..782B Altcode:
To verify the compatibility of results obtained from an analysis
of the G8-K4 giants' atmospheres carried out in the Crimea and Kiev,
independent investigations of the Alpha Ari atmosphere are performed. An
effective temperature of 4850 K and a log value of 2.6 are obtained. The
atmosphere's microturbulent velocity is 2.5 km/s. The abundances of
26 elements in the star's atmosphere are determined on the basis of
equivalent line widths using high-dispersion spectrograms.

---------------------------------------------------------
Title: Atmosphere of the K2III-STAR Alpha-Arietis
Authors: Berdyugina, S. V.; Boyarchuk, M. E.; Pavlenko, Y. V.; Savanov,
I. S.; Shavrina, A. V.
1991SvA....35..387B Altcode:
No abstract at ADS

---------------------------------------------------------
Title: Atmospheric chemical composition of the K0 giants ∈ Cyg
and ∈ Tau. III
Authors: Berdyugina, S. V.; Boyarchuk, M. E.; Savanov, I. S.
1991BCrAO..83...74B Altcode:
No abstract at ADS

---------------------------------------------------------
Title: Investigation of the atmospheres of cold giants based on
molecular spectra I. The CN molecule
Authors: Berdyugina, S. V.
1991BCrAO..83...89B Altcode:
No abstract at ADS

---------------------------------------------------------
Title: Discovery of High Linear Polarization at Brightness Minima
of Cq-Tauri
Authors: Berdyugin, A. V.; Berdyugina, S. V.; Grinin, V. P.; Minikulov,
N. K.
1990SvA....34..408B Altcode:
No abstract at ADS

---------------------------------------------------------
Title: Discovery of high linear polarization at brightness minima
of CQ Tau
Authors: Berdyugin, A. V.; Berdyugina, S. V.; Grinin, V. P.; Minikulov,
N. H.
1990AZh....67..812B Altcode:
Results are presented of simultaneous UBVRI observations (carried out in
Crimea during 1988/1989) of the polarization and light characteristics
of an isolated Ae Herbig star CQ Tau. During this period, several
decreases in light were observed, accompanied by considerable changes
in the polarization parameters. It was found that, while the linear
polarization of the star did not significantly differ from that of
neighboring stars during the bright state (V = 9.5 mag), a considerable
increase of the polarization degree was observed during the deep minimum
(V = 11.2 mag), together with strong variations of the position angle.