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 Bibcode: 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 Bibcode: 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 (<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 (>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 Bibcode: 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. Bibcode: 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. Bibcode: 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 Bibcode: 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 Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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 <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. Bibcode: 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. Bibcode: 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 Bibcode: 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 Bibcode: 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 < 0.005 kgf, and drive hysteresis < 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 Bibcode: 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 < 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 Bibcode: 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 Bibcode: 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 Bibcode: 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. Bibcode: 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&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 < 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. Bibcode: 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 < 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 (>3σ) polarization is found in 115 stars, and >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 http://cdsarc.u-strasbg.fr (ftp://130.79.128.5) or via http://cdsarc.u-strasbg.fr/viz-bin/cat/J/A+A/635/A46. 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. Bibcode: 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. Bibcode: 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&AS v30 1977; Tinbergen A&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. Bibcode: 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. Bibcode: 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 Bibcode: 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 (< 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. Bibcode: 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 http://cdsarc.u-strasbg.fr (ftp://130.79.128.5) or via http://cdsarc.u-strasbg.fr/viz-bin/cat/J/A+A/629/A83 Title: VizieR Online Data Catalog: Complexity of magnetic fields on red dwarfs (Afram+, 2019) Authors: Afram, N.; Berdyugina, S. V. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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 Bibcode: 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 Bibcode: 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. Bibcode: 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 Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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 Bibcode: 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 Bibcode: 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. Bibcode: 2018SPIE10700E..4IB Altcode: The Exo-Life Finder (ELF) will be an optical system with the resolving power of a >=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. Bibcode: 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. Bibcode: 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. Bibcode: 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 Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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 Bibcode: 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. Bibcode: 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 Bibcode: 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 Bibcode: 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 Bibcode: 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. Bibcode: 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. Bibcode: 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 Bibcode: 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 Bibcode: 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 http://cdsarc.u-strasbg.fr (http://130.79.128.5) or via http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/590/A54 Title: Infrared Dual-line Hanle diagnostic of the Coronal Vector Magnetic Field Authors: Dima, Gabriel; Kuhn, Jeffrey; Berdyugina, Svetlana Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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 http://cdsarc.u-strasbg.fr (ftp://130.79.128.5) or via http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/586/A87 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 Bibcode: 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. Bibcode: 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 Bibcode: 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 Bibcode: 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 Bibcode: 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 < 0.05% Authors: Harrington, David M.; Berdyugina, Svetlana V.; Kuzmychov, Oleksii; Kuhn, Jeffrey R. Bibcode: 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 Bibcode: 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 Bibcode: 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 Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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 http://cdsarc.u-strasbg.fr (ftp://130.79.128.5) or via http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/575/A89 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. Bibcode: 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 & 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. Bibcode: 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 http://www.aanda.org Title: VizieR Online Data Catalog: Center-to-limb polarization of FGK stars (Kostogryz+, 2015) Authors: Kostogryz, N. M.; Berdyugina, S. V. Bibcode: 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. Bibcode: 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. Bibcode: 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 Bibcode: 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. Bibcode: 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 Bibcode: 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. Bibcode: 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 Bibcode: 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 Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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 Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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 Bibcode: 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. Bibcode: 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. Bibcode: 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 <Blon> 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 Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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 & 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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 Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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&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. Bibcode: 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 & 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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 Bibcode: 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 >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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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, <Bz>, 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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 Bibcode: 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. Bibcode: 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 & 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. Bibcode: 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. Bibcode: 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. Bibcode: 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 < Bz > 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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 > 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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 <=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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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 & Usoskin (2003, A&A, 405, 1121) and Usoskin et al. (2005, A&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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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&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 & Solanki 2002, A&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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 2004IAUS..215..289T Altcode: No abstract at ADS Title: Evidence for the Hanle effect in molecular lines Authors: Berdyugina, S. V.; Fluri, D. M. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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 & 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. Bibcode: 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. Bibcode: 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 & 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 2003ASPC..307..181B Altcode: No abstract at ADS Title: Tomography of Stellar Non-Radial Pulsations Authors: Berdyugina, Svetlana V. Bibcode: 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. Bibcode: 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. Bibcode: 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&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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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 Bibcode: 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. Bibcode: 1999anot.conf..206B Altcode: No abstract at ADS Title: Doppler imaging of UX Ari (poster) Authors: Aarum, V.; Berdyugina, S. V.; Ilyin, I. V. Bibcode: 1999anot.conf..222A Altcode: No abstract at ADS Title: Nonaxisymmetric Stellar Dynamos Authors: Tuominen, I.; Berdyugina, S. V.; Korpi, M. J.; Rönty, T. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. >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 Bibcode: 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 (>=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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 1995ARep...39..761A Altcode: No abstract at ADS Title: Li-rich giants: evidence for convection mixing. Authors: Berdyugina, S. V.; Savanov, I. S. Bibcode: 1995MmSAI..66..425B Altcode: No abstract at ADS Title: Modeling of chemical anomalies of Am-star Authors: Savanov, I. S.; Berdyugina, S. V. Bibcode: 1995IAUS..176P.145S Altcode: No abstract at ADS Title: Doppler imaging by the Mean Information Principle Authors: Berdyugina, S. V. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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.