New Windows on Massive Stars, Asteroseismology, Interferometry and Spectropolarimetry

Proceedings of the International Astronomical Union IAU Symposium No. 307 IAU Symposium IAU Symposium 23-27 June 2014 Massive stars play a crucial role in the Universe: they are important drivers for the photometric and chemical evolution of galaxies; 307 Geneva, Switzerland they are sources of important elements, including those necessary for life; and, with their strong winds and supernova explosions, they feed the interstellar medium with momentum and kinetic energy, impacting on the star formation rate. Knowledge of the evolution 23-27 June 2014 307 23-27 June 2014 New Windows on of massive stars is important not only for stellar physics, but also for Geneva, Switzerland New Windows on probing the evolution of galaxies and their star formation histories Geneva, Switzerland throughout cosmic time. This volume provides an introduction to Massive Stars: these topics and to the techniques used to investigate the Massive Stars: properties of massive stars, including asteroseismology, spectropolarimetry, and interferometry. It highlights synergies Asteroseismology, between these new techniques and more classical methods, to create a synthetic view of massive stars, leading researchers Asteroseismology, Interferometry and towards new and innovative solutions to the most topical questions regarding the evolution of massive stars. Spectropolarimetry Interferometry and Proceedings of the International Astronomical Union Editor in Chief: Prof. Thierry Montmerle New Windows on This series contains the proceedings of major scientiﬁ c meetings Massive Stars: held by the International Astronomical Union. Each volume Spectropolarimetry contains a series of articles on a topic of current interest in Asteroseismology, astronomy, giving a timely overview of research in the ﬁ eld. With Interferometry contributions by leading scientists, these books are at a level and suitable for research astronomers and graduate students. Edited by Spectropolarimetry

Meynet Georges Meynet Georgy Groh Cyril Georgy Stee José Groh Philippe Stee

ISSN 1743-9213

International Astronomical Union International Astronomical Union Proceedings of the International Astronomical Union Proceedings of the International Astronomical Union

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IAU SYMPOSIUM No. 307

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Chief Editor THIERRY MONTMERLE, IAU General Secretary Institut d’Astrophysique de Paris, 98bis, Bd Arago, 75014 Paris, France [email protected]

Editor PIERO BENVENUTI, IAU Assistant General Secretary University of Padua, Dept of Physics and Astronomy, Vicolo dell’Osservatorio, 3, 35122 Padova, Italy [email protected]

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International Astronomical Union U U NEW WINDOWS ON MASSIVE STARS, ASTEROSEISMOLOGY, INTERFEROMETRY AND SPECTROPOLARIMETRY

PROCEEDINGS OF THE 307th SYMPOSIUM OF THE INTERNATIONAL ASTRONOMICAL UNION HELD IN GENEVA, SWITZERLAND JUNE 23–27, 2014

Edited by

GEORGES MEYNET Geneva Observatory, University of Geneva, CH-1290 Versoix, Switzerland CYRIL GEORGY Astrophysics group, EPSAM, Keele University, Lennard-Jones Labs, Keele, ST5 5BG, UK JOSEGROH´ Geneva Observatory, University of Geneva, CH-1290 Versoix, Switzerland and PHILIPPE STEE Observatoire de la Cˆote d’Azur - CNRS - UNSA and Boulevard de l’Observatoire, CS 34229, F06304 Nice Cedex 4, France

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ISBN 9781107078581 hardback ISSN 1743-9213

Preface...... xiii

The Organizing Committee ...... xv

Conference photograph ...... xvi

Participants...... xvii

Address by the Local Organizing Committee ...... xix

The advanced phases of massive stars and the explosive yields ...... 1 A. Chieffi & M. Limongi Physics of rotation: problems and challenges...... 9 A.Maeder&G.Meynet The Physics of Convection in Massive Stars ...... 20 C. A. Meakin PhysicsofMassLossinMassiveStars...... 25 J.Puls,J.O.Sundqvist&N.Markova A binary progenitor for the Type Ib Supernova iPTF13bvn ...... 37 M. C. Bersten Winds of metal-poor OB stars: Updates from HST-COS UV spectroscopy . .... 41 M. Garc´ıa, A. Herrero, F. Najarro, D. J. Lennon & M. A. Urbaneja Combining observational techniques to constrain convection in evolved massive star models...... 47 C. Georgy, H. Saio & G. Meynet Massive stars near the Eddington-limit, pulsations & mass-loss ...... 52 G. Gräfener Discovery of a Thorne-Zytkow˙ object candidate in the Small Magellanic Cloud . 57 E. M. Levesque, P. Massey, A. N. Zytkow˙ & N. Morrell A New Class of Wolf-Rayet Stars: WN3/O3s ...... 64 P. Massey, K. F. Neugent, N. Morrell & D. J. Hillier New prescriptions of turbulent transport from local numerical simulations . .... 70 V. Prat, F. Lignières & G. Lesur Rotational velocities of single and binary O-type stars in the Tarantula Nebula . 76 O. H. Ram´ırez-Agudelo, H. Sana, A. de Koter, S. Simón-D´ıaz, S.E.deMink,F.Tramper,P.L.Dufton,C.J.Evans,G.Gräfener, A. Herrero, N. Langer, D. J. Lennon, J. Ma´ız Apellániz, N. Markova, F. Najarro, J. Puls, W. D. Taylor & J. S. Vink,

Downloaded from https://www.cambridge.org/core. IP address: 170.106.35.229, on 30 Sep 2021 at 00:38:59, subject to the Cambridge Core terms of use, available at https://www.cambridge.org/core/terms. https://doi.org/10.1017/S1743921314006115 vi Contents Stellar Yields of Rotating First Stars: Yields of Weak Supernovae and Abundances of Carbon-enhanced Hyper Metal Poor Stars ...... 82 K. Takahashi, H. Umeda & T. Yoshida The Gaia-ESO Survey and Massive Stars ...... 88 R. Blomme, Y. Frémat, E. Gosset, A. Herrero, A. Lobel, J. Ma´ız Apellániz, T. Morel, I. Negueruela, T. Semaan, S. Simón-D´ıaz & D. Volpi Non-LTE Abundances in OB stars: Preliminary Results for 5 Stars in the Outer Galactic Disk ...... 90 G. A. Bragan¸ca, T. Lanz, S. Daflon, K. Cunha, C. D. Garmany, J. W. Glaspey, M. Borges Fernandes, M. S. Oey, T. Bensby & I. Hubeny Luminous Infrared Sources in the Local Group: Identifying the Missing Links in Massive Star Evolution ...... 92 N. Britavskiy, A. Z. Bonanos & A. Mehner Chemical abundances of fast-rotating OB stars...... 94 C. Cazorla, T. Morel, Y. Nazé&G.Rauw Massive star archeology in globular clusters ...... 96 W. Chantereau, C. Charbonnel & G. Meynet Linking 1D Stellar Evolution to 3D Hydrodynamic Simulations ...... 98 A. Cristini, R. Hirschi, C. Georgy, C. Meakin, D. Arnett & M. Viallet FirstResultsoftheAnalysisoftheWolf-RayetStarWR6...... 100 A. C. Gormaz-Matamala, A. Hervé, A. Chené, M. Curé & R. Mennickent. Evolution of the rotational properties and nitrogen surface abundances of B-Type stellar populations ...... 102 A. Granada, G. Meynet, S. Ekström, C. Georgy & L. Haemmerlé Delta-slow solution to explain B supergiant stars’ winds ...... 104 M. Haucke, I. Araya, C. Arcos, M. Curé, L. Cidale, S. Kanaan, R. Venero &M.Kraus Massive OB stars at varying Z ...... 106 A. Herrero, M. Garcia, S. Simón-D´ıaz, I. Camacho, C. Sab´ın-Sanjulián & N. Castro Massive stars: flare activity due to infalls of comet-like bodies ...... 108 S. Ibadov & F. S. Ibodov Study of environment and photosphere of 51 Oph...... 111 N. Jamialahmadi, Ph. Berio, B. Lopez, A. Meilland & Ph. Stee Line profile variability in spectra of hot massive stars ...... 113 A. Kholtygin, N. Sudnik & V. Dushin Discrete absorption components in the massive LBV Binary MWC 314...... 115 A. Lobel, C. Martayan, M. Corcoran, J. H. Groh & Y. Frémat The mass discrepancy problem in O stars of solar metallicity. Does it still exist? 117 N. Markova & J. Puls

Downloaded from https://www.cambridge.org/core. IP address: 170.106.35.229, on 30 Sep 2021 at 00:38:59, subject to the Cambridge Core terms of use, available at https://www.cambridge.org/core/terms. https://doi.org/10.1017/S1743921314006115 Contents vii Investigation of the brightest stars in the Cyg OB2 association ...... 119 O. Maryeva & S. Parfenov OHANA: Eta Carinae’s Variability in the Near-IR...... 121 A. Mehner, W.-J. de Wit, T. Rivinius & the Paranal VLTI group MarkovChainMonte-CarloModelsofStarburstClusters...... 123 J. Melnick A spectroscopic and photometric study of the interacting binary and double period variable HD 170582...... 125 R. E. Mennickent, G. Djuraˇsević, M. Cabezas, A. Cséki, J. Rosales, E. Niemczura, I. Araya & M. Curé The Close Binary Frequency of Wolf-Rayet Stars as a Function of Metallicity in M31andM33...... 127 K. F. Neugent & P. Massey FundamentalparametersofBtypestars...... 129 M.-F. Nieva A Search for Hot Subdwarf Companions to Rapidly-Rotating Early B Stars.... 131 G. J. Peters, D. R. Gies, L. Wang & E. D. Grundstrom An empirical pipeline for determining the viscosity parameter for Be star disks . 133 L. R. R´ımulo, A. C. Carciofi, T. Rivinius & X. Haubois Westerlund 1 is a Galactic Treasure Chest: The Wolf-Rayet Stars ...... 135 C. K. Rosslowe & P. A. Crowther Herschel/PACS: Constraining clumping in the intermediate wind region of OB stars 137 M. M. Rubio-D´ıez, F. Najarro, J. O. Sundqvist, A. Traficante, J. Puls, L. Calzoletti, A. Herrero, D. Figer & J. Martin-Pintado NGC 3293 revisited by the Gaia-ESO Survey ...... 140 T. Semaan, T. Morel, E. Gosset, J. Zorec, Y. Frémat, R. Blomme & A. Lobel Revisiting the Hunter diagram with the Geneva Stellar Evolution Code ...... 142 R. Simoniello, G. Meynet, S. Ekström, C. Georgy & A. Granada ThepropertiesofsingleWOstars...... 144 F. Tramper, S. M. Straal, G. Gräfener, L. Kaper, A. de Koter, N. Langer, H. Sana & J. S. Vink SpectralanalysisofLBVstarsinM31:AFAndandVar15...... 146 A. F. Valeev, O. Sholukhova & S. Fabrika VariableC–“atypical”LBVinM33?...... 148 K. Weis, R. M. Humphreys, B. Burggraf & D. J. Bomans Variational approach for rotating-stellar evolution in Lagrange scheme ...... 150 N. Yasutake & S. Yamada Wolf-RayetstarsfromVeryMassiveStars...... 152 N. Yusof

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Downloaded from https://www.cambridge.org/core. IP address: 170.106.35.229, on 30 Sep 2021 at 00:38:59, subject to the Cambridge Core terms of use, available at https://www.cambridge.org/core/terms. https://doi.org/10.1017/S1743921314006115 Contents ix Pulsations of massive stars beyond TAMS: effects of mass loss, diffusion, overshoot- ing...... 226 J. Ostrowski & J. Daszyńska-Daszkiewicz Deep Photospheric Emission Lines as Probes for Pulsational Waves...... 228 Th. Rivinius, M. Shultz & G. A. Wade Stability boundaries for massive stars in the sHR diagram ...... 230 H.Saio,C.Georgy&G.Meynet Asteroseismology of the SPB star HD 21071 ...... 232 W. Szewczuk & J. Daszyńska-Daszkiewicz Spectral Effects of Pulsations in Blue Supergiants ...... 235 S. Tomić, M. Kraus & M. E. Oksala Is λ Cep a pulsating star? ...... 237 J. M. Uuh-Sonda, P. Eenens & G. Rauw Seismic analysis of the massive β Cephei star 15 Canis Majoris ...... 239 P. Walczak & G. Handler Aninterferometricjourneyaroundmassivestars...... 241 A. Meilland & P. Stee Basics of Optical Interferometry: A Gentle Introduction ...... 252 G. T. van Belle The photosphere and circumstellar environment of the Be star Achernar ...... 261 D. M. Faes, A. Domiciano de Souza, A. C. Carciofi & P. Bendjoya Zooming into Eta Carinae with interferometry ...... 267 J. H. Groh Evidences for a large hot spot on the disk of Betelgeuse (α Ori)...... 273 M. Montargès, P. Kervella, G. Perrin, A. Chiavassa & J. B. Le Bouquin On the atmospheric structure and fundamental parameters of red supergiants . . 280 M. Wittkowski, B. Arroyo-Torres, J. M. Marcaide, F. J. Abellan, A. Chiavassa, B. Freytag, M. Scholz, P. R. Wood & P. H. Hauschildt Amplitude Modulation of Cepheid Radial Velocity Curves as a Systematic Source of Uncertainty for Baade-Wesselink Distances ...... 286 R. I. Anderson The impact of the rotation on the surface brightness of early-type stars ...... 288 M. Challouf, N. Nardetto, A. Domiciano de Souza, D. Mourard, H. Aroui, P. Stee & A. Meilland The circumstellar environment of the B[e] star GG Car: an interferometric modeling 291 A. Domiciano de Souza, M. Borges Fernandes, A. C. Carciofi & O. Chesneau Angular Diameters of O- and B-type Stars ...... 293 K. Gordon, D. Gies & G. Schaefer BinarityoftheLBVHRCar...... 295

Downloaded from https://www.cambridge.org/core. IP address: 170.106.35.229, on 30 Sep 2021 at 00:38:59, subject to the Cambridge Core terms of use, available at https://www.cambridge.org/core/terms. https://doi.org/10.1017/S1743921314006115 x Contents Th. Rivinius, H. M. J. Boffin, W. J. de Wit, A. Mehner, Ch. Martayan, S. Guieu & J.-B. Le Bouquin AMBER/VLTI Snapshot Survey on Circumstellar Environments ...... 297 Th. Rivinius, W. J. de Wit, Z. Demers, A. Quirrenbach & the VLTI Science Operations Team Recent highlights of spectropolarimetry applied to the magnetometry of massive stars...... 301 J. H. Grunhut Basics of spectropolarimetry ...... 311 J. D. Landstreet Magnetic Field - Stellar Winds Interaction ...... 321 A. ud-Doula The BinaMIcS project: understanding the origin of magnetic fields in massive stars throughclosebinarysystems...... 330 E. Alecian, C. Neiner, G. A. Wade, S. Mathis, D. Bohlender, D. Cébron, C. Folsom, J. Grunhut, J.-B. Le Bouquin, V. Petit, H. Sana, A. Tkachenko, A. ud-Doula & the BinaMIcS collaboration Revealing the Mass Loss Structures of Four Key Massive Binaries Using Optical Spectropolarimetry...... 336 J. R. Lomax TheBFieldsinOBStars(BOB)Survey...... 342 T. Morel, N. Castro, L. Fossati, S. Hubrig, N. Langer, N. Przybilla, M. Schöller, T. Carroll, I. Ilyin, A. Irrgang, L. Oskinova, F. R. N. Schneider, S. Simon D´ıaz, M. Briquet, J. F. González, N. Kharchenko, M.-F. Nieva, R.-D. Scholz, A. de Koter, W.-R. Hamann, A. Herrero, J. Ma´ız Apellániz, H. Sana, R. Arlt, R. Barbá, P. Dufton, A. Kholtygin, G. Mathys, A. Piskunov, A. Reisenegger, H. Spruit, & S.-C. Yoon Unraveling the variability of σ OriE ...... 348 M. E. Oksala, O. Kochukhov, J. Krtiˇcka,M.Prvák & Z. Mikuláˇsek Constraining general massive-star physics by exploring the unique properties of magnetic O-stars: Rotation, macroturbulence & sub-surface convection . . . 353 J. O. Sundqvist Linear line spectropolarimetry as a new window to measure 2D and 3D wind ge- ometries...... 359 J. S. Vink Discovery of Secular Evolution of the Atmospheric Abundances of Ap Stars . . . . 365 J. D. Bailey, J. D. Landstreet & S. Bagnulo The magnetic field of ζ OriA ...... 367 A. Blazère, C. Neiner, J-C. Bouret, A. Tkachenko & the MiMeS collaboration Spectropolarimetric study of selected cool supergiants ...... 369 V. Butkovskaya, S. Plachinda & D. Baklanova

Downloaded from https://www.cambridge.org/core. IP address: 170.106.35.229, on 30 Sep 2021 at 00:38:59, subject to the Cambridge Core terms of use, available at https://www.cambridge.org/core/terms. https://doi.org/10.1017/S1743921314006115 Contents xi Beam me up, Spotty: Toward a new understanding of the physics of massive star photospheres ...... 371 A. David-Uraz, G. Wade & S. Owocki Impact of rotation on the geometrical configurations of fossil magnetic fields . . . 373 C. Emeriau & S. Mathis A Simple Mean-Field Diagnostic from Stokes V Spectra ...... 375 K. G. Gayley & S. P. Owocki Linear Polarization and the Dynamics of Circumstellar Disks of Classical Be Stars 377 R. J. Halonen & C. E. Jones Multiple, short-lived ”stellar prominences” on O stars: the supergiant λ Cephei. 379 H. F. Henrichs & N. Sudnik Project VeSElkA : Preliminary results for CP stars recently observed with ES- PaDOnS...... 381 V. Khalack & F. LeBlanc Abundance analysis of HD 22920 spectra ...... 383 V. Khalack & P. Poitras FundamentalpropertiesofsingleOstarsintheMiMeSsurvey...... 385 F. Martins, A. Hervé, J.-C. Bouret, W. L. F. Marcolino, G. A. Wade, C. Neiner, E. Alecian & the MiMeS collaboration Spectropolarimetry and modeling of WR156...... 387 O. Maryeva The UVMag space project: UV and visible spectropolarimetry of massive stars 389 C. Neiner & the UVMag consortium Magnetic main sequence stars as progenitors of blue supergiants ...... 391 I. Petermann, N. Castro & N. Langer Magnetic CP stars in Orion OB1 association ...... 393 I. I. Romanyuk & E. A. Semenko Stellar magnetic fields from four Stokes parameter observations ...... 395 N. Rusomarov, O. Kochukhov & N. Piskunov Plasma Leakage from the Centrifugal Magnetospheres of Magnetic B-Type Stars 397 M. Shultz, G. Wade, T. Rivinius, J. Grunhut, V. Petit & the MiMeS Collaboration ξ1 CMa: An Extremely Slowly Rotating Magnetic B0.7 IV Star ...... 399 M. Shultz, G. Wade, T. Rivinius, W. Marcolino, H. Henrichs, J. Grunhut & the MiMeS Collaboration Magnetic fields and internal mixing of main sequence B stars ...... 401 G. A. Wade, C. P. Folsom, J. Grunhut, J. D. Landstreet & V. Petit Links between surface magnetic fields, abundances, and surface rotation in clusters andinthefield...... 404 N. Przybilla

Downloaded from https://www.cambridge.org/core. IP address: 170.106.35.229, on 30 Sep 2021 at 00:38:59, subject to the Cambridge Core terms of use, available at https://www.cambridge.org/core/terms. https://doi.org/10.1017/S1743921314006115 xii Contents Massive Star Astrophysics with the new Magellanic Cloud photometric survey MCSF...... 414 D. J. Bomans, A. Becker & K. Weis Asteroseismology and spectropolarimetry: opening new windows on the internal dynamics of massive stars ...... 420 S. Mathis & C. Neiner The Massive Star Population at the Center of the Milky Way ...... 426 F. Najarro, D. de la Fuente, T. R. Geballe, D. F. Figer & D. J. Hillier Accretion Signatures on Massive Young Stellar Objects...... 431 F. Navarete, A. Damineli, C. L. Barbosa & R. D. Blum TheX-raypropertiesofmagneticmassivestars...... 437 Y. Nazé, V. Petit, M. Rinbrand, D. Cohen, S. Owocki, A. ud-Doula & G. Wade Combining seismology and spectropolarimetry of hot stars ...... 443 C. Neiner, M. Briquet, S. Mathis & P. Degroote X-rays From Centrifugal Magnetospheres in Massive Stars ...... 449 C. Bard & R. Townsend Abundance study of two magnetic B-type stars in the Orion Nebula Cluster . . . 451 T. Morel Circumstellar Environments of MYSOs Revealed by IFU Spectroscopy ...... 453 F. Navarete, A. Damineli, C. L. Barbosa & R. D. Blum An X-ray surprise in a magnetic pulsator ...... 455 Y. Nazé New insights on Be shell stars from modelling their Hα emissionprofiles...... 457 J. Silaj, C. E. Jones, T. A. A. Sigut & C. Tycner 3D and Some Other Things Missing from the Theory of Massive Star Evolution 459 W. D. Arnett Asteroseismology of Massive Stars : Some Words of Caution...... 470 A. Noels, M. Godart, S. J. A. J. Salmon, M. Gabriel, J. Montalbán & A. Miglio Interferometryofmassivestars:thenextstep...... 480 Ph. Stee, A. Meilland & O. L. Creevey Spectropolarimetry of massive stars: Requirements and potential from today to 2030 ...... 490 G. A. Wade Observing programs, what are the priorities? ...... 499 G. Meynet & H. Henrichs Stellar Models: What is the future direction? ...... 504 A. ud-Doula

Author index ...... 505

A Universe without massive stars would be very different from the one we can observe. Indeed these stars are important drivers for the photometric and chemical evolution of galaxies, they are the sources of important elements for the building of living bodies, they feed with their strong winds and supernova explosion the interstellar medium with momentum and kinetic energy having thus an impact on the star formation rate. They are the progenitors of core collapse events and of the most energetic stellar explosions in the Cosmos, the Gamma Ray Bursts. They give birth to compact objects as neutron stars and black holes. From what precedes, one can figure out that knowing the evolution of massive stars is not only important for stellar physics, but also for probing the evolution of galaxies and their star formation history along the whole cosmic history. This subject also connects in a particularly strong and direct way the observations of nearby objects with that of far distant galaxies. In this context, the possibilities that became operative only recently to probe the interior of stars, to constrain the size of their convective cores and the way they rotate in their interiors through asteroseismology, to determine the strength and topology of their surface magnetic fields through spectropolarimetry and to measure their shape and the distribution of their circumstellar environments through interferometry opened new paths for investigating their properties. Associated with other more classical methods, as photometry and/or spectroscopy, these technics will change our understanding of massive star evolution and may show that beside the initial mass and the metallicity, the evolution of massive stars, either single or in close binary systems, may also depend on their axial rotation and on their surface magnetic field. Although for some of these technics, the application to massive stars is still in its infancy, we thought that it was time to convey astronomers from these different areas in order 1) to investigate how these technics can guide us towards new and innovative solutions to the most topical questions regarding the evolution of massive stars, 2) to allow the participants of different disciplines, and hopefully the readers of these proceedings, to grasp the essential of these observing methods and 3) to stimulate new ideas for using synergies between different observational technics. At the end of 2012, a letter of intent, followed by a detailed description of the project was sent to IAU. We were very pleased to receive in May 2013 the announcement that our project of Symposium was one of the 9 selected symposia among the 17 proposals. Began then the work of organizing the sessions and selecting the invited reviewers with the SOC. The present conference conveyed 138 astronomers from 28 countries. The scientific programs consisted in 6 sessions (Challenges in massive star evolution, Asteroseismology, Interferometry, Spectropolarimetry, Synergies between different techniques, and Towards a synthetic view), with 17 review talks, 33 contributed talks, 2 general discussions, and 2 poster sessions. Each session dedicated to one observational technics began with two review talks providing first a simple but rigorous presentation of the principles on which the observations are based and second a discussion of the main results obtained so far. We hope that the readers of these proceedings will take benefit from all these presentations as much as the participants of the symposium. We had also the pleasure to organize an outreach conference given by Coralie Neiner entitled Le magnétisme stellaire : son rôle sur la vie des étoiles et la nôtre, which attracted about 100 people.

Georges Meynet and Phillipe Stee, co-chairs SOC, Geneva, August 31, 2014

Scientiﬁc D. Arnett (USA) L. Cidale (Argentina) R. Hirschi (UK) E. Levesque (USA) M. Limongi (Italy) A. Maeder (Switzerland) P. Massey (USA) G. Meynet (co-chair, Switzerland) C. Neiner (France) A. Noels (Belgium) S. Owocki (USA) T. Rivinius (Chile) H. Saio (Japan) P. Stee (co-chair, France) R. Townsend (USA) G. Wade (Canada)

Local P. Eggenberger S. Ekstr¨om (co-chair) C. Georgy A. Granada J. Groh L. Haemmerl´e G. Meynet G. Priviterra G. Simond C. Tacoy (co-chair)

Acknowledgements

The symposium is sponsored and supported by the IAU Division G (Stars and Stellar Physics), by the IAU Commissions No. 25 (Astronomical Photometry and Polarimetry), No. 35 (Stellar Constitution), No. 36 (Theory of Stellar At- mospheres), the IAU Working Group on Active B Stars and the IAU Working Group on Massive Stars.

The Local Organizing Committee operated under the auspices of the Geneva Observatory, University of Geneva. Funded by the International Astronomical Union, Swiss National Science Foundation, Commission administrative, Geneva University, Geneva Observatory, University of Geneva, Faculty of Science, Geneva University, Rectorate of Geneva University, Swiss Society of Astronomy and Astrophysics, Soci´et´e de Physique et d’Histoire Naturelle, Geneva.

Conny Aerts, Institute of Astronomy, University of Leuven, Belgium [email protected] Evelyne Alecian, IPAG - Observatoire de Grenoble, France [email protected] Richard I. Anderson, Department of Astronomy, Geneva University, Switzerland [email protected] Rainer Arlt, Leibniz Institute for Astrophysics Potsdam, Germany [email protected] W. David Arnett,StewardObservatory,UniversityofArizona,USA [email protected] Dietrich Baade, European Southern Observatory, Garching, Germany [email protected] Jeffrey Bailey, Max Planck Institut für extraterrestrische Physik, Germany jeff[email protected] Fabio Barblan, Department of Astronomy, Geneva University, Switzerland [email protected] Christopher Bard, University of Wisconsin-Madison, USA [email protected] Melina Bersten, Kavli IPMU, Japan [email protected] Aurore Blazere,LESIA,France [email protected] Ronny Blomme, Royal Observatory of Belgium, Brussels, Belgium [email protected] Dominik Bomans, Astronomical Institute, Ruhr-University Bochum, Germany [email protected] Gustavo Bragan¸ca,Observatório Nacional/Observatoire de la Côte d’Azur, Nice, [email protected] France Nikolay Britavskiy, IAASARS, National Observatory of Athens, Greece [email protected] Varvara Butkovskaya, Crimean Astrophysical Observatory, Taras Shevchenko [email protected] National University, Kyiv, Ukraine Matteo Cantiello,KITP,USA [email protected] Alex Carciofi, Instituto de Astronomia, Geof´ısica e Ciências Atmosféricas, Brazil carciofi@usp.br Constantin Cazorla, Institut d’astrophysique, géophysique et océanographie, [email protected] University of Liège, Belgium Mounir Challouf,ObservatoiredelaCôte d’Azur, Nice, France [email protected] William Chantereau, Department of astronomy, Geneva University, Switzerland [email protected] Corinne Charbonnel, Department of astronomy, Geneva University, Switzerland, [email protected] and CNRS, France Alessandro Chieffi, INAF - Istituto di Astrofisica e Planetologia Spaziale, Italy alessandro.chieffi@inaf.it Andrea Cristini, Keele University, UK [email protected] Alexandre David-Uraz, Queen’s University/Royal Military College, Canada [email protected] Alex de Koter, Anton Pannekoek Institute for Astronomy, University of [email protected] Amsterdam, Netherlands Jacqueline den Hartogh, Keele University, UK [email protected] Armando Domiciano de Souza,ObservatoiredelaCôte d’Azur, Nice, France [email protected] Durand D’souza, Max Planck Institute for Astrophysics, Germany [email protected] Philippe Eenens, University of Guanajuato, Mexico [email protected] Patrick Eggenberger, Department of astronomy, Geneva University, Switzerland [email protected] Sylvia Ekström, Department of astronomy, Geneva University, Switzerland [email protected] Daniel Faes,IAG-USP,Brazil [email protected] Gaston Folatelli, Kavli IPMU, Japan [email protected] Luca Fossati, Argelander-Institut für Astronomie, Germany [email protected] Miriam Garc´ıa, Center for Astrobiology, Spain [email protected] Ken Gayley, University of Iowa, USA [email protected] Marcus Gellert, Leibniz Institute for Astrophysics, Potsdam, Germany [email protected] Cyril Georgy, Keele University, UK [email protected] Melanie Godart, Tokyo University, Japan [email protected] Katie Gordon, Georgia State University, USA [email protected] Alex Gormaz-Matamala, University of Concepción, Chile [email protected] Götz Gräfener, Armagh Observatory, UK [email protected] Anah´ı Granada, Department of astronomy, Geneva University, Switzerland [email protected] Nicolas Grevesse, Centre Spatial de Liège, UniversitédeLiège, Belgium [email protected] José Groh, Department of astronomy, Geneva University, Switzerland [email protected] Jason Grunhut, European Southern Observatory, Garching, Germany [email protected] Lionel Haemmerlé, Department of astronomy, Geneva University, Switzerland [email protected] Robbie Halonen, University of Western Ontario, Canada [email protected] Maximiliano Haucke, Facultad de Ciencias Astronómicas y Geof´ısicas, UNLP, [email protected] Argentina Huib Henrichs, University of Amsterdam, Netherlands [email protected] Artemio Herrero, Instituto de Astrofisica de Canarias, Spain [email protected] Raphael Hirschi, Keele University, UK [email protected] Subhon Ibadov, Institute of Astrophysics, Tajik Academy of Sciences, Tajikistan [email protected] Narges Jamialahmadi,ObservatoiredelaCôte d’Azur, Nice, France [email protected] Santosh Joshi, ARIES, Nainital, India [email protected] Viktor Khalack,Université de Moncton, Canada [email protected] Agnes Kim, Penn State Worthington Scranton, USA [email protected] Oleg Kochukhov, Uppsala University, Sweden [email protected] Michalis Kourniotis, IAASARS, National Observatory of Athens, Greece [email protected] Karolina Kubiak, Institut für Astrophysik, Austria [email protected] John Landstreet, Department of Physics & Astronomy, University of Western [email protected] Ontario, Canada Norbert Langer, Argelander-Institut für Astronomie, Universität Bonn, Germany [email protected] Emily Levesque, University of Colorado, Boulder, USA [email protected] Jean-Christophe Leyder, European Space Agency (ESA), Spain [email protected] Sergey Lisakov,ObservatoiredelaCôte d’Azur, Nice, France [email protected] Alex Lobel, Royal Observatory of Belgium, Belgium [email protected] Jamie Lomax, University of Oklahoma, USA [email protected] Catherine Lovekin, Mount Allison University, Canada [email protected] André Maeder, Department of astronomy, Geneva University, Switzerland [email protected] Nevena Markova, Institute of astronomy with National Astronomical [email protected] Observatory, Bulgaria Fabrice Martins, LUPM, CNRS & Montpellier University, France [email protected] Olga Maryeva, Special Astrophysical Observatory of the Russian Academy of [email protected] Sciences, Russian Federation Philip Massey, Lowell Observatory, USA [email protected] Stéphane Mathis, AIM Paris-Saclay, CEA/DSM/IRFU/SAp, France [email protected] Casey Meakin, University of Arizona, USA [email protected] Redouane Mecheri, Centre de Recherche en Astronomie, Astrophysique et [email protected] Géophysique (CRAAG), Algeria Andrea Mehner, European Southern Observatory, Chile [email protected] Anthony Meilland,ObservatoiredelaCôte d’Azur, Nice, France [email protected]

Jorge Melnick, European Southern Observatory, Chile [email protected] Ronald Mennickent, Universidad de Concepción, Chile [email protected] Georges Meynet, Department of astronomy, Geneva University, Switzerland [email protected] Andrea Miglio, School of Physics and Astronomy, University of Birmingham, [email protected] UK Miguel Montargès, LESIA - Observatoire de Paris, France [email protected] Ehsan Moravveji, Institute of Astronomy, KU Leuven, Belgium [email protected] Thierry Morel, Institut d’Astrophysique et de Géophysique, Liège, Belgium [email protected] Dawid Mo´zdzierski, Astronomical Institute, University of Wroclaw, Poland [email protected] Francisco Najarro, Centro de Astrobiolog´ıa, Spain [email protected] Felipe Navarete, University of Sao Paulo, Brazil [email protected] Yaël Nazé, Institut d’astrophysique, géophysique et océanographie, University [email protected] of Liège, Belgium Hilding Neilson, East Tennessee State University, USA [email protected] Coralie Neiner, LESIA, Paris-Meudon Observatory, France [email protected] Kathryn Neugent, Lowell Observatory, USA [email protected] Maria-Fernanda Nieva, Institute for Astro- and Particle Physics, University of [email protected] Innsbruck, Austria Tetiana Nikolaiuk, National academy of fine arts and architecture, Ukraine [email protected] Arlette Noels, Institut d’astrophysique et de géophysique - UniversitédeLiège, [email protected] Belgium Mary Oksala, Astronomical Institute, ASCR,ˇ Czech Republic [email protected] Jakub Ostrowski, Astronomical Institute, University of Wroclaw, Poland [email protected] Ilka Petermann, Argelander Institut für Astronomie, Germany [email protected] Geraldine Peters, University of Southern California, USA [email protected] Vincent Prat, Max-Planck-Institut für Astrophysik, Germany [email protected] Giovanni Privitera, Department of astronomy, Geneva University, Switzerland [email protected] Norbert Przybilla, Institute for Astro- and Particle Physics, University of [email protected] Innsbruck, Austria Joachim Puls, University Observatory Munich, Germany [email protected] Oscar Hernan Ram´ırez Agudelo, Anton Pannekoek Institute, Netherlands [email protected] Jared Rice, University of Nevada Las Vegas, USA [email protected] Thomas Rivinius, European Southern Observatory, Chile [email protected] Iosif Romanyuk, Special Astrophysical Observatory of Russian Academy of [email protected] Sciences, Russian Federation Christopher Rosslowe, Department of Physics and Astronomy, University of chris.rosslowe@sheffi eld.ac.uk Sheffield, UK Maria del Mar Rubio D´ıez, Centro de Astrobiolog´ıa (CSIC-INTA), Spain [email protected] Naum Rusomarov, Uppsala University, Sweden [email protected] Sophie Saesen, Department of astronomy, Geneva University, Switzerland [email protected] Hideyuki Saio, Astronomical Institute, Graduate School of Science, Tohoku [email protected] University, Japan Sébastien Salmon,UniversitédeLiège, Belgium [email protected] Thierry Semaan, Institut d’Astrophysique et de Géophysique, Universitéde [email protected] Liège, Belgium Tomer Shacham, Hebrew University of Jerusalem, Israel [email protected] Olga Sholukhova,SpecialAstrophysicalObservatory,RussianFederation [email protected] Matthew Shultz, European Southern Observatory, Chile / Queen’s University, [email protected] Canada Jessie Silaj, University of Western Ontario, Canada [email protected] Sergio Simón-D´ıaz, Instituto de Astrof´ısica de Canarias, Spain [email protected] Rosaria Simoniello, CEA - Service d’Astrophysique (SAP), France [email protected] Philippe Stee,ObservatoiredelaCôte d’Azur, Nice - CNRS, France [email protected] Natallia Sudnik,Saint Petersburg State University,Russian Federation [email protected] Jon Sundqvist, University of Munich, Germany [email protected] Wojciech Szewczuk, Astronomical Institute, Wroclaw University, Poland [email protected] Koh Takahashi, University of Tokyo, Japan [email protected] Andrew Tkachenko, Instituut voor Sterrenkunde, KU Leuven, Belgium [email protected] Sanja Tom ić, Astronomical Institute AVCR,ˇ Czech Republic [email protected] Frank Tram per, Astronomical Institute Anton Pannekoek, University of [email protected] Amsterdam, Netherlands Asif ud-Doula, Penn State Worthington Scranton, USA [email protected] Jorge Uuh-Sonda, Department of Astronomy, University of Guanajuato, [email protected] Mexico Gerard van Belle, Lowell Observatory, USA [email protected] Jorick Vink, Armagh Observatory, UK [email protected] Gregg Wade, RMC, Canada [email protected] Przemek Walczak, Nicolaus Copernicus Astronomical Center, Poland [email protected] Kerstin Weis, Astronomical Institute, Germany [email protected] Markus Wittkowski, European Southern Observatory, Germany [email protected] Nobutoshi Yasutake, Chiba Institute of Technology, Japan [email protected] Norhasliza Yusof, University of Malaya, Malaysia [email protected]

Dear colleagues,

This is a great pleasure to welcome you all here in Geneva and more precisely in Geneva University for this IAU Symposium number 307. Marcel Proust, the famous french author has written: The true exploration does not consist in discovering new landscapes, but in having new eyes. This sentence underlines the fact that the capacity to see what is around us with new methods or from a different viewpoint, opens the way to discoveries. The discovery of the principles of spectroscopy, in the mid of the nineteen century by Bunsen and Kirchoff, well illustrates this sentence. The stars had not changed but the way to look at them was new. Spectroscopy allowed to unveil the nature of stars and their surface composition. This discovery happened about 14 years after Auguste Comte a prominent French philosopher, made one of the worst intellectual predictions regarding the limits of astrophysics. He wrote, about the observations of stars: All investigations which are not ultimately reducible to simple visual observations are ... necessarily denied to us. While we can conceive of the possibility of determining their motions, we shall never be able by any means to study their chemical composition. Today, we use spectroscopy to measure chemical abundances, temperatures, velocities, rotations, ionization states, magnetic fields, pressure, turbulence, density, and many other properties of distant planets, stars, and galaxies. Spectroscopy is the richest source of information about the universe. So we have to be cautious in front of unbalanced statements that close for ever a field. We should never forget that new windows can open unexpectedly. This conference is dedicated to three observational technics that provide new views on stars. The technics which is the nearest from spectroscopy is spectropolarimetry. Measuring the polarization of the radiation field allows us to obtain complementary information about astrophysical objects that may remain hidden to the ordinary intensity spectrum. The polarized spectrum, in contrast to intensity, enables us to determine vector quantities, e.g. the magnetic field vector. Astronomical interferometers can produce higher-resolution astronomical images than any other type of telescope. At radio wavelengths, image resolutions of a few micro- arcseconds have been obtained, and image resolutions of a fractional milliarcsecond have been achieved at visible and infrared wavelengths. This allows to study the size, the shape and the circumstellar environment of stars, close enough for allowing this technic to be applied. Asteroseismology provides the tool to find the internal structure of stars. The pulsation frequencies give the information about the density profile of the region where the waves originate and travel. Asteroseismology helps to constrain other characteristics of stars such as mass and radius. We are here 138 astronomers from 29 countries for understanding a little better how nature is working and how these new windows provide new and complementary guidelines that can sharpen our knowledge. As organizers, we hope that through the talks and discussions, each of us will go back home with new ideas and new eyes to observe the stars.

Georges Meynet, for the LOC Geneva, 23 June 2014