ESO ASTROPHYSICS SYMPOSIA European Southern Observatory

Series Editor: Jacqueline Bergeron Springer-Verlag Berlin Heidelberg GmbH Lex Kaper Alexander W. Fullerton (Eds.)

Cyclical Variability in Stellar Winds

Proceedings of the ESO Workshop Held at Garching, Germany, 14 - 17 October 1997

Springer Volume Editors Lex Kaper Alexander W. Fullerton Astronomical Institute Department of Physics "Anton Pannekoek" and Astronomy University of Amsterdam University of Victoria Kruislaan 403 P.O. Box 3055 NL-1098 SJ Amsterdam Victoria, BC The Netherlands Canada V8W 3P6

Series Editor Jacqueline Bergeron European Southern Observatory Karl-Schwarzschild-Strasse 2 D-85748 Garching, Germany

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Cyclical variability in stellar winds : proceedings of the ESC workshop, held in Garching, Germany, 14 - 17 October 1997/ Lex Kaper ; Alexander W. Fullerton (ed.). - Berlin; Heidelberg; New York; Barcelona; Budapest; Hong Kong; London; Milan; Paris; Singapore; Tokyo: Springer, 1998 (ESC astrophysics symposia) ISBN 978-3-662-11392-9 ISBN 978-3-540-68597-5 (eBook) DOI 10.1007/978-3-540-68597-5

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© Springer-Verlag Berlin Heidelberg 1998 Originally published by Springer-Verlag Berlin Heidelberg New Yark in 1998

The use of general descriptive names, registered names, trademarks, etc. in this publication does not imply, even in the absence of a specific statement, that such names are exempt from the relevant protecti ve laws and regulations and therefore free for general use. Typesetting: Camera-ready by authors/editors Cover design: design & production GmbH, Heidelberg SPIN: 10651976 55/3144 - 5 43210 - Printed on acid-free paper Preface

Although it has long been known that stellar winds are variable, in recent years it has become increasingly clear that the fluctuations are not completely chaotic, but are often cyclical in nature. This is a property that seems to be shared by the winds of cool and hot stars, even though their outflows are driven by fundamentally different physical mechanisms. A key ingredient in both cases appears to be the presence of deep-seated structures due to phenomena like surface magnetic fields or pulsations, which alter the emergence of the wind from the stellar surface and impart a measure of cyclical regularity to the outflow. Since very similar models have been proposed to explain the cyclical wind variations observed in a wide variety of stars, the time was ripe for astrophysicists from many different sub-disciplines to come together and compare their various approaches. This was a primary motivation for the ESO Workshop on "Cyclical Variability in Stellar Winds", which was held at ESO Headquarters in Garching bei Miinchen from October 14 to 17, 1997. The timeliness of the meeting was demonstrated by the attendance of more than 100 astronomers from all over the world. A full program was developed by the Scientific Organizing Committee: Keith MacGregor (Chair), Torsten Bohm, Andrew Cameron, Claude Catala, Lee Hartmann, Huib Henrichs, Lex Kaper, Henny Lamers, Stan Owocki, Joachim PuIs, and Otmar Stahl. A special feature of this programme was the presentation of the latest results from the MUlti-SIte COntinuous Spectroscopy (MUSICOS) campaign of November 1996. We hope that these proceedings will provide a useful and up-to-date overview of the observations, interpretation, and modelling of the time-dependent mass outflows from all sorts of stars, ranging from young pre-main sequence objects to cool, solar-type stars to red supergiants and hot, massive stars. What the pro• ceedings do not record is the conference dinner in the (rotating) Olympia Turm at the Olympic Park in Munich, or the well-attended visit to the Augustiner pub. We would very much like to thank Christina Stoffer, Britt Sjoberg, and Saskia de Haas for their help in organizing and running the workshop, and Pamela Bris• tow for the preparation of the proceedings for publication. Ed Janssen designed the beautiful workshop poster. We are also very grateful for the generous fin• ancial support received from the European Southern Observatory. One of us (AWF) is similarly grateful to the DFG (through grant Pu 117/3-1) for financial support during the organization of the workshop. VI

Finally, we would like to thank all the workshop participants for the stimu• lating atmosphere they fostered during the workshop and their contributions to the proceedings.

Garching, May 1998 Le:c Kaper Ale:c Fullerton

Contents

Part 1. SETTING THE STAGE: WIND ACCELERATION MECHANISMS

Acceleration Mechanisms for Cool Star Winds K.B. MacGregor ...... 3

Thirty Years of Radiation-Driven Hot Star Winds L.B. Lucy ...... 16

A Thermo-Radiatively Driven, Analytlical 2-D Model for Stellar Outflows A. Kakouris ...... 28

Using ISO to Probe the Acceleration of Wolf-Rayet Winds R. Ignace, J.P. Cassinelli, P. Morris, J. C. Brown 29

A Critical Evaluation of Mass-Loss Rates and Wind Properties of Evolved Late-Type Stars J.1. Linsky, G.M. Harper, P.D. Bennett, et ai. 30

Variable Winds in Yellow Supergiants K. Gesicki, M. Schmidt ...... 40

Numerical Simulations of Dust-Driven AGB Winds: A Two-Fluid Model Y.J. W. Simis ...... 41

YSO Winds and Jets: Mechanisms and Variability L. Hartmann ...... 42

On the Origin of Relativistic Winds from Accreting Stars N.R. Ikhsanov, G. T. Birk ...... 53 x

Part 2. OBSERVATIONS OF CYCLICAL WIND VARIABILITY

The Solar Wind in Three Dimensions J. T. Gosling ...... 57

Observations of Wind Variability in Cool Stars A.K. Dupree ...... 69

Variations of Winds of Cool Giants in HOI J.A. Eaton ...... 82

Variability of the Circumstellar Shell of 89 Herculis J. Krempec-Krygier, M. Schmidt, K. Gesicki ...... 85

Wind Variability in the Hypergiant HR 8752 M. Schmidt, K. Gesicki ...... 86

Variable Dust Emission Observed in Miras LR. Little--Marenin ...... 87

Variable Water Maser Emission from Circumstellar Disks LR. Little--Marenin, P.J. Benson ...... 88

Systematic Variability in OB-Star Winds R.K. Prinja ...... 92

Cyclical Variability in O-Star Winds (The HOI Project) L. Kaper, A. Fullerton, D; Baade, et a1...... 103

Cyclic Polarization Variability of Bright 0 Stars D. McDavid ...... 108

Confirmation of a 2.3-Day Periodicity in the Wolf-Rayet Star WR 134: A Twin of EZ CMa? T. Morel, S. V. Marchenko, P.R.J. Eenens, et a1. 109

No Need for a White & Becker Disk-Like Wind in WR 140 A.M. T. Pollock...... 110

Phase Shifts Between Cyclical Spectral Parameters of P Cygni L Kolka...... 111

Long-Term Spectroscopic Variability of'TJ Carinae O. Stahl, A. Damineli ...... 112

A Kinematic Study of the LBV Nebula Around 'TJ Carinae K. Weis, W.J. Duschl, Y.-H. Chu ...... 113 XI

Cyclic Variability in BA-Type Supergiants A. Kaufer...... 114

Rotational Modulation of B Supergiant Winds D. Massa, A. W. Fullerton, R.K. Prinja 121

Expression of Turbulence and the Variability of Stellar Winds in Resonance Line Profiles A. Sapar, L. Sapar ...... ". . 125

Understanding A-Type Supergiants: Visible and Ultraviolet Spectral Variability E. Verdugo, A. Talavera, A.I. Gomez de Castro 126

Cyclic Variability in Be Star Winds: The Observations G.J. Peters ...... 127

Stellar Wind Variability of Be Star FY CMa H. Cao, J. Dachs ...... 134

Fundamental Parameters for Seven Be Stars Y. Fremat ...... 138

Wind and Jets in the Be Star 4 Herculis J. Kubat, P. Koubsky, P. Harmanec, et a1. 139

Variability of Be Stars Using Hipparcos Photometry A.M. Hubert, M. Floquet, A. Gomez, D. Morin 140

The Interrelation Between Long-Term Cycles and Rapid Variations in Be Stars: A Photometric View K. Pavlovski, Z. Ruzic, D. Dominis ...... 141

Long-Term Cyclical Circumstellar Changes and He I lpv in the Be Star EW Lacertae M. Floquet, A.M. Hubert, H. Cao, et a1...... 142

Wind Variability in PMS-Stars M. Pogodin ...... "...... 143

Wind and Accretion Variability in T Tauri Stars C.M. Johns-Krull...... 153

Hot Spots on Classical T Tauri Stars with High Mass-Loss Rates M. Fernandez, C. Eiroa, W. Schuster 160 XII

Anisotropic Outflows from Herbig Ae/Be Stars V. Grinin ...... 164

Variability in the Wind of the FU Ori Object Z Canis Majoris D. Choehol, M. Teodorani, F. Straiella, et al. 168

A Variability Study of High-Resolution Profiles of DL Tauri J.F. Gameiro, M. T. V. T. Lago ...... 169

The UV Variability of T Tauri Stars A.I. Gomez de Castro, M. Franqueira, N. Hu61amo, E. Verdugo 170

Spectroscopic Investigations of Cyclical Variability in the Gaseous Envelopes of Early-Type Emission-Line Stars M. Pogodin ...... ~ ...... 171

Polarimetric Studies of Cyclic Phenomena in the Circumstellar Envelopes of the Young Herbig Ae/Be Stars N. Beskrovnaya ...... 172

Comparing Observations of Cyclical Variability in Hot- and Cool-Star Winds D.J. Mullan ...... 173

Nitrogen V in the Wind of the Pre-main Sequence Herbig Ae Star AB Aurigae J.-C. Bouret, C. Catala, T. Simon ...... 183

Part 3. PROCESSES AFFECTING THE EMERGENCE OF THE STELLAR WIND

Line-Profile Variability as a Diagnostic for Non-radial Pulsation Mode Identification J. Telting, C. Sehrijvers ...... 187

NRP in Light and Colour: Diagnostic Value D. Vinkovic, K. Pavlovski ...... 195

Nonradial Pulsations in Relation to Wind Variability in Early-Type Stars D. BaadfJ ...... 196

Predicting the Outbursts of the Be Star p, Cen Th. Rivinius, D. Baade, S. Stefl, et al. 207 XIII

Surface Magnetic Fields of Non-degenerate Stars J.-F. Donati ...... 212

The Hanle Effect as a Probe of Stellar Magnetic Fields R. Ignace ...... 224

Photometric Monitoring of Spotted T Tauri Stars Th. Granzer, K.G. Strassmeier ...... 229

The Activity Cycle and Interaction of Stellar Winds in the Capella System M.M. Katsova, A.G. Shcherbakov ...... 230

Ha Line-Profile Variability in Chromospherically Active Stars M. Weber, A. WashuettJ, K.G. Strassmeier 231

Cyclical Variability in the Solar Wind W. Kundt ...... 232

Luminous Magnetic Rotator Theory J.P. Cassinelli ...... 237

Periodic Variability of ()1 Ori C O. Stahl...... 246

Rotating Loops in the Atmosphere of Rigel ((3 Orionis A) G. Israelian ...... 250

Constraints on Wind Structure from the Infrared and Radio Continuum of Hot Stars M. C. Runacres, R. Blomme ...... 254

Clumping-Corrected Mass-Loss Rates of WR Stars: Dependence on Stellar Parameters T. Nugis ...... 258

Formation of Clumps in the Wind of Wolf-Rayet Stars by Thermal Instability and Alfven Waves D.R. Gon~alves, v. Jatenco-Pereira, R. Opher 259 XIV

Part 4. MODELLING CYCLICAL VARIABILITY IN STELLAR OUTFLOWS

Understanding the Solar Wind E. Leer, V.H. Hansteen, T.E. Holzer ...... 263

The Solar Wind Modelled by Exact MHD Solutions J.J.G. Lima, K. Tsinganos ...... 273

Time-Dependent Behavior of Cool-Star Winds P. Woitke ...... 278

Atmospheric Dynamics and Stellar Winds of Long-Period Variables s. Hofner, U.G. J¢rgensen ...... 289

Pulsation and Stellar Winds: Some Lessons Learned from Dynamical Models of the Atmospheres of Cool Stars L.A. Willson, G.H. Bowen...... 294

The Mass-Loss Rate of C-Rich Mira Stars T. U. Arndt, A.J. Fleischer, E. Sedlmayr ...... 306

Molecular and Dust Features in Mass-Losing AGB Stars: Models and ISO Observations B. Aringer, F. Kerschbaum, S. Hofner, et al. 307

Variability of CO Line Profiles in AGB Stars W. Windsteig, S. Hofner, B. Aringer, E.A. Dorfi 308

Temporal Variations of CO Infrared Lines in Cool-Star Winds A. Gauger, J.M. Winters, A. Fleischer, J.J. Keady •...... 309

Cyclical Variability in MHD Disk Winds R. Ouyed, R.E. Pudritz ...... 310

Accretion Mass-Loss Relation and Variability in T Tauri Stars E. Gullbring ...... 316

The Wind of FU Orionis: Modelling the Atmosphere G. D'Angelo, L. Errico, M. T. Gomez, et al. 323

Numerical Modeling of Anisotropic Stellar Winds in Herbig Ae/Be Stars L. Tambovtseva, V. Grinin ...... 324 xv

Modelling Variability in Hot-Star Winds S.P. Owocki ...... 325

Semi-empirical Modelling of Cyclical Ha Line Profile Variability of 0 Stars J.A. de Jong ...... ;...... 336

Long-Term Cyclic V /R Variations in Be Stars G.J. Savonije ...... 337

Large, Oscillating Be Star Circumstellar Disks w. Hummel, R. W. Hanuschik, M. Vrancken 343

Variabilities in Be-Star Disks in Be/X-Ray Binaries A. T. Okazaki ...... 344

V /R Variability in Be/X-Ray Binaries 1. Negueruela ...... 345

Part 5. THE MUSICOS 1996 CAMPAIGN

MUlti-SIte COntinuous Spectroscopy: Previous MUSICOS Campaigns C. Catala ...... 349

MUSIC OS Observations of SU Aurigae Y.G. Unruh, J.-F. Donati, et a1. 355

Short-Term Spectroscopic Variability in the Pre-Main-Sequence Herbig Ae Star AB Aur During the MUSICOS 96 Campaign C. Catala, J.-F. Donati, T. Bohm, et a1. 361

Flares and Circumstellar Material Around the Fast-Rotating Giant FK Comae J.M. Oliveira, B.H. Foing, P. Sonnen trucker, et a1. 373

First Results of the November 1996 MUSICOS Campaign on the 07.5111 Star, Persei H. Henrichs, J. de Jong, G. Catala, et al...... 374

MUSICOS 1996 Campaign on the 8 Scuti Star V480 Tau J. Hao, H. Cao, T. Kennelly, et al...... 380 XVI

Part 6. FUTURE PERSPECTIVE

Metallicity Dependence of Stellar Outflows and Their Variability J. PuIs, U. Springmann, S.P. Owocki ...... 389

Non-LTE Departure Coefficients of Hydrogen J. van Gent ...... 401

Outflows in Quasars: Radiative Acceleration and Variability N. Arav ...... 402

Author Index ...... 413 List of Participants

Name Institution

Nahum Arav Theoretical Physics, Caltech arav~tapir.caltech.edu Bernhard Aringer Institut fur Astronomie, Universitat Wien aringer~astro.ast.univie.ac.at Thorsten U. Arndt Inst. f. Astronomie und Astrophysik, Technische Universitat Berlin Arndt~physik.tu-berlin.de Dietrich Baade European Southern Observatory dbaade~eso.org Nicole Berruyer Lab. G.-D. Cassini, Observatoire de la Cote d'Azur nicole~obs-niceofr Nina Beskrovnaya Pulkovo Observatory beskr~pulkovo.spb.su Ronny Blomme Astrophysics, Royal Observatory Belgium Ronny.Blomme~oma.be Jean-Claude Bouret Lab. d' Astrophysique de Toulouse, o bservatoire Midi-Pyrenees bouret~obs-mip.fr Huilai Cao Beijing Astronomical Observatory caohl~baoOl.bao.ac.cn Joseph P. Cassinelli Astronomy Dept., Univ. of Wisconsin cassinelli~astro.wisc.edu Drahomir Chochol Astron. Inst., Slovak Academy of Sciences chochol~auriga.ta3osk Francesco Damiani Osservatorio Astronomico di Palermo damiani~oapa.astropa.unipa.it Gennaro D'Angelo Dept. Physics, Univ. of Naples "Federico II" dangeloOastrna.na.astro.it XVIII

Jeroen A. de Jong Astron. Inst., Univ. of Amsterdam jdj«lastro.uva.nl

Jean-Fran~ois Donati Lab. d' Astrophysique, o bservatoire Midi-Pyrenees donati~obs-mip.fr Andrea K. Dupree Center for Astrophysics, Cambridge, Mass. adupreeGcfa.harvard.edu Joel A. Eaton CElS, Tennessee State University eaton~coe.tnstate.edu James P. Emerson Physics Dept., Queen Mary & Westfield College j.p.emersonGqmw.ac.uk Matilde Fernandez Max-Planck-Institut fur Extraterr. Physik matilde~mpe.mpg.de Bernard H. Foing Space Science Dept., European Space Agency bfoing~estec.esa.nl Yves Fremat Groupe d'Astrophysique et de Spectroscopie, Universite de Mons-Hainaut fremat~umh.ac.be Alex Fullerton Universitiits-Sternwarte Munchen alex~usm.uni-muenchen.de Jorge Gameiro Centro Astrofisica da Universidade do Porto jgameiroGastro.up.pt Andreas Gauger Max-Planck-Institut fur Radioastronomie gauger~speckle.mpifr-bonn.mpg.de Krzysztof Gesicki Physics and Astronomy, Centrum Astronomii UMK, Torun gesicki~astri.uni.torun.pl Jack T. Gosling Space and Atmospheric Sciences, Los Alamos National Laboratory jgosling~lanl.gov Thomas Granzer University of Vienna, Institute for Astronomy granzerGastro.ast.univie.ac.at Vladimir Grinin Astron. Inst., St. Petersburg University grinin~VG1723.spb,edu grinin~crao.crimea.ua Martin Groenewegen Max-Planck-Institut fur Astrophysik groen~mpa-garching.mpg.de Detlef Groote Universitiit Hamburg, Hamburger Sternwarte dgrooteGhs.uni-hamburg.de XIX

Erik L. Gullbring Center for Astrophysics, Cambridge, Mass. egullbringGcfa. harvard. edu Jinxin Hao Beijing Astronomical Observatory hjxGbaoOl.bao.ac.cn Lee W. Hartmann Center for Astrophysics, Cambridge, Mass. hartmannGcfa.harvard.edu Huib F. Henrichs Astron. Inst., Univ. of Amsterdam huibGastro.uva.nl Susanne Hofner Niels Bohr Inst., Univ. of Copenhagen hoefnerGstella.nbi.dk Anne Marie Hubert DASGAL, Obs. de Paris, Section de Meudon anne-marie. hubertGobspm. fr Wolfgang Hummel Universitats-Sternwarte Miinchen hummelGusm.uni-muenchen.de Richard Ignace Dept. of Physics and Astronomy, University of Glasgow ricoGastro.gla.ac.uk Nazar Ikhsanov Institut fiir Astronomie und Astrophysik, Universitat Miinchen ikhsanovGusm.uni-muenchen.de Garik Israelian Instituto de Astrofisica de Canarias giHliac.es Istvan Jankovics Gothard Astrophysical Observatory, Eotvos Lorand University ijankoviGgothard.hu Vera Jatenco-Pereira Instituto Astronomico e Geofisico - USP, Sao Paulo jatencoGorion.iagusp.usp.br Christopher M. Johns-Krull Space Sci. Lab., Univ. California, Berkeley cmjGsunburst.ssl.berkeley.edu Alexander Kakouris Physics Department, University of Athens akakourGatlas.uoa.gr Lex Kaper European Southern Observatory lkaper«leso.org Maria Katsova Sternberg Astronomical Institute, Moscow mariaGsai.msu.su Andreas Kaufer Landessternwarte Heidelberg-Konigstuhl A.KauferGlsw.uni-heidelberg.de Indrek Kolka Tartu Observatory indrekGaai.ee xx

Jiri Kubat Astronomical Institute, Ondrejov k;ubat42sunstel.asu.cas.cz Wolfgang Kundt Institut fUr Astrophysik, Universitiit Bonn wkundt42astro.uni-bonn.de Henny Lamers Astronomical Instititute, Utrecht University hennyl42sron.ruu.nl Egil Leer Inst. of Theoretical Astrophys., Univ. of Oslo egil.leer42astro.uio.no Joao J.G. Lima Centro de Astrofisica, Universidade do Porto jlima42astro.up.pt Jeffrey L. Linsky JILA, University of Colorado, Boulder jlinsky42jila.colorado.edu Irene R. Little-Marenin Center for Astrophysics & Space Astronomy, University of Colorado, Boulder ilittle42casa.colorado.edu Leon B. Lucy ST-ECF llucy42eso.org Keith B. MacGregor National Center for Atmospherit: Research, High Altitude Obs., Boulder, Colorado mac42hao.ucar.edu Derck Massa NASA/GSFC massa~xfiles.gsfc.nasa.gov David McDavid Limber Observatory dmd42astro.as.utexas.edu Thierry Morel Dept. de Physique, Univ. de Montreal morel42astro.umontreal.ca Dermott J. Mullan Bartol Research Institute, University of Delaware, Newark mullan42bartol.udel.edu Ignacio Negueruela Astrophysics Group, EEP, Liverpool John Moores University ind42starul.1ivjm.ac.uk Andrzej Niedzielski Centre for Astronomy, N. Copernicus Univ(!rsity, Torun aniedzi42astri.uni.torun.pl Tiit Nugis Tartu Observatory nugis42aai.ee Atsuo Okazaki Hokkai-Gakuen University, Sapporo okazaki42elsa.hokkai-s-u.ac.jp XXI

Joana Oliveira Solar System Division, ESTEC/ESA joana~so.estec.esa.nl Rachid Ouyed Dept. of Physics & Astronomy, St. Marys University, Halifax, Nova Scotia rouyedCap.stmarys.ca Stanley P. Owocki Bartol Research Institute, University of Delaware, Newark owocki~bartol.udel.edu Luca Pasquini European Southern Observatory Ipasquin~eso.org Kresimir Pavlovski Faculty of Geodesy, Hvar Observatory, Zagreb Univeristy kresimir~geof.hr Geraldine J. Peters Space Sciences Center, Univ. of Southern California, Los Angeles gjpetersCmucen.usc.edu Peter Petrenz Institut fiir Astronomie und Astrophysik, Universitiit Miinchen uhl0lbv~usm.uni-muenchen.de Mikhail Pogodin Astrophys. Dept., Pulkovo Observatory pogodin~pulkovo.spb.su Andy Pollock ISO Observatory, Villafranca del Castillo apollock~iso.vilspa.esa.es Nina Polosukhina-Chuvaeva Crimean Observatory, Nauchny polo~crao.crimea.ua Raman K. Prinj a Department of Physics and Astronomy, University College London rkp~star.ucl.ac.uk Joachim PuIs Universitiitssternwarte Miinchen uhl01aw~usm.uni-muenchen.de Thomas Rivinius Landessternwarte Heidel berg-Konigstuhl T.Rivinius~lsw.uni-heidelberg.de Mark Runacres Astrophysics, Royal Observatory Belgium mrunacre~oma.be Lili Sapar Tartu Observatory lillilDaai.ee Gerrit Jan Savonije Astron. Inst., Dniv. of Amsterdam gertjan~astro.uva.nl Yvonne Simis Leiden Observatory simis~strw,leidenuniv.nl XXII

Otmar Stahl Landessternwarte Heidelberg-Konigstuhl O.StahlClsw.uni-heidelberg.de Stanislav Stefl Astronomical Institute, Academy of Sciences of the Czech Republic, Ondfejov ssteflCsunstel.asu.cas.cz Raphael Steinitz Dept. of Physics, Ben Gurion University raphaelCbgumail.bgu.ac.il Larisa Tambovtseva Laboratory of the Physics of Stars, Central Astronomical Observatory, Pulkovo tambCpulkovo.spb.su John H. Telting Isaac Newton Group of Telescopes, ASTRON/NFRA, Santa Cruz de La Palma jhtCing.iac.es Yvonne C. Unruh Institute of Astronomy, University of Vienna ycuCvenus.ast.univie.ac.at Jeroen van Gent Astronomical Instititute, Utrecht University gentCfys.ruu.nl Eva Verdugo ISO Project, VILSPA - ESA evCvilspa.esa.es Albert Washiittl Institute for Astronomy, University of Vienna wasiCastro.ast.univie.ac.at Michael Weber Institute for Astronomy, University of Vienna weberCastro.ast.univie.ac.at Kerstin Weis Inst. fiir Theor. Astrophysik, Heidelberg kweisCita.uni-heidelberg.de Ulf Wessolowski Max-Planck-Institut fiir Extraterr. Physik uuwCmpe-garching.mpg.de Lee Anne Willson Department of Physics and Astronomy, Iowa State University lwillsonCiastate.edu Walter Windsteig Institut fiirAstronomie, UniversWit Wien windsteigCauro.ast.univie.ac.at Peter Woitke Institut fiir Astronomie und Astrophysik, Technische Universitat Berlin woitkeCphysik.tu-berlin.de Bernhard Wolf Landessternwarte Heidelberg-Konigstuhl bwolfClsw.uni-heidelberg.de Kutluay Yiice Astronomy and Space Dept., Ankara Univ. kyuceCastro1. science. ankara. edu.tr