WOLF-RA YET STARS: BINARIES, COLLIDING WINDS, EVOLUTION

INTERNATIONAL ASTRONOMICAL UNION UNION ASTRONOMIQUE INTERNATIONALE

WOLF-RAYET STARS: BINARIES, COLLIDING WINDS, EVOLUTION PROCEEDINGS OF THE 163RD SYMPOSIUM OF THE INTERNATIONAL ASTRONOMICAL UNION, HELD IN LA BIODOLA, ELBA, ITALIA, MAY 2-6, 1994

EDITED BY

KAREL A. VAN DER HUCHT Space Research Organization Netherlands, Utrecht, The Netherlands

and PEREDUR M. WILLIAMS Royal Observatories, Edinburgh, Scotland, United Kingdom

SPRINGER-SCIENCE+BUSINESS MEDIA, B.V.

A C.I.P. Catalogue record for this book is available from the Library of Congress

ISBN 978-0-7923-3184-1 ISBN 978-94-011-0205-6 (eBook) DOI 10.1007/978-94-011-0205-6

Printed on acid-free paper

All Rights Reserved © 1995 Springer Science+Business Media Dordrecht Originally published by Kluwer Academic Publishers in 1995 No part of the material protected by this copyright notice may be reproduced or utilized in any form or by any means, electronic or mechanical including photocopying, recording or by any information storage and retrieval system, without written permission from the publisher.

TABLE OF CONTENTS

Preface

xlii

The Orlaaisin& CommiUee

xv

Conference photopph

xvi

List of partieipauta

xix

WELCOMING ADDRESSES Chairman Local Organizing Committee, Federico Ferri..i Chairman Scientific: Organizing Committee, Kare' A. lIa.. der Hlelat AN'HISTORICAL INTRODUCTION, Li..d,e, F. Smitla 1971 revisited; fOll8ils alive and dead

1 2 3

SESSION L - Chair: Li..the, F. Smith Basie parameters, properties of sinaJ.e Wolf-Rayet .tars

K.A. lIa.. der Haelat Basic parameters and general properties of Wolf-Rayet stars. (l,,"ited)

7

N. Langer Structure and evolution of massive single stars and their relevance for close binary systems (I..mted)

15

L.I. Smitla Properties of hot massive stars from studies of their ring nebulae (I,,"ited)

24

I.S. Niclao', The interstellar medium around Wolf-Rayet stars: clues to evolution (I..mted)

34

K.-H. Hofma ...., G. WeigeU, W. SeggeVliIB Resolution and evolution of the core of the giant Un region NGC 3603

43

Senion I poster summaries

L.F. Smith, M.M. Slaam, A.F.I. Moffa' Philosophy of classification for WN stars

48

K. Rocla01l1icz Ultraviolet classification of Wolf-Rayet stars

60

A. Nie4zielslri

62

L. Georgiell, M.M. IlIa ..Oll Line profile variability of EZ CMa

54

1.1. A..toklain, J.-F. Bertm..d, R. Lamo..tag.. e, A.F.J. Moffa' The absence of a short period in the WN6 star EZ Canis Majoris

66

C. Llo,4, D.J. Stickland Periodic variations in the WE data of UD 60896

68

S. Upine Wavelet analysis of variable Wolf-Rayet emission lines

60

II. Antokhin, J.-F. Bertmnd, R. Lamontagne, A.F.J. Moffat 3.5 hour periodic variability of WR66 (HD 134877, WN8): the first example of non-radial pulsations among Wolf-Rayet stars?

62

A search for spectral variability in WRI

vi P. Bmtschi Pulsations of Wolf-Rayet stars: observational results for five Wolf-Rayet stars

64

I.. Nom, V.F. POIC4f'O, C. Ro"i, R. Viotti Multiwavelength study of the WO star Sand 2

66

V.F. POIC4f'O, R. Viotti, C. Ro,,4 I.. Norci The WO stars and their environment

68

F. BrigAenti, A. D'Ercole Ring nebulae around moving Wolf-Rayet stars

70

G. G.m.-Se,.,.., M.-M. M.e £OUl, N. £Cnger The imprint of m888ive stellar evolution on eircumstellar gas

72

A. M.neAGllo, G. G.rc(.-Seg.m, Y.-H. CA. High resolution mAS images of large shells around Wolf-Bayet stars

74

S. MeregAelli, T. Belloni ROSAT observations oC the HII region RCW49

76

A. Nola, M. crampin, M. Sirianni, P. Greenfield, D.A. GolimowHi The inner MI-67 nebula: coronagraphic imaging and echeUe observations

78

G. Testor Wolf-Rayet and OF stars in the OB associations LHIOI and LHI04 in the LMC

81

M. Azzoparrli; G. M.mlorio, 1. Bre,sacAer, G. Testor A search Cor WoIC-Rayet stars in NGC 300

83

S.K. G6rn" A. Acker, G. SlaBinsk., B. StenAolm, R. 7;lenda [Wolf-Rayetj-type central stars of planetary nebulae

85

SESSION D - CA.ir: Sir Ro6ert Wilson Model atmospheres for single Wolf-Rayet stars 1.1. Ardokh;n Observational aspects oC WoIC-Rayet atmospheres (Invite4)

87

P. W. Morri. Continuum and emission line observations of Wolf"Rayet stars: single and "WR+abs" objects (Invite4)

96

W.-R. Hamana Model atmospheres and spectral analyses of Wolf-Rayet stars (Invited)

105

D.J. Hillier Status of WolC-Rayet models (Invited)

116

W. ScAm.': Hydrodynamic line-blanketed atmospheres of Wolf-Rayet stars (Inviled)

127

S.P. Owoch, K.G. Ga,le, The dynamics of Wolf-Rayet winds (Invite4)

138

P.A. CrowtAer, £.J. Smith, D.J. Hillier The evolutionary status of WNL stars

147

Session D poster summaries P.A. Crowther, £.1. Smi'h, A.J. Willis The physical nature of WRS (WN6/WC4)

152

vii M.J. Dalto", P.A. Crowther, A.J. Willi. An empirical study of Wolf-Bayet stellar wind ionization stratification

154

P.R.J. Eenen" P.M. Williams

156

New analysis of Wolf-Bayet infrared lines K.G. Gayley, S.P. Owocki

The non-isotropic diffusion approximation in Wolf-Rayet winds

158

A.F. Kholtygin

160

T. Nugis

162

A clump model for Wolf-Rayet star atmospheres New determinations of the chemical composition of Wolf-Rayet stars E. Sardola,a Re" A. HefTero, J. Puis

164

L.C. do. Santos, V. JaCenco-Pereira, R. Opher

166

D. Schaerer

168

U. Springmann, J. Puis

170

Synthetic line profiles from unified model atmospheres AICven waves and radiation pressure in the winds oC WolC-Rayet stars Multi-line transfer and line-blanketing in a clumpy WolC-Rayet wind The 'momentum problem' oC WolC-Rayet stars: can it be explained by the multiple scattering mechanism? D. Eichler, A. Bar Shalom, Y. Oreg

172

U. Wessolow,li, W.-R. Homann, L. Koesterle, D.J. Hillier, J. Puis

174

Thick winds Crom WolC-Rayet stars

X-ray emission from WolC-Rqet stars

SESSION III - Choir: Gloria Koenigs6erger Anisotropic mass loss, disk formation R.E. Schulte-Lad6ecl

Spectropolarimetry and wind asymmetries of WolC-Rayet stars (Invited)

176

J.C. Brown, L.L. Richardson

186

J.P. Ca.,ine"i, R. Ignoct, J.E. Bjorkman

191

WolC-Rqet star variability and wind inhomogeneities Winds from rotating WolC-Rayet stars: the wind-compressed zone model (Invited) G. Shoviv

Optically thick winds in novae (Invited)

203

SESSION IV - Chair: Allan J. Willis Properties of Wolf-Rayet binaries A.F.J. Moffat

213

V.S. Niemela

223

K. Annul Spectroscopic observations oC the long-period Wolf-Rayet binaries UO 193793 and UO 192641

231

G.M. Hill, A.B. Underhill

235

Properties of WolC-Rayet binaries: the key to underStanding WolC-Rayet .tars (InviCed) Revised Wolf-Rqet binary orbits and new binaries (Invited)

WR+O binaries observed from the OAO

viii Session IV poster summaries

C. Llo,d, D.I. Sticfeland

239

Wind absorption effeets in the NIV 1718A line in the WN4+05 binary DO 90657

G. RIa"w, I.-M. Vreu, E. GOlIset, D. H"IIIemelcers, P. Magain, I. Manfroid, M. Rem" K. Roclaowicz A seven year campaign on WR 22

241

P.M. Veen, A.M. van Genderen, M.A. W. Verlaeijen, K.A. tlGn der Huclat A radial-lelocity curve for WR46 (WN3p)

243

V.S. Niemela, R.B. Barba, M.M. Shara The radial velocity variations of WR46 (WN3p)

245

l.-F. Bertrand Evidence for shocking behaviour in WR133 (HO 190918, WN4.5+09.51)

248

M.F. Corcoran, I.R. Stevenll, A.M. T. Pollock, I.H. Swanlc, S.N. Slaore, G.L. Rawle,

250

X-ray variability in V444 Cygni: evidence for colliding winds

V.S. Niemela, W. Seggew;,s, A.F.I. Moffat

251

The multiple system Sk-67°18 in the LMC

R.H. Bar6., V.S. Niemela

254

The changing speetrum and orbital motion of the SMC Wolf-Rayet binary HO 5980

L. Georgiev, N. Kaltcheva

256

UBVRI polarimetry of Wolf-Rayet stars

L.L. Richarrhon, I.C. Brown

258

C. V. Rodrigues, A.M. Magallalies

260

Polarimetric vers1ls photometric variability of Wolf-Rayet star winds Polarization in Wolf-Rayet binaries: Monte Carlo simulations

SESSION V - Chair: Antlaon, F.I. Moffat Stellar winds and massive binary evolution

A.M. Cherepaslachalc Optical and X-ray observations of stellar winds in Wolr-Rayet binaries (Int/ited)

262

L. Kaper

271

A. Maeder

280

I.P. De Greve

291

D. Scheerer, A. de Koter, W. Schmutz

300

Stellar winds in high-mass X-ray binaries (Invited) Wolf-Rayet stars in galaxies and the role of binaries and hydrodynamics (Invited) The evolution of close binary stars: conditions in the winds (Invited) Complete stellar models for massive stars

H. Broun, N. Langer

New massive close binary models and the

26AI

305 yield of the WR component of'Y Vel

H. Nussbaumer Similarities and differences between WolC-Rayet winds and symbiotic novae (Invited)

309

Session V poster summariel

G. Me,net

WoIC-Rayet stars in starbursts

318

ix L. Den" A. Brel8(Jn, C. Chiosi New models for Wolr-Rayet stars: global diffusion

320

K.J.R. 0de,aarti Chemical evolution and mixing processes in massive stars

322

E.I. Sf.rilsin Semi-convection mixing and its influence on case B m8811-exchange in massive binaries

324

J. Fliegner, N. Langer Models of rotating WolC-Rayet stars

326

E.J.A. Mears, E.P.J. van den Heuvel The galactic number of WoIC-Rayet stars produced via close binary evolution

329

P.A. Crowther, L.J. Smith, A.J. Willis MCAIB - A dormant LBV in M33?

331

G.L. Isme/ian, A.G. Nikoghossian, L. V. Tambovtseva Dynamics of the wind of LBV stars

333

SESSION VI- Chair: Andre Maeder Dust Cormation near WoIC-Rayet stars and other circumstellar phenomena

P.M. Williams Dust formation around WC stars (Invited)

335

I. Cherchneff, A.G.G.M. Tidens Dust formation in hot stellar winds (Invited)

346

V.G. Zubko The physics of carbon dust around WC stars

355

M. Cohen An lHAS-based search for new dusty WCL WolC-Rayet stars

359

M.F. Bode Episodic dust formation in astrophysical sources (Invited)

363

Session VI poster summaries T. Nugis IR excesses of late-type WC stars: no dust needed in most cases

371

SESSION VII - Chair: Peredur M. Williams Hydrodynamics and high-energy physics oC colliding winds

D.R. Gies Colliding winds in Ootype binaries (Invited)

373

T. W. Bergho/er, J.N.M.M. Schmitt The ROSAT view of the massive eclipsing Ootype binary system 29 UW Canis Majoris

382

N. St-Louis UV and optical spectroscopic observations of colliding winds in WR+O binaries (Invited)

388

S. V. Marchenko Wind-wind collision effects in close massive WR+O binaries (Invited)

397

P. Bartzakos, A.F.J. Moffat A spectroscopic search for colliding winds in a complete sample oC WC/WO stars in the Magellanic Clouds

406

x S. repine Effects of wind clumping on colliding winds

411

S. LiA,., A colliding wind model for WR79

416

R. Welder Simulations of colliding winds in 3 dimensions

420

O.A. Tsiopa The colliding wind-formed structures of supernova precursors

425

A.M. T. Pollock The X-ray view of the Wolt-Rayet stars (Invited)

429

R.L. White, W. Chen Theory and observations oC non-thermal phenomena in hot m888ive binaries (Invited)

438

R.H. Becker, R.L. White An eight year study of the radio emiBBion Crom the Wolf·Rayet binary HD 193793 (Invited)

450

Y. Hervieuz A CCD spectroscopic orbit and line-variability near periastron for HD 193793

460

K.P. Panov, J. Stegert, W. Seggewiss UBV photometry oC the Wolf-Rayet stars WR137 and WR140

464

D. Y.A. Setia Gunawan, K.A. van der Hueld, P.M. William., L. Kaper, H. Henrichs, W.M. Wam.teker . IUE monitoring of WRI40 (WC7+04-5)

466

S.L. Skinner, F. Naga.e, K. Koyama, Y. Maeda, Y. T.doi ASCA X-ray observstions oC the WoIC-Rayet stars HD 193793 and HD 93162

471

A.I. Willi., H. Schild, I.R. Steven, Colliding-wind X-rays in 'Y Velorum (WC8+09I)

476

S. Mereghetti, T. Belloni, F. Haberl, W. Voges X-ray selected WolC-Rayet stars

481

I.R. Steven. Colliding stellar winds: X-ray emission and instabilities (Invited)

486

V. V. U,ov Hydrodynamics and high-energy physics of Wolf-Rayet colliding winds (Invited)

495

Session

vn poster summaries

P.M. Williams, K.A. van der Hacht, T.A. n. Spoelstra, J.P. Swaanenvelt Radio light-curves and circumstellar mapping of the colliding wind binary WRl40

504

R.E. Sclaulte-Ladbeck, K.H. Nordsieck, K.S. Bjorkman, M.R. Meade, B.L. Babler Spectropolarimetric monitoring of WR140

506

D. Y.A. Setia Gunawan, K.A. van der Hucht, D.I. Stickland, C. Lloyd, P.M. Williams, W. Wamsteker An ultraviolet radial velocity orbit for WR140 (WC7+04-5)

508

A.M. T. Pollock, M.F. Coreoran, I.R. Slevens, P.M. Williams, K.A. van der Hucht ASCA X·ray spectroscopy of WR140 near periastron

510

A.M. T. Pollock, F. Haberl, M.F. Coreoran The ROSAT PSPC survey of the Wolf-Rayet stars

512

xi 518

A.C. Rove"" Search for TeV .,.-raY8 from Wolf-Rayet stars . 1.1. AntoiAin, S. V. MarcAenko, A.F.1. Moffa'

InteDSive narrow-band continuum photometric monitoring of the WN5+06 binary V444 Cygni: evidence for wind collision?

520

I.R. Stevens, A.M. T. Pollock Stagnation-point flow in colliding-wind binary systems

522

M. Jardine, H.R. Allen, A.M. T. Pollock Magnetic annihilation in colliding-wind binary systems

523

R. Walder, D. Folini

525

.

Instabilities in colliding winds

SESSION V1U - Claair: Regina E. Sclaulte-Lad6eck Hydrodynamics and high-energy physics of winds accreting on neutrons stars and black holes M.H. IIan Kerkwijk

527

Cygnus X-3 an evolutionary missing link found? (Invited) G. Koenigs6e"er

538

R.I. Davis, M.F. Bode, K.A. van der Haclat, P.M. Williams

547

Line profile variations in WR + collapsed companion systems (Invited) Radio images oC WolC-Rayet 147 B.E. Zlai/yaev, V.R. Klalllack, I.A. Verl,sk

550

Some results oC high-speed two-channel photometry oC Wolf-Rayet stars with suspected compact companions E.I.A. Mears, A.J.M. Piters OeBe stars with possible compact companions observed at X-rays

554

Session VUI poster summaries K.A. van der Huclat, P.M. Williams, T.A.l1. Spoelstra, J.P. Swaanenvelt Radio monitoring oCthe non-thermal Wolf-Rayet objects WR125, WR146 and WR147 S. V. Marclaenko, 1.1. AntoUin, J.-F. Bertrand, R. Lamontagne, A.F.J. Moffat, A. Piceno, J.M. Mattlaews

Search for short-time periodic variations among WR+c binaries

559

562

SESSION IX - SUMMARY P.S. Conti

565

AUTHOR INDEX

573

OBJECT INDEX

575

Summary talk (Invited)

PREFACE The first ideas for the symposium were generated at exquisite outdoor lunches on Bali during the Wolf-Rayet IAU Symposium No. 143. At the time it was felt that in a subsequent IAU symposium on WR stars, binary aspects should receive more attention, notably after the growing recognition that many observations of spectral and photometric variability at all accessible wavelengths have someting to do with colliding winds or other forms of wind interaction. Tradition prescribes that IAU symposia on hot massive stars take place in high luminosity beach resorts, and after Buenos Aires, Qualicum Beach, Cozumel, Porto Heli and Bali, Elba sounded like a reasonable place. Therefore we were only too pleased with the suggestion of Francesca Matteucci and the invitation of Federico Ferrini, of the Elba International Physics Center and the University of Pisa, to host the symposium in La Biodola (Elba), Italy. This meeting is part of an extended programme of events marking the 650th anniversary of the University of Pisa. A candidate Scientific Organizing Committee was invited in late 1991, and following approval by the IAU Executive Committee in May 1993, quorums of the SOC met at various occasions, lately during the Brussels colloquium on Evolution of Massive Stars, August 1993. Such gatherings and extensive e-mail communication subsequently established the program for the symposium. The basic structure agreed upon was: basic parameters and general properties of WR stars; state of the art model atmospheres for WR stars; anisotropic mass loss and disk formation of WR stars; properties of WR binaries; influence of stellar winds on mass transfer in hot massive binary evolution; dust formation near WC stars and other circumstellar phenomena; and hydrodynamics and high-energy physics of colliding winds in WR+O binaries and of WR winds interacting with compact objects. In the spirit of IAU Symposia, we sought to leaven the hot massive star community with expertise from other fields, such as novae and dust chemistry, and feature results from the latest missions, such as ROSAT and ASCA. Within this framework 20 invited reviews, 38 invited oral contributions, and 76 poster papers were presented at the symposium, entertaining 111 astronomers from 24 countries. The Local Organizing Committee under the expert guidance of Federico Ferrini and Antonella Sapere did an excellent job, not only in hosting us at an extremely efficient and pleasant venue, but also in distributing the financial support from the IAU, the ISF, and some local sponsors. Thanks to the cooperation of the authors, most manuscripts arrived in time and in reasonable shape, thus alleviating the task of the editors. The discussion administration was in the able hands of Daniella Villani of Pisa xiii

University. Decipherment of discussion forms was skilfully performed by Dorothy Skedd of the Royal Observatories, Edinburgh. Four years ago we departed from Bali, and have been wandering about on the high seas of thought in the ship of science to make landfall on Elba, to refuel and for fresh supplies, or in other words, for a week of exchange and stimulation. And while the waves of the Mediterranean Sea were crashing constantly on the beach of La Biodola Bay, waves of information from new observations and refined theories came crashing continuously onto the participants. Did we get it all straight? Perhaps not the tower of Pisa, but many directions for future research have been straightened out to various degrees, and we all will have found motivation and incentives to carryon. Certainly, some years from now we shall land on another fertile beach, to discuss Wolf-Rayet stars from new aspect angles. A possible topic with broad interest could be 'Massive stars in starbursts' but Wolf-Rayet stars impinge on so many areas of astronomy that other topics will compete. But how can we live up to the expectations of the Executive Committee of the IAU? Where to convene after Elba? Waterloo has no beach and St. Helena limited gastronomic resources. Still, we have years and lots of work ahead to find our bearings. May these proceedings be a compass to guide us in the ocean of research on massive stars in general and on Wolf-Rayet stars in particular, till the next Wolf-Rayet symposium looms at the horizon. Karel A. van der Hucht £3 Peredur M. Williams

THE ORGANIZING COMMITTEE

SCIENTIFIC Patrice Bouchet (Chile) Jacques Breysacher (Germany) Anatol M. Cherepaschuk (Russia) Ed B. Churchwell (U.S.A.) JiPi De Greve (Belgium) Ed P.J. van den Heuvel (The Netherlands) Bambang Hidayat (Indonesia) Karel A. van der lIucht (chairman, The Netherlands)

Gloria Koenigsberger (Mexico) Francesca Matteucci (Italia) Anthony F.J. Moffat (Canada) Werner Schmutz (Switzerland) Regina E. Schulte·Ladbeck (U.S.A.) Michael M. Shara (U .S.A.) Peredur M. Williams (Scotland) Allan J. Willis (England)

LOCAL

B. Barsella (UP)

Federico Ferrini (chairman, UP)

M. Stiavelli (SNS)

Symposium secretary:

Antonella Sapere (EIPC)

The symposium was sponsored by IAU Commission 36 and co-sponsored by IAU Commissions 29, 35, 40 and 44.

The Local Organizing Committee operated under the auspices of the Elba International Physics Center, the University of Pisa , the Agenzia Spa,ziale Italiana, the Azienda Autonoma di Soggiorno e Turismo dell'Isola d'Elba. and the International Science Foundation, Washington DC, U.S.A.

xv

1 2 3 4 5 6 7 8 9 10 11 12 13

Conti Khalack

Ca.uinelli

mrs Bershofer Rauw Wa.lder Mancha-do

Villa.ni

Owocki Shaviv Weuolowski Saniola.ya.

Hamann

14 15 16 17 18 19 20 21 22 23 24 25 26

Maga.1hies Richa.rdson Za.mir Bode Rovero Pollock Bartzakos

Brighenti Hill

Garda-Segura. Meynet Veen Mergeheiii

27 28 29 30 31 32 33 34 35 36 37 38 39 Moffa.t Willia.ms Smilh LF Maeder Cohen Bertra.nd Brown Testor Breysa.cher Stevens Bouchet

Ba.rba.

Hervieux

52

48 49 50 51

47

45 46

H

40 41 42 43

Muratorio Polcaro Niedzielski Meuu Niemela. Zubko Khollygin Cherchneff Nugis Berghofer G6rny Rochowicz Eenens

53 55 56 57 58 59 60 61 62 63 64 65

54

Ivanov De Greve Annuk Gies Hillier Schmutz Harrington Blomme Cherepalchuk Springma.n Lloyd Fliegner Boha.nna.n

72 73 H 75 76 77 78

71

66 67 68 69 70

Kaper van der Hucht Nota

Seggewis8 PerinoUo

Luhrs

van Kerkwijk Nussba.umer 0degaa.rd

Miller Koenigsberger Braun

79 80 81 82 83 84 85 86 87 88 89

Tsiopa.

Berruyer Setia. Gunawa.n Lepine Jatenco-Pereira.

Nord

Corcora.n Marchenko Ferrini

PARTICIPANTS K. Annuk, Tartu Astrophysical Observatory, Toravere, Estonia

1.1. Anthokin, Sternberg Astronomical Institute, Moscow, Russia R. Barba, Osservatorio Astronomico, La Plata, Argentina P. Bartzak08, Departement de Physique, Universite de Montreal, P.Q., Canada R.H. Becker, Physics Department, University of California, Davis, CA, U.S.A. T.W. Berghofer, Max-Planck-Institute fUr Extraterrestrische Physik, Garching bei Munchen, B.R.D. N. Denuyer, Observatoire de la Cote d'Azur, Laboratoire G.D. Cassini, Nice, France J.-F. Bertrand, Departement de Physique, Universite de Montreal, P.Q., Canada R. Blomme, Koninklijke Sterrenwacht, Brussel, Belgie M.F. Bode, Astrophysics Group, Liverpool John Moores University, Liverpool, U.K. B. Bohannan, Kitt Peak National Observatory, Tucson, AZ, U.S.A. P. Bouchet, European Southern Observatory, La Silla, Chile P. Bratschi, Observatoire de Geneve, Sauverny, Switzerland H. Braun, Max-Planck-Institut rur Astrophysik, Garching bei Munchen, B.R.D. J. Breysacher, European Southern Observatory, Garching bei Munchen, B.R.D. F. Brighenti, Dipartimento di Astronomia, Universita di Bologna, Bologna, Italia J.C. Brown, Department of Physics & Astronomy, University of Glasgow, Scotland, U.K. J.P. Cassinelli, Washburn Observatory, University of Wisconsin, Madison, WI, U.S.A. l.M. Cherchneff, Royal Observatory, Edinburgh, Scotland, U.K. A.M. Cherepashchuk, Sternberg Astronomical Inst.itute, Moscow, Russia M. Cohen, Radio Astronomy Laboratory, University of California, Berkeley, CA, U.S.A. P.S. Conti, JILA, University of Colorado, Boulder, CO, U.S.A. M. Corcoran, USRA I Goddard Space Flight Center, Greenbelt, MD, U.S.A. P.A. Crowther, Depart.ment of Physics & Astronomy, UCL, London, U.K. M.J. Dalton, Department of Physics & Astronomy, UCL, London, U.K. J.-P. De Greve, Astrofysisch Instituut VUB, Brussel, Belgie L. Deng, International School for Advanced Studies, Trieste, Italia P.R.J. Eenens, Instituto de Astronomia della UNAM, Ensenada, BC, Mexico F. Ferrini, Dipartimento di Fisica, Universita di Pisa, Italia J. Fliegner, Max-Planck-Institut fUr Astrophysik, Garching bei Miinchen, B.R.D. G. Garcia-Segura, Astronomy Department, University of Illinois, Urbana, IL, U.s.A. K. Gayley, Bartol Research Institute, Newark, DE, U.S.A. L.N. Georgiev, Department of Astronomy, Sofia University, Sofia, Bulgaria D.R. Gies, Dept. of Physics & Astronomy, Georgia State University, Atlanta, GA, U.S.A. S.K. Gorny, Nicolaus Copernicus Astronomical Center, Torun, Poland W.-R. Hamann, Institut fur Theoretische Physik & Sternwarte der Universitiit, Kiel, B.R.D. I. Harrington, Physics Department, Ben Gurion University of the Negev, Beer-Sheva, Israel Y. Hervieux, Departement de Phl'sique, Universite de Montreal, P.Q., Canada G. Hill, Departement de Physique, Universite de Montreal, P.Q., Canada D.J. Hillier, Dept. of Physics & Astronomy, University of Pittsburgh, PA, U.S.A. K.A. van der Hueht, Stichting Ruimteonderzoek Nederland, Utrecht, Nederland G. Israeli an, Byurakan Observatory, Armenia M.M. Ivanov, Department of Astronomy, Sofia University, Sofia, Bulgaria V. Jatenco-Pereira, Insiituto Astronomico e Geofisico, Universidade de Siio Paulo, Brazil L. Kaper, Sterrenkundig Instituut Anton Pannekoek, Universiteit van Amsterdam, Nederland M.H. van Kerkwijk, California Institute of Technology, Pasadena, CA, U.S.A. V.R. Khalack, Main Astronomical Observatory, Golosiyiv, Kiev, Ukraine A.F. Kholtygin, Astronomical Institute, University of St. Petersburg, Petrodviretz, Russia G. Koenigsberger, Instituto de Astronomia, Universidad Nacional Autonoma de Mexico, Mexico N. Langer, Max-Planck-Institut fUr Astrophysik, Garching bei Munchen, B.R.D. S. Lepine, Departement de Physique, Universite de Montreal, P.Q., Canada C. Lloyd, Rutherford Appleton Laboratory, Chilton, Didcot, U.K. S. Luhrs, Astronomisches Institut, Universitiit Munster, B.R.D. A. Maeder, Observatoire de Geneve, Sauverny, Switzerland A.M. Magalhaes, Instituto Astronomico e Geofisico, Universidade de Siio Paulo, Brazil A. Manchado, Instituto de Astrofisica de Canarias, La Laguna, Tenerife, Espana

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xx S.V. Marchenko, Instituto de Astronomia, Universidad Nacional Autonoma de Mexico, Mexico S. Mereghetti, Istituto di Fisica Cosmica del CNR, Milano, Italia E.J .A. Meurs, Dublin Institute for Advanced Studies, School of Cosmic Physics, Dublin, Ireland G. Meynet, Observatoire de Geneve, Sauverny, Switzerland G.J. Miller, Department of Astronomy, San Diego State University, San Diego, CA, U.S.A. A.F.J. Moffat, Departement de Physique, Universite de Montreal, P.Q., Canada P.W. Morris, JILA, University of Colorado, Boulder, CO, U.S.A. G. Muratorio, Observatoire de Marseille, Marseille, France J.S. Nichols, IUE Observatory/CSC, NASA/GSFC, Greenbelt, MD, U.S.A. A. Niedzielski, Instytut Astronomii, Uniwersytet Mikolaja Kopernika, Torun, Poland V.S. Niemela, Instituto de Astronomia y Fisica del Espado, Buenos Aires, Argentina L. Nord, Max-Planck-Institut fur Extraterrestrische Physik, Garching-bei-Miinchen, B.R.D. A. Nota, Space Telescope Science Institute, Baltimore, MD, U.S.A. T. Nugis, Tartu Astrophysical Observatory, Toravere, Estonia H. Nussbaumer, Institut fUr Astronomie, ETH Zentrum, Zurich, Switzerland K.J .R. 0degaard, Institute of Theoretical Astrophysics, University of Oslo, Norway S.P. Owocki, Bartol Research Institute, University of Delaware, Newark, DE, U.S.A. M. Perinotto, Dipartimento di Astrollomia e Scienza dello Spazio, Firenze, Italia V.F. Polearo, Istituto di Astrofisica Spaziale, Frascati, Italia. A.M.T. Pollock, Comput.er & Scientific Co. Ltd., SHeffield, U.K. O.R. Pols, Institute of Astronomy, Cambridge, U.K. G. Rauw, Institut d'Astropbysique, Uniw)rsite de Liege, Belgique 1. Richardson, Department of Physics & Astronomy, University of Glasgow, Scotland, U.K. K. Rachowicz, Institute of Astronomy, Nicolaus Copernicus University, Torun, Poland C. Rossi, Istituto di Astrofisica Spaziale, Frascati, Italia A.C. Ravero, Whipple Observatory, Smithsonian Astrophysical Observatory, Amado, AZ, U.S.A. E. Santolaya, Instituto de Astrofisica de CanariM, La Laguna, Tcnerife, Espana D. Schaerer, Observatoire de Gencve, Sauverny, Switzerland W. Schmutz, Institut fUr Astronomie, ETII Zentrum, Ziirich, Switzerland R.E. Schulte-Ladbeck, Dept. of Physics & Astronomy, University of Pittsburgh, PA, U.S.A. W. Seggewiss, Univcrsitiit.s-St.crnwarl.c BOlin, Observatorium Hoher List, Daun, B.R.D. D.Y.A. Setia Gunawan, Stiehl,ing Ruimteonderzoek Nederland, Utrecht, Nederland G. Shaviv, Asher Space Research Institute, Technion City, Haifa, Israel M. Sirianni, Dipartimento di Astronomia dell' Universita di Padova, Padova, ltalia S.L. Skinner, Institute of Space and Astronautical Science, Kanagawa, Japan L.F. Smith, University of Sidney, NSW, Australia L.J. Smith, Department of Physics & Astronomy, UCL, London, U.K. U. Springmann, Institut fiir Astronomie und Astrophysik, Universitat Munchen, B.R.D. I.R. Stevens, School of Physics & Space Research, Universit.y of Birmingham, Birmingham, U.K. D.J. Stickland, Space Science Division, Rutherford Appleton Laboratory, Chilton, U.K. N. St-Louis, Departement de Physique, Universite de Montreal, P.Q., Canada G. Testor, Observatoire de Meudon, DAEC, Meudon, France O. Tsiopa, Central Ast.rononomical Observatory, Pulkovo, St. Petersburg, Russia V.V. Usov, Physics Department, Weizmann Institute of Science, Rehovot, Israel P.M. Veen, Sterrenwacht Leiden, Rijksulliversiteit Leiden, Leiden, Nederland D. Villani, Dipartimcnto di Fisica, Universita di Pisa, Italia J.M. Vreux, Instit.ut d'Astropbysique, Universite de Liege, Belgique R. Walder, Institut fiir Astronomie, ETH Zentrum, Zurich, Switzerland U. Wessolowski, Institut fiir Theoretische Physik & Sternwarte der Universitiit, Kiel, B.R.D. R.I.. White, Space Telescope Science Institute, Baltimore, MD, U.S.A. P.M. Williams, Royal Observatory, Blackford Hill, Edinburgh, Scotland, U.K. A.J. Willis, Department of Physics & Astronomy, UCL, London, U.K. R. 'Wilson, Department of Physics & Astronomy, UCL, London, U.K. R. Zamir, Physics Department, Nuclear Research Center - Negev, Beer Sheva, Israel V.G. Zubko, Main Astronomical Observatory, Golosiyiv, Kiev, Ukraine

WELCOMING ADDRESS BY THE CHAIRMAN OF THE LOC

Ladies and Gentlemen, It is a pleasure and an honour for me to welcome you on Elba. You are the participants to the first IA U Symposium held at the Elba International Physics Center. Let me spend a few words on how this came about. In 1988, Stefano Fantoni, nuclear physicist at the Department of Physics at the University of Pisa (used to come on vacation to Elba), and me (I was born on Elba), while drinking coffee entertained the idea of organizing a workshop on Physics on Elba. A few months later the Director of the Azienda di Soggiorno e Turismo - the local touristic orgnization - informed me that there was in construction a conference room in Marciana Marina and urged me to advertise this among the academics of the University of Pi sa. Immediately Stefano and me decided to use this facility and we began to organize workshops devoted to Many Body physics, our discipline. The Elba International Physics Center was born. Since them we had several workshop (32 in total) devoted to nuclear physics, molecular dynamics, solid state physics, biophysics, and obviously, astrophysics. Indeed the first workshop was on astrophysics: in September 1989 the EIPC hosted the workshop: 'Chemical and Dynamical Evolution of Galaxies'. Including the workshops in program for this year, we had in total eight astrophysical workshops and a school of astronomy for Italian PhD students. We appreciated in particular the interest of the European Southern Observatory, which organized three ESO Workshops at the EIPC. At the end ofthe previous IAU Symposium on Wolf-Rayet stars on Bali, my good friend and co-worker Francesca Matteucci, who has been on Elba as organizer and participant to the first few workshops, suggested this locality as host of the future IAU Symposium on WR stars to Karel van der Hucht. And so you are here! Fundamental to this reality has been Karel, the true engine of the organization. Decisive the contribution of the member of SOC. Absolutely precious Antonella and her collaborators. Thanks are due to Bruno Barsella and Massimo Stiavelli who helped me in the preparation of the Abstract Booklet. We acknowledge the economic support from the International Astronomical Union, the International Science Foundation, the Dipartimento di Fisica dell'Universita di Pisa, the Agenzia Spaziale It ali ana via a local grant of our group in Pisa and the Azienda di Soggiorno e Turismo dell'Elba. Finally, I wish you a pleasant stay in Elba and a really successful Symposium. Now I sit in my row, ready to learn a lot about Wolf-Rayet stars, which, from my personal perspective, are a fundamental key piece in the jigsaw puzzle of galactic evolution. Federico Ferrini

K. A. van tier Hucht and P. M. Williams (eds.), Wolf-Royet Stars: Binaries, CoIUdlng Winds, Evolution, I. el99SlAU.

WELCOMING ADDRESS BY THE CHAIRMAN OF THE SOC

Ladies and Gentlemen, Dear Colleagues,

It is with a feeling of great pleasure that I welcome you all on behalf of the Scientific Organizing Committee. We are delighted with the hospitality extended to us by the Elba International Physics Centre and the Univerisity of Pisa, and thank the chairman of the Local Organizing Committee, Prof. Dr. Federico Ferrini and his staff for their remarkable efforts. Sponsored jointly by the International Astronomical Union and the Elba International Physics Center, this occasion is the sixth in the series of IAU symposia on hot massive stars, after No. 49 (Argentina 1971), No. 83 (Canada 1978), No. 99 (Mexico 1981), No. 116 (Greece 1985) and No.143 (Indonesia 1990). Those symposia, together with related colloquia and workshops on hot massive stars, have been the principle fora that have reviewed the status quo, witnessed the announcements of discoveries, and contributed to the stimulus for the future. This symposium will follow that tradition. Wolf-Rayet binaries, their colliding winds and massive binary evolution are the main topics of the symposium. Recent observations and theoretical studies on the interaction between hot massive binary components have brought us more insight and more problems. Binary interaction can nowadays be observed over almost the entire electromagnetic spectrum, which should add to more complete models and constrain the number of free parameters in theories. Studies of the prototypes V444 Cygni and HD 193793 encourage us to observe all Wolf-Rayet binaries in much more detail, and each system will appear to be unique. Seated here are 111 astronomers from 24 countries. You all have worked very hard to prepare for this week. I am confident that this symposium, with your valuable contributions and active participation, will serve its purpose and confront us all with thought-provoking ideas and stimulus for years to come. Karel A. van der Hucht 2 K. A. van der Hueht and P. M. Williams (eds.). Wolf-Rayet Stars: Binaries. Colliding Winds. Evolution. 2. CI995IAU.