WOLF-RAYET STARS: OBSERVATIONS, PHYSICS, EVOLUTION INTERNATIONAL ASTRONOMICAL UNION UNION ASTRONOMIQUE INTERNA TIONALE SYMPOSIUM No. 99 HELD AT COZUMEL, MEXICO, SEPTEMBER 18-22, 1981 WOLF-RAYET STARS: OBSERVATIONS, PHYSICS, EVOLUTION EDITED BY C. W. H. DE LOORE Astrophysicallnstitute, Vrije Universiteit Brussel, Belgium and Universitair Centrum, Antwerpen, Belgium and A. J. WILLIS University College, London, United Kingdom D. REIDEL PUBLISHING COMPANY DORDRECHT : HOLLAND! BOSTON: U.S.A.! LONDON: ENGLAND Ubrary of Congress Cataloging in Publication Data Main entry under title: Wolf-Rayet stars: observations, physics, evolution At head of title: International Astronomical Union. Includes index. 1. Wolf-Rayet stars-Congresses. I. Loore, Camiel W. H. de. II. Willis, A. J. (Allan J.) III. International Astronomical Union. QB843.W6W64 1982 523.8 82-11243 ISBN -13: 978-90-277-1470-1 e-ISBN -13: 978-94-009-7910-9 DOl: 10.1007/978-94-009-7910-9 Published on behalf of the International Astronomical Union by D. Reidel Publishing Company, P. 0. Box I7, 3300 AA Dordrecht, Holland All Rights Reserved Copyright © I 982 by the International Astronomical Union Sold and distributed in the U.S.A. and Canada by Kluwer Boston, Inc., 190 Old Derby Street, Hingham, MA 02043, U.S.A. In all other countries, sold and distributed by Kluwer Academic Publishers Group, P.o. Box 322, 3300 AH Dordrecht, Holland D. Reidel Publishing Company is a member of the Kluwer Group 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 informational storage and retrieval system, without written permission from the publisher TABLE OF CONTENTS PREFACE xi THE ORGANISING COMMITTEES xv LIST OF PARTICIPANTS xix SESSION 1 - THE WOLF-RAYET PHENOMENON P.S.CONTI: Wolf-Rayet phenomena (Invited lecture) 3 W.SCHMUTZ: The effective temperatures of early WR stars. 23 B.HIDAYAT, K.SUPELLI and K.A. VAN DER HUCHT: The galactic distribution of WR stars. 27 E.M.LEEP: Line strengths in WN stars. 41 A.B.UNDERHILL: Hot mantles, moderate photospheres for WR stars. 47 C. DE LOORE, P.HELLINGS and H.J.G.L.M.LAMERS: Corrections for hydrostatic atmospheric models: radii and effective temperatures of WR stars. 53 D.G.TURNER: Preliminary results of a new study of the intrinsic properties of WR stars. 57 D.R.FLORKOWSKI: Radio observations of HD 193793. 63 C.STERKEN and C. DE LOORE: Near-infrared photometry of southern galactic WR stars. 67 P .M.WILLIAMS: Infrared ( 1.4 - 4.1 ]Jm ) spectra of WR stars. 73 D.G.HUMMER, M.J •B ARLOW and P.J • STOREY: The infrared recombination- line spectra of lolR stars. 79 SESSION 2 - THE CHEMISTRY OF THE WOLF-RAYET STARS A.J.WILLIS: The chemical composition of the WR stars ( Invited lecture ) 87 C.D.GARMANY and P.S.CONTI: Chemical composition of WR stars: Abundant evidence for anomalies. 105 vi TABLE OF CONTENTS D.N.PERRY and P.S.CONTI: H/He ratios for WN stars in the LMC and the Galaxy. 109 L.J.SMITH and A.J.WILLIS: The CIN ratio in IVN and we stars. 113 D.VANBEVEREN: On the chemical abundances, evolutionary stage and bolometric magnitude of WR stars. 117 P.MASSEY: Absolute spectrophotometry of WR stars: are the colors the same? 121 T.NUGIS: An explanation of the radio flux mystery of HD 192163 and empirical models for WN stars. 127 T.NUGIS: Carbon abundance in WC stars. 131 R.WEHRSE: Synthetic spectra for WN stars. 135 L.HOUZIAUX and A.HECK: Carbon abundance in the we II star CPD -5608032. 139 SESSION 3 - MASS LOSS FROM WR STARS: OBSERVATIONS & THEORY M.J.BARLOW: Observations of mass loss from OB and WR stars. ( Invited lecture ) 149 J.P.CASSINELLI: Theories for the winds from WR stars ( Invited lecture) 173 D.C.ABBOTT: The theory of radiation driven stellar winds and the WR phenomenon. ( Invited lecture) 185 P.S.THE, K.A. VAN DER HUCHT and M.ARENS: The influence of the ratio of total to selective extinction on the determination of the mass loss rate of WR stars from IR excess measurements. 197 N.PANAGIA and M.FELLI: On the properties of the WR stars and their mass loss. 203 W.ROBBRECHT, C. DE LOORE and G.OLSON: A hot corona model for O-stars and WR stars. 209 D.C.ABBOTT, J.H.BIEGING and E.CHURCHWELL: Radio continuum measurements of mass loss from WR stars. 215 D.E.HOGG: Radio emission from WR stars. 221 J.D.HILLIER: Infrared spectroscopy of WN stars. 225 TABLE OF CONTENTS vii N.PANAGIA, E.G. TANZI and M.TARENGHI: The near-IR properties of selected h'N stars in the Large Magellanic Cloud 231 J.M.VREUX, M.DENNEFELD and Y.ANDRILLAT: Near IR observations of galactic WN stars 237 W.M.RUMPL: Line formation in winds with enhanced equatorial mass loss rates and its application to the WR star HD 50896. 243 SESSION 4 - OBSERVATIONS OF HOLF-RAYET BINARIES P.MASSEY: I.JR stars with massive companions. ( Invited lecture ) 251 A.F.J.MOFFAT: WR stars with compact companions. ( Invited lecture ) 263 K.A. VAN DER HUCHT, P.S.CONTI and A.J.WILLIS: The iron curtain of WC9 stars. 277 R.LAMONTAGNE and A.F.J.MOFFAT: A spectroscopic search for duplicity among a complete sample of northern galactic WR stars. 283 I.LUNDSTROM and B.STENHOLM: Is HD 164270 a long-period eclipsing binary ? 289 V.S.NIEMELA and R.H.MENDEZ: A spectral study of HD 50896. 295 V.S.NIEMELA: Observations of new WR binaries. 299 P.PISMIS and A.QUINTERO: The velocity field of S 308. the ring nebula around the WN5 star HD 50896. 305 F.BEECKMANS, C.A.GRADY, F.MACCHETTO and K.A. VAN DER HUCHT: Spectral variations of Theta Muscae ( WC6+09.5I ) in the ultraviolet. 311 J.BREYSACHER, A.F.J.MOFFAT and V.S.NIEMELA: The WR eclipsing binary HD 5980 in the SMC 317 SESSION 5 - EVOLUTIONARY STATUS OF WOLF-RAYET STARS C.CHIOSI: The evolution of massive stars: the production of "single WR stars. ( IVlvae.d te.c.:tMe. ) 323 C. DE LOORE: The evolution of massive stars - the production of binary WR stars. ( IVlvae.d te.ctMe. ) 343 viii TABLE OF CONTENTS G.BERTELLI and C.CHIOSI: Gradients in supergiant and WR stars across the galactic plane. 359 D.VANBEVEREN and C.DE LOORE: On the expected frequency of WR + compact star systems. A.MAEDER: Properties of the scenario for the formation of WR stars as post-red supergiants. 3'71 A.TUTUKOV and L.YUNGELSON: Origin and evolution of Wolf-Rayet stars. 3'7'7 G.GIURICIN and F.MARDIROSSIAN: The maSSlve eclipsing binary RY Scuti. 383 M.J.BARLOW and D.G.HUMMER: The WO Wolf-Rayet stars. G.F.BISIACCHI, J.LOPEZ and C.FIRMANI: The ON stars: a wider spectroscopic definition. 393 . P.HELLINGS, F.VANSINA, W.PACKET, C.DOOM, J.P.DE GREVE and C.DE LOORE: On the structure and evolution of the OB companions in Wolf-Rayet binaries. 39'7 C.DOOM and J.P.DE GREVE: The occurrence of different Wolf-Rayet phases in massive close binaries. 403 A.MAEDER: The various scenarios leading to WR stars: their relative importance and the role of mixing. 405 SESSION 6 - LOW MASS WOLF-RAYET STARS RING NEBULAE A.RENZINI: Low mass Wolf-Rayet stars: theory 413 ( Inv~ed papeh ) S.R.HEAP: Subluminous Wolf-Rayet stars: observations. 423 ( Inv~ed papeh ) A.J.WILLIS and D.J.STICKLAND: The peculiar binary system HD 45166 (SdO+B8V?). 44'7 P.BENVENUTI, M.PERINOTTO and A.J.WILLIS: The UV spectrum of the central star of NGC 40. 453 R.H.MENDEZ and V.S.NIEMELA: A reclassification of WC and "0 VI" central stars of planetary nebulae and comparison with population I WC stars. 45'7 T ABLE OF CONTENTS ix J.N.HECKATHORN, F.C.BRUH\mILER and T.R.GULL: A new search for nebulae surrounding Holf-Rayet stars. 463 Y.-H.CHU: Ring nebulae associated with Holf-Rayet stars. 469 M.C.LORTET, G.TESTOR and V.NIEMELA: Ring nebulae around Hc6 stars: NGC 635, around HD 15,504. M.ROSADO, G.MONNET, A.LAVAL and Y.GEORGELIN: Kinematics of the ring-shaped nebula N206 in the LMC. 4,9 A.TUTUKOV: HR stars with ring nebulae. 485 D.J.STICKLAND and A.J.HILLIS: IUE observations of the HN-C star HD 62910. 491 SESSION , - HOLF-RAYET STARS IN EXTERNAL GALAXIES C.FIRMANI: Observations and the Holf-Rayet evolutionary scenarlO. 499 ( lectune ) I~vited A.F.J.MOFFAT: Holf-Rayet stars in the Magellanic Clouds: spectroscopic binaries and masses. 515 ( ) I~vited lect~e J.BREYSACHER and M.AZZOPARDI: Absolute magnitudes of Wolf- Rayet stars: the WN3 and WN4 sub-classes in the LMC. 523 Y.ANDRILLAT, M.DENNEFELD and J.M.VREUX: Near infrared observations of Magellanic WN stars. 52, M.M.SHARA and A.F.J.MOFFAT: The first detection of Wolf-Rayet stars in M31. 531 I.LUNDSTROM and B.STENHOLM: Wolf-Rayet 'stars In open clusters and associations. 539 J.MELNICK: The Wolf-Rayet stars In 30 Doradus. P.S.CONTI: Spectra of the Wolf-Rayet stars in 30 Doradus 551 M.ROSA and S.D'ODORICO: NGC 604: a giant H II region dominated by many WR stars. 555 S.D'ODORICO and M.ROSA: Wolf-Rayet stars associated to giant regions of star formation. 55, x TABLE OF CONTENTS J.P.CASSINELLI, J.S.MATHIS and B.D. SAVAGE: The central object of the 30 Doradus nebula, a supermassive star 563 SESSION 8 - X-RAY DATA - MISCELLANEOUS TOPICS - GENERAL DISCUSSION D.KUNTH: Wolf~Rayet stars in emission-line galaxies 569 A.B. UNDERHILL: Comments on the significance of the positions of population I Wolf-Rayet stars in the HR diagram 571 A.F.J.MOFFAT, C.FIRMANI,I.S.McLEAN and W. SEGGEWISS: Time-dependent X-ray observations of Wolf-Rayet binaries with O-type and with suspected compact companions 577 G.F.BISIACCHI, C.FIRMANI and E.DE LARA: Lines profile variations and binarity in Wolf-Rayet stars 583 W.T.SANDERS, J.P.CASSINELLI and K.A.VAN DER HUCHT: X-rays from Wolf-Rayet stars observed by the Einstein observatory 589 L.F.SMITH: Summary of symposium 597 P.S.CONTI(Chairman): Open discussion 605 SUBJECT INDEX 615 PREFACE The formative ideas for this symposium originated in 1978 at the IAU Symposium No. 83 on "Mass Loss and Evolution of O-type Stars" held at Qualicum Beach, Vancouver Island, Canada - WR stars generally figure prominently in O-star meetings and vice versa! Following general appro val by the IAU Executive Committee the initial ideas were cemented at a subsequent meeting, IAU Colloquium No. 59 on "The Effects of Mass Loss on Stellar Evolution", held at Miramare, Trieste, Italy in 1980, which was attended by the ma,jority of the present Scientific Organising Committee and at which meeting the outline programme for this symposium was formulated. 1981 was considered an appropriate year in which to hold a meeting on WR stars, since the last IAU Symposium devoted to this stellar class had been held a decade earlier, in Buenos Aires (IAU Sym posium No. 49), and during this intervening period a wealth of new observational material had been obtained for WR stars together with significant advances on the theoretical front. The venue for this sym posium was chosen from the requirement, which can be inferred from the above, that a meeting on 'hot' stars take place in an appropriate, sunny climate and followed upon the excellent suggestion of Dr. C. Firmani to hold the symposium in Mexico. The aim of this meeting was to bring to gether both observers and theoreticians working in the WR and related fields, to present and discuss recent results in order to see what con sensus exists as to the physical and chemical properties of the WR stars, their evolutionary status and their links with other stellar classes. On the observational front, the comparatively recent advent of sophisticated space instrumentation such as the IUE and Einstein satel lites, have enabled the first detailed observations of many stars to be made at ultraviolet and X-ray wavelengths, whilst improved ground-based techniques and new telescopes have extended our knowledge of the stellar wind Infrared and Radio emissions as vTell as bringing many WR stars in the Magellanic Clouds under detailed scrutiny. These observational advances have been accompanied, and often stimulated, significant ad vances in the theoretical interpretation of WR spectra and theoretical studies of the evolution of massive single stars and binary systems In which mass loss and/or mass exchange plays a significant role. Following an opening session dealing with the general properties and deduced physical conditions of Pop I WR stars, Session 2 addressed the long-standing question of their chemical composition; a topic of much uncertainty and controversy throughout the history of WR studies. Recent attempts to quantitatively analyse both optical and ultraviolet spectra conclude that the WR stars are very hydrogen deficient (although a very recent result is that there is no one-to-one relation between R/Re and WN subtype) and have He/C/N ratios that are broadly consistent with those expected theoretically to occur through the exposition of nuclear processed material at various stages of late H-burning (WN stars) xi C. W. H. de Loore and A. J. Willis (eds.), Wolf-Rayet Stars: ObseYilations, Physics, Evolution, xi-xiv. Copyright ©1982 by the IAU.