Wolf-Rayet Stars
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NAT-L INST OF STANDARDS & TECH R.I.C. A11101110167 Symposium on Wolf-Ra/Wolf-Ravet -star*- n QC100 .U57 V307;1968 C^°NBi%^^!'^^i^.o Sjy ( : \ F.cr^i' 8ii|: llie IJuited Slates DepsFlmesit of Ccmiioj^v UNITED STATES DEPARTMENT OF COMMERCE • C. R. Smith, Secretary NATIONAL BUREAU OF STANDARDS • A. V. Astin, Director Wolf-Rayet Stars Proceedings of a Symposium held at The Joint Institute for Laboratory Astrophysics University of Colorado Boulder, Colorado, June 10-14, 1968 Edited by Katharine B. Gebbie and Richard N. Thomas JILA Institute for Basic Standards National Bureau of Standards Boulder, Colorado 80302 Held under the joint sponsorship of The American Astronomical Society, Harvard College Observatory The Joint Institute for Laboratory Astrophysics Smithsonian Astrophysical Observatory Partially Supported by the National Science Foundation , \) National Bureau of Standards Special Publication 307 , » » »- Issued December 1968 For sale by the Superintendent of Documents, U.S. Government printing Office Washington, D.C. 20402 - Price $3 National Bureau ef Standards JAN 1 4 1369 142810 at 100 ABSTRACT A symposium on Wolf-Rayet stars was held at the Joint Institute for Laboratory Astrophysics on the campus of the University of Colorado, Boulder, Colorado, 10-14 June 1968. The Wolf-Rayet stars represent the most extreme example studied of an interaction between aerodynamic motions and a radia- tion field to produce a high temperature, large- scale plasma in a steady but non-equilibrium state. As such these stars provide a perfect example of the kind of gaseous ensemble that JILA was created to study. In order to understand them, we require a knowledge of gases with temperatures between 10** and 10 °K and differential velocities between 0 and 10^ km/sec. In particular we need information on radiative and collisional atomic cross sections for a wide range of ions, on collective interactions of ions and photons, on methods of diagnostic spectro- scopy, and on velocity fields generated by convec- tive, gravitational, nuclear, radiative, rotational, thermal, and other instabilities. The material of the symposium was divided into four broad topics: the distribution, physical properties and evolution- ary status of Wolf-Rayet stars; the detailed features of their spectra; the interpretations of these features and the models on which they are based; and finally a survey of the material and ideas arising out of the symposium itself. This volume contains the intro- ductory summaries of each of these broad topics, to- gether with an edited version of the discussions which followed. Key words: atomic cross sections, atmospheric aerodynamics, diagnostic spectroscopy, non-equili- brium gases, stellar instability, Wolf-Rayet stars. Library of Congress Catalogue Card No. : 6 8-62108 , CONTENTS Preface v Acknowledgments vii List of Participants ix Opening Remarks Richard N. Thomas 1 Prologue The Wolf-Rayet Stars: Informal Perspective C. S. Beats 7 Part A. THE FEATURES OF THE SYSTEM OF WOLF-RAYET STARS 21 Chairman: Cecilia Payne-Gaposchkin Introductory Speaker: Lindsey F. Smith 23 DISCUSSION 65 Part B. A SURVEY OF SPECTROSCOPIC FEATURES OF WOLF- RAYET STARS 101 Chairman: Jorge Sahade Introductory Speaker: Leonard V, Kuhi 103 DISCUSSION 144 Part C. SPECTROSCOPIC DIAGNOSTICS, INTREPRETATION AND ATMOSPHERIC MODELS 181 Chairman: Lawrence H. Alter Introductory Speaker: Anne B. Underhitt 183 DISCUSSION 203 Part D. SUMMARY OF PROBLEMS, IDEAS, AND CONCLUSIONS ON THE PHYSICAL STRUCTURE OF THE WOLF-RAYET STARS 2 37 Introductory Speaker: Richard N. Thomas 239 DISCUSSION 251 iii , " The Spectriom of V444 Cygni ; Freddo, F. A.; Ap. J. , £1, 515, 1936. There was a remarkable pygmi Who arrived from V444 Cygni. He said, as he grope. Through his old spectroscope, "It's them emission lines that intrygmi ! from "Aerodynamic Phenomena in Stellar Atmospheres - a Bibliography", Technical Note No. 30 (1959) U.S. Department of Commerce National Bureau of Standards. iv . PREFACE The symposium on Wolf-Rayet stars, sponsored jointly by the American Astronomical Society, the Harvard College Observatory, the Joint Institute for Laboratory Astrophysics (JILA) , and the Smithsonian Astrophysicai Observatory was held at JILA, 10 to 14 June 196 8. It was one of a series of symposia that JILA has undertaken to sponsor in collaboration with other institutions on topics of current interest in overlapping areas of aerodynamics, astrophysics, atomic physics, chemical physics, and the physics of high temperature gases. The Organizing Committee consisted of C. Payne- Gaposchkin, K. B. Gebbie , L. Goldberg, and R. N. Thomas. There were thirty-eight invited participants, and a number of graduate students and scientists in related fields attended as auditors. The sympo- sium was modeled after the Cosmical Gas Dynamics Symposia, which are sponsored jointly by the Inter- national Astronomical Union and the International Union of Theoretical and Applied Mechanics. Each of the four formal sessions consisted of a survey paper followed by general discussion during which partici- pants were encouraged to present their views and results where relevant. There were no contributed papers The National Science Foundation made a generous grant toward the publication of these proceedings and other expenses of the symposium. The balance of the costs were covered by JILA (the University of Colorado and the National Bureau of Standards) In all the work connected with the symposium, we have been wholly dependent on Robert N. Alvis, Execu- tive Officer of JILA, Mrs, Robert J. Low, whose ex- perience in running symposia is incomparable, and Judy Schlepp, our secretary for astrophysics. As- sisting them were Anne Cannon, Cordelle Yoder, and Mary LaCasse. All technical facilities were coor- dinated by Stuart Jordan, who was on loan to us from the NASA Goddard Space Flight Center. He was assisted by three JILA graduate students, Stephen Hill, David Van Blerkom, and Kenneth Ziebarth. We are also in- debted to the JILA administrative and technical ser- vices and, in particular, to William Kellet, Victor Holliger, and Floyd Howerton. The cooperation of Mr. J. K. Emery of the University of Colorado Pub- V lications Services is gratefully acknowledged. Alice Levine has overseen from start to finish the editing and preparation of the camera copy for these proceedings. To her professionalism and good sense of fun, we owe not only the appearance and timing of this volume but also our own enjoyment in editing it. Although each participant received and corrected a draft of his remarks, the responsibility for the final editing is ours. For instant responses to demands for additional figures and references, we are grateful to many of the participants and also to a number of their colleagues who did not attend the symposium. We were fortunate in being guided to the quick and inexpensive form of these proceedings by the Publications Office of the National Bureau of Standards and, in particular, by W. R. Tilley, J. E. Carpenter, and Betty L. Oberholtzer. The typescript was prepared by Paulina Thure. Katharine B. Gebbie 1 September 196 8 Richard N. Thomas ACKNOWLEDGMENTS We wish to thank the publishers of the follow- ing publications and the authors of a number of pa- pers for permission to use figures and tables. Annals of the Astronomical Observatory of Harvard College Annual Review of Astronomy and Astrophysics (Annual Reviews, Inc.) Astrophysical Journal (The University of Chicago Press) Bulletin of the Astronomical Institutes of the Netherlands (North-Holland Publishing Company) 'Canadian Journal of Research (Canada Department of Mines and Resources) I.A.U. Symposiiim No. 34 Planetary Nebulae (D. Reidel Publishing Company, Dordrecht, Holland) Monthly Notices of the Royal Astronomical Society (Blackwell Scientific Publications, Oxford) Publications of the Dominion Astrophysical Observa- tory (Department of the Interior Canada) Publications of the Lick Observatory (University of California Press) M. S. Burland H. D. Curtis W. A. Hiltner C. R. Lynds vii PARTICIPANTS L. H. ALLER, Department of Astronomy, University of California, Los Angeles, California C. S. BEALS, Manotick, Ontario, Canada M. S. BESSELL, Yerkes Observatory, Williams Bay, Wisconsin K. BRACHER, Department of Astronomy, Whitman College, Walla Walla, Washington J. CASTOR, JILA, University of Colorado, Boulder, Colorado A. N. COX, J-15, Los Alamos Scientific Laboratory, P. O. Box 1663, Los Alamos, New Mexico J. COX, JILA, University of Colorado, Boulder, Colorado W. DEINZER, JILA, University of Colorado, Boulder, Colorado S. I. GAPOSCHKIN, Harvard College Observatory, 60 Garden Street, Cambridge, Massachusetts R. H. GARSTANG, JILA, University of Colorado, Boulder, Colorado K. B. GEBBIE, JILA, University of Colorado, Boulder, Colorado R. HANBURY BROWN, Department of Astronomy, The University of Sydney, Sydney, New South Wales, Australia C. HANSEN, JILA, University of Colorado, Boulder, Colorado R. M. HJELLMING, National Radio Astronomy Observatory, Edgemont Dairy Road, Charlottesville, Virginia D. G. HUMMER, JILA, University of Colorado, Boulder, Colorado H. M. JOHNSON, Department 52-10, Building 202, Lockheed Missiles and Space Company, 3251 Hanover Street, Palo Alto, California S. JORDAN, Solar Physics Laboratory Branch, Building 2, NASA-Goddard Space Flight Center, Greenbelt, Maryland R. KANDEL, NASA- Institute for Space Studies, 2880 Broadway, New York, New, York L. V. KUHI , Department of Astronomy, University of California, Berkeley, California K.