Epedeie Oling

NASA §'.?-i>C EPEDEIE OLING If NASASP-383 CEPHEID MODELING The proceedings of a conference and workshop held at Goddard Space Flight Center, Greenbelt, Maryland, July 29,1974 Edited by DAVID FISCHEL AND WARREN M. SPARKS Goddard Space Flight Center Prepared by NASA Goddard Space Plight Center Scientific and Technical Information Office 1975 NATIONAL AERONAUTICS AND SPACE ADMINISTRATION Washington, D.C. The requirement for the use of the International System of Units (SI) has been waived for this document under the authority of NPD 2220.4, paragraph 5.d. For sale by the National Technical Information Service Springfield, Virginia 22161 Price - $9.50 PREFACE The primary motivation for organizing this Cepheid Modeling Conference was to attempt to compare what different researchers obtained using similar techniques and to resolve any differences. We felt that such a conference could be extremely fruitful, if we could get most of the active investigators together. Of course, it followed that such a forum would be useful in elucidating the advantages and differences between newer techniques and the older ones. Inevitably, the vehicle for such discussions revolves around current research, and that leads to discussing future research based upon the available numerical tools and past experience. So the form of the meeting evolved from our first idea of an informal discussion into a two-day meeting, with sessions on some new observations, new techniques and current results, and a session devoted to an intercomparison of different computer codes. In order to compare codes, we selected a model known to be well imbedded in the classical Cepheid instability strip, which we called the "Standard Model." The parameters of the model were 4 M®, and 1.234 X 1037 erg/s with the composition appropriate to D. King's opacity table 4a. Eight independent codes from 11 participants provided 13 models, 10 of which are reviewed ,in -this volume. The Conference, held on July 29, 1974, was composed of 10 papers. Each speaker was allowed approximately 30 minutes, which included a discussion period. The atmosphere was very informal, and the speakers did not always adhere closely to their prepared manu- scripts, which are published as submitted in the first part of thi%solume. Some of the discussion which occurred during paper presentations have been moved to the end of the talk and are so noted. This was necessitated by the common departure of the speakers from the formal text. A transcript of the discussions was prepared from a tape recording. Unfortunately, the tape was inadvertently turned off during the discussion of Davis' paper and ran off the end of the reel once. Consequently, we are missing the end of the discussion of Davis' paper and all of the discussion of Christy's and Karp's papers. The Workshop, held oh July 30, 1974, was composed solely of conversation after short extemporaneous presentations by the model makers. The second part of this volume was prepared totally from the transcripts of the tapes. We have attempted to preserve the informal conversational flavor of the Workshop, and have done only minor editing. The sheer volume of material and a desire to go to press as soon as possible precluded the dispersal of the edited transcripts to the participants for further editing. Since the bulk of transcription pertained to the second day, we applied the same rules to the first day's discussion out of simplicity. 111 A number of editorial techniques have been employed. We have occasionally inserted a phrase or word for clarification, since the tone of voice or the facing of the speaker to another participant is unreproducible in text. These editorial insertions are usually enclosed in square brackets ([]). We have used an ellipsis (...) when a speaker became inaudible, did not finish his sentence, or was interrupted and continued a few lines later in the text. Pauses, parenthetical expressions, and asides are characterized by a dash (—). Purposely deleted discussion is represented by five asterisks (*****). Examples are the discussion of which way to move overlay graphs, what units to use in tables, notation, and so forth. Finally, we have added a few editors' notes, enclosed in square brackets, in order to elucidate the discussion. Now, in reading the discussions of both days, please remember that you are reading what the participants said in a very informal atmosphere among friends and colleagues. If we have misquoted or misidentified anyone, we offer our sincere apologies. The tapes have been reviewed five times; some passages, dozens of times. Simultaneous discussions, soft voices, or talking away from the microphones frequently made accurate transcription impossible, and there are probably a goodly number of errors. We regret missing those words, but there is little more we could do in the time available. We preferred not to rewrite the occasional German construction used by Dr. von Sengbusch and, possibly, mis- quote him. IV ACKNOWLEDGMENTS The Goddard Cepheid Conference and Workshop, in our opinion, was a great success. For this, we would like to extend our appreciative thanks to each of the participants, since they made it the success it was. In addition, we would like to especially thank Drs. Robert F. Christy and Arthur N. Cox for chairing the morning and afternoon sessions of the Con- ference, respectively. Somehow, they encouraged considerable discussion and yet ended on tune. The most difficult job of all was handled magnificently by Dr. Norman H. Baker, who moderated the Workshop. We cannot thank him enough. The logistical problem of getting slides to and from reproduction facilities, keeping notes on who spoke from the floor, and other menial tasks were handled by a levy of students who held Summer Research Assistantships in the Laboratory for Optical Astronomy. They were John J. Cowen, William S. Gilmore, Denise A. Langel-Frey, and Paul A. Marionni, all from the University of Maryland, and Deborah J. Hamill of the American University Summer Program. We wish to thank them for their invaluable aid. Last, but not least, we would like to thank the Goddard Space Flight Center for sponsoring the Cepheid Modeling Conference and Workshop. David Fischel Warren M. Sparks Page intentionally left blank Page intentionally left blank PARTICIPANTS GODDARD CEPH0D MODfUNG CONFERENCE AND WOMSMOP David R. Alexander Wichita State University Norman H. Baker Columbia University Theodore A. Bednarek University of Toronto Albert Boggess Goddard Space Flight Center Nancy W. Boggess NASA Headquarters Robert F. Christy California Institute of Technology Bruce C. Cogan Mt. Stromlo Observatory John J. Cowen University of Maryland Arthur N. Cox National Science Foundation Cecil G. Davis Los Alamos Scientific Laboratory Richard P. Fancy Montgomery College David Fischel Goddard Space Flight Center Denise A. Langel-Frey University of Maryland William S. Gilmore University of Maryland Deborah J. Hamill Goddard Space Flight Center, American University Program I. Patrick Harrington University of Maryland Stephen J. Hill Michigan State University Dennis R. Hollars New Mexico State University James L. Hutchinson LASP University of Colorado AlanH. Karp University of Maryland David S. King University of New Mexico Paul A. Marionni University of Maryland Sidney B. Parsons University of Texas Nancy G. Roman ., NASA Headquarters Jeffrey D. Rosendhal NASA Headquarters Kurt von Sengbusch / Max-Planck Institute for Physics and Astrophysics M. A. J. Snijders Goddard Space Flight Center, NAS/NRC Fellow William H. Spangenberg Los Alamos Scientific Laboratory Warren H. Sparks Goddard Space Flight Center Robert F.,Steffingwerf J.I.LA., University of Colorado K. S. Krishna Swamy Goddard Space Flight Center. NAS/NRC Fellow vii Page intentionally left blank Page intentionally left blank i • t V iff CONflMft *«* PREFACE Hi ACKNOWLEDGMENTS * PARTICIPANTS vtt CONFERENCE . I Welcoming Remarks Albert Boggess -3 Ultraviolet Observations of Classical Cepheids by OAO-2 /. L. HutcMnson 5 Shock Waves in a Beta Doradus Model Stephen], mi 31 Mean Colors of Cepheids A.N. Cox and C G. Davis 43 Pulsation of Double-Mode Cepheids and Comments on the froMem of Cepheid Masses D. S. King and C /. Hansen, R. R. Ron, R. F. Stettbtgwerf. mi J.P.Cox $7 Hydrodynamic Effects in the Atmospheres of Variable Stan Cecil G. Davis, Jr. and Susan S. Bunker 71 The Hertzsprung Progression in Cepheid Calculations R. F, Christy 85 Hydrodynamic Models of a Cepheid Atmosphere AlanHKarp 99 Numerical Techniques for the Linear, Nonadbbatfc Stdar I Theodore Andrew Bednarek 115 Stability of Nonlinear Periodic Pulsation of Stellar Envelopes Kurt von Sengbusch ,. 129 The Cepheid Mode Problem R. F. Stetttngwerf 137 WORKSHOP 157 APPENDIX 307 ix CONFERENCE Page intentionally left blank Page intentionally left blank 2. WELCOMING REMARKS Albert Boggess Goddard Space Flight Center I am here, in part, as a surrogate for Dr. John Clark, who is Director of Goddard Space Flight Center. He always makes a point of coming and saying a few welcoming words to each of the many scientific conferences that go on at Goddard and whenever his busy schedule permits, he stays and frequently participates in the discussions. I think he does this in part because he gets a vicarious pleasure out of watching and listening to people who are doing active research. In any case, not only he, but all of us are delighted to have you here. I think a very small, informal group like this is one of the most satisfying forms of scientific exchange. It gives an opportunity for active workers in the field to exchange ideas without the distraction of a larger meeting, where one frequently must explain or defer to those with less extensive knowledge and more casual interest. We hope you find your two days here productive ones, and certainly we will do what we can to make it enjoyable. Page intentionally left blank Page intentionally left blank ULTRAVIOLET OBSERVATIONS OF CLASSICAL CEPHEIDS BY OAO-2 J.

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