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Spectrum Formation in Stars with Steady-State Extended Atmospheres

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Spectrum Formation in Stars with Steady-State Extended Atmospheres ot 9uiiw»». Rational Bureau Admin. Library, t-01 * v, %ferenCg 5^ nc {Q taken fr0iT3 f,:i)rar OCT 2 8 1970 ^ y- NBS SPECIAL PUBLICATION 332 Spectrum Formation in Stars With Steady-State Extended Atmospheres ITED STATES DEPARTMENT OF COMMERCE Maurice H. Stans, Secretary NATIONAL BUREAU OF STANDARDS Lewis M. Branscomb, Director Spectrum Formation in Stars With Steady - State Extended Atmospheres Proceedings of the International Astronomical Union Colloquium No. 2, Commission 36 Munich, Germany, April 16-19, 1969 Edited by H. G. Groth and P. Wellmann Universitats-Sternwarte Munchen Institut fur Astronomie und Astrophysik Miinchen, Germany Publication 332 \) , National Bureau of Standards Special * • » Nat. Bur. Stand. (U.S.), Spec. Publ. 332, 342 pages (August 1970) CODEN: XNBSA Issued August 1970 For sale by the Superintendent of Documents, U.S. Government Printing Office, Washington, D.C. 20402 (Order by SD Catalog No. C13.10:332), Price $1.75 NATIONAL BUREAU OF STANDARD FEB 1 2 19/1 ~< ' GENERAL ABSTRACT r> J Commission 36 of the International Astronomical Union sponsored a symposium on Spectrum Formation in Ex- tended Stellar Atmospheres held 16 - 19 April, 1969. The host was the Observatory of the University of Munich. A major problem is the definition of what is meant by an extended stellar atmosphere. There are intuitive notions in the literature, but the question of specific definitions in various kinds of objects was discussed. Questions of what specifi- cally cause the anomalous extent were largely by- passed. Attention focused mainly on the type spec- trum to be expected in various situations. The spectral features to be expected in both static and dynamic atmospheres, including and excluding depar- tures from LTE, were discussed. The symposium was divided into four sections: A. Type of Problems Which Exist; B. Theoretical Methods for Handling Non-LTE Problems; C. Chromospheres and Coronae of Stars; D. Summary. This volume contains the mms of the formal papers that were presented plus an edited and abridged version of the discussions following each paper. Key words: extended atmospheres; non-LTE; chromo- spheres; coronae; non-classical atmospheres. Foreword The planning of this colloquium on Extended Stellar Atmospheres was carried out by Dr. A. B. Underhill, President of Commission 36, and the Organizing Committee of Commission 36, comprised of Drs. K. H. Bohm, R. Cayrel, J. T. Jefferies, V. V, Ivanov, R. N. Thomas, and S. Ueno in close collaboration with Drs. P. Wellmann and H. Groth whose kind invitation gave rise to the idea. This colloquium is one of a series that have been spon- sored by Commission 36 on problems in stellar atmospheres. The aim of these colloquia has been to hold a working session among a number of people vitally interested in the problem, and to provide an inexpensive and readily accessible volume of the proceedings, which can be used by all inter- ested in the subject, especially students and young researchers. A number of United States fed- eral laboratories having strong programs in astron- omy have been hosts to these colloquia and editors- publishers of the proceedings. These include the National Bureau of Standards through the Joint In- stitute for Laboratory Astrophysics, the Smithson- ian Astrophysical Observatory, and now the Goddard Space Flight Center. These proceedings, published by NBS for JILA, follow the approach explored with the publication of the proceedings of the Symposium on Wolf-Rayet Stars, hosted by JILA in 1968. Dr. R. N. Thomas, aided by Alice Levine , of the JILA staff have provided the link between the formal editors, Drs. Wellmann and Groth, and the NBS pub- lications group, under Betty L. Oberholtzer. The typescript was prepared by Breta Triolo. Lewis M. Branscomb, Director iii : CONTENTS Preface vii Participants viii Part A. TYPE OF PROBLEMS THAT EXIST 1 Chairmen: P. Swings P. Wellmann A. B. Underhill Definition of the Types of Prob- lems that Exist in Steady-state Extended Atmospheres (introductory paper) 3 R. N. Thomas Definition of the Physical Prob- lems Connected with Extended Atmospheres 3 8 K. H. Bohm and Extended Atmospheres of Planetary J. Cassinelli: Nuclei 54 H. Nussbaumer: The N IV X5820 Multiplet in WN Stars 61 R. Grant Athay A Self-Consistent Model Atmosphere and R. C. Program with Applications to Solar Canf ield 01 Resonance Lines 65 Part B. THEORETICAL METHODS FOR HANDLING NON-LTE PROBLEMS 8 5 Chairmen: R . N. Thomas^ A. G. Hearn G. Rybicki Theoretical Methods of Treating Line Formation Problems in Steady- state Extended Atmospheres (intro- ductory paper) 8 7 C. Magnan: Application of Monte Carlo Methods in Transfer Problems 119 W. Kalkofen: Line Formation in Moving Atmo- spheres 120 D. H. Menzel Laser Action in Non-LTE Atmo- spheres 134 H. P. Jones and Line Formation in Multi-Dimen- A. Skumanich: sional Media 138 H. Gerola and The Continuous Spectrum of Hydro- N. Panagia: gen in a Low-Density envelope 171 R. Grant Athay Bandwidth Requirements in Spectral Line Transfer Calculations 1 7 9 I. P. Grant and Comparison of Discrete Space and G. E. Hunt: Differential Equation Methods in Non-LTE Transfer Problems 18 9 T. R. Carson: Coherent Line Formation with Depth Dependent Parameters 226 Part C. CHROMOSPHERES AND CORONAE OF STARS 23 9 Chairmen: j. c. Pecker^ D. G. Hummer F. Praderie What Do We Know Through Spectral Information on Stellar Chromo- spheres and Coronas? (introductory paper) 241 R. N. Thomas What Should We Do To Know More About Chromospheres and Coronae of Stars? (introductory paper) 259 H. G. Groth: Observations of c Aurigae Stars and Their Interpretation 283 P. Wellmann The Ionization in Nova Atmo- spheres 290 v A. H. Vaughan, Jr. Circums tellar Call K lines in G, and A. Skumanich: and M Giants and Supergiants 29 5 R. W. Hillendahl: A Physical Mechanism for the Gen- eration of Extended Stellar Atmo- spheres 300 Part D. SUMMARY 3 21 J. C. Pecker: Concluding Remarks 323 vi . PREFACE This colloquium was one of similar colloquia of Commission 36 held in the past few years. The president of Commission 36, Professor A. B. Underhill, planned this colloquium, while the staff members of the Universitats-Sternwarte Munchen were responsible for the local organization. There was an urgent need to discuss problems connected with the structure of extended atmospheres and line formation in these atmospheres Each session of the colloquium had one or two introductory papers followed by discussion. The number of contributed papers was limited. There was no case where the chairman was forced to cut off the discussion because of lack of time, but there was an important criticism by J. C. Pecker and R. N. Thomas: "This colloquium has absolutely no point, if it is so formal that no one ventures to say anything except the older people who think they know what they are doing anyway. It is very important that the younger people take part in the discussion." When compiling these proceedings we have tried to report the discussion remarks as far as possible, when they were relevant to the problem. The paper by G. Rybicki arrived only as the manuscript of this conference was going to press. We were forced to omit the discussion of this paper from the proceed- ings because the discussion could not be understood without the paper. We are very grateful to Anne B. Underhill for the decision to hold this colloquium at Munich. We thank all participants of the conference for coming to our institute. H. G. Groth P. Wellmann vii PARTICIPANTS R. C. ALTROCK, Sacramento Peak Observatory, Sunspot, New Mexico 88349 R. G. ATHAY, High Altitude Observatory, Boulder, Colorado, 80302 K. H. BOHM, Department of Astronomy, University of Washington, Seattle, Washington 98105 R. C. CANFIELD, Sterrewacht Sonnenborgh, Servaas Bolwerk 13, Utrecht, Netherlands F. CAPUTO, Laboratorio di Astrofisica, Casella Postale 67, 00044 Frascati (Roma), Italia T. R. CARSON, University Observatory, Buchanan Gardens, St. Andrews, Scotalnd, U.K. J. M. le CONTEL, Observatoire de Paris, 61 Avenue e de 1'Observ. Paris 14 , France Y. CUNY, Observatoire de Paris, Section d 'Astro- physique, 92 Meudon, France A. M. DELPLACE, Observatoire de Meudon, Meudon 92, France S. DUMONT, Observatoire de Meudon, 9 2 Meudon, France G. H. ELST, Sterrewacht, Ringlaan 3, Brussel 18, Belgium H. GEROLA, Universidad de Buenos Aires, Facultad de Ciencias Exactas y Naturales , Depto de Fisica, Buenos Aires, Argentina N. GOKDOGAN, University Obs . Astronomi Kursiisii, Beyazit, Istanbul, Turkey G. GONCZI, Laboratoire d ' Astrophysique , Faculte des Sciences, Av. Valrose, 06 Nice, France I. P. GRANT, Atlas Computer Laboratory, Chilton, Didcot Berkshire, England H. G. GROTH, Universitats-Sternwarte Munchen, 8 Miinchen 80, Scheinerstr . 1 , Germany A. G. HEARN, Culham Laboratory, Abingdon, Berkshire, England R. HERMAN, 7 bis rue Trudon, 9 2 Antony, France T. HIRAYAMA, Tokyo Astr. Obs. Univ. of Tokyo, Mitaka, Tokyo, Japan R. W. HILLENDAHL, Lockheed Palo Alto Research Laboratories 3251 Hanover Street, Palo Alto, California 94304 M. HOTINLI, University Obs. Astronomi Kiirsusu, Beyazit, Istanbul, Turkey L. HOUZIAUX, Department d 'Astrophysique , Faculte des Sciences, Plaine de Nimy, Mons , Belgium D. G. HUMMER, JILA, University of Colorado, Boulder, Colorado 80302 K. HUNGER, Institut fur theoretische Physik, Technische Univ. Berlin, 1 Berlin 10, Ernst- Reuter-Platz , Germany viii G. E. HUNT, Atlas Computer Laboratory, Chilton, Didcot, Berkshire, England W. KALKOFEN, Harvard and Smithsonian Observatories, Cambridge, Massachusetts 02138 H. LAMERS , Sterrewacht Sonnenborgh, Servaas Bolwerk 13, Utrecht, Netherlands A. MARTINI, Laboratorio di Astrofisica, Casella Postale 67, 00044 Frascati , Italy 1 CHR. MAGNAN, Institut d Astrophysique , 98 bis BD e Arago, Paris (14 ) , France D. H. MENZEL, Harvard College Observatory, Cambridge, Massachusetts 02138 D. MUGGLESTONE, Department of Theoretical Physics, University of Queensland, Australia L. NEVEN, Sterrewacht, Ringlaan 3, Brussel 18, Belgium H. NUSSBAUMER, Physics Department, University College, Gower Street, London W.C.I.
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