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69-22,173 MARKOWITZ, Allan Henry, 1941- a STUDY of STARS This dissertation has been microfilmed exactly u received 6 9 -2 2 ,1 7 3 MARKOWITZ, Allan Henry, 1941- A STUDY OF STARS EXHIBITING COM­ POSITE SPECTRA. The Ohio State University, Ph.D., 1969 A stron om y University Microfilms, Inc., Ann Arbor, Michigan A STUDY OF STARS EXHIBITING COMPOSITE SPECTRA DISSERTATION Presented in Partial Fulfillment of the Requirements for the Degree Doctor of Philosophy in the Graduate School of The Ohio State University By Allan Henry Markowitz, A.B., M.Sc. ******** The Ohio S ta te U n iv e rsity 1969 Approved by UjiIjl- A dviser Department of Astronomy ACKNOWLEDGMENTS It is a sincere pleasure to thank my adviser, Professor Arne Slettebak, who originally suggested this problem and whose advice and encouragement were indispensable throughout the course of the research. I am also greatly indebted to Professor Philip Keenan for help in classifying certain late-type spectra and to Professor Terry Roark for instructing me in the operation of the Perkins Observatory telescope, I owe a special debt of gratitude to Dr. Carlos Jaschek of the La Plata Observatory for his inspiration, advice, and encourage­ ment. The Lowell Observatory was generous in providing extra telescope time when the need arose. I wish to particularly thank Dr. John Hall for this and for his interest. I also gratefully acknowledge the assistance of the Perkins Observatory staff. To my wife, Joan, I owe my profound thanks for her devotion and support during the seemingly unending tenure as a student. I am deeply grateful to my mother for her eternal confidence and to my in-laws for their encouragement. ii VITA October 22, 1941 Born - Jersey City, New Jersey 1963 ........................... A.B., University of California, Los Angeles, California 1964-1968 . Teaching Assistant, Department of Astronomy, The Ohio State University, Columbus, Ohio 1966 ........................... M.Sc., The Ohio State University, Columbus, Ohio PUBLICATIONS "Spectrum Variations in the Peculiar A Star 73 Draconis" (co-author with W. K. Bonsack), Publications of the Astronomical Society of the Pacific, Vol. 79, pp. 235-254, 1967. "New Metallic-Line A Stars", Publications of the Astronomical Society of the Pacific (in press) . FIELDS OF STUDY Major Field: Astrophysics Studies in Spectroscopy, Professors Philip C. Keenan and K. Narahari Rao. Studies in Physical Foundations of Astrophysics. Professors Walter K. Bonsack, Eugene R. Capriotti, Wave H. Shaffer, and L. Carlton Brown. Studies in Theoretical Astrophysics. Professor George Collins Studies in Stellar Systems. Professors Carlos Jaschek and Walter E. Mitchell, Jr. Studies in Radio Astronomy. Professors John D. Kraus and H sien C. Ko. iii TABLE OF CONTENTS Page ACKNOWLEDGMENTS i i VITA i i i LIST OF TABLES v i LIST OF ILLUSTRATIONS v i i C hapter I . INTRODUCTION ............................................ 1 Definition of a Composite Stellar Spectrum ......................... 1 Summary o f P revious W o r k ...................................................................... 2 Purpose of This Investigation ...................................................... 7 I I . OBSERVATIONS ............................................................................................................ 8 I I I . SPECTRAL CLASSIFICATION ............................................................................ 9 Problems in Classification ..... ...................................... 9 Description of "Characteristic" Composite Spectrum . ..................................................... 10 Classification Criteria ...................................................................... 12 Type B Type A Metallic-Line A Stars Type F Type G Type K Type M Comparison with Other Published W ork ............................................16 IV. AXIAL ROTATIONAL V E L O C IT IE S ........................................................................22 Method of Determination ...............................................................................22 E r r o r s ................................................................................................................... 24 D i s c u s s i o n ..................................................................................................................25 V. ARTIFICIAL COMPOSITE SPECTRA........................................................................29 Method of Production and Selection of Types .... 29 Description of Types ................................................................................ 34 AOV + GOII AOV + G8III B5V + K3II iv TABLE OF CONTENTS--Continued Page Chapter VI. RESULTS AND DISCUSSION............................................................................................45 APPENDIX A ..................................................................................................................................................58 APPENDIX B ..................................................................... 75 APPENDIX C ..................................................................................................................................................78 REFERENCES................................................................................................................................................. 80 v LIST OF TABLES Table Page 1. Mean rotational velocities for e a rly -ty p e s ta r s ...................................................................................................... 26 2. Mean equatorial velocities for early-type stars ...................................................... .........28 3. Standards used in making artificial composites ............................. 31 U. Relative exposure times for artificial c o m p o s i t e s ......................................................................................................................... 33 5. Statistical data for composite s ta rs ...........................................................55 vi LIST OF ILLUSTRATIONS Figure Page 1. Comparison of spectral types determined photo- electrically by Bahng with those from this study. Early-type components only ................................................ 17 2. Comparison of spectral types determined by Bahng with those from this study. Late-type components o n ly .......................................................................................... 18 3. Comparison of Bahng luminosity classes with those from this study. Late-type components o n ly ...................... 19 4. Comparison of spectral types determined by Kuhi with those from this study. Late-type components o n ly ................................................................................................. 20 5. Comparison of luminosity classes determined by Kuhi with those from this study. Late-type components o n ly .............................................................................................. 21 6. AOV + GOII urtificial composite spectra ....... 35 7. AOV + G8III artificial composite spectra .................................... 36 8. B5V + K3II artificial composite sp e c tra ................................ 37 9. Spectral type distribution of early-type c o m p o n e n ts ........................................................................................................... 49 10. Distribution of late-type components with spectral type and luminosity class ...................................... 51 11. H-R diagram of composite s ta rs ............................................................ 52 vii I. Introduction Stars exhibiting a composite spectrum form a group intermediate in separation between close spectroscopic binaries and the relatively widely separated visual binaries. Despite their potential importance in leading to a better understanding of the nature of double stars and their usefulness in providing a check upon current theories of stellar evolution there has been only one systematic study of com­ posite spectra, performed thirty years ago at this observatory by J. Allen Hynek (1938), DEFINITION OF A COMPOSITE STELLAR SPECTRUM Before Hynek's study and the more recent literature are critically examined, it is necessary to define the term "composite stellar spectrum". Broadly speaking, the term composite spectrum can be applied to a spectrum displaying two sets of lines, each ascribable to a definite spectral type. Within this general definition we may distinguish several classes of systems: (1) Close binaries consisting of two apparently normal stars (in the sense that they can be uniquely placed in the H-R diagram) whose spectra cannot be individually observed. (2) Close binaries in which there are interaction effects be­ tween the components, severely complicating the spectra. (3) Peculiar objects, including the symbiotic stars, which display a combination of a low temperature absorption spectrum with high excitation emission lines; 17 Leporis; HZ 9; and others. 2 Among the first class we may distinguish a subclass of stars whose binary nature is evident from the nature of their observed spectral lines alone, independent of any radial velocity variations. Also among the f i r s t c la s s we may d is tin g u is h known clo se v is u a l binaries and some double-line spectroscopic binaries. Others of the latter subclass can be placed in the second class. In this study we intend to limit ourselves to those stars mentioned in the first subclass above. These display a spectrum in which the strength and character of the lines can be attributed to two different
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