STUDY OF LI-RICH KGIANTS A THESIS SUBMITTED FOR THE DEGREE OF DOCTOR OF PHILOSOPHY IN THE FACULTY OF SCIENCE CALICUT UNIVERSITY BY BHARAT KUMAR YERRA INDIAN INSTITUTE OF ASTROPHYSICS BANGALORE - 560 034, INDIA AUGUST 2011 To my parents and friends... For my part I know nothing with any certainty, but the sight of the stars makes me dream. DECLARATION I hereby declare that the matter contained in the thesis entitled “Study of Li-rich K Giants” is the result of investigations carried out by me at the Indian Institute of Astro- physics under the supervision of Dr. B. Eswar Reddy. This thesis has not been submitted for the award of any degree, diploma, associateship, fellowship etc. of any University or Institute. Bharat Kumar Yerra (Candidate) Indian Institute of Astrophysics Bangalore-560034, India CERTIFICATE This is to certify that the matter contained in the thesis entitled “Study of Li-rich K Giants” submitted to Calicut University by Mr. Bharat Kumar Yerra for the award of the degree of Doctor of Philosophy in the Faculty of Science, is based on the results of investigations carried out by him under my supervision and guidance, at the Indian Institute of Astrophysics. This thesis has not been submitted for the award of any degree, diploma, associateship, fellowship etc. of any University or Institute. Dr. B. Eswar Reddy (Supervisor) Indian Institute of Astrophysics Bangalore-560034, India ACKNOWLEDGEMENTS This dissertation would not have been possible without the guidance and the help of sev- eral individuals who in one way or another contributed and extended their valuable assis- tance in the preparation and completion of this study. First and foremost, my utmost gratitude to my thesis supervisor Dr. B. Eswar Reddy whose guidance, sincerity, and encouragement i never forget. It has been an honour to be his first Ph.D student. He has taught me, both conciously and unconciously, how good astronomical spectroscopy is done. I express my sincere gratitude to the role model for stellar spectroscopist in the world, Prof. David L. Lambert, for being my collobarotor, for providing the spectra, and for his suggestions and fruitful discussions, without which this thesis would not have possible. I am thankful to Dr. Muthumariappan for his encouragement and fruitful discussions. I am grateful to the Director of Indian Institute of Astrophysics, Prof. S. S. Hasan for giving me the opportunity to work in this institute and providing all the support and facilities required for research work. I thank all the members of the Board of Graduate Studies for the help and support that have been provided throughout the course of my work. I am grateful to the instructors who light the passion for astronomy during the course work. I am grateful to the members of my doctoral committee, Dr. Biman N. Nath, Prof. A. V. Raveendran, Prof. R .T. Gangadhara, Dr. Gajendra Pandey for useful comments and suggestions which imporved my research work. I express my sincere thanks to IIA faculities, Dr. Gajendra pandey, Dr. Annapurni, Dr. Anupama, Dr. Sivarani, Dr. Sunetra, Dr. Aruna, Dr. Sushma, Prof. Mallik, Prof. N. K. Rao for their friendly approch which enabled me to have fruitful discussions. I am thankful to IIA library staff, and the Librarian Ms. Christina Birdie for providing all the assistance required in making the books and journals available for reference. I thank the staff members of Administrative division of IIA for the required assistance and help they have provided in time at each steps during my fellowship period. My sincere thanks to all the technical staff including Dr. Baba, Mr. Fayaz and Mr. Ashok for helping with computer related issues. I thank Prof. B. R. S. Babu, Dr. M. M. Musthafa and all the faculty of Department of Physics, Calicut university for their valuable advice and suggestions. My sincere thanks goes to the administrative staff of the department and CDC for helping me during reg- istration and submission. I would like to take this opportunity to thank the faculty in MSc Period, Prof. Bolanath padhy, and my teachers from school and college days whose valuable tips and encouragement provided me a platform to write this thesis. I thank the faculty and present/former staff of CREST, Dr. D. K. Sahu, Dr. P. Pari- har, Dr. B. C. Bhatt, Dr. Shanti kumar, Mahalakshmi, Aman, Ravi, Ramya, Sasikumar, Ritu, and Manjunath for the help and guidance they provided for observations with HCT through out the research period. I thank all the staff of VBO Kavalur, Dr. Muneer (former observatory incharge), Dr. Muthu mariappan, Mr. Anbazhagan, Mr. Ravi, Mr. Srinivasa Rao, Mr. Ramachandran, Mr. Pukhalendhi, Mr. Murthy, Mr. Appakutty, Mr. Jayakumar, Mr. Velu, Mr. Kuppusamy, Mr. Selvakumar, Mr. Sivakumar, Mr. Dinakaran, Mr. Ra- machandran and Mr. Ramesh for the help and guidance they provided for observations with VBT and 1-m telescope through out the research period. For reading the manuscript of this thesis I would like to express my heartiest thanks to Ms. Sandra Rajiva and also to my friends, Pradeep and Vigeesh for their time and helpful comments. I thank Avijeet and Prasanth for helping me in Mathematica. My time at IIA and Bhaskara was made enjoyable in large part due to many friends and groups that became a part of my life. I dont say just thanks to Vigeesh, Blesson, Ramya and Uday as i never forget their love, caring and support. I miss you guys a lot. I thank Pradeep and Suresh for their support in final days. I thank my batchmate friends, Ramya, Ananta, Tapan, Rumpa, and Girjesh for their wonderful company in first and subsequent years. I still remember those course work days when we used to have maggi in mid nights etc. I would like to thank my senior friends: Nagu, Malay, Ravi, Mahesh, Nataraj, and Veeresh for their encouragement in intial days in IIA. I extend my heartfelt thanks to my junior friends: Sreeja, Smitha, Indu, Sindhu, Drisya, Hema, Madhu, Sumangala, Anusha, Anantha Chandu, Krishna, Sudhakar, Arun, Sam, Ratnu, sugar, subham, Sajal for making my stay at IIA and Bhaskara memorable. Where would I be without my family? My parents deserve special mention for their inseparable support and prayers. My mother, Lakshmi, and father, Lakshmana Rao, are the one who sincerely raised me with their caring and gently love. Bujji, thanks for being supportive and caring sibling. My brother-in-law, Devi prasad, whose words are inspirational, thanks for the encouragement. Naughty and cute niece, Kavya, is the one whose cheerful smile driven me till the end of the thesis. It is a pleasure to thank my old (gold) friends: Bhanu, Chandu, Durga, Ganesh, Jaggu, Krishna mama, Kshitish, Kiran (K, A, Ch) , Simadri, Sudheer, Surya for their encourage- ment and belief that driven me to complete this thesis. Finally, I would like to thank everybody who was important to the successful realiza- tion of thesis, as well as expressing my apology that if I could not mention personally one by one. TABLE OF CONTENTS SUMMARY v LIST OF FIGURES xiii LIST OF TABLES xix 1 REVIEW OF LITERATURE 1 1.1 GENERAL INTRODUCTION ......................... 1 1.2 EVOLUTION OF STARS AND THE HR DIAGRAM ............. 3 1.2.1 PRE-MAIN SEQUENCE PHASE .................. 4 1.2.2 MAIN SEQUENCE .......................... 4 1.2.3 POST-MAIN SEQUENCE ...................... 6 1.3 LITHIUM IN THE UNIVERSE ........................ 12 1.3.1 PRIMORDIAL LITHIUM ...................... 13 1.3.2 GALACTIC LITHIUM ........................ 15 1.4 LITHIUM IN STARS ............................. 20 1.4.1 ACTIVE STARS ........................... 22 1.4.2 SUPERGIANTS ........................... 22 1.4.3 AGB STARS ............................ 23 1.4.4 WEAK G-BAND STARS ...................... 23 1.4.5 G- AND K- GIANTS ........................ 24 1.5 OUTLINE OF THESIS ............................ 25 2 DATA RESOURCES AND ANALYSIS TOOLS 29 2.1 ASTRONOMICAL SPECTRA ........................ 29 2.1.1 OBSERVING FACILITIES ...................... 31 2.1.2 DATA ACQUISITION ........................ 35 2.2 DATA REDUCTIONS ............................ 35 2.3 DATA ANALYSIS .............................. 38 i TABLE OF CONTENTS 2.3.1 ATOMIC DATA ........................... 40 2.3.2 MODEL ATMOSPHERES ...................... 41 2.3.3 MOOG............................... 42 2.4 OTHER RESOURCES ............................ 45 3 SURVEY FOR LI-RICH GIANTS 47 3.1 INTRODUCTION ............................... 47 3.2 SAMPLE SELECTION ............................ 49 3.2.1 SAMPLES ON H-R DIAGRAM ................... 50 3.3 OBSERVATIONS ............................... 53 3.3.1 SPECTRA FROM HFOSC ON 2-M HCT.............. 55 3.3.2 SPECTRA FROM UAGS ON 1-M CZT............... 56 3.3.3 SPECTRA FROM OMRS ON 2.3-M VBT ............. 56 3.3.4 REDUCTIONS ............................ 56 3.4 IDENTIFICATION OF LI-RICH GIANTS FROM LOW RESOLUTION SPECTRA 58 3.5 RESULTS AND DISCUSSION ........................ 64 3.6 CONCLUSIONS ............................... 68 4 HIGH RESOLUTION SPECTROSCOPY: LI, CNO AND 13C ABUNDANCES OF NEW LI-RICH GIANTS 69 4.1 INTRODUCTION ............................... 69 4.1.1 A BRIEF ACCOUNT OF NEWLY IDENTIFIED LI-RICH K GIANTS . 70 4.2 OBSERVATIONS AND DATA REDUCTION . 71 4.3 ATMOSPHERIC AND OTHER STELLAR PARAMETERS . 74 4.3.1 PHOTOMETRY ........................... 75 4.3.2 HIGH RESOLUTION SPECTROSCOPY . 78 4.4 ABUNDANCES ............................... 86 4.4.1 LITHIUM .............................. 86 4.4.2 Carbon, Nitrogen, and Oxygen................... 92 4.4.3 The 12C/13C Ratio.......................... 94 4.5 DISCUSSION AND CONCLUSIONS ..................... 94 5 SUPER LI-RICH GIANTS WITH ANOMALOUS LOW 12C/13C RATIO 101 5.1 INTRODUCTION ...............................101 5.2 SUPER LI-RICH GIANTS . 102 5.3 DISCUSSION AND CONCLUSION . 104 ii TABLE OF CONTENTS 5.3.1 LI AND 12C/13C AT THE RGB BUMP . 105 6 INFRARED EXCESS VS LITHIUM 111 6.1 INTRODUCTION ...............................111 6.2 SAMPLE SELECTION ............................112 6.3 INFRARED EXCESS .............................113 6.3.1 NEAR-INFRARED CCDM . 114 6.3.2 FAR-INFRARED CCDM . 115 6.4 GEOMETRY OF THE CIRCUMSTELLAR DUST .