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Massive Stars: Life and Death

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Massive Stars: Life and Death Massive Stars: Life and Death Dissertation Presented in Partial Fulfillment of the Requirements for the Degree Doctor of Philosophy in the Graduate School of The Ohio State University By Jos´eLuis Prieto Katunari´c Graduate Program in Astronomy The Ohio State University 2009 Dissertation Committee: Professor Krzysztof Z. Stanek, Advisor Professor Christopher S. Kochanek Professor John F. Beacom Copyright by Jos´eL. Prieto 2009 ABSTRACT Although small in number, massive stars are critical to the formation and evolution of galaxies. They shape the interstellar medium of galaxies through their strong winds and ultra-violet radiation, are a major source of the heavy elements enriching the interstellar medium, and are the progenitors of core-collapse supernovae and gamma-ray bursts, which are among the most energetic explosions in the Universe and mark the death of a massive star. Still, our understanding of the connection between massive stars and supernovae from observations is fairly limited. In this dissertation, I present new observational evidence that shows the importance of metallicity, mass-loss, and binarity in the lives and deaths of massive stars. We investigate how the different types of supernovae are relatively affected by the metallicity of their host galaxy. We take advantage of the large number of spectra of star-forming galaxies obtained by the Sloan Digital Sky Survey and their overlap with supernova host galaxies. We find strong evidence that type Ib/c supernovae are occurring in higher-metallicity host galaxies than type II supernovae. We discuss various implications of our findings for understanding supernova progenitors and their host galaxies, including interesting supernovae found in low-metallicity hosts. ii We present the discovery of the progenitors of SN 2008S and the luminous transient in NGC 300 in archival data obtained with the Spitzer Space Telescope. They are deeply dust-enshrouded massive stars, with extremely red mid-infrared colors compared to other massive stars, and relatively low bolometric luminosities 4 (≈ 5 × 10 L⊙). We discuss the implications of these findings for the evolution and census of “low-mass” massive stars (i.e., ∼8 − 12 M⊙), and we connect it with theoretical discussions of electron-capture supernovae near this mass range, explosive birth of massive white dwarfs, and massive star outbursts. We present a Spitzer low-resolution mid-infrared spectrum of the luminous transient in NGC 300. The spectrum shows that the transient is very luminous in the mid-infrared and most of the pre-existing progenitor dust survived the explosion. Furthermore, the spectrum shows strong, broad emission features that are observed in Galactic carbon-rich proto-planetary nebulae. These observations support our conclusions of an explosive event on a massive carbon-rich AGB or post-AGB star as the origin of the transient in NGC 300 and SN 2008S. We present extensive ugrizY HJKs photometry and optical spectroscopy of SN 2005gj. These data show that SN 2005gj is the second possible case, after SN 2002ic, of a thermonuclear explosion in a dense circumstellar environment. The interaction of the supernova ejecta with the dense circumstellar medium is stronger than in SN 2002ic. iii Finally, we present the discovery of a peculiar eclipsing binary in a variability survey of the dwarf galaxy Holmberg IX undertaken with the Large Binocular Telescope. The binary has a period of 271 days, and is composed of two yellow supergiants that are overflowing their Roche lobes. Such systems must be rare, and indeed we only note one similar system in the Small Magellanic Cloud. We propose that these systems may be the progenitors of supernovae that appeared to have yellow-supergiant progenitors. iv A mis padres, Alicia y Rodolfo. v ACKNOWLEDGMENTS I am very grateful of so many people that in different ways have helped me these years during grad school and before. In particular, I don’t think I would have made it without the continuous support and encouragement of my adviser, Kris Stanek, my family, and Linda. First let me say Gracias to Kris, I will come back to my family and Linda at the end. I feel very fortunate that I had the chance to meet Kris and work with him over the last three years. Kris has shaped my way to see, think about, and do astronomy and science in general. He has always been the most supportive person, almost in unthinkable ways by (for example) letting me continue working in supernova-related topics and encouraging me to pursue exciting ideas and projects that came up along the way. We had many discussions about astronomy and science, new ideas for research projects, and his yard (among other topics). I enjoyed very much all of them. He also shared with me his vast experience and knowledge of gamma-ray bursts, the distance scale, variable stars, and photometry (to name just a few). His stories and experiences of other people working in the field and how “not to do” science were always very enriching. I also enjoyed playing ping-pong and sledding at his house. I will miss him much. vi I am also very grateful of John Beacom, Chris Kochanek, and Todd Thompson. They were always happy to help, support, and encourage me. I learned a lot from many extensive discussions we had, including Kris, about massive stars and supernovae. Chris, with his amazing fundamental knowledge of astronomy and physics, always had time to share his thoughts and help with papers and new ideas. I appreciate very much the advice and help of John and Chris with my English and scientific writing. I also thank Chris and John for being part of my defense committee. I think it will be hard to find a person with more energy and excitement about astronomy than Todd, and I hope I can at least have a fraction of that. Most of the theoretical interpretation in this dissertation, particularly about the dusty transients, were Todd’s ideas. Mi amigo Todd, thank you for sharing all that knowledge about several areas in astrophysics and for so many discussions about science and Espa˜nol. I hope that Todd at least learned this from me, and doesn’t forget it: Pablo Neruda was Chilean. I thank Oleg Gnedin for advising me in my first project at OSU. It was hard to work in a purely theoretical project on globular clusters, but with a lot of help, advice and patience of Oleg, we could finally finish it and publish a paper on the results. My big thanks to Darren DePoy for letting me work in the SDSS-II Supernova Search, for sharing his observing experience and stories, and for organizing the supernova follow-up campaigns with the MDM 2.4m telescope. Here I have to give special thanks to all my fellow graduate students that went observing to MDM and vii participated in the 3 campaigns, to all the MDM staff for maintaining the telescopes and instruments and also for their help, and to Rick Pogge for being always there to help when something came up with the instrument, telescope or control system. It wouldn’t have been possible to carry out this extensive follow-up project without them. I thank the SDSS-II Supernova Search and the Carnegie Supernova Project groups for contributing most of the photometric data for SN 2005gj. I learned a lot from working in the SDSS-II Supernova Search, and I am especially grateful to Masao Sako and Peter Garnavich. I thank Kris Sellgren for sharing part of her experience and knowledge of infrared astronomy with me. Kris was very enthusiastic to teach me about mid-infrared spectra of proto-planetary nebula and other infrared sources. Going all the way back to high school, I thank my physics teacher Jimena Scarich, she was very important in my early science education and interest in physics and astronomy. I would like to thank also my undergraduate adviser at Universidad Cat´olica, Alejandro Clocchiatti, who introduced me to the exciting field of supernovae, always supported me, and helped me get a position doing supernova research at CTIO after undergrad. At Cat´olica, I also enjoyed very much working with Felipe Barrientos, and I thank him for teaching me how to use Perl and PDL, which had been very useful tools since. At CTIO, working with Nick Suntzeff and Armin Rest was a really great experience. I am indebted to Nick and Armin (and also others of the supernova group in Tololo, especially Kevin Krisciunas) for giving viii me the great opportunity to work in very exciting scientific projects during that year and for introducing me to participate in two big scientific collaborations, Essence and Supermacho. The environment at the Astronomy Department was always nice and friendly, and this made a big difference in the day-to-day life. I thank the Department office staff, especially Kristy Scheckelhoff, for helping so much with all the paper work. Also David Will and Michael Savage for so much help and assistance with computers. I am also grateful of all the faculty for organizing morning coffee, I enjoyed very much many discussions and learned quite a bit about very different areas in astronomy. I also appreciate all the work put by faculty to make the graduate courses useful and interesting (including order of magnitude) and I thank them for that. I thank many conversations over lunches and dinners with fellow graduate students and friends, especially Julio Chanam´e, Roberto Assef, and Subo Dong. Outside work, I very much enjoyed spending time with Max Montenegro and family, they always made me feel like at home. I would like to thank my family, especially my parents to whom I would like to dedicate this dissertation.
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