On the Development and Applications of Automated Searches for Eclipsing Binary Stars A thesis presented by Jonathan Devor to The Department of Astronomy in partial fulfillment of the requirements for the degree of Doctor of Philosophy in the subject of arXiv:0811.0017v1 [astro-ph] 3 Nov 2008 Astronomy Harvard University Cambridge, Massachusetts 13 February 2008 c 2008, by Jonathan Devor All rights reserved. Dissertation Advisor: Prof. David B. Charbonneau Jonathan Devor On the Development and Applications of Automated Searches for Eclipsing Binary Stars Abstract Eclipsing binary star systems provide the most accurate method of measuring both the masses and radii of stars. Moreover, they enable testing tidal synchronization and circularization theories, as well as constraining models of stellar structure and dynamics. With the recent availability of large-scale multi-epoch photometric datasets we were able to study eclipsing binary stars en masse. In this thesis, we analyzed 185,445 light curves from ten TrES fields, and 218,699 light curves from the OGLE II bulge fields. In order to manage such large quantities of data, we developed a pipeline with which we systematically identified eclipsing binaries, solved for their geometric orientations, and then found their components’ absolute properties. Following this analysis we assembled catalogs of eclipsing binaries with their models, computed statistical distributions of their properties, and located rare cases for further follow-up, including T-Cyg1-03378, which has unusual eclipse timing variations. Of particular importance are low-mass eclipsing binaries, which are rare yet critical for resolving the ongoing mass-radius discrepancy between theoretical models and observations. To this end, we have discovered over a dozen new low-mass eclipsing binary candidates and spectroscopically confirmed the masses of five of them. One of these confirmed candidates, T-Lyr1-17236, is especially interesting because of its long orbital period. We examined T-Lyr1-17236 in detail and found that it is consistent with the magnetic disruption hypothesis. Both the source code of our pipeline and the complete list of our candidates are freely available. iii Contents Abstract..................................... iii Acknowledgments................................ ix 1 Introduction 1 1.1 A Brief Historical Overview of Eclipsing Binary Analysis . 4 1.2 APrimeronParameterExtraction . 7 1.3 ASimpleBinaryLightCurveGenerator . 11 1.4 ChapterSummaries............................ 15 2 Solutions for 10,000 Eclipsing Binaries in the Bulge Fields of OGLE II Using DEBiL 19 2.1 Introduction................................ 20 2.2 Motivation................................. 22 2.3 Method .................................. 26 2.3.1 The First Tier – Finding the Period . 27 2.3.2 The Second Tier – DEBiL Fitter . 29 2.3.3 Limitations . 36 2.4 Tests.................................... 38 2.5 Results................................... 39 2.5.1 Population Distributions . 44 2.5.2 ExtremeSystems ......................... 49 iv 2.6 Conclusions ................................ 50 2.7 Appendix-StatisticalTests . 52 2.7.1 FitnessScore ........................... 52 2.7.2 ScatterScore ........................... 53 2.7.3 Waviness.............................. 54 2.8 Appendix-DensityEstimation . 55 3 A Novel Approach to Analyzing Eclipsing Binaries in Large Photo- metric Datasets 63 3.1 Introduction................................ 64 3.2 Express Method for Eclipsing Component Identification (MECI-express) 66 3.3 Method for Eclipsing Component Identification (MECI) . 67 3.4 Conclusions ................................ 70 4 MECI: A Method for Eclipsing Component Identification 73 4.1 Introduction................................ 74 4.2 Motivation................................. 76 4.2.1 Characterizing the Binary Stellar Population . 76 4.2.2 Identifying Low-Mass Main-Sequence EBs . 78 4.2.3 EBsasStandardCandles. 79 4.3 Method .................................. 81 4.3.1 Stage1: FindingtheOrbitalParameters . 81 4.3.2 Stage 2: Finding the Absolute Stellar Parameters . 83 4.3.3 Assessing the Likelihood of a Binary Pairing . 86 4.3.4 Optimization . 88 4.4 TestingMECI............................... 89 4.4.1 ObservedSystems......................... 90 4.4.2 SimulatedSystems ........................ 91 v 4.4.3 Limitations . 100 4.5 Conclusions ................................ 102 5 Identification, Classifications, and Absolute Properties of 773 Eclips- ing Binaries Found in the TrES Survey 103 5.1 Introduction................................ 104 5.2 Method .................................. 107 5.3 Results................................... 132 5.3.1 Low-MassEBs .......................... 157 5.3.2 EccentricEBs........................... 159 5.3.3 AbnormalEBs .......................... 168 5.4 Conclusions ................................ 171 5.5 Appendix - Rejecting Single-Eclipse EB Models . 173 5.6 Appendix - Description of the Catalog Fields . 174 6 T-Lyr1-17236: A Long-Period Low-Mass Eclipsing Binary 179 6.1 Introduction................................ 180 6.2 Initial Photometric Observations . 182 6.3 Follow-up Photometric Observations . 186 6.4 SpectroscopicObservations. 190 6.5 OrbitalAnalysis.............................. 195 6.6 PhysicalParameters ........................... 202 6.7 ChromosphericActivity . .. .. 207 6.8 Comparison with Models and Conclusions . 209 7 Conclusions and Future Work 215 7.1 Low-Mass Candidates with At Least Three RV Measurements . 218 7.1.1 T-CrB0-10759........................... 224 vi 7.1.2 T-Cyg1-12664........................... 228 7.1.3 T-Tau0-04859 ........................... 231 7.1.4 T-Tau0-07388 ........................... 234 7.2 Low-Mass Candidates with Fewer than Three RV Measurements . 237 7.2.1 T-And0-04829........................... 240 7.2.2 T-And0-20382........................... 243 7.2.3 T-CrB0-14232........................... 246 7.2.4 T-Dra0-03021 ........................... 249 7.2.5 T-Dra0-07116 ........................... 252 7.3 T-Cas0-07656: A Pulsating Eclipsing Binary . 256 7.4 T-Cyg1-03378: A Binary with Large O-C Eclipse Timing Variations . 258 References 266 vii “The only way to realize the full scientific benefit of our observations is to share the data with our competition.” –Bohdan Paczy´nski (1940 - 2007) For my Family. Acknowledgments Alfr´ed R´enyi once said, and many others subsequently paraphrased him, that “a mathematician is a device for turning coffee into theorems.” Indeed, in the hard-nosed professional world we live in, be it academic or otherwise, it is easy to forget all the human elements that must fall into place for one to be able to produce original work. In the years leading up to graduate school, I was extraordinarily fortunate to be surrounded by friends, family, and teachers who provided me with continuous support and guidance. My parents, who would patiently answer an unending stream of questions from a very persistent child, would later encourage me to follow my heart’s desire, wherever it might lead me. My decision to spend over a half-decade in school to study Astronomy, was never once questioned. However, as so often the case, my path to Astronomy was by no means a straightforward one. Carl Sagan’s Cosmos provided me with the first major push in this direction, and numerous visits to the San Francisco Exploratorium and the Boston Museum of Science cemented my love for the physical sciences at a young age. However, if it was not for an inspirational high school physics teacher named Reuben Tel-Dan, I would probably never have considered further studying physics in college. After serving in the Israeli military, I enrolled at the Hebrew University of Jerusalem, where I would meet a second inspirational teacher– Avishai Dekel. I first met Professor Dekel at a talk he gave during a freshman survey course. In that lecture I was first introduced to the concepts of dark matter, dark energy, and the concordance model of cosmology. He concluded with the current attempts to simulate the Universe at ix the grandest scales. I was immediately hooked, and proceeded to work in his group until my graduation. It is due to this experience that I chose to go to graduate school, while most of my friends were pursuing jobs at high tech companies. My first encounter with Harvard University resulted in a bit of a culture shock due to its immense range of possibilities, both academically and otherwise. In the following years I would make a point of trying as many activities as I could, sometimes to the dismay of my professors, from rowing in crew and Dragon Boat teams, to building robots that play soccer. When it came time to choose a research topic I had a very difficult time settling on a single project. I was naturally drawn to the search for Exoplanets, which was at that time and probably still is, ranked as the sexiest topic in Astronomy. However, following the sage advice of Bob Noyse and Dimitar Sasselov, I decided to start with something easier and more of a “sure thing”– finding eclipsing binary stars. This topic was intended to be a stepping stone, to get my feet wet, however the more I learned about eclipsing binaries, the more interested I got. The two most attractive aspects of this field were the fact that the necessary observational data were already available from the OGLE team and others, and the fact that even a quick perusal through this data reveals strange and curious variable stars that no one had ever studied before. My first attempts at automatic clustering