DETECTING AND CHARACTERIZING STELLAR COMPANIONS TO EXOPLANET HOST STARS A thesis presented to the faculty of AS San Francisco State University In partial fulfilment of The Requirements for PH VS - W 5 g Master of Science In Physics: Astronomy by Justin Wittrock San Francisco, California December 2016 Copyright by Justin Wittrock 2016 CERTIFICATION OF APPROVAL I certify that I have read DETECTING AND CHARACTERIZING STELLAR COMPANIONS TO EXOPLANET HOST STARS by Justin Wittrock and that in my opinion this work meets the criteria for approv­ ing a thesis submitted in partial fulfillment of the requirements for the degree: Master of Science in Physics: Astronomy at San Francisco State University. Dr. Stephen Kane, PhD Astrophysics Associate Professor of Physics and Astronomy Dr. Adrienne Cool, PhD Astronomy Professor of Physics and Astronomy D^/Joseph Barranco, PhD Astropf Associate Professor of Physics and Astronomy DETECTING AND CHARACTERIZING STELLAR COMPANIONS TO EXOPLANET HOST STARS Justin Wittrock San Francisco State University 2016 A factor that can affect the detection of exoplanets is the binarity of the host stars. Such a factor cannot be easily dismissed since the multiplicity of the stellar systems within our own Milky Way are quite common and that such systems can place further constraints on orbital dynamics and evolution. We used the Differential Speckle Survey Instrument (DSSI) at the Gemini-North Observatory to obtain AO images at 692 nm and 880 nm bands. From our survey, we detect stellar companions to the known exoplanet host stars HD 2638 and HD 164509. The stellar companion to HD 2638 has been previously detected, but the companion to HD 164509 is newly discovered. The results from observations and the stellar isochrone models are consistent with the detected companions being late-type M dwarfs. The non- detection of stellar companions to the remaining systems provides constraints on the possible presence of additional planets in those systems. I certify that the Abstract is a correct representation of the content of this thesis. Date ACKNOWLEDGMENTS I’d like to thank the people who have supported and encouraged me in my reaching the academic goals. I give my thanks to my parents for their loving support, especially when I'm so far away from home. I also want to thank the SFSU faculty, students, and the entire Physics & Astronomy Department. Ever since my arrival nearly 2 1/2 years ago, my knowledge and experience have exploded, and I have become progressively confident of my skill sets and am more prepared for the increasingly challenging path in the future. I give my thanks to my thesis defense committees Stephen Kane, Adrienne Cool, and Joe Barranco for their time and support. Thank you Stephen for your tireless support, guidance, and effort while my stay at SFSU; you have made it possible for me to get where I am at now. It has been a real pleasure learning from you, and I look forward to continue working with you in the future! v TABLE OF CONTENTS 1 Introduction....................................................................................................... 1 2 Observations and Target Selections.................................................................. 4 2.1 Stellar Companion S u rv e y .......................................................................... 4 2.2 Background on HD 164509 and HD 2638 ................................................. 15 3 Data Reduction................................................................................................. 18 4 Results........................................................................................................................ 47 4.1 Discoveries of Stellar Companions.................................................................47 4.1.1 HD 2638 ............................................................................................ 48 4.1.2 HD 164509 ................................................................................... 49 4.1.3 Stellar Isochrone F ittin g ................................................................... 50 4.1.4 Proper Motion and Astrometry ............................................. 52 4.2 Constraints on Presence of Stellar Companions...........................................54 5 Implications of the Orbital D ynam ics.................................................................. 63 6 Conclusion..................................................................................................................67 References......................................................................................................................... 69 vi LIST OF TABLES Table Page 2.1 Stellar Properties of Kepler and ROBO-AO RV Exoplanet Host Stars with Null-Detection I ............................................................................. 6 2.1 Stellar Properties of Kepler and ROBO-AO RV Exoplanet Host Stars with Null-Detection I .................................................................................. 7 2.1 Stellar Properties of Kepler and ROBO-AO RV Exoplanet Host Stars with Null-Detection I .................................................................................. 8 2.1 Stellar Properties of Kepler and ROBO-AO RV Exoplanet Host Stars with Null-Detection I .................................................................................. 9 2.1 Stellar Properties of Kepler and ROBO-AO RV Exoplanet Host Stars with Null-Detection I .................................................................................. 10 2.2 Stellar Properties of Kepler and ROBO-AO RV Exoplanet Host Stars with Null-Detection I I ............................................................................... 10 2.2 Stellar Properties of Kepler and ROBO-AO RV Exoplanet Host Stars with Null-Detection I I ................................................................................... 11 2.2 Stellar Properties of Kepler and ROBO-AO RV Exoplanet Host Stars with Null-Detection I I ................................................................................... 12 2.2 Stellar Properties of Kepler and ROBO-AO RV Exoplanet Host Stars with Null-Detection I I ............................................................................... 13 2.2 Stellar Properties of Kepler and ROBO-AO RV Exoplanet Host Stars with Null-Detection I I ............................................................................... 14 2.3 Stellar k, Planetary Properties............................................................... 16 vii 4.1 DSSI Astrometry & Photometry Results................................................... 48 4.2 Stellar Companion Isochrone Fitting R esults............................................. 51 4.3 Limiting M agnitudes.......................................................................................56 4.3 Limiting M agnitudes.......................................................................................57 4.3 Limiting M agnitudes.......................................................................................58 4.3 Limiting M agnitudes.......................................................................................59 4.3 Limiting M agnitudes.......................................................................................60 4.3 Limiting M agnitudes.......................................................................................61 4.3 Limiting M agnitudes.......................................................................................62 viii LIST OF FIGURES Figure Page 3.1 Top left and top right are Gemini DSSI speckle images of HD 2638 at 692 nm and 880 nm, respectively. The field-of-view is 2.8" x 2.8". As indicated in both images, North is up and East is to the left. The source in the center is HD 2638, and a bright source to the bottom and slightly to the left of the main star is the stellar companion. Bot- ton left and bottom right are sensitivity plots of HD 2638 at 692 nm and 880 nm, respectively. Each plot shows the limiting magnitude (difference between local maxima and minima) as a function of ap­ parent separation from HD 2638 in arcsec. The dashed line is a cubic spline interpolation of the 5a detection limit. Both plots were gen­ erated from top left and right corresponding images. Both images and sensitivity plots indicate the presence of stellar companion with magnitude differences of 4 and 3, respectively, and separation of 0.5". The Gemini diffraction limits are 0.021” and 0.027” at 692 nm and 880 nm, respectively........................................................................... 21 ix 3.2 Top left and top right are Gemini DSSI speckle images of HD 164509 at 692 nm and 880 nm. The field-of-view is 2.8" x 2.8” . As indicated in both images, North is up and East is to the left. The source in the - ft IL ■ center is HD 164509, ana a Bright source to the bottom and right of the main star is the stellar companion. The arrow in the left image in­ dicates the location of the companion. Bottom left and bottom right are sensitivity plots of HD 164509 at 692 nm and 880 nm, respec­ tively. Each plot shows the limiting magnitude (difference between local maxima and minima) as a function of apparent separation from HD 164509 in arcsec. The dashed line is a cubic spline interpolation of the 5a detection limit. Both plots are generated from top left and right corresponding images. Both images and sensitivity plots indi­ cate the presence of stellar companion with magnitude difference of 4 and separation of 0.5" at 880 nm.