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Planets in Binary Systems: Studies with Precise Radial Velocities and High-Resolution Imaging

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Planets in Binary Systems: Studies with Precise Radial Velocities and High-Resolution Imaging UC Berkeley UC Berkeley Electronic Theses and Dissertations Title Planets in Binary Systems: Studies with Precise Radial Velocities and High-Resolution Imaging Permalink https://escholarship.org/uc/item/7520w1zk Author Hirsch, Lea Publication Date 2018 Peer reviewed|Thesis/dissertation eScholarship.org Powered by the California Digital Library University of California Planets in Binary Systems: Studies with Precise Radial Velocities and High-Resolution Imaging By Lea Hirsch A dissertation submitted in partial satisfaction of the requirements for the degree of Doctor of Philosophy in Astrophysics in the Graduate Division of the University of California, Berkeley Committee in charge: Professor James Graham, Chair Professor Eugene Chiang Professor Burkhard Militzer Summer 2018 Planets in Binary Systems: Studies with Precise Radial Velocities and High-Resolution Imaging Copyright 2018 by Lea Hirsch 1 Abstract Planets in Binary Systems: Studies with Precise Radial Velocities and High-Resolution Imaging by Lea Hirsch Doctor of Philosophy in Astrophysics University of California, Berkeley Professor James Graham, Chair Nearly half of all solar-type stars have at least one stellar or brown dwarf companion, and planets around G- and K-type stars appear to be quite common. Yet the impact of stellar multiplicity on planets, and on our understanding of planets, is not well understood. In this thesis, I describe a combination of work to study the interplay between stellar and planetary companions, using the combination of radial velocity and high-resolution imaging observations. First, planets discovered by transit surveys like the Kepler Mission are sensitive to a detection and characterization bias due to stellar companions. The light of unresolved binary companions dilutes the transit of the planet, making it appear shallower than it is. This causes planet sizes in binary systems to be underestimated, and sensitivity to small planets to be overestimated. In Chapter2, I combined multi-wavelength observations of stellar companions detected within 200of 170 Kepler Object of Interest hosts, to assess whether these companions were physically associated with the planet host stars. I found that stellar companions within 100 had a ≥ 80% likelihood of being bound. I used the compiled imaging observations of the bound stellar companions in this sample to determine the factor by which planet radii in these systems were underestimated. I determined that an average radius correction factor of XR = 1:65 must be applied to planets orbiting stars with unresolved stellar companions, assuming the planets are equally likely to orbit either of the stars in a binary system. This means that planets in unresolved binary systems may have radii underestimated by an average of 65%. This effect is particularly important for Kepler stars with minimal ground-based follow-up; by performing a combination of spectroscopic and imaging observations on Kepler planet hosts, it is possible to reduce the effect of stellar companions by finding or ruling out binary companions in large regions of parameter space. Second, stellar companions likely impact the formation and evolution of planetary sys- tems. To probe these effects, I focused on the solar neighborhood, studying sun-like stars within 25 pc using Doppler spectroscopy as well as adaptive optics and speckle imaging 2 techniques. I built up methodology for performing joint orbital fits to combinations of radial velocity, astrometric, and photometric data by assessing the orbit of HD 159062in Chapter3. HD 159062 is a nearby binary system consisting of a G dwarf and a newly-discovered white +0:09 dwarf companion. I determined that the white dwarf must have a mass of 0:54−0:03M . Its combined radial velocities, astrometry, and photometry are inconsistent with it being either a brown dwarf or a main sequence star. In Chapter4, I extended this joint orbital analysis technique to make use of imaging non-detections to place constraints on orbiting planets. In this study, we focused on the nearby adolescent K dwarf, Eridani, whose giant planet was detected in three decades of radial velocity monitoring. Using deep M-band coronographic imaging that resulted in no detection of the planet, upper limits were placed on the mass of the giant planet. The combination of the RV data and constraints from the non-detection of the planet allowed the mass and inclination of the planet to be determined more precisely than with the RV data alone. Finally, I performed a simultaneous RV and imaging survey for both stellar and planetary companions to sun-like stars in the solar neighborhood in Chapter5. By comparing the planet occurrence rates in binary systems to those in single star systems, we can begin to untangle the effects of stellar companions on planet formation. I found that the occurrence rate of planets with masses between 0.1 and 10 MJand with semi-major axes between 0.1 and 10 AU is statistically equivalent in single star and binary star systems. I also determined that all known planet-hosting binary systems in the 25 pc sun-like star sample had separations wider than 100 AU. This indicates that wide binary companions do not seem to strongly impact the planet formation process, but that the planet occurrence rate in binary systems may decrease for systems with smaller binary separations. i To Miriam and Howard Hirsch ii Contents List of Figuresv List of Tables vii Acknowledgments viii 1 Introduction1 1.1 Stellar Multiplicity................................1 1.1.1 Multiplicity in the Solar Neighborhood.................1 1.2 The Effects of Stellar Companions on Planets.................2 1.2.1 Theories of Exoplanet Formation and Evolution............2 1.2.2 Previous Observational Constraints...................4 1.2.3 Characterization of Transiting Planets.................5 1.3 Combining Radial Velocities and Imaging....................6 1.4 This Thesis....................................7 2 Assessing the Effect of Stellar Companions from High-Resolution Imaging of Kepler Objects of Interest 10 2.1 Introduction.................................... 10 2.2 Sample....................................... 12 2.2.1 KOI Host Stars.............................. 12 2.2.2 Stellar Companions............................ 15 2.3 Determining Physical Association of Companion Stars............. 16 2.3.1 Interstellar Extinction.......................... 21 2.3.2 Comparison with Stellar Population Models.............. 22 2.4 Bound Companions to Kepler Planet Hosts................... 23 2.5 Planet Radius Corrections............................ 28 2.6 Conclusions.................................... 35 3 Combining Radial Velocities and Direct Imaging to Constrain the Orbit of the White Dwarf Companion to HD 159062 38 3.1 Introduction.................................... 38 3.2 Observations and Data Reduction........................ 41 Contents iii 3.2.1 Radial Velocity Observations....................... 41 3.2.2 High-Resolution Imaging......................... 41 3.3 Astrometry and Common Proper Motion.................... 46 3.4 HD 159062 B is not a Brown Dwarf....................... 46 3.5 Orbital Analysis.................................. 48 3.5.1 White Dwarf Cooling Models...................... 50 3.5.2 Total system age............................. 52 3.6 Discussion..................................... 55 3.7 Conclusions.................................... 55 4 Deep exploration of Eridani with Keck Ms-band vortex coronagraphy and radial velocities: mass and orbital parameters of the giant exoplanet 57 4.1 Introduction.................................... 57 4.1.1 Eridani’s debris disk.......................... 57 4.1.2 Eridani’s putative planet........................ 59 4.1.3 This chapter................................ 59 4.2 Doppler Spectroscopy............................... 60 4.2.1 RV observations.............................. 60 4.2.2 RV data analysis............................. 61 4.3 High contrast imaging.............................. 62 4.3.1 High contrast imaging observations................... 62 4.3.2 Image post-processing.......................... 63 4.4 Results....................................... 63 4.4.1 Robust detection limits from direct imaging.............. 63 4.4.2 Tests on the RV Data.......................... 68 4.4.3 Combining constraints from imaging and RV.............. 75 4.5 Discussion..................................... 78 4.5.1 Choice of evolutionary models...................... 81 4.5.2 Constraints on the system’s age and inclination............ 82 4.5.3 Planet-disk interactions......................... 85 4.6 Conclusion..................................... 89 5 Understanding the Impacts of Stellar Companions on Planet Formation and Evolution: A Survey of Stellar and Planetary Companions within 25 pc 97 5.1 Introduction.................................... 97 5.2 25 pc Sample................................... 99 5.3 High-Resolution Imaging Observations..................... 99 5.3.1 Lick/ShaneAO.............................. 100 5.3.2 Palomar/PHARO............................. 104 5.4 Radial Velocity Observations........................... 104 5.4.1 Keck/HIRES............................... 105 Contents iv 5.4.2 APF/Levy................................. 106 5.5 Stellar Companions................................ 106 5.5.1 Sensitivity to Stellar Companions.................... 111 5.6 Planetary Companions.............................. 115 5.6.1 Blind Planet Search............................ 115 5.6.2 New Planet Detections.........................
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