The Frequency of Binary Companions Around KELT Planet Host Stars

I conducted a search for binary companion stars around 10 stars hosting hot Jupiter exoplanets from the KELT survey and a large comparison sample of stars shown by KELT to not host transiting hot Jupiters. The goal of the survey was to determine whether hot Jupiter hosts are more likely to have stellar companions than the general population of stars. The primary stars are bright (7.5 < V < 11) and of similar distance from Earth (100 < d < 300 pc). In this dissertation, I present the results of my observations using the Differential Speckle Survey Instrument (DSSI) on the 3.5-meter WIYN telescope and LMIRCam on the Large Binocular Telescope Interferometer (LBTI), on the 2x8.4-meter Large Binocular Telescope. Across both instruments, I observed 10 of the 16 KELT planet hosts which are visible from the Northern Hemisphere and 71 comparison stars, discovering seven new potential companions and re-observing four previously known possible binary systems, as well as one confirmed binary system. I estimate the distances and masses of each binary system, as well as place lower limits on their orbital periods. I also provide an estimate of the chance alignment probability for our observed candidate binaries. I find that the KELT planet hosts have a stellar companion fraction of 50+-8:1% compared to 36.8+-6.3% for the comparison sample. This is a 1.6-sigma excess, indicating that hot Jupiter hosts are slightly more likely to have stellar binary companions.