Robo-AO Kepler Survey V: The effect of physically associated stellar companions on planetary systems

The Keplerlight curves used to detect thousands of planetary candidates are susceptible to dilution due to blending with previously unknown nearby stars. With the automated laser adaptive optics instrument, Robo-AO, we have observed 620 nearby starsaround 3857 planetary candidates host stars. Many of the nearby stars, however, are not bound to the KOI. In this paper, we quantify the association probability between each KOI and detected nearby starsthrough several methods. Galactic stellar models and the observed stellar densityare used to estimate the number and properties of unbound stars. We estimate the spectral type and distance to 145 KOIs with nearby starsusing multi-band observations from Robo-AO and Keck-AO. We find most nearby starswithin 1" of a Keplerplanetary candidate are likely bound, in agreement with past studies. We use likely bound starsas well as the precise stellar parameters from the California KeplerSurvey to search for correlations between stellar binarity and planetary properties. No significant difference between the binarity fraction of single and multiple planetsystems is found, and planethosting starsfollow similar binarity trends as field stars, many of which likely host their own non-aligned planets. We find that hot Jupitersare ~4x more likely than other planetsto reside in a binary starsystem. We correct the radius estimates of the planetcandidates in characterized systems and find that for likely bound systems, the estimated planetary candidate radii will increase on average by a factor of 1.77, if either staris equally likely to host the planet. We find that the planetary radius gap is robust to the impact of dilution, and find an intriguing 95%-confidence discrepancy between the radius distribution of small planetsin single and binary systems.