ROBO-AOKEPLERPLANETARY CANDIDATE SURVEY. II. ADAPTIVE OPTICS IMAGING OF 969KEPLEREXOPLANET CANDIDATE HOST STARS

We initiated the Robo-AO Kepler Planetary Candidate Survey in 2012 to observe each Kepler exoplanet candidate host star with high angular resolution, visible light, laser adaptive optics (AOs) imaging. Our goal is to find nearby stars lying in Kepler's photometric apertures that are responsible for the relatively high probability of false-positive exoplanet detections and that cause underestimates of the size of transit radii. Our comprehensive survey will also shed light on the effects of stellar multiplicity on exoplanet properties and will identify rare exoplanetary architectures. In this second part of our ongoing survey, we observed an additional 969 Kepler planet candidate hosts and we report blended stellar companions up to Delta m approximate to 6 that contribute to Kepler's measured light curves. We found 203 companions within approximate to 4 " of 181 of the Kepler stars, of which 141 are new discoveries. We measure the nearby star probability for this sample of Kepler planet candidate host stars to be 10.6% +/- 1.1% at angular separations up to 2 5, significantly higher than the 7.4% +/- 1.0% probability discovered in our initial sample of 715 stars; we find the probability increases to 17.6% +/- 1.5% out to a separation of 4." 0. The median position of Kepler Objects of Interest (KOIs) observed in this survey are 1.degrees 1 closer to the galactic plane, which may account for some of the nearby star probability enhancement. We additionally detail 50 Keck AO images of Robo-AO observed KOIs in order to confirm 37 companions detected at a <5 sigma significance level and to obtain additional infrared photometry on higher significance detected companions.