INFLUENCE OF STELLAR MULTIPLICITY ON PLANET FORMATION. I. EVIDENCE OF SUPPRESSED PLANET FORMATION DUE TO STELLAR COMPANIONS WITHIN 20 AU AND VALIDATION OF FOUR PLANETS FROM THE<i>KEPLER</i>MULTIPLE PLANET CANDIDATES

Abstract

The planet occurrence rate for multiple stars is important in two aspects.\nFirst, almost half of stellar systems in the solar neighborhood are multiple\nsystems. Second, the comparison of the planet occurrence rate for multiple\nstars to that for single stars sheds light on the influence of stellar\nmultiplicity on planet formation and evolution. We developed a method of\ndistinguishing planet occurrence rates for single and multiple stars. From a\nsample of 138 bright (KP &lt;13.5) Kepler multi-planet candidate systems, we\ncompared the stellar multiplicity rate of these planet host stars to that of\nfield stars. Using dynamical stability analyses and archival Doppler\nmeasurements, we find that the stellar multiplicity rate of planet host stars\nis significantly lower than field stars for semi-major axes less than 20 AU,\nsuggesting that planet formation and evolution are suppressed by the presence\nof a close-in companion star at these separations. The influence of stellar\nmultiplicity at larger separations is uncertain because of search in-\ncompleteness due to a limited Doppler observation time baseline and a lack of\nhigh resolution imaging observation. We calculated the planet confidence for\nthe sample of mutlti-planet candidates, and find that the planet confidences\nfor KOI 82.01, KOI 115.01, KOI 282.01 and KOI 1781.02 are higher than 99.7% and\nthus validate the planetary nature of these four planet candidates. This sample\nof bright Kepler multi-planet candidates with refined stellar and orbital\nparameters, planet confidence estimation, and nearby stellar companion\nidentification offers a well-characterized sample for future theoretical and\nobservational study.\n