ALMOST ALL OFKEPLER'S MULTIPLE-PLANET CANDIDATES ARE PLANETS

Abstract

We present a statistical analysis that demonstrates that the overwhelming majority of Kepler candidate multiple transiting systems (multis) indeed represent true, physically-associated transiting planets. Binary stars provide the primary source of false positives among Kepler planet candidates, implying that false positives should be nearly randomly-distributed among Kepler targets. In contrast, true transiting planets would appear clustered around a smaller number of Kepler targets if detectable planets tend to come in systems and/or if the orbital planes of planets encircling the same star are correlated. There are more than one hundred times as many Kepler planet candidates in multi-candidate systems as would be predicted from a random distribution of candidates, implying that the vast majority are true planets. Most of these multis are multiple planet systems orbiting the Kepler target star, but there are likely cases where (a) the planetary system orbits a fainter star, and the planets are thus significantly larger than has been estimated, or (b) the planets orbit different stars within a binary/multiple star system. We use the low overall false positive rate among Kepler multis, together with analysis of Kepler spacecraft and ground-based data, to validate the closely-packed Kepler-33 planetary system, which orbits a star that has evolved somewhat off of the main sequence. Kepler-33 hosts five transiting planets with periods ranging from 5.67 to 41 days.

SOPHIE velocimetry ofKeplertransit candidates

“…Bouchy et al 2009b;Mayor et al 2016). Furthermore, those multiple candidates have a very low a priori probability of being false positives (Lissauer et al 2012. Therefore, our predicted increase in false positives towards small planet candidates should be mostly concentrated on the candidates that are not in multiple systems.…”

“…As pointed out by the authors, the extrapolation of the falsepositive rate from this small sample, which represents 1.1% only of the planet candidates known today, to the entire sample of candidates, should be done with caution. Among these 51 Spitzer targets, 33 of them are orbiting in multiple systems that are known to have a very low a priori probability of being false positives (Lissauer et al 2012. The 18 remaining ones are relatively small planets, and only two are EGPs 10 .…”

An independent planet search in theKeplerdataset

“…Furthermore, the detection of a reliable second (or third, etc. ) signal in the same LC dramatically reduces the remaining chances of false positives so that nearly all multi-transiting LCs are indeed of planetary origin (Lissauer et al 2012;Fabrycky et al 2012a). The true distribution of single-versus multi-transiting planets systems in itself is also of interest to understand the planet formation theory (Figueira et al 2012).…”

An explorative approach for inspectingKeplerdata

“…While the primary goal of both missions was the detection of solid exoplanets, the continuous monitoring of 150, 000 variable main sequence stars allowed a very detailed study of their variability behaviour. While astroseismology (Gilliland et al 2010) and exoplanet detection (Lissauer et al 2012) greatly benefit from those observations, many objects remain unlabelled. The labelling of (quasi-) periodic sources is quite reliable (e.g., Benko et al 2010;Slawson et al 2011), however, a large fraction of the objects that show no periodic behaviour remains unclassified.…”