Planetary Candidates Observed by Kepler, III: Analysis of the First 16 Months of Data

TL;DR

This paper reports the discovery and analysis of over 2,300 new planet candidates from Kepler data, emphasizing improved vetting methods, detailed characterization, and the potential for finding Earth-sized planets in habitable zones.

Contribution

It introduces enhanced vetting metrics and analysis techniques that increase catalog reliability and detail the properties of new planet candidates from the first 16 months of Kepler data.

Findings

Identification of 1,091 new planet candidates, increasing total to over 2,300.

Notable increase in small planet candidates and those with longer orbital periods.

Evidence of continued growth in multi-candidate systems and potential for Earth-size habitable zone planets.

Abstract

New transiting planet candidates are identified in sixteen months (May 2009 - September 2010) of data from the Kepler spacecraft. Nearly five thousand periodic transit-like signals are vetted against astrophysical and instrumental false positives yielding 1,091 viable new planet candidates, bringing the total count up to over 2,300. Improved vetting metrics are employed, contributing to higher catalog reliability. Most notable is the noise-weighted robust averaging of multi-quarter photo-center offsets derived from difference image analysis which identifies likely background eclipsing binaries. Twenty-two months of photometry are used for the purpose of characterizing each of the new candidates. Ephemerides (transit epoch, T_0, and orbital period, P) are tabulated as well as the products of light curve modeling: reduced radius (Rp/R*), reduced semi-major axis (d/R*), and impact parameter (b). The largest fractional increases are seen for the smallest planet candidates (197% for candidates smaller than 2Re compared to 52% for candidates larger than 2Re) and those at longer orbital periods (123% for candidates outside of 50-day orbits versus 85% for candidates inside of 50-day orbits). The gains are larger than expected from increasing the observing window from thirteen months (Quarter 1-- Quarter 5) to sixteen months (Quarter 1 -- Quarter 6). This demonstrates the benefit of continued development of pipeline analysis software. The fraction of all host stars with multiple candidates has grown from 17% to 20%, and the paucity of short-period giant planets in multiple systems is still evident. The progression toward smaller planets at longer orbital periods with each new catalog release suggests that Earth-size planets in the Habitable Zone are forthcoming if, indeed, such planets are abundant.