Kepler Input Catalog: Photometric Calibration and Stellar Classification

TL;DR

The paper details the methods for photometric calibration and stellar classification used in the Kepler Input Catalog, enabling accurate target selection for the Kepler Mission by estimating stellar parameters with Bayesian techniques.

Contribution

It introduces a Bayesian approach to derive stellar parameters and classify stars in the Kepler Input Catalog, improving reliability over previous methods.

Findings

Photometric repeatability is typically 2% for stars brighter than magnitude 15.

Stellar classifications are reliable within +/- 200 K in Teff and +/- 0.4 dex in log(g).

Main-sequence and giant star distinction is reliable with over 98% confidence for Teff <= 5400 K.

Abstract

We describe the photometric calibration and stellar classification methods used to produce the Kepler Input Catalog (KIC). The KIC is a catalog containing photometric and physical data for sources in the Kepler Mission field of view; it is used by the mission to select optimal targets. We derived atmospheric extinction corrections from hourly observations of secondary standard fields within the Kepler field of view. Repeatability of absolute photometry for stars brighter than magnitude 15 is typically 2%. We estimated stellar parameters Teff, log(g), log (Z), E_{B-V} using Bayesian posterior probability maximization to match observed colors to Castelli stellar atmosphere models. We applied Bayesian priors describing the distribution of solar-neighborhood stars in the color-magnitude diagram (CMD), in log (Z)$, and in height above the galactic plane. Comparisons with samples of stars classified by other means indicate that in most regions of the CMD, our classifications are reliable within about +/- 200 K and +/- 0.4 dex in log (g). It is difficult to assess the reliability of our log(Z) estimates, but there is reason to suspect that it is poor, particularly at extreme Teff. Of great importance for the Kepler Mission, for Teff <= 5400 K, the distinction between main-sequence stars and giants has proved to be reliable with better than 98% confidence. The KIC is available through the MAST data archive.