Candidate Planets in the Habitable Zones of Kepler Stars
Abstract
A key goal of the Kepler mission is the discovery of Earthsize transiting planets in "habitable zones" where stellar irradiance maintains a temperate climate on an Earthlike planet. Robust estimates of planet radius and irradiance require accurate stellar parameters, but most Kepler systems are faint, making spectroscopy difficult and prioritization of targets desirable. The parameters of 2035 host stars were estimated by Bayesian analysis and the probabilities p _{HZ} that 2738 candidate or confirmed planets orbit in the habitable zone were calculated. Dartmouth Stellar Evolution Program models were compared to photometry from the Kepler Input Catalog, priors for stellar mass, age, metallicity and distance, and planet transit duration. The analysis yielded probability density functions for calculating confidence intervals of planet radius and stellar irradiance, as well as p _{HZ}. Sixtytwo planets have p _{HZ} > 0.5 and a most probable stellar irradiance within habitable zone limits. Fourteen of these have radii less than twice the Earth; the objects most resembling Earth in terms of radius and irradiance are KOIs 2626.01 and 3010.01, which orbit late K/Mtype dwarf stars. The fraction of Kepler dwarf stars with Earthsize planets in the habitable zone (η_{⊕}) is 0.46, with a 95% confidence interval of 0.310.64. Parallaxes from the Gaia mission will reduce uncertainties by more than a factor of five and permit definitive assignments of transiting planets to the habitable zones of Kepler stars.
 Publication:

The Astrophysical Journal
 Pub Date:
 June 2013
 DOI:
 10.1088/0004637X/770/2/90
 arXiv:
 arXiv:1301.2384
 Bibcode:
 2013ApJ...770...90G
 Keywords:

 astrobiology;
 methods: statistical;
 planetary systems;
 stars: fundamental parameters;
 stars: statistics;
 techniques: photometric;
 Astrophysics  Earth and Planetary Astrophysics;
 Astrophysics  Solar and Stellar Astrophysics
 EPrint:
 Accepted to The Astrophysical Journal on 26 April 2013