Monday, January 14, 2013

1301.2384 (Eric Gaidos)

Candidate Planets in the Habitable Zones of Kepler Stars    [PDF]

Eric Gaidos
A Bayesian analysis was used to determine the host star parameters of 2740 candidate and confirmed Kepler transiting planets and estimate the probability pHZ that a planet lies within its star's habitable zone, i.e., that the incident stellar irradiation lies between the threshholds for the runaway wet greenhouse and polar CO2-condensing "snowball" climate states. This analysis is based on photometry from the Kepler Input Catalog, an ensemble of Dartmouth Stellar Evolution Program models, and priors for stellar mass, age, metallicity, distance, as well as a constraint from the duration of the planet transit, and yields probability density functions for stellar parameters with which confidence intervals of planet radius and incident stellar flux as well as pHZ are calculated. Fifty-two planets have pHZ > 0.5 and a most probable stellar irradiation within the habitable zone limits. Five of these have estimated radii less than twice the Earth, but the majority are super-Earth to Neptune size, and 8 are gas giants which could host habitable exomoons. Another is possibly not a planet, but a brown dwarf or ultracool star. The planet candidate most resembling Earth in terms of size and irradiation is KOI 3010.01, which orbits a late K or early M dwarf. Parallaxes from the Gaia mission will reduce errors in planet radius and irradiance by at least a factor of 5, permitting definitive assignments of transiting planets to habitable zones of Kepler stars and, eventually, studies of any correlations of planet properties with position in those zones.
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