Fundamental Properties of Kepler Planet-Candidate Host Stars using Asteroseismology

TL;DR

This study uses asteroseismology to accurately determine fundamental properties of 66 Kepler planet-hosting stars, revealing systematic biases in previous stellar classifications and refining planet size estimates.

Contribution

It provides new asteroseismic solutions for four stars, increases the number of stars with such data, and compares stellar properties with prior catalogs to identify biases and improve planet characterization.

Findings

Spectroscopic radii for subgiants and giants are systematically underestimated.

Most cool main-sequence hosts are confirmed as dwarfs.

Revised stellar properties lead to significant changes in planet candidate classifications.

Abstract

We have used asteroseismology to determine fundamental properties for 66 Kepler planet-candidate host stars, with typical uncertainties of 3% and 7% in radius and mass, respectively. The results include new asteroseismic solutions for four host stars with confirmed planets (Kepler-4, Kepler-14, Kepler-23 and Kepler-25) and increase the total number of Kepler host stars with asteroseismic solutions to 77. A comparison with stellar properties in the planet-candidate catalog by Batalha et al. shows that radii for subgiants and giants obtained from spectroscopic follow-up are systematically too low by up to a factor of 1.5, while the properties for unevolved stars are in good agreement. We furthermore apply asteroseismology to confirm that a large majority of cool main-sequence hosts are indeed dwarfs and not misclassified giants. Using the revised stellar properties, we recalculate the radii for 107 planet candidates in our sample, and comment on candidates for which the radii change from a previously giant-planet/brown-dwarf/stellar regime to a sub-Jupiter size, or vice versa. A comparison of stellar densities from asteroseismology with densities derived from transit models in Batalha et al. assuming circular orbits shows significant disagreement for more than half of the sample due to systematics in the modeled impact parameters, or due to planet candidates which may be in eccentric orbits. Finally, we investigate tentative correlations between host-star masses and planet candidate radii, orbital periods, and multiplicity, but caution that these results may be influenced by the small sample size and detection biases.