Accurate, Empirical Radii and Masses of Planets with Gaia Parallaxes

Accurate, Empirical Radii and Masses of Planets with Gaia Parallaxes

Authors:

Stassun et al

Abstract:

We present new, empirical measurements of the radii of 132 stars that host transiting planets. These stellar radii are determined using only direct observables---the bolometric flux at Earth, the stellar effective temperature, and the parallax newly provided by the Gaia first data release---and thus are virtually model independent, extinction being the only free parameter. We also determine each star's mass using our newly determined radius and the stellar density, itself a virtually model independent quantity from the previously published transit analysis. The newly determined stellar radii and masses are in turn used to re-determine the transiting planet radii and masses, once again using only direct observables. The uncertainties on the stellar radii and masses are typically 8% and 30%, respectively, and the resulting uncertainties on the planet radii and masses are 9% and 22%, respectively. These accuracies are generally larger than the previously published model-dependent precisions of 5% and 6% on the planet radii and masses, respectively, but the newly determined values are purely empirical. We additionally report stellar radii for 366 stars that host radial-velocity (non-transiting) planets, with a typical achieved accuracy in the radii of 2%. Most importantly, the stellar bolometric fluxes and angular radii reported here---with typical accuracies of 1.7% and 1.8%, respectively---will serve as a fundamental data set to permit the re-determination of the planet radii and masses with the {\it Gaia\} second data release to 3% and 5% accuracy, comparable to or better than currently published precisions, but in an entirely empirical fashion.