Wednesday, December 14, 2016

Accurate, Empirical Radii and Masses of Planets with Gaia Parallaxes


Stassun et al


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.

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