TESS Asteroseismic Masses and Radii of Red Giants with (and without) Planets

Abstract We present a study of asteroseismically derived surface gravities, masses, and radii of a sample of red giant stars both with and without confirmed planetary companions using TESS photometric light curves. These red giants were drawn from radial velocity surveys, and their reported properties in the literature rely on more traditional methods using spectroscopy and isochrone fitting. Our asteroseismically derived surface gravities achieved a precision of ∼0.01 dex; however, they were on average ∼0.1 dex smaller than the literature. The systematic larger gravities of the literature could plausibly present as a systematic overestimation of stellar masses, which would in turn lead to overestimated planetary masses of the companions. We find that the fractional discrepancies between our asteroseismically determined parameters and those previously found are typically larger for stellar radii (∼10% discrepancy) than for stellar masses (<5% discrepancy). However, no evidence of a systematic difference between methods was found for either fundamental parameter. Two stars, HD 100065 and HD 18742, showed significant disagreement with the literature in both mass and radii. We explore the impacts of updated stellar properties on inferred planetary properties and caution that red giant radii may be more poorly constrained than uncertainties suggest.