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

TL;DR

This study uses TESS data to derive precise asteroseismic surface gravities, masses, and radii of red giants with and without planets, revealing potential systematic differences from traditional methods and implications for planetary property estimates.

Contribution

It provides asteroseismic measurements of red giant stars' fundamental parameters, highlighting discrepancies with literature values and their impact on planetary characterization.

Findings

Asteroseismic surface gravities have ~0.01 dex precision but are ~0.1 dex smaller than literature values.

Discrepancies are larger for stellar radii (~10%) than for masses (<5%).

No systematic difference between methods was found overall.

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 $\sim$0.01 dex; however, they were on average $\sim$0.1~dex smaller than the literature. The systematic larger gravities of the literature could plausibly present as a systematic overestimation of stellar masses, which would in turn lead to overestimated planetary masses of the companions. We find that the fractional discrepancies between our asteroseismically-determined parameters and those previously found are typically larger for stellar radii ($\sim$10% discrepancy) than for stellar masses ($<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 on updated stellar properties on inferred planetary properties and caution that red giant radii may be more poorly constrained than uncertainties suggest.