Using JWST transits and occultations to determine $\sim 1\%$ stellar radii and temperatures of low-mass stars

Abstract

Using JWST observations of a primary transit and two secondary eclipses for GJ 1214b, we determine an eccentricity that is more precise than a decade of HARPS data, which enables us to measure the stellar density to 2.62%. Coupled with a prior on the stellar mass from a dynamically calibrated K-$M_{\ast }$ relation, we determine $R_{\ast }$ to 1.13% -- 3 times more precise than any other published analysis of this system. Then, using the bolometric flux from an spectral energy distribution model, we determine $T_{\mathrm{eff}}$ to 1.39% -- 40% more precise than systematic floors from spectroscopy. Within the global model, these also improve the planetary radius and insolation. This is a proof of concept for a new method to determine accurate $R_{\ast }$ and $T_{\mathrm{eff}}$ to a precision currently achieved for only a small number of low-mass stars. By applying our method to all high signal-to-noise ratio planetary transits and occultations, we can expand the sample of precisely measured stars without assuming tidal circularization and calibrate new relations to improve our understanding of all low-mass stars.

Published in ApJL, 13 pages, 4 figures, 4 tables. Updated to match proofs

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• Evidence for an Atmosphere on the Ultra-Short Period super-Earth HD 3167 b
• Sub-Neptunes as Soot Factories: Deep Atmosphere Hydrocarbon Formation and Quenching as the Origin of Sub-Neptune Aerosol Trends