The GALAH Survey: Using Galactic Archaeology to Refine our Knowledge of TESS Target Stars

TL;DR

This study combines GALAH, TESS, and Gaia data to create a detailed catalog of stellar properties, refining exoplanet parameters and analyzing host star compositions to better understand potential planetary compositions.

Contribution

It provides a self-consistent catalog of stellar parameters for over 47,000 stars, improving exoplanet characterization and analyzing elemental ratios to infer planetary compositions.

Findings

Derived stellar masses and radii with 5% precision.

Revised parameters for several TESS planetary systems, questioning some planetary classifications.

Found that 36% of stars have elemental ratios similar to the Sun, indicating potential for rocky planets.

Abstract

An unprecedented number of exoplanets are being discovered by the Transiting Exoplanet Survey Satellite (TESS). Determining the orbital parameters of these exoplanets, and especially their mass and radius, will depend heavily upon the measured physical characteristics of their host stars. We have cross-matched spectroscopic, photometric, and astrometric data from GALAH Data Release 2, the TESS Input Catalog and Gaia Data Release 2, to create a curated, self-consistent catalog of physical and chemical properties for 47,285 stars. Using these data we have derived isochrone masses and radii that are precise to within 5\%. We have revised the parameters of three confirmed, and twelve candidate, TESS planetary systems. These results cast doubt on whether CTOI-20125677 is indeed a planetary system since the revised planetary radii are now comparable to stellar sizes. Our GALAH-TESS catalog contains abundances for up to 23 elements. We have specifically analysed the molar ratios for C/O, Mg/Si, Fe/Si and Fe/Mg, to assist in determining the composition and structure of planets with $R_p < 4R_\oplus$. From these ratios, 36% fall within 2 sigma of the Sun/Earth values, suggesting that these stars may host rocky exoplanets with geological compositions similar to planets found within our own Solar system.