Terrestrial Exoplanet Internal Structure Constraints Are Not Limited by Host Star Spectroscopic Analysis

Exoplanet mass and radius inferences, and therefore internal structure constraints, are based on host star mass and radius inferences.  Accurate, precise, homogeneous, and self-consistent exoplanet internal structure constraints therefore demand accurate, precise, homogeneous, and self-consistent host star mass, radius, and elemental abundance inferences.  Published terrestrial exoplanet internal structure constraints have often been based on host star mass, radius, and elemental abundance inferences that are not self-consistent.  For 20 solar-type stars known to host terrestrial exoplanets, we use all available astrometric and photometric data plus high-resolution optical spectroscopy to infer accurate, precise, homogeneous, and self-consistent photospheric and fundamental stellar parameters as well as elemental abundances.  We infer updated planetary masses and radii using these data plus Doppler and transit observables and then use our complete data set to derive the strongest possible constraints on the internal structures of these terrestrial planets.  We repeat these same analyses using the high-quality catalogs of photospheric stellar parameters and elemental abundances from SDSS DR17 APOGEE and Brewer et al. (2016, 2018) to assess the impact of differing photospheric stellar parameters and elemental abundance inference approaches on terrestrial exoplanet internal structure modeling.