A Preliminary Analysis of GDR3 Metallicities for Exoplanet Hosts

Abstract

There are long-established correlations between exoplanet properties and the metallicities of their host stars. For example, gas giants have a higher occurrence rate around stars with higher metallicities. With the release of Gaia DR3 (GDR3), we now have access to a massive new sample of metallicities derived from Gaia's photometric BP/RP and RVS instruments to investigate these trends further. However, these metallicity values must be validated against the literature before any widespread use. I start by cross-matching GDR3 against the NASA Exoplanet Archive and the TESS TOI Catalog, isolating GDR3's data on exoplanet and exoplanet candidate host stars. After applying recommended calibrations to GDR3's spectroscopic and photometric metallicity data, I compared the host star metallicity in GDR3 to the metallicities in LAMOST DR8 and GALAH DR3. Both photometric and spectroscopic metallicities correlated well with literature values. However, the photometric metallicity showed evidence of systematic errors. Next, I demonstrate that GDR3's metallicities are consistent with LAMOST metallicities across all magnitude ranges. Nevertheless, correlation with GALAH decreases for dimmer stars in almost all cases. Reflecting this trend, Gaia correlation with GALAH is shown to be best for the largest, hottest stars in the subset. Finally, I show that GDR3's photometric and spectroscopic metallicities show evidence of the well-established correlation between gas giants' occurrence and host star metallicity. I also present evidence for a potential correlation between planet multiplicity and host star metallicity. However, a more robust statistical study is needed to verify this trend.