The Metallicities of Stars With and Without Transiting Planets

TL;DR

This study compares the metallicities of stars with and without small transiting planets in the Kepler field, finding no significant difference, which suggests that small planet occurrence is not strongly dependent on host star metallicity.

Contribution

It provides a homogeneous analysis of stellar metallicities for stars with and without small planets, clarifying the metallicity correlation for terrestrial-sized exoplanets.

Findings

Stars with and without small planets have statistically indistinguishable metallicities.

Homogeneous analysis confirms no strong metallicity dependence for small planet hosts.

Results support that small planet occurrence is similar across a range of stellar metallicities.

Abstract

Host star metallicities have been used to infer observational constraints on planet formation throughout the history of the exoplanet field. The giant planet metallicity correlation has now been widely accepted, but questions remain as to whether the metallicity correlation extends to the small terrestrial-sized planets. Here, we report metallicities for a sample of 518 stars in the Kepler field that have no detected transiting planets and compare their metallicity distribution to a sample of stars that hosts small planets (Rp < 1.7 R_Earth). Importantly, both samples have been analyzed in a homogeneous manner using the same set of tools (Stellar Parameters Classification tool; SPC). We find the average metallicity of the sample of stars without detected transiting planets to be [m/H]_SNTP,dwarf = -0.02 +- 0.02 dex and the sample of stars hosting small planets to be [m/H]_STP = -0.02 +- 0.02 dex. The average metallicities of the two samples are indistinguishable within the uncertainties, and the two-sample Kolmogorov-Smirnov test yields a p-value of 0.68 (0.41 sigma), indicating a failure to reject the null hypothesis that the two samples are drawn from the same parent population. We conclude that the homogeneous analysis of the data presented here support the hypothesis that stars hosting small planets have a metallicity similar to stars with no known transiting planets in the same area of the sky.