On the Metal-Richness of M Dwarfs with Planets

TL;DR

This study challenges previous assumptions by showing that M dwarfs with planets are generally metal-rich, using a new calibration that corrects earlier underestimations of metallicity.

Contribution

The paper introduces a new photometric metallicity calibration for M dwarfs and demonstrates that planet-hosting M dwarfs are typically metal-rich, aligning with higher-mass star trends.

Findings

Previous calibrations underestimated M dwarf metallicities by 0.32 dex.

M dwarfs with planets are systematically metal-rich.

New calibration aligns M dwarf metallicity distribution with that of FGK dwarfs.

Abstract

Knowledge of the metallicities of M dwarfs rests predominantly on the photometric calibration of Bonfils and collaborators, which predicts that M dwarfs in the solar neighborhood, including those with known planets, are systematically metal-poor compared to their higher-mass counterparts. We test this prediction using a volume-limited sample of low-mass stars, together with a subset of M dwarfs with high-metallicity, F, G amd K wide binary companions. We find that the Bonfils et al. photometric calibration systematically underestimates the metallicities of our high-metallicity M dwarfs by an average of 0.32 dex. We derive a new photometric metallicity calibration and show that M dwarfs with planets appear to be systematically metal-rich, a result that is consistent with the metallicity distribution of FGK dwarfs with planets.