On the Metal-Richness of M Dwarfs with Planets

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.

ApJ Accepted (April 19, 2009). 4 pages, 4 figures, 2 tables. Version 2 fixes an error in the order of the text. The last two paragraphs of Section 2.1 are moved to their correct location at the end of Section 3. Removed mention of dashed line in Figure 4 caption