Metallicity of M dwarfs: A comparative study of photometric metallicity scales

V. Neves, X. Bonfils, N. C. Santos

Abstract.
The determination of the stellar parameters of M dwarfs is of prime importance in the fields of galactic, stellar and planetary astronomy. M stars are the least studied galactic component regarding their fundamental parameters. Yet, they are the most numerous stars in the galaxy and contribute to more than half of its total (baryonic) mass. In particular, we are interested in their metallicity in order to study the star-planet connection and to refine the planetary parameters. Here we present a comparative test of five metallicity calibrations of M dwarfs proposed in the literature. Our test sample is made of 22 M dwarfs, companion of widely separated (> 5 arcsec) F-, G- or K- dwarfs with known or newly measured metallicity. We included M dwarfs with reliable V photometry only by restricting our sample to stars with V uncertainty lower than ~0.03 dex. Among all calibrations, we find that Schlaufman & Laughlin (2010) provides a lower offset and residuals against our sample and, ultimately, we used that larger sample to update and marginally improve their calibration. Despite better V photometry than used in previous studies the dispersion remains largely in excess given [Fe/H] and photometric uncertainties, suggesting it has physical roots. Finally, we also present preliminary work on a new, high-precision spectroscopic calibration involving the direct measurement of high-resolution spectra of M dwarfs.

XXI Encontro Nacional de Astronomia e Astrofisica
Coimbra, Portugal
setembro 2011

Tipo: Comunicação oral