Metallicity of M dwarfs: The link to exoplanets

Abstract

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 most 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. As a preliminary result we present a test of the metallicity calibrations of Bonfils et al. Following B05, three papers with different calibrations were published: JA09, SL10, and Rojas-Ayala et al. (2010) (hereafter RA10). Each work claims a calibration with a better precision than the previous ones, and in general, poor V photometry is identified as a serious limitation. In order to address the photometric limitation, only M stars with precise V photometry ( σ < 0.04 mag) were selected. Most stars have V magnitude uncertainties of 0.01 or 0.02 mag. Note that the RA10 calibration was not tested because it requires IR indices that we do not have. This test will be done in the near future.We found that the metallicity values of our stars (obtained from the FGK primary component) are in reasonable agreement with the [Fe/H] values obtained with all calibrations, as can be seen in Fig. 1. However, our calibrators are found to be more metal poor (on average) than both JA09 and SL10 calibrations.A better photometry did not improve the dispersion measured around the different calibrations. This means that precision on V photometry may not be the main limitation in the derivation of the [Fe/H] calibration. Table 1. shows a quantitative comparison between the calibrations. We note that the rms, RM S P and the R 2 ap values were offset-corrected. In general, the calibrations have similar offsets, rms, RM S P , and correlation coefficients. 443at https://www.cambridge.org/core/terms. https://doi