A new visual spectroscopic metallicity scale for M dwarfs: a 'Super-Index' approach
V. Neves, X. Bonfils, N. C. Santos, X. Delfosse, T. Forveille, F. Allard, S. Udry
Several recent publications propose calibrations that provide the metallicity of an M dwarf from its Ks band absolute magnitude and its V-Ks color, but disagree at the ±0.1 dex level. We compared these calibrations using a sample of 23 M dwarfs, which we selected as wide (>5 arcsec) companions of F-, G-, or K-dwarfs with metallicities measured on a homogeneous scale. We also include only M dwarfs which have V band photometry measured to better than 0.03 mag. The results are used to refine the existing calibrations. We also present a new M dwarf metallicity calibration based on the measurement of 4441 spectroscopic lines of 55 stars taken from high-resolution HARPS GTO M dwarf spectra. This "Super Index" calibration uses initial [Fe/H] values obtained with our photometric calibration (Neves 2011). We refine the precision of the calibration to a dispersion value lower than 0.10 dex. Using this calibration we study the [Fe/H] correlation with the frequency of planets and with the planetary parameters (planetary mass, period, and eccentricity) of the 103 star HARPS GTO M dwarf sample.
17th Cambridge Workshop on Cool Stars, Stellar Systems and the Sun