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Centro de Astrofísica da Universidade do Porto

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

Abstract.
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
Barcelona, Spain
June 2012

Type: Poster

Institute of Astrophysics and Space Sciences

Institute of Astrophysics and Space Sciences (IA) is a new but long anticipated research infrastructure with a national dimension. It embodies a bold but feasible vision for the development of Astronomy, Astrophysics and Space Sciences in Portugal, taking full advantage and fully realizing the potential created by the national membership of the European Space Agency (ESA) and the European Southern Observatory (ESO). IA resulted from the merging the two most prominent research units in the field in Portugal: the Centre for Astrophysics of the University of Porto (CAUP) and the Center for Astronomy and Astrophysics of the University of Lisbon (CAAUL). It currently hosts more than two-thirds of all active researchers working in Space Sciences in Portugal, and is responsible for an even greater fraction of the national productivity in international ISI journals in the area of Space Sciences. This is the scientific area with the highest relative impact factor (1.65 times above the international average) and the field with the highest average number of citations per article for Portugal.

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