The CARMENES search for exoplanets around M dwarfs: different roads to radii and masses of the target stars

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Aims. We determine the radii and masses of 293 nearby, bright M dwarfs of the CARMENES survey. This is the first time that such a large and homogeneous high-resolution (R > 80, 000) spectroscopic survey has been used to derive these fundamental stellar parameters. Methods. We derived the radii using Stefan-Boltzmann’s law. We obtained the required effective temperatures T_(eff) from a spectral analysis and we obtained the required luminosities L from integrated broadband photometry together with the Gaia DR2 parallaxes. The mass was then determined using a mass-radius relation that we derived from eclipsing binaries known in the literature. We compared this method with three other methods: (1) We calculated the mass from the radius and the surface gravity log g, which was obtained from the same spectral analysis as T_(eff). (2) We used a widely used infrared mass-magnitude relation. (3) We used a Bayesian approach to infer stellar parameters from the comparison of the absolute magnitudes and colors of our targets with evolutionary models. Results. Between spectral types M0 V and M7 V our radii cover the range 0.1 Rꙩ < R < 0.6 Rꙩ with an error of 2–3% and our masses cover 0.09 Mꙩ < M < 0.6 Mꙩ with an error of 3–5%. We find good agreement between the masses determined with these different methods for most of our targets. Only the masses of very young objects show discrepancies. This can be well explained with the assumptions that we used for our methods.
© ESO 2019. We thank the anonymous referee for a very quick and very constructive report. Furthermore, we thank T. Boyajian and A. W. Mann for helpful discussions during the preparation of this manuscript. CARMENES is an instrument for the Centro Astronómico Hispano-Alemán de Calar Alto (CAHA, Almería, Spain). CARMENES is funded by the German Max-PlanckGesellschaft (MPG), the Spanish Consejo Superior de Investigaciones Científicas (CSIC), the European Union through FEDER/ERDF FICTS-2011-02 funds, and the members of the CARMENES Consortium (Max-Planck-Institut für Astronomie, Instituto de Astrofísica de Andalucía, Landessternwarte Königstuhl, Institut de Ciències de l’Espai, Institut für Astrophysik Göttingen, Universidad Complutense de Madrid, Thüringer Landessternwarte Tautenburg, Instituto de Astrofísica de Canarias, Hamburger Sternwarte, Centro de Astrobiología and Centro Astronómico Hispano-Alemán), with additional contributions by the Spanish Ministry of Science through projects AYA2016-79425-C3-1/2/3- P, ESP2016-80435-C2-1-R, AYA2015-69350-C3-2-P, and AYA2018-84089, the Spanish Ministerio de Educación y Formación Profesional through fellowship FPU15/01476, the German Science Foundation through the Major Research Instrumentation Programme and DFG Research Unit FOR2544 “Blue Planets around Red Stars”, the Klaus Tschira Stiftung, the states of Baden-Württemberg and Niedersachsen, and by the Junta de Andalucía. CdB acknowledges the funding of his sabbatical position through the Mexican national council for science and technology (CONACYT grant CVU No. 448248). This publication makes use of VOSA, developed under the Spanish Virtual Observatory project, the VizieR catalog access tool (Ochsenbein et al. 2000) and the SIMBAD database (Wenger et al. 2000), operated both at CDS, Strasbourg, France, and the interactive graphical viewer and editor for tabular data TOPCAT (Taylor 2005).
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