The CARMENES search for exoplanets around M dwarfs

Different roads to radii and masses of the target stars^⋆

¹ Hamburger Sternwarte, Gojenbergsweg 112, 21029 Hamburg, Germany
e-mail: aschweitzer@hs.uni-hamburg.de
² Departamento de Astrofísica, Centro de Astrobiología (CSIC-INTA), ESAC Campus, Camino Bajo del Castillo s/n, 28691 Villanueva de la Cañada, Madrid, Spain
³ Departamento de Física de la Tierra y Astrofísica and UPARCOS-UCM (Unidad de Física de Partículas y del Cosmos de la UCM), Facultad de Ciencias Físicas, Universidad Complutense de Madrid, 28040 Madrid, Spain
⁴ Instituto de Astrofísica de Canarias, Vía Láctea s/n, 38205 La Laguna, Tenerife, Spain
⁵ Departamento de Astrofísica, Universidad de La Laguna, 38206 La Laguna, Tenerife, Spain
⁶ Instituto Nacional de Astrofísica, Óptica y Electrónica, Luis Enrique Erro 1, Sta. Ma. Tonantzintla, Puebla, Mexico
⁷ Max-Planck-Institut für Astronomie, Königstuhl 17, 69117 Heidelberg, Germany
⁸ Centro de Astrobiología (CSIC-INTA), Carretera de Ajalvir km 4, 28850 Torrejón de Ardoz, Madrid, Spain
⁹ Institut de Ciències de l’Espai (CSIC-IEEC), Can Magrans s/n, Campus UAB, 08193 Bellaterra, Barcelona, Spain
¹⁰ Institut d’Estudis Espacials de Catalunya (IEEC), C/ Gran Capità 2-4, 08034 Barcelona, Spain
¹¹ Institut für Astrophysik, Georg-August-Universität, Friedrich-Hund-Platz 1, 37077 Göttingen, Germany
¹² Landessternwarte, Zentrum für Astronomie der Universtät Heidelberg, Königstuhl 12, 69117 Heidelberg, Germany
¹³ Instituto de Astrofísica de Andalucía (IAA-CSIC), Glorieta de la Astronomía s/n, 18008 Granada, Spain
¹⁴ Centro Astronómico Hispano-Alemán (CSIC-MPG), Observatorio Astronómico de Calar Alto, Sierra de los Filabres, 04550 Gérgal, Almería, Spain
¹⁵ School of Physics and Astronomy, Queen Mary, University of London, 327 Mile End Road, London E1 4NS, UK
¹⁶ Thüringer Landessternwarte Tautenburg, Sternwarte 5, 07778 Tautenburg, Germany

Received: 21 December 2018
Accepted: 25 March 2019

Abstract

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 R_⊙ <  R <  0.6 R_⊙ with an error of 2–3% and our masses cover 0.09 ℳ_⊙ < ℳ< 0.6ℳ_⊙ 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.