The CARMENES search for exoplanets around M dwarfs

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 < 0.6 M 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.Article published by EDP Sciences A68, page 1 of 16 A&A 625, A68 (2019)

The CARMENES search for exoplanets around M dwarfs

“…Despite the great similarity between the two stars, we determined slightly different mass values for the A and B stellar components (0.69±0.07 and 0.64±0.07 M , respectively), suggesting that the A stellar member is about 7% more massive than the B component. Furthermore, they are also consistent with the masses derived by Schweitzer et al (2019).…”

“…The best-fit orbital period is P = 24.40 ± 0.04 d, and the planet has a minimum mass of 9.2 ± 1.1 M ⊕ (computed by adopting the mass of 0.64 ± 0.07 M for the parent star, as determined here). This planetary minimum mass would be 8.9±1.2 M ⊕ if the stellar mass determined by Schweitzer et al (2019) were adopted instead. The planet candidate GJ 338 Bb is located at an orbital separation of 0.142 ± 0.014 au from its parent M0-type star, and despite its proximity, the planetary orbit appears to be slightly eccentric (e = 0.25 ± 0.13), although given the error bar of the eccentricity, the orbit is also compatible with an almost circular orbit.…”

“…To find the best Keplerian solution to the orbit of the stellar pair, and based on our knowledge of the system, any orbital solution has to reproduce the observed astrometric and radial velocity data and to be compliant with the following: a) The total mass of the system should fall in the interval 1.03-1.38 M , which is obtained from the 1σ smallest and largest individual values assigned to each component in Table B.1 of Schweitzer et al (2019). According to these authors, the most likely total mass of the system is 1.187 ± 0.063 M .…”

“…(3) Derived by adopting the mass of 0.64 ± 0.07 M for the parent star. (4) Derived with stellar mass determined bySchweitzer et al (2019). (5) For Bond albedo in the interval 0.65-0.0.…”

The CARMENES search for exoplanets around M dwarfs

“…These efforts are motivated by the fact that M dwarfs Notes. 2MASS: Skrutskie et al (2006); Cab16 Caballero et al (2016); DA18: Díez Alonso et al (2019); Gaia Gaia Collaboration et al (Gaia DR2;; Pas18: Passegger et al (2018); HIP: Perryman et al (1997); Rei18: Reiners et al (2018b); Ros39: Ross (1939); Schw19: Schweitzer et al (2019).…”