The CARMENES search for exoplanets around M dwarfs

Abstract

We present precise photospheric parameters of 282 M dwarfs determined from fitting the most recent version of PHOENIX models to high-resolution CARMENES spectra in the visible (0.52–0.96 μm) and NIR wavelength range (0.96–1.71 μm). With its aim to search for habitable planets around M dwarfs, several planets of different masses have been detected. The characterization of the target sample is important for the ability to derive and constrain the physical properties of any planetary systems that are detected. As a continuation of previous work in this context, we derived the fundamental stellar parameters effective temperature, surface gravity, and metallicity of the CARMENES M-dwarf targets from PHOENIX model fits using a χ2 method. We calculated updated PHOENIX stellar atmosphere models that include a new equation of state to especially account for spectral features of low-temperature stellar atmospheres as well as new atomic and molecular line lists. We show the importance of selecting magnetically insensitive lines for fitting to avoid effects of stellar activity in the line profiles. For the first time, we directly compare stellar parameters derived from multiwavelength range spectra, simultaneously observed for the same star. In comparison with literature values we show that fundamental parameters derived from visible spectra and visible and NIR spectra combined are in better agreement than those derived from the same spectra in the NIR alone.

CARMENES input catalogue of M dwarfs

“…RUWE < 1.41; Fig. 7) and do not have close companions (Cortés-Contreras et al 2017;Baroch et al 2018), extreme values of metallicity (Alonso-Floriano et al 2015a;Passegger et al 2018Passegger et al , 2019Passegger et al , 2020, young ages (Tal-Or et al 2018), or large-amplitude photometric variability (Díez . We also fitted another quadratic polynomial to the M G versus G−J data Notes.…”

“…20). Next, we compared our T eff from VOSA with the values from the works referred to in the previous paragraph, except from Gaia Collaboration (2018a), plus from Passegger et al (2019), who in turn compared their T eff with those from Rojas-Ayala et al (2012), Gaidos & Mann (2014), Maldonado et al (2015, Rajpurohit et al (2018a), . From the top left panel in Fig.…”

“…Determining precise stellar parameters of M dwarfs and how their uncertainties propagate to those of their planets is, therefore, of paramount importance. Many efforts have been undertaken in this respect, including empirical determination of masses, radii, and their relation to luminosity (Veeder 1974;Henry & McCarthy 1993;Chabrier & Baraffe 1997;Delfosse et al 2000;Bonfils et al 2005;Mann et al 2015Mann et al , 2019Terrien et al 2015;Benedict et al 2016;Schweitzer et al 2019), effective temperature, surface gravity, and metallicity (Casagrande et al 2008;Rojas-Ayala et al 2013;Montes et al 2018;Passegger et al 2018Passegger et al , 2019Rajpurohit et al 2018a), or activity and rotation periods (Stauffer & Hartmann 1986;Reid et al 1995;Hawley et al 1996Hawley et al , 2014Morales et al 2008;Newton et al 2015;Jeffers et al 2018;Díez Alonso et al 2019;Schöfer et al 2019).…”

Stellar atmospheric parameters of FGK-type stars from high-resolution optical and near-infrared CARMENES spectra

“…This allowed us to prevent wrong line identification throughout the visual inspection of the reference spectra. Further details on the telluric correction of the CARMENES spectra can be found in Passegger et al (2019). A full description of the correction will appear in a forthcoming publication of the CARMENES series (Nagel et al 2019).…”

The CARMENES search for exoplanets around M dwarfs

“…We have corrected an error in Passegger et al (2019) in the calculation of the stellar surface gravity log g from literature masses and radii provided by Gaidos & Mann (2014) and Mann et al (2015). The mass and radius were interchanged in the formula, g = GM/R 2 which resulted into too high log g values for the earliest M dwarfs.…”