Passegger, V. M.; Reiners, A.; Jeffers, S. V.; Wende-von Berg, S.; Schöfer, P.; Caballero, J. A.; Schweitzer, A.; Amado, P. J.; Béjar, V. J. S.; Cortés-Contreras, M.; Hatzes, A. P.; Kürster, M.; Montes, D.; Pedraz, S.; Quirrenbach, A.; Ribas, I.; Seifert, W.
Bibliographical reference
Astronomy and Astrophysics, Volume 615, id.A6, 11 pp.
Description
Context. The new CARMENES instrument comprises two high-resolution and
high-stability spectrographs that are used to search for habitable
planets around M dwarfs in the visible and near-infrared regime via the
Doppler technique. Aims: Characterising our target sample is
important for constraining the physical properties of any planetary
systems that are detected. The aim of this paper is to determine the
fundamental stellar parameters of the CARMENES M-dwarf target sample
from high-resolution spectra observed with CARMENES. We also include
several M-dwarf spectra observed with other high-resolution
spectrographs, that is CAFE, FEROS, and HRS, for completeness.
Methods: We used a χ2 method to derive the stellar
parameters effective temperature Teff, surface gravity logg,
and metallicity [Fe/H] of the target stars by fitting the most recent
version of the PHOENIX-ACES models to high-resolution spectroscopic
data. These stellar atmosphere models incorporate a new equation of
state to describe spectral features of low-temperature stellar
atmospheres. Since Teff, logg, and [Fe/H] show degeneracies,
the surface gravity is determined independently using stellar
evolutionary models. Results: We derive the stellar parameters
for a total of 300 stars. The fits achieve very good agreement between
the PHOENIX models and observed spectra. We estimate that our method
provides parameters with uncertainties of σTeff = 51 K,
σlog g = 0.07, and σ[Fe/H] = 0.16, and
show that atmosphere models for low-mass stars have significantly
improved in the last years. Our work also provides an independent test
of the new PHOENIX-ACES models, and a comparison for other methods using
low-resolution spectra. In particular, our effective temperatures agree
well with literature values, while metallicities determined with our
method exhibit a larger spread when compared to literature results.
Full Table A.1 is only available at the CDS via anonymous ftp to
http://cdsarc.u-strasbg.fr (
http://130.79.128.5) or via
http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/615/A6
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