Bibcode
Schöfer, P.; Jeffers, S. V.; Reiners, A.; Shulyak, D.; Fuhrmeister, B.; Johnson, E. N.; Zechmeister, M.; Ribas, I.; Quirrenbach, A.; Amado, P. J.; Caballero, J. A.; Anglada-Escudé, G.; Bauer, F. F.; Béjar, V. J. S.; Cortés-Contreras, M.; Dreizler, S.; Guenther, E. W.; Kaminski, A.; Kürster, M.; Lafarga, M.; Montes, D.; Morales, J. C.; Pedraz, S.; Tal-Or, L.
Bibliographical reference
Astronomy and Astrophysics, Volume 623, id.A44, 17 pp.
Advertised on:
3
2019
Journal
Citations
87
Refereed citations
83
Description
Context. The Calar Alto high-Resolution search for M dwarfs with
Exo-earths with Near-infrared and optical Echelle Spectrographs
(CARMENES) survey is searching for Earth-like planets orbiting M dwarfs
using the radial velocity method. Studying the stellar activity of the
target stars is important to avoid false planet detections and to
improve our understanding of the atmospheres of late-type stars.
Aims: In this work we present measurements of activity indicators at
visible and near-infrared wavelengths for 331 M dwarfs observed with
CARMENES. Our aim is to identify the activity indicators that are most
sensitive and easiest to measure, and the correlations among these
indicators. We also wish to characterise their variability.
Methods: Using a spectral subtraction technique, we measured
pseudo-equivalent widths of the He I D3, Hα, He I
λ10833 Å, and Pa β lines, the Na I D doublet, and the
Ca II infrared triplet, which have a chromospheric component in active M
dwarfs. In addition, we measured an index of the strength of two TiO and
two VO bands, which are formed in the photosphere. We also searched for
periodicities in these activity indicators for all sample stars using
generalised Lomb-Scargle periodograms. Results: We find that the
most slowly rotating stars of each spectral subtype have the strongest
Hα absorption. Hα is correlated most strongly with He I
D3, whereas Na I D and the Ca II infrared triplet are also
correlated with Hα. He I λ10833 Å and Paβ show
no clear correlations with the other indicators. The TiO bands show an
activity effect that does not appear in the VO bands. We find that the
relative variations of Hα and He I D3 are smaller for
stars with higher activity levels, while this anti-correlation is weaker
for Na I D and the Ca II infrared triplet, and is absent for He I
λ10833 Å and Paβ. Periodic variation with the rotation
period most commonly appears in the TiO bands, Hα, and in the Ca
II infrared triplet.
The full version of Table A.1 is only available at the CDS via anonymous
ftp to http://cdsarc.u-strasbg.fr
(ftp://130.79.128.5) or via http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/623/A44
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