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The CARMENES search for exoplanets around M dwarfs: variability of the He I line at 10 830 Å

The He I infrared (IR) triplet at 10 830 Å is known as an activity indicator in solar-type stars and has become a primary diagnostic in exoplanetary transmission spectroscopy. He I IR lines are a tracer of the stellar extreme-ultraviolet irradiation from the transition region and corona. We study t...

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Main Authors: Fuhrmeister, Birgit (Author) , Czesla, S. (Author) , Hildebrandt, L. (Author) , Nagel, E. (Author) , Schmitt, J. H. M. M. (Author) , Jeffers, S. V. (Author) , Caballero, J. A. (Author) , Hintz, D. (Author) , Johnson, E. N. (Author) , Schöfer, P. (Author) , Zechmeister, M. (Author) , Reiners, A. (Author) , Ribas, I. (Author) , Amado, P. J. (Author) , Quirrenbach, Andreas (Author) , Nortmann, L. (Author) , Bauer, F. F. (Author) , Béjar, V. J. S. (Author) , Cortés-Contreras, M. (Author) , Dreizler, S. (Author) , Galadí-Enríquez, D. (Author) , Hatzes, A. P. (Author) , Kaminski, Adrian (Author) , Kürster, M. (Author) , Lafarga, M. (Author) , Montes, D. (Author)
Format: Article (Journal)
Language:English
Published: 10 August 2020
In: Astronomy and astrophysics
Year: 2020, Volume: 640
ISSN:1432-0746
DOI:10.1051/0004-6361/202038279
Online Access:Verlag, lizenzpflichtig, Volltext: https://doi.org/10.1051/0004-6361/202038279
Verlag, lizenzpflichtig, Volltext: https://www.aanda.org/articles/aa/abs/2020/08/aa38279-20/aa38279-20.html
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Author Notes:B. Fuhrmeister, S. Czesla, L. Hildebrandt, E. Nagel, J.H.M.M. Schmitt, S.V. Jeffers, J.A. Caballero, D. Hintz, E.N. Johnson, P. Schöfer, M. Zechmeister, A. Reiners, I. Ribas, P.J. Amado, A. Quirrenbach, L. Nortmann, F.F. Bauer, V.J.S. Béjar, M. Cortés-Contreras, S. Dreizler, D. Galadí-Enríquez, A.P. Hatzes, A. Kaminski, M. Kürster, M. Lafarga, and D. Montes
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Summary:The He I infrared (IR) triplet at 10 830 Å is known as an activity indicator in solar-type stars and has become a primary diagnostic in exoplanetary transmission spectroscopy. He I IR lines are a tracer of the stellar extreme-ultraviolet irradiation from the transition region and corona. We study the variability of the He I triplet lines in a spectral time series of 319 M dwarf stars that was obtained with the CARMENES high-resolution optical and near-infrared spectrograph at Calar Alto. We detect He I IR line variability in 18% of our sample stars, all of which show H<i>α<i/> in emission. Therefore, we find detectable He I variability in 78% of the sub-sample of stars with H<i>α<i/> emission. Detectable variability is strongly concentrated in the latest spectral sub-types, where the He I lines during quiescence are typically weak. The fraction of stars with detectable He I variation remains lower than 10% for stars earlier than M3.0 V, while it exceeds 30% for the later spectral sub-types. Flares are accompanied by particularly pronounced line variations, including strongly broadened lines with red and blue asymmetries. However, we also find evidence for enhanced He I absorption, which is potentially associated with increased high-energy irradiation levels at flare onset. Generally, He I and H<i>α<i/> line variations tend to be correlated, with H<i>α<i/> being the most sensitive indicator in terms of pseudo-equivalent width variation. This makes the He I triplet a favourable target for planetary transmission spectroscopy.
Item Description:Gesehen am 18.09.2020
Physical Description:Online Resource
ISSN:1432-0746
DOI:10.1051/0004-6361/202038279

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