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 th...

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Detalles Bibliográficos
Autores: Fuhrmeister, Birgit, Czesla, S., Hildebrandt, L., Nagel, Evangelos, Schmitt, Jürgen H. M. M., Jeffers, Sandra V., Caballero, J. A., Hintz, D., Johnson, E.N., Schöfer, P., Zechmeister, Mathias, Reiners, Ansgar, Ribas, Ignasi, Amado, Pedro J., Quirrenbach, Andreas, Nortmann, L., Bauer, Florian Franz, Béjar, Victor J. S., Cortés-Contreras, M., Dreizler, Stefan, Galadí-Enriquez, D., Hatzes, Artie P., Kaminski, Adrian, Kürster, M., Lafarga, M., Montes, David
Tipo de recurso: artículo
Estado:Versión publicada
Fecha de publicación:2020
País:España
Institución:Consejo Superior de Investigaciones Científicas (CSIC)
Repositorio:DIGITAL.CSIC. Repositorio Institucional del CSIC
OAI Identifier:oai:digital.csic.es:10261/222716
Acceso en línea:http://hdl.handle.net/10261/222716
Access Level:acceso abierto
Palabra clave:Stars: activity
Stars: chromospheres
Stars: late-type
Descripción
Sumario: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 Hα in emission. Therefore, we find detectable He I variability in 78% of the sub-sample of stars with Hα 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 Hα line variations tend to be correlated, with Hα 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. © 2020 ESO.

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