The CARMENES search for exoplanets around M dwarfs. The He I triplet at 10830 Å across the M dwarf sequence

The He I infrared (IR) triplet at 10 830 Å is an important activity indicator for the Sun and in solar-type stars, however, it has rarely been studied in relation to M dwarfs to date. In this study, we use the time-averaged spectra of 319 single stars with spectral types ranging from M0.0 V to M9.0...

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Detalles Bibliográficos
Autores: Fuhrmeister, Birgit, Czesla, S., Hildebrandt, L., Nagel, Evangelos, Schmitt, Jürgen H. M. M., Hintz, D., Johnson, E.N., Sanz-Forcada, J., Schöfer, P., Jeffers, Sandra V., Caballero, J. A., Zechmeister, Mathias, Reiners, Ansgar, Ribas, Ignasi, Amado, Pedro J., Quirrenbach, Andreas, Bauer, Florian Franz, Béjar, Victor J. S., Cortés-Contreras, M., Díez-Alonso, E., Galadí-Enriquez, D., Guenther, E. W., Kaminski, Adrian, Kürster, M., Lafarga, M., Montes, David, Dreizler, Stefan
Tipo de recurso: artículo
Estado:Versión publicada
Fecha de publicación:2019
País:España
Institución:Consejo Superior de Investigaciones Científicas (CSIC)
Repositorio:DIGITAL.CSIC. Repositorio Institucional del CSIC
OAI Identifier:oai:digital.csic.es:10261/204206
Acceso en línea:http://hdl.handle.net/10261/204206
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 an important activity indicator for the Sun and in solar-type stars, however, it has rarely been studied in relation to M dwarfs to date. In this study, we use the time-averaged spectra of 319 single stars with spectral types ranging from M0.0 V to M9.0 V obtained with the CARMENES high resolution optical and near-infrared spectrograph at Calar Alto to study the properties of the He I IR triplet lines. In quiescence, we find the triplet in absorption with a decrease of the measured pseudo equivalent width (pEW) towards later sub-types. For stars later than M5.0 V, the He I triplet becomes undetectable in our study. This dependence on effective temperature may be related to a change in chromospheric conditions along the M dwarf sequence. When an emission in the triplet is observed, we attribute it to flaring. The absence of emission during quiescence is consistent with line formation by photo-ionisation and recombination, while flare emission may be caused by collisions within dense material. The He I triplet tends to increase in depth according to increasing activity levels, ultimately becoming filled in; however, we do not find a correlation between the pEW(He IR) and X-ray properties. This behaviour may be attributed to the absence of very inactive stars (LX/Lbol < -5.5) in our sample or to the complex behaviour with regard to increasing depth and filling in.© ESO 2019

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