The CARMENES search for exoplanets around M dwarfs Radial-velocity variations of active stars in visual-channel spectra

Context. Previous simulations predicted the activity-induced radial-velocity (RV) variations of M dwarfs to range from similar to 1 cm s(-1) to similar to 1 km s(-1), depending on various stellar and activity parameters. Aims. We investigate the observed relations between RVs, stellar activity, and...

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Autor: Montes Gutiérrez, David
Tipo de recurso: artículo
Fecha de publicación:2018
País:España
Institución:Universidad Complutense de Madrid (UCM)
Repositorio:Docta Complutense
Idioma:inglés
OAI Identifier:oai:docta.ucm.es:20.500.14352/12248
Acceso en línea:https://hdl.handle.net/20.500.14352/12248
Access Level:acceso abierto
Palabra clave:52
H-alpha emission
Low mass stars
Planet
Rotation
Jitter
Systems
Astrofísica
Astronomía (Física)
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spelling The CARMENES search for exoplanets around M dwarfs Radial-velocity variations of active stars in visual-channel spectraMontes Gutiérrez, David52H-alpha emissionLow mass starsPlanetRotationJitterSystemsAstrofísicaAstronomía (Física)Context. Previous simulations predicted the activity-induced radial-velocity (RV) variations of M dwarfs to range from similar to 1 cm s(-1) to similar to 1 km s(-1), depending on various stellar and activity parameters. Aims. We investigate the observed relations between RVs, stellar activity, and stellar parameters of M dwarfs by analyzing CARMENES high-resolution visual-channel spectra (0.5-1 mu m), which were taken within the CARMENES RV planet survey during its first 20 months of operation. Methods. During this time, 287 of the CARMENES-sample stars were observed at least five times. From each spectrum we derived a relative RV and a measure of chromospheric Ha emission. In addition, we estimated the chromatic index (CRX) of each spectrum, which is a measure of the RV wavelength dependence. Results. Despite having a median number of only 11 measurements per star, we show that the RV variations of the stars with RV scatter of >10 m s(-1) and a projected rotation velocity upsilon sin i > 2 km s(-1) are caused mainly by activity. We name these stars "active RV-loud stars" and find their occurrence to increase with spectral type: from similar to 3% for early-type M dwarfs (M0.0-2.5 V) through similar to 30% for mid-type M dwarfs (M3.0-5.5 V) to >50% for late-type M dwarfs (M6.0-9.0 V). Their RV-scatter amplitude is found to be correlated mainly with upsilon sin i. For about half of the stars, we also find a linear RV-CRX anticorrelation, which indicates that their activity-induced RV scatter is lower at longer wavelengths. For most of them we can exclude a linear correlation between RV and H alpha emission. Conclusions. Our results are in agreement with simulated activity-induced RV variations in M dwarfs. The RV variations of most active RV-loud M dwarfs are likely to be caused by dark spots on their surfaces, which move in and out of view as the stars rotate.EDP Sciences S AUniversidad Complutense de Madrid20182018-06-2520182018-06-25journal articlehttp://purl.org/coar/resource_type/c_6501info:eu-repo/semantics/articleapplication/pdfhttps://hdl.handle.net/20.500.14352/12248reponame:Docta Complutenseinstname:Universidad Complutense de Madrid (UCM)Inglésengopen accesshttp://purl.org/coar/access_right/c_abf2info:eu-repo/semantics/openAccessoai:docta.ucm.es:20.500.14352/122482026-06-02T12:44:21Z
dc.title.none.fl_str_mv The CARMENES search for exoplanets around M dwarfs Radial-velocity variations of active stars in visual-channel spectra
title The CARMENES search for exoplanets around M dwarfs Radial-velocity variations of active stars in visual-channel spectra
spellingShingle The CARMENES search for exoplanets around M dwarfs Radial-velocity variations of active stars in visual-channel spectra
Montes Gutiérrez, David
52
H-alpha emission
Low mass stars
Planet
Rotation
Jitter
Systems
Astrofísica
Astronomía (Física)
title_short The CARMENES search for exoplanets around M dwarfs Radial-velocity variations of active stars in visual-channel spectra
title_full The CARMENES search for exoplanets around M dwarfs Radial-velocity variations of active stars in visual-channel spectra
title_fullStr The CARMENES search for exoplanets around M dwarfs Radial-velocity variations of active stars in visual-channel spectra
title_full_unstemmed The CARMENES search for exoplanets around M dwarfs Radial-velocity variations of active stars in visual-channel spectra
title_sort The CARMENES search for exoplanets around M dwarfs Radial-velocity variations of active stars in visual-channel spectra
dc.creator.none.fl_str_mv Montes Gutiérrez, David
author Montes Gutiérrez, David
author_facet Montes Gutiérrez, David
author_role author
dc.contributor.none.fl_str_mv Universidad Complutense de Madrid
dc.subject.none.fl_str_mv 52
H-alpha emission
Low mass stars
Planet
Rotation
Jitter
Systems
Astrofísica
Astronomía (Física)
topic 52
H-alpha emission
Low mass stars
Planet
Rotation
Jitter
Systems
Astrofísica
Astronomía (Física)
description Context. Previous simulations predicted the activity-induced radial-velocity (RV) variations of M dwarfs to range from similar to 1 cm s(-1) to similar to 1 km s(-1), depending on various stellar and activity parameters. Aims. We investigate the observed relations between RVs, stellar activity, and stellar parameters of M dwarfs by analyzing CARMENES high-resolution visual-channel spectra (0.5-1 mu m), which were taken within the CARMENES RV planet survey during its first 20 months of operation. Methods. During this time, 287 of the CARMENES-sample stars were observed at least five times. From each spectrum we derived a relative RV and a measure of chromospheric Ha emission. In addition, we estimated the chromatic index (CRX) of each spectrum, which is a measure of the RV wavelength dependence. Results. Despite having a median number of only 11 measurements per star, we show that the RV variations of the stars with RV scatter of >10 m s(-1) and a projected rotation velocity upsilon sin i > 2 km s(-1) are caused mainly by activity. We name these stars "active RV-loud stars" and find their occurrence to increase with spectral type: from similar to 3% for early-type M dwarfs (M0.0-2.5 V) through similar to 30% for mid-type M dwarfs (M3.0-5.5 V) to >50% for late-type M dwarfs (M6.0-9.0 V). Their RV-scatter amplitude is found to be correlated mainly with upsilon sin i. For about half of the stars, we also find a linear RV-CRX anticorrelation, which indicates that their activity-induced RV scatter is lower at longer wavelengths. For most of them we can exclude a linear correlation between RV and H alpha emission. Conclusions. Our results are in agreement with simulated activity-induced RV variations in M dwarfs. The RV variations of most active RV-loud M dwarfs are likely to be caused by dark spots on their surfaces, which move in and out of view as the stars rotate.
publishDate 2018
dc.date.none.fl_str_mv 2018
2018-06-25
2018
2018-06-25
dc.type.none.fl_str_mv journal article
http://purl.org/coar/resource_type/c_6501
dc.type.openaire.fl_str_mv info:eu-repo/semantics/article
format article
dc.identifier.none.fl_str_mv https://hdl.handle.net/20.500.14352/12248
url https://hdl.handle.net/20.500.14352/12248
dc.language.none.fl_str_mv Inglés
eng
language_invalid_str_mv Inglés
language eng
dc.rights.none.fl_str_mv open access
http://purl.org/coar/access_right/c_abf2
dc.rights.openaire.fl_str_mv info:eu-repo/semantics/openAccess
rights_invalid_str_mv open access
http://purl.org/coar/access_right/c_abf2
eu_rights_str_mv openAccess
dc.format.none.fl_str_mv application/pdf
dc.publisher.none.fl_str_mv EDP Sciences S A
publisher.none.fl_str_mv EDP Sciences S A
dc.source.none.fl_str_mv reponame:Docta Complutense
instname:Universidad Complutense de Madrid (UCM)
instname_str Universidad Complutense de Madrid (UCM)
reponame_str Docta Complutense
collection Docta Complutense
repository.name.fl_str_mv
repository.mail.fl_str_mv
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score 15,301629

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