Magnetism, rotation, and nonthermal emission in cool stars: average magnetic field measurements in 292 M dwarfs
Stellar dynamos generate magnetic fields that are of fundamental importance to the variability and evolution of Sun-like and low-mass stars, and for the development of their planetary systems. As a key to understanding stellar dynamos, empirical relations between stellar parameters and magnetic fiel...
| Autores: | , , |
|---|---|
| Tipo de recurso: | artículo |
| Fecha de publicación: | 2022 |
| País: | España |
| Institución: | Universidad Complutense de Madrid (UCM) |
| Repositorio: | Docta Complutense |
| Idioma: | inglés |
| OAI Identifier: | oai:docta.ucm.es:20.500.14352/72652 |
| Acceso en línea: | https://hdl.handle.net/20.500.14352/72652 |
| Access Level: | acceso abierto |
| Palabra clave: | 52 Pre-main-sequence Stellar rotation Model chromospheres Input catalog Active stars H-alpha Solar Mass Line Evolution Astrofísica |
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Magnetism, rotation, and nonthermal emission in cool stars: average magnetic field measurements in 292 M dwarfsMontes Gutiérrez, DavidCaballero, J. A.otros, ...52Pre-main-sequenceStellar rotationModel chromospheresInput catalogActive starsH-alphaSolarMassLineEvolutionAstrofísicaStellar dynamos generate magnetic fields that are of fundamental importance to the variability and evolution of Sun-like and low-mass stars, and for the development of their planetary systems. As a key to understanding stellar dynamos, empirical relations between stellar parameters and magnetic fields are required for comparison to ab initio predictions from dynamo models. We report measurements of surface-average magnetic fields in 292 M dwarfs from a comparison with radiative transfer calculations; for 260 of them, this is the first measurement of this kind. Our data were obtained from more than 15 000 high-resolution spectra taken during the CARMENES project. They reveal a relation between average field strength, ⟨B⟩, and Rossby number, Ro, resembling the well-studied rotation–activity relation. Among the slowly rotating stars, we find that magnetic flux, Φ_(B), is proportional to rotation period, P, and among the rapidly rotating stars that average surface fields do not grow significantly beyond the level set by the available kinetic energy. Furthermore, we find close relations between nonthermal coronal X-ray emission, chromospheric Hα and Ca H&K emission, and magnetic flux. Taken together, these relations demonstrate empirically that the rotation–activity relation can be traced back to a dependence of the magnetic dynamo on rotation. We advocate the picture that the magnetic dynamo generates magnetic flux on the stellar surface proportional to rotation rate with a saturation limit set by the available kinetic energy, and we provide relations for average field strengths and nonthermal emission that are independent of the choice of the convective turnover time. We also find that Ca H&K emission saturates at average field strengths of ⟨B⟩≈800 G while Hα and X-ray emission grow further with stronger fields in the more rapidly rotating stars. This is in conflict with the coronal stripping scenario predicting that in the most rapidly rotating stars coronal plasma would be cooled to chromospheric temperatures.EDP ScienciesUniversidad Complutense de Madrid20222022-06-1020222022-06-10journal articlehttp://purl.org/coar/resource_type/c_6501info:eu-repo/semantics/articleapplication/pdfhttps://hdl.handle.net/20.500.14352/72652reponame:Docta Complutenseinstname:Universidad Complutense de Madrid (UCM)Inglésengopen accesshttp://purl.org/coar/access_right/c_abf2info:eu-repo/semantics/openAccessoai:docta.ucm.es:20.500.14352/726522026-06-02T12:44:21Z |
| dc.title.none.fl_str_mv |
Magnetism, rotation, and nonthermal emission in cool stars: average magnetic field measurements in 292 M dwarfs |
| title |
Magnetism, rotation, and nonthermal emission in cool stars: average magnetic field measurements in 292 M dwarfs |
| spellingShingle |
Magnetism, rotation, and nonthermal emission in cool stars: average magnetic field measurements in 292 M dwarfs Montes Gutiérrez, David 52 Pre-main-sequence Stellar rotation Model chromospheres Input catalog Active stars H-alpha Solar Mass Line Evolution Astrofísica |
| title_short |
Magnetism, rotation, and nonthermal emission in cool stars: average magnetic field measurements in 292 M dwarfs |
| title_full |
Magnetism, rotation, and nonthermal emission in cool stars: average magnetic field measurements in 292 M dwarfs |
| title_fullStr |
Magnetism, rotation, and nonthermal emission in cool stars: average magnetic field measurements in 292 M dwarfs |
| title_full_unstemmed |
Magnetism, rotation, and nonthermal emission in cool stars: average magnetic field measurements in 292 M dwarfs |
| title_sort |
Magnetism, rotation, and nonthermal emission in cool stars: average magnetic field measurements in 292 M dwarfs |
| dc.creator.none.fl_str_mv |
Montes Gutiérrez, David Caballero, J. A. otros, ... |
| author |
Montes Gutiérrez, David |
| author_facet |
Montes Gutiérrez, David Caballero, J. A. otros, ... |
| author_role |
author |
| author2 |
Caballero, J. A. otros, ... |
| author2_role |
author author |
| dc.contributor.none.fl_str_mv |
Universidad Complutense de Madrid |
| dc.subject.none.fl_str_mv |
52 Pre-main-sequence Stellar rotation Model chromospheres Input catalog Active stars H-alpha Solar Mass Line Evolution Astrofísica |
| topic |
52 Pre-main-sequence Stellar rotation Model chromospheres Input catalog Active stars H-alpha Solar Mass Line Evolution Astrofísica |
| description |
Stellar dynamos generate magnetic fields that are of fundamental importance to the variability and evolution of Sun-like and low-mass stars, and for the development of their planetary systems. As a key to understanding stellar dynamos, empirical relations between stellar parameters and magnetic fields are required for comparison to ab initio predictions from dynamo models. We report measurements of surface-average magnetic fields in 292 M dwarfs from a comparison with radiative transfer calculations; for 260 of them, this is the first measurement of this kind. Our data were obtained from more than 15 000 high-resolution spectra taken during the CARMENES project. They reveal a relation between average field strength, ⟨B⟩, and Rossby number, Ro, resembling the well-studied rotation–activity relation. Among the slowly rotating stars, we find that magnetic flux, Φ_(B), is proportional to rotation period, P, and among the rapidly rotating stars that average surface fields do not grow significantly beyond the level set by the available kinetic energy. Furthermore, we find close relations between nonthermal coronal X-ray emission, chromospheric Hα and Ca H&K emission, and magnetic flux. Taken together, these relations demonstrate empirically that the rotation–activity relation can be traced back to a dependence of the magnetic dynamo on rotation. We advocate the picture that the magnetic dynamo generates magnetic flux on the stellar surface proportional to rotation rate with a saturation limit set by the available kinetic energy, and we provide relations for average field strengths and nonthermal emission that are independent of the choice of the convective turnover time. We also find that Ca H&K emission saturates at average field strengths of ⟨B⟩≈800 G while Hα and X-ray emission grow further with stronger fields in the more rapidly rotating stars. This is in conflict with the coronal stripping scenario predicting that in the most rapidly rotating stars coronal plasma would be cooled to chromospheric temperatures. |
| publishDate |
2022 |
| dc.date.none.fl_str_mv |
2022 2022-06-10 2022 2022-06-10 |
| 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/20.500.14352/72652 |
| url |
https://hdl.handle.net/20.500.14352/72652 |
| 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 Sciencies |
| publisher.none.fl_str_mv |
EDP Sciencies |
| dc.source.none.fl_str_mv |
reponame:Docta Complutense instname:Universidad Complutense de Madrid (UCM) |
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Universidad Complutense de Madrid (UCM) |
| reponame_str |
Docta Complutense |
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Docta Complutense |
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| repository.mail.fl_str_mv |
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15,300719 |