The CARMENES search for exoplanets around M dwarfs: Rubidium abundances in nearby cool stars

Due to their ubiquity and very long main-sequence lifetimes, abundance determinations in M dwarfs provide a powerful and alternative tool to GK dwarfs to study the formation and chemical enrichment history of our Galaxy. In this study, abundances of the neutron-capture elements Rb, Sr, and Zr are de...

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Autores: Abia, C., Tabernero, H. M., Korotin, S. A., Montes, David, Marfil, E., Caballero, J. A., Straniero, O., Prantzos, Nikos, Ribas, Ignasi, Reiners, Ansgar, Quirrenbach, Andreas, Amado, Pedro J., Béjar, Victor J. S., Cortés-Contreras, M., Dreizler, Stefan, Henning, Thomas, Jeffers, Sandra V., Kaminski, Adrian, Kürster, M., Lafarga, M., López-Gallifa, Á., Morales, Juan Carlos, Nagel, Evangelos, Passegger, V.M., Pedraz, S., Rodríguez-López, Cristina, Schweitzer, Andreas, Zechmeister, Mathias
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:10261/223731
Acceso en línea:http://hdl.handle.net/10261/223731
Access Level:acceso abierto
Palabra clave:Nuclear reactions
Stars: late-type
Stars: abundances
Nucleosynthesis
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dc.title.none.fl_str_mv The CARMENES search for exoplanets around M dwarfs: Rubidium abundances in nearby cool stars
title The CARMENES search for exoplanets around M dwarfs: Rubidium abundances in nearby cool stars
spellingShingle The CARMENES search for exoplanets around M dwarfs: Rubidium abundances in nearby cool stars
Abia, C.
Nuclear reactions
Stars: late-type
Stars: abundances
Nucleosynthesis
title_short The CARMENES search for exoplanets around M dwarfs: Rubidium abundances in nearby cool stars
title_full The CARMENES search for exoplanets around M dwarfs: Rubidium abundances in nearby cool stars
title_fullStr The CARMENES search for exoplanets around M dwarfs: Rubidium abundances in nearby cool stars
title_full_unstemmed The CARMENES search for exoplanets around M dwarfs: Rubidium abundances in nearby cool stars
title_sort The CARMENES search for exoplanets around M dwarfs: Rubidium abundances in nearby cool stars
dc.creator.none.fl_str_mv Abia, C.
Tabernero, H. M.
Korotin, S. A.
Montes, David
Marfil, E.
Caballero, J. A.
Straniero, O.
Prantzos, Nikos
Ribas, Ignasi
Reiners, Ansgar
Quirrenbach, Andreas
Amado, Pedro J.
Béjar, Victor J. S.
Cortés-Contreras, M.
Dreizler, Stefan
Henning, Thomas
Jeffers, Sandra V.
Kaminski, Adrian
Kürster, M.
Lafarga, M.
López-Gallifa, Á.
Morales, Juan Carlos
Nagel, Evangelos
Passegger, V.M.
Pedraz, S.
Rodríguez-López, Cristina
Schweitzer, Andreas
Zechmeister, Mathias
author Abia, C.
author_facet Abia, C.
Tabernero, H. M.
Korotin, S. A.
Montes, David
Marfil, E.
Caballero, J. A.
Straniero, O.
Prantzos, Nikos
Ribas, Ignasi
Reiners, Ansgar
Quirrenbach, Andreas
Amado, Pedro J.
Béjar, Victor J. S.
Cortés-Contreras, M.
Dreizler, Stefan
Henning, Thomas
Jeffers, Sandra V.
Kaminski, Adrian
Kürster, M.
Lafarga, M.
López-Gallifa, Á.
Morales, Juan Carlos
Nagel, Evangelos
Passegger, V.M.
Pedraz, S.
Rodríguez-López, Cristina
Schweitzer, Andreas
Zechmeister, Mathias
author_role author
author2 Tabernero, H. M.
Korotin, S. A.
Montes, David
Marfil, E.
Caballero, J. A.
Straniero, O.
Prantzos, Nikos
Ribas, Ignasi
Reiners, Ansgar
Quirrenbach, Andreas
Amado, Pedro J.
Béjar, Victor J. S.
Cortés-Contreras, M.
Dreizler, Stefan
Henning, Thomas
Jeffers, Sandra V.
Kaminski, Adrian
Kürster, M.
Lafarga, M.
López-Gallifa, Á.
Morales, Juan Carlos
Nagel, Evangelos
Passegger, V.M.
Pedraz, S.
Rodríguez-López, Cristina
Schweitzer, Andreas
Zechmeister, Mathias
author2_role author
author
author
author
author
author
author
author
author
author
author
author
author
author
author
author
author
author
author
author
author
author
author
author
author
author
author
dc.contributor.none.fl_str_mv Ministerio de Ciencia e Innovación (España)
European Commission
Universidad Complutense de Madrid
Fundação para a Ciência e a Tecnologia (Portugal)
NASA
Consejo Superior de Investigaciones Científicas [https://ror.org/02gfc7t72]
dc.subject.none.fl_str_mv Nuclear reactions
Stars: late-type
Stars: abundances
Nucleosynthesis
topic Nuclear reactions
Stars: late-type
Stars: abundances
Nucleosynthesis
description Due to their ubiquity and very long main-sequence lifetimes, abundance determinations in M dwarfs provide a powerful and alternative tool to GK dwarfs to study the formation and chemical enrichment history of our Galaxy. In this study, abundances of the neutron-capture elements Rb, Sr, and Zr are derived, for the first time, in a sample of nearby M dwarfs. We focus on stars in the metallicity range-0.5 ≲ [Fe/H] ≲ +0.3, an interval poorly explored for Rb abundances in previous analyses. To do this we use high-resolution, high-signal-to-noise-ratio, optical and near-infrared spectra of 57 M dwarfs observed with CARMENES. The resulting [Sr/Fe] and [Zr/Fe] ratios for most M dwarfs are almost constant at about the solar value, and are identical to those found in GK dwarfs of the same metallicity. However, for Rb we find systematic underabundances ([Rb/Fe] < 0.0) by a factor two on average. Furthermore, a tendency is found for Rb-but not for other heavy elements (Sr, Zr)-to increase with increasing metallicity such that [Rb/Fe] ≳ 0.0 is attained at metallicities higher than solar. These are surprising results, never seen for any other heavy element, and are difficult to understand within the formulation of the s-and r-processes, both contributing sources to the Galactic Rb abundance. We discuss the reliability of these findings for Rb in terms of non-LTE (local thermodynamic equilibrium) effects, stellar activity, or an anomalous Rb abundance in the Solar System, but no explanation is found. We then interpret the full observed [Rb/Fe] versus [Fe/H] trend within the framework of theoretical predictions from state-of-the-art chemical evolution models for heavy elements, but a simple interpretation is not found either. In particular, the possible secondary behaviour of the [Rb/Fe] ratio at super-solar metallicities would require a much larger production of Rb than currently predicted in AGB stars through the s-process without overproducing Sr and Zr. © 2020 ESO.
publishDate 2020
dc.date.none.fl_str_mv 2020
2020
2020
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spelling The CARMENES search for exoplanets around M dwarfs: Rubidium abundances in nearby cool starsAbia, C.Tabernero, H. M.Korotin, S. A.Montes, DavidMarfil, E.Caballero, J. A.Straniero, O.Prantzos, NikosRibas, IgnasiReiners, AnsgarQuirrenbach, AndreasAmado, Pedro J.Béjar, Victor J. S.Cortés-Contreras, M.Dreizler, StefanHenning, ThomasJeffers, Sandra V.Kaminski, AdrianKürster, M.Lafarga, M.López-Gallifa, Á.Morales, Juan CarlosNagel, EvangelosPassegger, V.M.Pedraz, S.Rodríguez-López, CristinaSchweitzer, AndreasZechmeister, MathiasNuclear reactionsStars: late-typeStars: abundancesNucleosynthesisDue to their ubiquity and very long main-sequence lifetimes, abundance determinations in M dwarfs provide a powerful and alternative tool to GK dwarfs to study the formation and chemical enrichment history of our Galaxy. In this study, abundances of the neutron-capture elements Rb, Sr, and Zr are derived, for the first time, in a sample of nearby M dwarfs. We focus on stars in the metallicity range-0.5 ≲ [Fe/H] ≲ +0.3, an interval poorly explored for Rb abundances in previous analyses. To do this we use high-resolution, high-signal-to-noise-ratio, optical and near-infrared spectra of 57 M dwarfs observed with CARMENES. The resulting [Sr/Fe] and [Zr/Fe] ratios for most M dwarfs are almost constant at about the solar value, and are identical to those found in GK dwarfs of the same metallicity. However, for Rb we find systematic underabundances ([Rb/Fe] < 0.0) by a factor two on average. Furthermore, a tendency is found for Rb-but not for other heavy elements (Sr, Zr)-to increase with increasing metallicity such that [Rb/Fe] ≳ 0.0 is attained at metallicities higher than solar. These are surprising results, never seen for any other heavy element, and are difficult to understand within the formulation of the s-and r-processes, both contributing sources to the Galactic Rb abundance. We discuss the reliability of these findings for Rb in terms of non-LTE (local thermodynamic equilibrium) effects, stellar activity, or an anomalous Rb abundance in the Solar System, but no explanation is found. We then interpret the full observed [Rb/Fe] versus [Fe/H] trend within the framework of theoretical predictions from state-of-the-art chemical evolution models for heavy elements, but a simple interpretation is not found either. In particular, the possible secondary behaviour of the [Rb/Fe] ratio at super-solar metallicities would require a much larger production of Rb than currently predicted in AGB stars through the s-process without overproducing Sr and Zr. © 2020 ESO.CARMENES is an instrument for the Centro Astronomico Hispano-Aleman (CAHA) at Calar Alto (Almeria, Spain), operated jointly by the Junta de Andalucia and the Instituto de Astrofisica de Andalucia (CSIC). CARMENES was funded by the Max-Planck-Gesellschaft (MPG), the Consejo Superior de Investigaciones Cientificas (CSIC), the Ministerio de Economia y Competitividad (MINECO) and the European Regional Development Fund (ERDF) through projects FICTS-2011-02, ICTS-2017-07-CAHA-4, and CAHA16-CE-3978, and the members of the CARMENES Consortium (Max-Planck-Institut fur Astronomie, Instituto de Astrofisica de Andalucia, Landessternwarte Konigstuhl, Institut de Ciencies de l'Espai, Institut fur Astrophysik Gottingen, Universidad Complutense de Madrid, Thuringer Landessternwarte Tautenburg, Instituto de Astrofisica de Canarias, Hamburger Sternwarte, Centro de Astrobiologia and Centro Astronomico Hispano-Aleman), with additional contributions by the MINECO, the Deutsche Forschungsgemeinschaft through the Major Research Instrumentation Programme and Research Unit FOR2544 "Blue Planets around Red Stars", the Klaus Tschira Stiftung, the states of Baden-Wurttemberg and Niedersachsen, and by the Junta de Andalucia. We acknowledge financial support from the Agencia Estatal de Investigacion of the Ministerio de Ciencia e Innovacion, the Universidad Complutense de Madrid, the Fundacao para a Ciencia e a Tecnologia, the Generalitat de Catalunya, ERDF, and NASA through projects PGC2018-095317-B-C21, PID2019-109522GB-C51/2/3/4, PGC2018-098153-B-C33, AYA2016-79425-C3[1,2,3]-P, FPU15/01476, UID[B,P]/04434/2020, PTDC/FIS-AST/28953/2017, POCI-01-0145-FEDER-028953, SEV-2015-0548, SEV-2017-0709, MDM-20170737, NNX17AG24G, and the CERCA programme.Peer reviewedEDP SciencesMinisterio de Ciencia e Innovación (España)European CommissionUniversidad Complutense de MadridFundação para a Ciência e a Tecnologia (Portugal)NASAConsejo Superior de Investigaciones Científicas [https://ror.org/02gfc7t72]202020202020info:eu-repo/semantics/articlehttp://purl.org/coar/resource_type/c_6501Publisher's versioninfo:eu-repo/semantics/publishedVersionhttp://hdl.handle.net/10261/223731reponame:DIGITAL.CSIC. 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