Understanding the unusual X-ray emission properties of the massive, close binary WR 20a: A high energy window into the stellar wind initiation region

The problem of explaining the X-ray emission properties of the massive, close binary WR 20a is discussed. Located near the cluster core of Westerlund 2, WR 20a is composed of two nearly identical Wolf-Rayet stars of 82 and 83 solar masses orbiting with a period of only 3.7 days. Although Chandra obs...

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Detalles Bibliográficos
Autores: Montes, G., Ramirez-Ruiz, E., De Colle, F., Strickler, R.
Tipo de recurso: artículo
Estado:Versión aceptada para publicación
Fecha de publicación:2013
País:España
Institución:Consejo Superior de Investigaciones Científicas (CSIC)
Repositorio:DIGITAL.CSIC. Repositorio Institucional del CSIC
OAI Identifier:oai:digital.csic.es:10261/406904
Acceso en línea:http://hdl.handle.net/10261/406904
Access Level:acceso abierto
Palabra clave:Binaries: close
Hydrodynamics
Rayet
Stars: individual (WR 20a)
Stars: winds, outflows
Stars: Wolf
X-rays: stars
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spelling Understanding the unusual X-ray emission properties of the massive, close binary WR 20a: A high energy window into the stellar wind initiation regionMontes, G.Ramirez-Ruiz, E.De Colle, F.Strickler, R.Binaries: closeHydrodynamicsRayetStars: individual (WR 20a)Stars: winds, outflowsStars: WolfX-rays: starsThe problem of explaining the X-ray emission properties of the massive, close binary WR 20a is discussed. Located near the cluster core of Westerlund 2, WR 20a is composed of two nearly identical Wolf-Rayet stars of 82 and 83 solar masses orbiting with a period of only 3.7 days. Although Chandra observations were taken during the secondary optical eclipse, the X-ray light curve shows no signs of a flux decrement. In fact, WR 20a appears slightly more X-ray luminous and softer during the optical eclipse, opposite to what has been observed in other binary systems. To aid in our interpretation of the data, we compare with the results of hydrodynamical simulations using the adaptive mesh refinement code Mezcal which includes radiative cooling and a radiative acceleration force term. It is shown that the X-ray emission can be successfully explained in models where the wind-wind collision interface in this system occurs while the outflowing material is still being accelerated. Consequently, WR 20a serves as a critical test-case for how radiatively driven stellar winds are initiated and how they interact. Our models not only procure a robust description of current Chandra data, which cover the orbital phases between 0.3 and 0.6, but also provide detailed predictions over the entire orbit. © 2013. The American Astronomical Society. All rights reserved.We thank A. Bonanos, M. Krumholz, L. Lopez, A. Mac- Fadyen, J. Maund, S. Owocki, A. Raga, A. Rosen, and A. Vigna-G´omez for helpful discussions. We also thank the ref- eree for providing constructive comments and help in improv- ing the contents of this paper. Computations were performed on the UCSC Hyades and Laozi computer clusters. We acknowl- edge support from the David and Lucille Packard Foundation, NSF grants MRI-1229745 and AST-0847563, DGAPA-PAPIIT- UNAM grant IA101413-2, and CSIC JAE-PREDOC fellowshipPeer reviewedIOP PublishingDavid and Lucile Packard FoundationNational Science Foundation (US)Universidad Nacional Autónoma de MéxicoConsejo Superior de Investigaciones Científicas (España)Consejo Superior de Investigaciones Científicas [https://ror.org/02gfc7t72]2025202520132025info:eu-repo/semantics/articlehttp://purl.org/coar/resource_type/c_6501Postprintinfo:eu-repo/semantics/acceptedVersionhttp://hdl.handle.net/10261/406904reponame:DIGITAL.CSIC. Repositorio Institucional del CSICinstname:Consejo Superior de Investigaciones Científicas (CSIC)Ingléshttp://dx.doi.org/10.1088/0004-637X/777/2/129Síinfo:eu-repo/semantics/openAccessoai:digital.csic.es:10261/4069042026-05-22T06:33:51Z
dc.title.none.fl_str_mv Understanding the unusual X-ray emission properties of the massive, close binary WR 20a: A high energy window into the stellar wind initiation region
title Understanding the unusual X-ray emission properties of the massive, close binary WR 20a: A high energy window into the stellar wind initiation region
spellingShingle Understanding the unusual X-ray emission properties of the massive, close binary WR 20a: A high energy window into the stellar wind initiation region
Montes, G.
Binaries: close
Hydrodynamics
Rayet
Stars: individual (WR 20a)
Stars: winds, outflows
Stars: Wolf
X-rays: stars
title_short Understanding the unusual X-ray emission properties of the massive, close binary WR 20a: A high energy window into the stellar wind initiation region
title_full Understanding the unusual X-ray emission properties of the massive, close binary WR 20a: A high energy window into the stellar wind initiation region
title_fullStr Understanding the unusual X-ray emission properties of the massive, close binary WR 20a: A high energy window into the stellar wind initiation region
title_full_unstemmed Understanding the unusual X-ray emission properties of the massive, close binary WR 20a: A high energy window into the stellar wind initiation region
title_sort Understanding the unusual X-ray emission properties of the massive, close binary WR 20a: A high energy window into the stellar wind initiation region
dc.creator.none.fl_str_mv Montes, G.
Ramirez-Ruiz, E.
De Colle, F.
Strickler, R.
author Montes, G.
author_facet Montes, G.
Ramirez-Ruiz, E.
De Colle, F.
Strickler, R.
author_role author
author2 Ramirez-Ruiz, E.
De Colle, F.
Strickler, R.
author2_role author
author
author
dc.contributor.none.fl_str_mv David and Lucile Packard Foundation
National Science Foundation (US)
Universidad Nacional Autónoma de México
Consejo Superior de Investigaciones Científicas (España)
Consejo Superior de Investigaciones Científicas [https://ror.org/02gfc7t72]
dc.subject.none.fl_str_mv Binaries: close
Hydrodynamics
Rayet
Stars: individual (WR 20a)
Stars: winds, outflows
Stars: Wolf
X-rays: stars
topic Binaries: close
Hydrodynamics
Rayet
Stars: individual (WR 20a)
Stars: winds, outflows
Stars: Wolf
X-rays: stars
description The problem of explaining the X-ray emission properties of the massive, close binary WR 20a is discussed. Located near the cluster core of Westerlund 2, WR 20a is composed of two nearly identical Wolf-Rayet stars of 82 and 83 solar masses orbiting with a period of only 3.7 days. Although Chandra observations were taken during the secondary optical eclipse, the X-ray light curve shows no signs of a flux decrement. In fact, WR 20a appears slightly more X-ray luminous and softer during the optical eclipse, opposite to what has been observed in other binary systems. To aid in our interpretation of the data, we compare with the results of hydrodynamical simulations using the adaptive mesh refinement code Mezcal which includes radiative cooling and a radiative acceleration force term. It is shown that the X-ray emission can be successfully explained in models where the wind-wind collision interface in this system occurs while the outflowing material is still being accelerated. Consequently, WR 20a serves as a critical test-case for how radiatively driven stellar winds are initiated and how they interact. Our models not only procure a robust description of current Chandra data, which cover the orbital phases between 0.3 and 0.6, but also provide detailed predictions over the entire orbit. © 2013. The American Astronomical Society. All rights reserved.
publishDate 2013
dc.date.none.fl_str_mv 2013
2025
2025
2025
dc.type.none.fl_str_mv info:eu-repo/semantics/article
http://purl.org/coar/resource_type/c_6501
Postprint
info:eu-repo/semantics/acceptedVersion
format article
status_str acceptedVersion
dc.identifier.none.fl_str_mv http://hdl.handle.net/10261/406904
url http://hdl.handle.net/10261/406904
dc.language.none.fl_str_mv Inglés
language_invalid_str_mv Inglés
dc.relation.none.fl_str_mv http://dx.doi.org/10.1088/0004-637X/777/2/129
Sí
dc.rights.none.fl_str_mv info:eu-repo/semantics/openAccess
eu_rights_str_mv openAccess
dc.publisher.none.fl_str_mv IOP Publishing
publisher.none.fl_str_mv IOP Publishing
dc.source.none.fl_str_mv reponame:DIGITAL.CSIC. Repositorio Institucional del CSIC
instname:Consejo Superior de Investigaciones Científicas (CSIC)
instname_str Consejo Superior de Investigaciones Científicas (CSIC)
reponame_str DIGITAL.CSIC. Repositorio Institucional del CSIC
collection DIGITAL.CSIC. Repositorio Institucional del CSIC
repository.name.fl_str_mv
repository.mail.fl_str_mv
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