The circumstellar environment and evolutionary status of the supergiant B[e] star Wd1-9
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Título: | The circumstellar environment and evolutionary status of the supergiant B[e] star Wd1-9 |
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Autor/es: | Clark, J. Simon | Ritchie, Ben W. | Negueruela, Ignacio |
Grupo/s de investigación o GITE: | Astrofísica Estelar (AE) |
Centro, Departamento o Servicio: | Universidad de Alicante. Departamento de Física, Ingeniería de Sistemas y Teoría de la Señal |
Palabras clave: | Stars: evolution | Stars: emission line | Circumstellar matter | Stars: individual: Wd1-9 |
Área/s de conocimiento: | Astronomía y Astrofísica |
Fecha de publicación: | 15-oct-2013 |
Editor: | EDP Sciences |
Cita bibliográfica: | Astronomy & Astrophysics. 2013, 10/03/13. doi:10.1051/0004-6361/201321412 |
Resumen: | Context. Historically, supergiant (sg)B[e] stars have been difficult to include in theoretical schemes for the evolution of massive OB stars. Aims. The location of Wd1-9 within the coeval starburst cluster Westerlund 1 means that it may be placed into a proper evolutionary context and we therefore aim to utilise a comprehensive multiwavelength dataset to determine its physical properties and consequently its relation to other sgB[e] stars and the global population of massive evolved stars within Wd1. Methods. Multi-epoch R- and I-band VLT/UVES and VLT/FORS2 spectra are used to constrain the properties of the circumstellar gas, while an ISO-SWS spectrum covering 2.45−45μm is used to investigate the distribution, geometry and composition of the dust via a semi-analytic irradiated disk model. Radio emission enables a long term mass-loss history to be determined, while X-ray observations reveal the physical nature of high energy processes within the system. Results. Wd1-9 exhibits the rich optical emission line spectrum that is characteristic of sgB[e] stars. Likewise its mid-IR spectrum resembles those of the LMC sgB[e] stars R66 and 126, revealing the presence of equatorially concentrated silicate dust, with a mass of ~10−4M⊙. Extreme historical and ongoing mass loss (≳ 10−4M⊙yr−1) is inferred from the radio observations. The X-ray properties of Wd1-9 imply the presence of high temperature plasma within the system and are directly comparable to a number of confirmed short-period colliding wind binaries within Wd1. Conclusions. The most complete explanation for the observational properties of Wd1-9 is that it is a massive interacting binary currently undergoing, or recently exited from, rapid Roche-lobe overflow, supporting the hypothesis that binarity mediates the formation of (a subset of) sgB[e] stars. The mass loss rate of Wd1-9 is consistent with such an assertion, while viable progenitor and descendent systems are present within Wd1 and comparable sgB[e] binaries have been identified in the Galaxy. Moreover, the rarity of sgB[e] stars - only two examples are identified from a census of ~ 68 young massive Galactic clusters and associations containing ~ 600 post-Main Sequence stars - is explicable given the rapidity (~ 104yr) expected for this phase of massive binary evolution. |
Patrocinador/es: | JSC gratefully acknowledges the support of an RCUK fellowship. IN has been funded by grant AYA2010-21697-C05-05 from the Spanish Ministerio de Ciencia e Innovación (MICINN). |
URI: | http://hdl.handle.net/10045/33811 |
ISSN: | 0004-6361 (Print) | 1432-0746 (Online) |
DOI: | 10.1051/0004-6361/201321412 |
Idioma: | eng |
Tipo: | info:eu-repo/semantics/article |
Revisión científica: | si |
Versión del editor: | http://dx.doi.org/10.1051/0004-6361/201321412 |
Aparece en las colecciones: | INV - Astrofísica Estelar - Artículos de Revistas |
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