A VLT/FLAMES survey for massive binaries in Westerlund 1 VIII. Binary systems and orbital parameters
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Título: | A VLT/FLAMES survey for massive binaries in Westerlund 1 VIII. Binary systems and orbital parameters |
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Autor/es: | Ritchie, Ben W. | Clark, J. Simon | Negueruela, Ignacio | Najarro de la Parra, Francisco |
Grupo/s de investigación o GITE: | Astrofísica Estelar (AE) |
Centro, Departamento o Servicio: | Universidad de Alicante. Departamento de Química Física |
Palabras clave: | Stars: evolution | Supergiants | Binaries: general | Techniques: radial velocities |
Área/s de conocimiento: | Astronomía y Astrofísica |
Fecha de publicación: | 14-abr-2022 |
Editor: | EDP Sciences |
Cita bibliográfica: | Astronomy & Astrophysics. 2022, 660: A89. https://doi.org/10.1051/0004-6361/202142405 |
Resumen: | Context. The galactic cluster Westerlund 1 contains a rich population of evolved, massive stars. A high binary fraction has been inferred from previous multi-wavelength observations. Aims. We use multi-epoch spectroscopy of a large sample of early-type stars in Westerlund 1 to identify new binaries and binary candidates in the cluster. Methods. VLT/FLAMES was used with the GIRAFFE spectrograph in HR21 mode to obtain spectra of ∼100 OB stars over a 14-month baseline in 2008 and 2009, supplemented with follow-up observations in 2011 and 2013. Radial velocities were obtained from strong Paschen series absorption lines in the I-band. Results. We identify 20 new OB I–III binaries, a WN9h binary, and a WC9d binary, greatly increasing the number of directly confirmed binary systems in Westerlund 1, while 12 O9−9.5 Iab−III stars are identified as candidate binaries based on radial velocity changes that are inconsistent with photospheric variability. The 173.9 day SB1 W1030 represents the first longer-period system identified in the cluster, while the determination of a 53.95 day period for W44 (WR L) makes it the first Wolf-Rayet binary in Westerlund 1 with a confirmed orbital period greater than ten days. Our results suggest the binary fraction in the OB population is at least ∼40%, and may be significantly higher. Conclusions. These results demonstrate that binary systems can be effectively identified in the population of OB I−III stars evolving off the main sequence in Westerlund 1. Future multi-epoch surveys will be able to fully characterise this population. |
Patrocinador/es: | This research is partially supported by the Spanish Government Ministerio de Ciencia, Innovación y Universidades under grant PGC2018-093741-B-C21 (MICIU/AEI/FEDER, UE). I.N. is also supported by the Generalitat Valenciana through grant PROMETEO/2019/041. F.N. acknowledges financial support through Spanish grant PID2019-105552RB-C41 (MINECO/MCIU/AEI/FEDER) and from the Spanish State Research Agency (AEI) through the Unidad de Excelencia “María de Maeztu”-Centro de Astrobiología (CSIC-INTA) project No. MDM-2017-0737. |
URI: | http://hdl.handle.net/10045/123452 |
ISSN: | 0004-6361 (Print) | 1432-0746 (Online) |
DOI: | 10.1051/0004-6361/202142405 |
Idioma: | eng |
Tipo: | info:eu-repo/semantics/article |
Derechos: | © ESO 2022 |
Revisión científica: | si |
Versión del editor: | https://doi.org/10.1051/0004-6361/202142405 |
Aparece en las colecciones: | INV - Astrofísica Estelar - Artículos de Revistas |
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Ritchie_etal_2022_A&A.pdf | 760,84 kB | Adobe PDF | Abrir Vista previa | |
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