A hidden population of Wolf-Rayet stars in the massive galactic cluster Westerlund 1

Abstract

We report the discovery of a hitherto undetected population of Wolf-Rayet stars in the young galactic open cluster Westerlund 1. Optical spectroscopy of the cluster identified 11 such objects; provisional classification suggests that 6 are nitrogen rich (WN) and 5 carbon rich (WC). Including the previously identified Blue, Yellow and Red Super- & Hypergiants, Westerlund 1 clearly has a very rich population of massive post-Main Sequence objects. To date, the post-MS population of Westerlund 1 is significantly larger than that of any other galactic young open cluster - with the possible exception of the Arches - implying that it is potentially amongst the most massive young clusters yet identified in the Local Group.

3 figures; uses new A&A style (included) Letter accepted for publication in Astronomy & Astrophysics

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Cited by in corpus (29)

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• A Study of Cyg OB2: Pointing the Way Towards Finding Our Galaxy's Super Star Clusters
• Intermediate to low-mass stellar content of Westerlund 1
• Constraining Globular Cluster Formation Through Studies of Young Massive Clusters: I. A lack of ongoing star formation within young clusters
• Diffuse, Non-Thermal X-ray Emission from the Galactic Star Cluster Westerlund 1
• The distance and neutral environment of the massive stellar cluster Westerlund 1
• The Starburst Cluster Westerlund 1: The Initial Mass Function and Mass Segregation
• A serendipitous survey for variability amongst the massive stellar population of Westerlund 1
• MSX Mid infrared imaging of massive star birth environments. II: Giant HII regions
• A VLT/FLAMES survey for massive binaries in Westerlund 1: I. first observations of luminous evolved stars
• Signatures of hadronic cosmic rays in starbursts? High-energy photons and neutrinos from NGC253
• New Galactic Wolf-Rayet stars, and candidates. An annex to The VIIth Catalogue of Galactic Wolf-Rayet Stars
• Variability of Young Massive Stars in the Galactic Super Star Cluster Westerlund 1
• Radio emission from the massive stars in the Galactic Super Star Cluster Westerlund 1
• Massive Star Formation in the W49 Giant Molecular Cloud: Implications for the Formation of Massive Star Clusters
• A Rich Population of X-ray Emitting Wolf-Rayet Stars in the Galactic Starburst Cluster Westerlund 1
• MASSCLEAN - MASSive CLuster Evolution and ANalysis Package - Description and Tests
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• Further Wolf-Rayet stars in the starburst cluster Westerlund 1
• A newly identified Luminous Blue Variable in the galactic starburst cluster Westerlund 1
• A VLT/FLAMES survey for massive binaries in Westerlund 1. III. The WC9d binary W239 and implications for massive stellar evolution
• Hadronic processes within collective stellar winds
• An ALMA 3mm continuum census of Westerlund 1
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• Diffuse Thermal X-Ray Emission in the Core of the Young Massive Cluster Westerlund 1
• Five WC9 stars discovered in the AAO/UKST H-alpha Survey
• The stellar population of the star forming region G61.48+0.09