The Wolf-Rayet population of Westerlund 1

Hadfield, L. J.; Crowther, P. A.; Negueruela, I.; Clark, J. S. and Vacca, W. D. (2008). The Wolf-Rayet population of Westerlund 1. In: de Koter, Alex; Smith, Linda J. and Waters, L. B. F. M. eds. Mass Loss from Stars and the Evolution of Stellar Clusters. Astronomical Society of the Pacific Conference Series, 388. San Francisco: Astronomical Society of the Pacific, pp. 169–170.



New NTT/SOFI near-IR narrow-band imaging and spectroscopy reveals an additional four Wolf-Rayet (WR) stars in the massive cluster Westerlund 1, bringing the total WR population to 24. Sixteen of the WR stars in Wd1 have been classified WN5–11, while eight are WC8–9. An observed WR to RSG/YHG ratio of ∼3 suggests an age of 4.5–5.0 Myr, with WR stars descended from 40–55MSolar progenitors. On the basis of dust and hard X-ray emission, we estimate that 40–65% are probable members of massive star binary systems.

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