EDP Sciences
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Volume 396, Number 3, December IV 2002
Page(s) L25 - L29
Section Letters
DOI http://dx.doi.org/10.1051/0004-6361:20021623

A&A 396, L25-L29 (2002)
DOI: 10.1051/0004-6361:20021623


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

J. S. Clark1 and I. Negueruela2, 3

1  Department of Physics and Astronomy, University College London, Gower Street, London, WC1E 6BT, England, UK
2  Observatoire de Strasbourg, 11 rue de l'Université, 67000 Strasbourg, France
3  Dpto. de Física, Ingeniería de Sistemas y Teoría de la Señal, Universidad de Alicante, Apdo. 99, 03080 Alicante, Spain

(Received 2 October 2002 / Accepted 7 November 2002)

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 & 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.

Key words: stars: evolution -- stars: Wolf Rayet -- galaxies: starbursts

Offprint request: J. S. Clark, jsc@star.ucl.ac.uk

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© ESO 2002