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Detection of additional Wolf-Rayet stars in the starburst cluster Westerlund 1 with SOAR

Groh, J. H., Damineli, A., Teodoro, M., Barbosa, C. L. 2006, A&A, 457, 591

Context: The young starburst cluster Westerlund 1 is one of the most massive clusters in the Local Group, harboring a huge population of massive stars.

Aims:We searched for additional Wolf-Rayet stars in Westerlund 1.

Methods: The targets were selected based on 1 μm narrow-band imaging of the cluster carried out at OPD/LNA (Brazil), and then confirmed as Wolf-Rayet stars by K-band spectroscopy performed at the 4.1 m SOAR telescope (Chile).

Results: We report the detection of 3 additional Wolf-Rayet stars in Westerlund 1. Together with previous works, this increases the population of Wolf-Rayet stars detected in the cluster to 22 members. Moreover, a K-band spectrum of the Luminous Blue Variable W243, which apparently implies a higher temperature than that derived from optical spectra taken in 2003, is presented for the first time. The WC9 star WR-F was also observed, showing clear evidence of dust emission in the K-band.