2006A&A...457..591G

The young starburst cluster Westerlund 1 is one of the most massive clusters in the Local Group, harboring a huge population of massive stars. We searched for additional Wolf-Rayet stars in Westerlund 1. The targets were selected based on 1µm 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 4.1m SOAR telescope (Chile). 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.