A VLT/FLAMES survey for massive binaries in Westerlund 1: I. first observations of luminous evolved stars

Understand

Multiwavelength observations of the young massive cluster Westerlund 1 have revealed evidence for a large number of OB supergiant and Wolf-Rayet binaries.

• However, in most cases these findings are based on secondary binary characteristics such as hard X-ray emission and/or non-thermal radio spectra and hence provide little information on binary properties such as mass ratio and orbital period.
• To overcome this shortcoming we have initiated a long temporal baseline, VLT/FLAMES+GIRAFFE multi-epoch radial velocity survey that will provide the first direct constraints on these parameters.
• This study presents first results from twenty of the most luminous supergiant stars in Wd1.