MIKE sp. of 6 yellow supergiants of Westerlund 1

Here we present visual-wavelength echelle spectra of six YHG candidates in the Galactic cluster Westerlund 1, and we compare them to known YHGs, IRC +10420 and Hen 3-1979. We find that the six YHG candidates do not exhibit any metal emission lines, nor do they show strong H{alpha} emission, and as such do not meet the criteria necessary to be classified as YHGs.

In conjunction with their moderate luminosities of log(L/L_{sun}_)=4.7-5.4 estimated from optical/infrared photometry, we suggest instead that they are normal yellow supergiants (YSGs) with more modest initial masses around 15-20M_{sun}_. This adds additional support to the hypothesis that Wd1 is a multiage cluster with an older age than previously assumed, and is not a ~5Myr old cluster caught at a very specific transitional point when single-star evolution might yield Wolf-Rayet stars, luminous blue variables, RSGs, and YHGs in the same cluster.