Program: GN-2013B-Q-108

Blue supergiants are evolved massive stars that are known to display strong line profile variability. In addition, their photospheric lines present a broadening component in excess to, but of the same order as pure rotational broadening, called macroturbulence. These two simultaneously appearing spectral line features have recently been identified as being caused by stellar pulsations. These pulsations might trigger phases of enhanced mass loss. Indications for variable mass-loss rates are seen in, e.g., the strength and shape of the Halpha lines, however, Halpha itself is a poor indicator for pulsational activity, because it forms over a large wind region. Instead, the Br alpha line in the L-band was proven to be a sensitive mass-loss diagnostics. We propose to use GNIRS to obtain time-series in Br alpha for two pulsating blue supergiants. These time series will allow us to directly determine, for the first time, the link between pulsations and mass loss in these stars.