Program: GN-2015B-Q-2

Evolved massive stars, like luminous blue variables (LBVs) and B[e] supergiants (B[e]SGs), undergo strong, often eruptive mass-loss phases, emphasizing their importance for stellar and galactic evolution. The differences in total mass and energy during these two phases can, however, be huge. For proper predictions of final stages in massive star evolution, it is hence crucial to resolve the populations of these stars and to study their proper mass-loss history. The optical spectra of LBVs in quiescent (hot) phase are generally indistinguishable from those of B[e]SGs. However, near-infrared K-band spectra have recently been proven to provide the ideal tool to distinguish hot LBVs fron B[e]SGs, as only the latter display strong CO band emission. Therefore, we propose to use GNIRS to obtain medium-resolution K-band spectra for a sample of recently identified hot LBV candidates in the galaxy M33, to resolve the LBV and B[e]SG populations and to study their mass-loss history.