The wind of Variable C in M33 (an LBV in eruption)

Roberta M. Humphreys (1), Kris Davidson(1), Michael S. Gordon(1), Kerstin Weis(2), Birgitta Burggraf(2), D. J. Bomans(2), and John C. Martin(3)

(1) University of Minnesota
(2) Ruhr Universitaet, Bochum
(3) University of Illinois, Springfield

We discuss the spectrum of Var C in M33 obtained just before the onset of its current brightening and recent spectra during its present "eruption" or optically thick wind stage. These spectra illustrate the typical LBV transition in apparent spectral type or temperature that characterizes the classical LBV or S Dor-type variability. LBVs are known to have slow, dense winds during their maximum phase. Interestingly, Var C had a slow wind even during its hot, quiescent stage in comparison with the normal hot supergiants with similar temperatures. Its outflow or wind speeds also show very little change between these two states.

Reference: Astrophysical Journal Letters, 2014, 782, L21
Status: Manuscript has been accepted