Metallicity Dependent Wolf-Rayet winds?. PAUL CROWTHER. Introduction. Wolf-Rayet (WR) stars represent the final, pre-core collapse phase in the evolution of very massive stars;
Denser winds than O stars, so WR spectra are dominated by emission lines rather than absorption lines
WN stars expected to dominate in IZw18, but signature of WC stars dominates (Brown et al. 2002)
early late early late
Milky Way WC stars followed generic Nugis & Lamers (2000) calibration (red).
LMC stars followed similar relation (green), offset by -0.2 dex (Crowther et al. 2002).
Log(dM/dt) = 1.38 log(L/Lo) -12.35
Observational evidence for slower winds at low Z? Only amongst individual WO stars (= early WC).
High density WR winds will lead to efficient recombination from high (`early’) to low (`late’) ions. Opposite is true for low density WR winds, as observed at low metallicity.
LMC template stars required to derive reliable WR populations in 0.5 Z starburst galaxy NGC3125.
130 WN20 WC