Physical Properties of Wolf-Rayet Stars

The striking broad emission line spectroscopic appearance of Wolf-Rayet (WR) stars has long defied analysis, owing to the extreme physical conditions within their line- and continuum-forming regions. Recently, model atmosphere studies have advanced sufficiently to enable the determination of stellar temperatures, luminosities, abundances, ionizing fluxes, and wind properties. The observed distributions of nitrogen- (WN) and carbon (WC)-sequence WR stars in the Milky Way and in nearby star-forming galaxies are discussed; these imply lower limits to progenitor masses of ∼25, 40, and 75 M ⊙ for hydrogen-depleted (He-burning) WN, WC, and H-rich (H-burning) WN stars, respectively. WR stars in massive star binaries…