The Wolf-Rayet Stars

Abstract

Wolf-Rayet stars are few in number and their spectra are easily recognised, for wide emission lines dominate the spectrum. The Wolf-Rayet stars form one of the few groups of stars which are named after astronomers. Wolf and Rayet (1867) at the Paris Observatory used a visual spectrometer to examine the spectra of stars and they noted that the spectra of the stars now known as HD 191765, HD 192103, and HD 192641 consist of broad bands of emission superposed on a weak continuous spectrum rather than of relatively narrow absorption lines crossing a continuous spectrum as is usual with stars. The emission features are sometimes referred to as bands. This word is used only to signify that the emission features are rather broad with steep sides. These emission features are due to spectral lines from several ionised atoms, and often two or more spectral lines blend together. Molecular bands are not present in the spectra of Wolf-Rayet stars.