The Spectra of Wolf-Rayet Stars at High Dispersion

Abstract

The Wolf-Rayet stars have perhaps the most spectacular spectra among the various celestial species that have been examined with the aid of the spectrograph. The wide emission lines that provide a striking display continue to be the enigma they have been for decades. Progress, however, in evaluating the contributions to the spectrum by different ions has been fairly complete, thanks to the splendid efforts in the laboratory by Edlen and his collaborators. Many lists of wavelengths of individual features exist from the studies of Plaskett, Beals, Cecilia Payne and Swings. Efforts at identification have been such as to provide a list of likely contributors, that by wavelength position and plausible intensity could be present in the emission band at a specified wavelength. The large width of the lines form the principal limitation. For, one can have a wide limit of coincidence in wavelength with resultant emission features that are complexes covering well over a hundred Ångstrőms. The wide nature of these complexes have perhaps encouraged in the past the use of low spectral resolution only, for the many studies that have been carried out. Seldom has one used the resolutions and dispersions that have been usefully employed for the study of the more common relatively narrow absorption lined objects. This situation pertaining to the Wolf-Rayet stars is happily undergoing a change in recent years when coudé spectra with the larger telescopes are becoming increasingly available. The southern hemisphere has been particularly rich in these objects both in variety of behaviour and in having many bright ones, and one can, therefore, justifiably hope that our information on these objects will progress henceforth with remarkable rapidity.