The VV Cephei Stars

This paper summarizes the photometric and spectroscopic investigations of the 13 known W Cephei-type binaries.The cool primaries are found to be luminous supergiants with irregular or semiregular light variations of less than a magnitude.Descriptions of the spectra of both the hot and cool stars as well as the peculiar emission features are given.Variations in the spectrum are noted and, when possible, their relation to the orbital cycle is discussed.The periods are characteristically long-of the order of a decade or more.Orbital studies indicate that the components have masses in excess of 30 solar masses.The location of these objects in associations or very near the galactic plane implies that they are recently evolved.High dispersion studies of W Cep itself give evidence for steady mass loss from the primary.The relation of these systems to the much wider pair of stars in a Scorpii is considered.