Visual and ultraviolet spectrum of the eclipsing binary V367 Cygni.

Abstract

V 367 Cyg is a single spectrum eclipsing binary (P = 18.6 d) classified as Beta Lyrae type. Spectroscopic observations during two successive cycles confirm previous studies and indicate that the shell spectrum does not vary greatly and does not present appreciable expansional velocity. The radial velocity of the shell lines may be explained by a ring surrounding the whole system and by a stream moving toward the observer which becomes observable in the vicinity of the second quadrature. The IUE low resolution spectra confirm the values for the effective temperature and gravity derived from the visual spectrum of the primary (Te = 8000 K, log g = 1.5) and to derive the effective temperature and luminosity of the companion (a main sequence star, Te = 10000 K) which according to the UBV light curves was expected to be cooler than the primary. Hence the body eclipsing the primary and eclipsed by it is not the companion but a cooler disk around the secondary. Several emission features of excitation higher than would be expected from the temperature of the two stars are present in the far UV spectrum.