Random variations in the ultraviolet spectrum of β Lyrae

The results of a program of low-resolution scanning of β Lyr in the ultraviolet spectral region using the OAO-2 spacecraft are presented. This spectrophotometry indicates that longward of lambda 2200 the ultraviolet spectrum of β Lyr is similar to that of a normal B8 star. However, at shorter wavelengths the spectrum is dominated by line emission features. In the lambda lambda 1200-1650 region the inferred continuum is substantially weaker than expected for a normal B8 star. Large cycle-to-cycle variations in the flux shortward of lambda 1800 were apparent in scans obtained at the same orbital phases; however, the strong emission features remained reasonably constant during the 1970 observations, showing random variations uncorrelated with orbital motion on the time scale of a few hours. A possible exception to this behavior is N v lambda 1240 which seemed to vary in a way suggesting a physical connection with processes affecting the β Lyr far-ultraviolet light curves. The inferred continuum in the lambda lambda 1200-1800 region, however, exhibited the light variation expected of an eclipsing binary with tidally distorted components. It is argued that the far-ultraviolet light variation observed by Kondo, McCluskey, and Eaton (1976) is produced by the same mechanism producing the light variation in the longer wavelengths. Further, in the absence of a strong ultraviolet continuum, it is inferred that the high degree of ionization observed in this system is the result of collisional processes occurring in a small, hot region associated with the secondary component