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Significant variations have been seen on time scales as short as two weeks in the ultraviolet line profiles of the 20-year period eclipsing binary system VV Cephei. VV Cep consists of an M supergiant primary which fills its Roche lobe at periastron and a hot, probably main-sequence companion surrounded by a disk. Both the primary and secondary are 20 $M_{\sun}$ objects.
Stencel et al. (PASP 105, 45) monitored VV Cep in the ultraviolet every two weeks from 1991 June - Oct. They integrated the 1200 - 2000 \AA and 2000 - 3200 \AA fluxes, finding these wavelength regions to vary together for the most part, with larger variation seen in the short-wavelength region. Over some of these two-week intervals, the integrated short-wavelength flux varied by nearly a factor of two.
The high-resolution IUE spectra of VV Cep are very complex. Numerous emission features (mostly Fe II) are superimposed on an absorption spectrum similar to those seen during chromospheric eclipse in the $\zeta Aur$ binaries. A few regions of spectrum which probably represent a continuum from the B star and/or its accretion disk can be identified. At some times the line profiles in the chromosphere-like absorption spectrum are symmetric, but more often, many of them have additional broad absorption features superimposed on them, which may be either red- or blue-shifted. Over the 1991 monitoring period, the high-resolution spectra have shown at least some degree of this additional redshifting. The strength and velocity distribution within these additional redshifted components frequently varied significantly over the two-week intervals.
Over the 1991 monitoring period, the highest integrated flux levels seen corresponded to spectra in which the continuum regions were seen to be higher and which had minimal additional redshifts. The lowest integrated flux levels corresponded to spectra with reduced continuum, and signficant extra redshifts.
