Variability in the UV resonance lines of the cataclysmic variable V795 Herculis (PG-1711 + 336)

Abstract

Variability in the UV resonance lines from the cataclysmic variable V795 Her is investigated on the basis of a total of 28 IUE SWP low-resolution spectra. Significant line profile fluctuations are evident in the C IV 1549 and Si IV 1400 doublets on time-scales down to less than about 30 min. There is little or no evidence for changes in N V 1240. Only C IV 1549 is occasionally seen in emission; the morphology of this profile changes from an absorption-dominated line to an emission-dominated one in a few hours. Although no correlations are evident between changes in the Si IV and C IV line strengths and the mooted orbital period of V795 Her (about 2.6 hr), the present time-series analyses of the UV data suggest an approximately 4.8-hr periodic modulation in the line profile variability. Constraints on the origin and geometry of the line formation are discussed on the basis of these UV data. Alternative specifications for departures from axial symmetry are suggested.