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Orbital and stochastic far-ultraviolet variability in the nova-like system V3885 Sgr




Highly time-resolved time-tagged FUSE satellite spectroscopic data are analysed to establish the far-ultraviolet (FUV) absorption line characteristics of the nova-like cataclysmic variable binary, V3885 Sgr. We determine the temporal behaviour of low (Lyβ, C iii, N iii) and high (S iv, P v, O vi) ion species, and highlight corresponding orbital phase modulated changes in these lines. On average, the absorption troughs are blueshifted due to a low-velocity disc wind outflow. Very rapid (5 min) fluctuations in the absorption lines are isolated, which are indicative of stochastic density changes. Doppler tomograms of the FUV lines are calculated which provide evidence for structures where a gas stream interacts with the accretion disc. We conclude that the line depth and velocity changes as a function of orbital phase are consistent with an asymmetry that has its origin in a line-emitting, localized disc–stream interaction region.