Recurrent novae at quiescence: systems with giant secondaries

Spectroscopic and photometric behaviour of the class of recurrent novae wit h giant secondaries (T Coronae Borealis, RS Ophiuchi, V3890 Sagittarii and V745 Scorpii) at quiescence are presented in this study. The hot component in these systems is variable, with the variability manifesting as variabili ty in the ultraviolet luminosity, the ultraviolet and optical emission line fluxes and in the UBV/visual magnitudes. The variations are uncorrelated w ith the binary orbital motion. The observed ultraviolet+optical spectral ch aracteristics of the hot component in these systems can be explained by a w hite dwarf+accretion disc embedded in an envelope of wind from the M giant secondary. We suggest that the observed variations are a result of (a) fluc tuations in the mass accretion rate; (b) changes in the column density of t he absorbing wind envelope, which is optically thick.