The ‘outside‐in’ outburst of HT Cassiopeiae

We present results from photometric observations of the dwarf nova system HT Cas during the eruption of 1995 November. The data include the first two-colour observations of an eclipse on the rise to outburst. They show that during the rise to outburst the disc deviates significantly from steady-state models, but the inclusion of an inner-disc truncation radius of about 4Rwd and a ‘flared’ disc of semi-opening angle of 10° produces acceptable fits. The disc is found to have expanded at the start of the outburst to about 0.41RL1, as compared with quiescent measurements. The accretion disc then gradually decreases in radius reaching < 0.32RL1 during the last stages of the eruption. Quiescent eclipses were also observed prior to and after the eruption and a revised ephemeris is calculated.