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 4R_wd 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 0.41R_L1, as compared with quiescent measurements. The accretion disc then gradually decreases in radius reaching <0.32R_L1 during the last stages of the eruption. Quiescent eclipses were also observed prior to and after the eruption and a revised ephemeris is calculated.