UBV images of the Z Cha accretion disc in outburst

Images of the accretion disc in the dwarf nova Z Cha are derived from UBV photometry of two eclipses obtained in the early stage of the 1983 March outburst. Two-colour and colour–magnitude diagrams for the accretion disc demonstrate that its surface consists of opaque thermal radiators. We derive a distance of 105±20 (KR/400 km s−1) pc, where KR is the assumed radial velocity semi-amplitude of the red dwarf companion star. Temperatures in the disc range from ∼7 000 K at its outer rim to ∼40 000 K near the white dwarf at its centre. The radial temperature profile is consistent with steady mass transfer at the rate |10-8.9±0.3M_⁻¹|⁠.