High-speed photometry of Z Chamaeleontis during outbursts

High-speed white-light photometry of the dwarf nova Z Cha at time resolutions of 4 or 5 s is given for six supermaxima and one ordinary maximum observed during the period 1973-84. Measurements of the superhump amplitudes and eclipse parameters enable correlations to be found with time after the appearance of superhumps and with phase Φ0 in orbit of the superhump maximum. The depth of eclipse increases systematically during superoutburst, and the width of eclipse decreases. However, both depth and width of eclipse are functions of Φ0. Eclipse asymmetries occur which are also a function of Φ0. From an analysis of the correlations we deduce that at early stages of the superoutburst the source of the superhump light is partially eclipsed by the secondary star, which implies that the source is not a bright spot on the secondary. (author)