OBSERVATIONS OF RAPID BLUE VARIABLES .14. Z CHAMAELEONTIS

Z Cha is a dwarf nova and an eclipsing binary with a period of 107 min. We have made high speed photometric observations both at normal light and during outburst.The observations at normal light lead to a model for the system in which the bright spot is abnormally situated. Non-synchronous rotation of the secondary may account for this. The eclipse, which is total, shows the disappearance of both the white dwarf primary and the bright spot. During outburst the eclipses get wider and become partial. These observations clearly establish that the outburst is centred on the primary. The eclipses at maximum light show that the whole disc around the primary is bright. It is suggested that the disc is heated by a thermal pulse or shock wave originating in the outbursting white dwarf. A simple model for the subsequent cooling of the disc leads to a disc mass of 10-5Mo. Oscillations in the light curve with a period of 27.67 s were present during outburst. © 1974 Royal Astronomical Society.