H 0139-68: high-speed optical photometry of an AM-Herculis type binary system

High-speed optical photometry is reported of the source H 0139-68 obtained on the AAT, at time resolutions of 1 and 2 s, in order to search for evidence of short time-scale periodicities or flickering. Transient periodic pulsations, on time-scales from 5 to 500 s, are present in the data, but no evidence is found for persistent periodic optical pulsations on time-scales less than the primary period. The high-speed data has also been combined with other lower time resolution data obtained over 9 months to derive the period of the binary system as 113.638 +- 0.002 min, by identification of an accurately repeating light-curve signature. (author)