High time resolution observations of Cataclysmic Variables with OPTIMA

The high-speed photometer `OPTIMA', short for Optical Pulsar Timing Analyzer, was used to record optical (450-950 nm) light curves of selected cataclysmic variables of type AM Her (Polars) with sub-second temporal resolution. The objects RX J0704+62, RX J0953+14, and EK UMa were re-observed several years after their discovery to provide up to date light curves with good statistics. The eclipsing binary DP Leo, which had been observed during 20 years previous to the OPTIMA measurements, was shown to have an orbital ephemeris with a quadratic term. For HU Aqr we have collected data over the years 1999 to 2007. HU Aqr evolved in luminosity from a high state in 2000 to a low state that persists since 2001. We detected variability in HU Aqr in the form of optical flashes with timescales of seconds.