AN OPTIMIZED TIME SCREENING ALGORITHM FOR ROSAT PSPC AND HRI OBSERVATIONS

We have developed a model-independent time screening optimization algo rithm to cope with significant contamination spikes in the ROSAT PSPC/ HRI background light-curves. The rejection criteria are based on the m aximization of faint sources signal-to-noise ratio. The algorithm tuni ng parameters have been optimized through performing a wide set of run s on both simulated and real data. We have verified that the applicati on of our selection criteria to the case of long exposure PSPC observa tions yields an increase of the number of faint sources (SNR < 6 sigma ) of up to 100% with a rejection of up to the 8% of the exposure time. At the same time, we obtain an average signal-to-noise ratio gain of 3% for the sources detected in both the unscreened and screened images . The algorithm, even though currently optimized for the instrumentati on on board ROSAT, can be easily generalized for data analysis of othe r imaging X-ray detectors.