An optimized time screening algorithm for ROSAT PSPC and HRI observations

Istituto ed Osservatorio Astronomico "G.S. Vaiana", Piazza del Parlamento 1, I-90134 Palermo, Italy e-mail: bocchino@oapa.astropa.unipa.it, barbera@oapa.astropa.unipa.it, sciorti@oapa.astropa.unipa.it

Send offprint request to: F. Bocchino

Received: 5 June 1997
Accepted: 20 October 1997

Abstract

We have developed a model-independent time screening optimization algorithm to cope with significant contamination spikes in the ROSAT PSPC/HRI bacground light-curves. The rejection criteria are based on the maximization of faint sources signal-to-noise ratio. The algorithm tuning parameters have been optimized through performing a wide set of runs on both simulated and real data. We have verified that the application of our selection criteria to the case of long exposure PSPC observations yields an increase of the number of faint sources (SNR ) 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 instrumentation on board ROSAT, can be easily generalized for data analysis of other imaging X-ray detectors.