The Hamburg Identification Program of Rosat All-Sky Survey Sources

Abstract

The ROSAT All Sky Survey (RASS), performed between July 1990 and February 1991, provided about 60,000 X-ray sources in a soft X-ray band (0.1–2.4keV) with a flux limit of approximately 5 × 10^-13 ergs cm^-2 s^-1 for exposure times of 400sec (a typical value in low ecliptic latitudes). A wealth of information can be extracted from the RASS source content and many objects deserve (or have already deserved) extensive follow-up studies. However, this possibility is limited by the fact that the nature of most of the RASS sources is unknown i.e., they are unclassified. A correlation with the SIMBAD data base yields only identifications for about one third of the RASS sources.