2001ApJ...553L.109H

We have used the ROSAT All-Sky Survey (RASS) observations at the north ecliptic pole (NEP) to construct a catalog of X-ray-emitting objects that is both deep and contiguous. We give here an overview of this NEP Survey. Our catalog fully exploits the capabilities of the RASS since the only criterion for inclusion is the source significance and location on the sky. There are 445 unique sources above a flux of ∼2x10^–14 ergs.s^–1.cm^–2 (0.5-2.0 keV) in the 80.7 deg² region that we consider. We have optically identified 99.6% of these sources and have obtained redshifts for the extragalactic objects. The main constituents of the catalog are active galactic nuclei (AGNs; 49.0%), stars (34.3%), and groups and clusters of galaxies (14.4%). We provide the NEP Survey selection function (solid angle searched above a given flux limit), the AGNs, the clusters of galaxies, and the BL Lacertae X-ray logN(>S)-logS distribution as well as the catalog redshift distributions for AGNs and clusters.