The medium sensitivity survey - A new sample of X-ray sources with optical identifications and the revised extragalactic log N-log S

Abstract

The Einstein Observatory Medium Sensitivity Survey has been extended. 49 new, high galactic latitude X-ray sources have been detected in ≡150 IPC fields (≡40 deg<SUP>2</SUP>) with sensitivities in the range 7×10<SUP>-14</SUP> to 2×10<SUP>-12</SUP>ergs cm<SUP>-2</SUP>s<SUP>-1</SUP>. The optical program undertaken to identify these new sources has yielded a virtual 100% identification rate. These sources have been combined with those previously selected resulting in a sample of 112 serendipitous X-ray sources. Of these, 75% are associated with extragalactic objects, and 25% are identified with galactic stars. Active galactic nuclei (AGNs-quasars and Seyfert galaxies) constitute the large majority of the extragalactic population (68%). The log N-log S relations for the two classes of objects for which enough statistics are present, AGNs and clusters of galaxies, have been computed.