The ROE/NRL Cluster Catalog: II. Correlation with Serendipitous Einstein X-Ray Sources

Abstract

A large number of x-ray sources were discovered serendipitously during the Einstein Mission. One set, brought together as the medium sensitivity survey (Maccacaro et al. 1982) and the extended medium sensitivity surveys (Stocke et al. 1991), comprised sources found in the field of the imaging proportional counter during observations of specific objects. The other comprised sources found when the observatory maneuvered from one target to the next and the imaging proportional counter was functioning. During such maneuvers, a half degree swath of sky was scanned and occasionally a bright source would be detected. Such sources were catalogued as the slew survey (Elvis et al. 1991). For both surveys, substantial effort has gone into obtaining optical and radio counterparts to the x-ray sources. We have correlated these catalogs with the ROE/NRL cluster catalog obtained from the UK Schmidt Survey (UKSS) of the southern hemisphere in order to determine independently which x-ray sources in the Einstein Mission intensity range originate in clusters of galaxies to the limit of the UKSS material. The details of the correlation analysis and a description of our catalog is given in the previous paper (Gursky et al., paper I, this volume).