The Einstein galactic plane survey : statistical analysis of the complete X-ray sample.

A flux-limited survey of the galactic plane using the Einstein Imaging Proportional Counter has been conducted, discovering 71 point-like X-ray sources exceeding a five sigma threshold. These sources are statistically analyzed, and it is concluded that the number-flux relation for low-flux galactic plane X-ray sources has a slope of -1.10, significantly steeper than the about -0.5 found for bright sources by Uhuru and Ariel V. The sample contains about 46 percent coronal sources, about 31 percent extragalactic sources, and about 23 percent galactic accretion sources. Thus, about 16 new galactic accretion sources have been discovered. The approximate number density of such sources is consistent with their being cataclysmic variables and other accreting white dwarfs. Faint galactic plane sources are significantly concentrated toward the galactic bulge, and those near the bulge exhibit a flatter number-flux relation than those at higher galactic latitudes and longitudes. This indicates a different source population with a less isotropic distribution.