DETECTION OF THE ANGULAR-CORRELATION OF FAINT X-RAY SOURCES

We have analyzed a set of deep ROSAT observations with a total ski cov erage of 40 deg(2) to search for clustering of faint X-ray sources. Us ing the resulting catalog of discrete X-ray sources, we detect, for th e first time in the X-ray band, a positive correlation on angular scal es of 0'5-10'. When corrected for a bias due to limited spatial resolu tion, which amplifies the correlation, the observed angular correlatio n function agrees well with that expected from the spatial correlation of optically selected quasars provided that they comprise an apprecia ble fraction (greater than or equal to 50%) of detected X-ray sources.