Distribution of the brightest X-ray sources

Brightest sources in the ROSAT pointings as well as in the All-Sky Survey generate disproportionately high fraction of the total X-ray background (XRB) fluctuations. The autocorrelation function of the soft XRB indicates that substantial fraction of the XRB variations over a wide range of angular scales is associated with relatively few bright sources. Possible explanation of this effect are listed. It is likely that most of the fluctuations of the XRB are not produced by source clustering represented by the standard power law autocorrelation function with the canonical index of -1.8.