Core radius R_c distribution for the 17,000 0.5–2 keV sources detected in the Swift GRB fields as a function of the source off-axis angle. The triangles with error bars show the mean size of the point sources and the standard deviation about the mean. The line shows the ﹩3\sigma ﹩ size cut used to separate point sources (solid line) from extended sources (open squares). The upper and right histograms show the R_c and off-axis angle histograms for point sources (blue) and extended sources (red).