Diagnostics of Neutron Star and Black Hole X-Ray Binaries with X-Ray Shot Widths

A statistic w, the differential coefficient of the mean absolute difference of an observed lightcurve, is proposed for timescale analysis of shot widths. The shortest width of random shots can be measured by the position of the lower cut-off in the timescale spectrum of w. We use the statistic to analyze X-ray lightcurves from a sample of neutron star and black hole binaries and the results show that the timescale analysis can help us distinguish between neutron star binaries and black hole binaries. The analysis can further reveal the structure and dynamics of accretion disks around black holes.