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2.12. V / Vmax, Count and Peak Flux Distributions

The limiting fluence observed by BATSE is approx 10-7 ergs/cm2. The actual fluence of the strongest bursts is larger by two or three orders of magnitude. A plot of the number of bursts vs. the peak flux depicts clearly a paucity of weak bursts. This is manifested by the low value of <V / Vmax>, a statistic designed to measure the distribution of sources in space [177]. A sample of the first 601 bursts has <V / Vmax> = .328 ± 0.012, which is 14sigma away from the homogeneous flat space value of 0.5 [178]. Correspondingly, the peak count distribution is incompatible with a homogeneous population of sources in Euclidean space. It is compatible, however, with a cosmological distribution (see Fig. 10). The distribution of short bursts has a larger <V / Vmax> and it is compatible with a homogeneous Eucleadian distribution [77, 78, 79].