Physical difference between the short and long gamma-ray bursts

We provided separate bivariate log-normal distribution fits to the BATSE short and long burst samples using the durations and fluences. We show that these fits present evidence for a power-law dependence between the fluence and the duration, with statistically significant different indexes for the long and short subgroups. We argue that the effect is probably real, and the two subgroups are different physical phenomena. This may provide a potentially useful constraint for models of long and short bursts.