STANDARD GAMMA-RAY BURSTS, DIRTY FIREBALLS, AND THE EXCLUDED MIDDLE

It is shown that the contribution of faint gamma-ray bursts (GRBs) to the total all-sky GRB energy flux is small. The all-sky flux of GRBs appears to be 5.3 x 10(-3) erg cm(-2) yr(-1), with little additional component hidden within weak or otherwise undetectable GRBs. This significantly constrains physical models of GRBs and dirty fireballs, suggesting a rather sharp dichotomy between them should the latter exist.