The Cannonball Model of Gamma Ray Bursts: Spectral and Temporal   Properties of the Gamma Rays
  Recent observations suggest that gamma ray bursts (GRBs) and their afterglows are produced by highly relativistic jets emitted in supernova explosions. We have proposed that the result of the event is not just a compact object plus the ejecta: within days, a fraction of the parent star falls back to produce a thick accretion disk. The subsequent accretion generates jets and constitutes the GRB ``engine'', as in the observed ejection of relativistic ``cannonballs'' of plasma by microquasars and active galactic nuclei. Here we investigate the production of a GRB as the jetted cannonballs exit the supernova shell reheated by their collision with it, emitting highly forward-collimated radiation. Each cannonball corresponds to an individual pulse in a GRB. We cannot predict the timing sequence of these pulses, but the Cannonball Model fares very well in describing the total energy, energy spectrum, and time-dependence of the individual pulses. 
Arnon Dar and Alvaro De R\'ujula