The Energy of Gamma-Ray Bursts

The energy of a Gamma-Ray Burst is one of the most interesting factors that can help determining the origin of these mysterious explosions. After the discovery that GRBs are cosmological it was thought, for a while that they are standard candles releasing ∼ 1051ergs. Redshift measurements that followed the discovery of GRB afterglow revealed that GRBs are (i) further than what was initially believed and (ii) have a very wide luminosity function. Some bursts revealed an enormous energy release with a record estimate of 1.4 × 1054ergs for GRB990123. The energy budget was stretched even further when it was suggested that the conversion efficiency of producing gamma-rays is low. The realization that GRBs are beamed changed this perspective and brought the energy budget of GRBs down back to a ”modest” ∼ 5× 1050ergs. I discuss here various estimates showing that GRB energy is narrowly distributed and discuss the implications of this conclusion to GRB models.