SIMBAD references

The origin of gamma-ray bursts continues to be a great mystery. Here we review some of the relevant physics and model features. While no clear solution exists at the present time, the parameter space for Galactic halo models is becoming very constrained. Cosmological models on the other hand require both enormous total energy and the concentration of that energy into a small mass. This implies compact objects, perhaps accreting black holes of stellar size. We consider black hole models in some detail and emphasize that jets from accretion disks around black hole of stellar mass might precess. We also discuss ``failed'' Ib supernovae, and binary neutron star mergers. Some global constraints on both halo and cosmological models are discussed and some ``generic'' scenarios are proposed. Future directions for solving the burst mystery are suggested.