Models

What Are They?
Such enormous amounts of energy suggest a gravitational source. Two popular ideas are the merger of two black holes or the merger of two neutron stars. However, although such events might yield the required energy, it is not clear that they can be made consistent with all the observations. Thus, the source of gamma ray bursts remains one of the most important mysteries in modern cosmology.

SOURCE: http://antwrp.gsfc.nasa.gov/apod/ap950827.html