We think that gamma ray bursts and gamma ray quasars, are two classes of gamma ray sources; at least two anyway!
There are a few quasars which seem to be beaming energy out of their cores, and the Earth just happens to be located along the axis of these beams to see a powerful gamma-ray source blaring at us down through the millions of light years. These shine steadily over hours, minutes and months with little or no changes in their brightness.
There are also gamma-ray burst sources which flare up in fractions of a second to up to several minutes, and then vanish. Astronomers have no clue as to what is producing them, other than they must be far away because they do not follow the pattern in the sky of the stars in the Milky Way, or nearby clusters of galaxies. The most likely explanation involves colliding, or imploding neutron stars, because the inferred sizes of the emitting regions have to be no more than 10 kilometers.
The above image shows a gamma ray burst identified with a galaxy. Here's the note about it at Astronomy POD
"Do the powerful explosions known as gamma-ray bursts (GRBs) originate in galaxies? This subject took on new light yesterday with the release of a Hubble Space Telescope image of the sky surrounding GRB 990123. This burst was first detected only two weeks ago and cataloged as one of the most powerful GRBs ever. The optical transient (OT) counterpart to the GRB can be seen as the bright spot just below center. Once so bright it was briefly visible with just binoculars, this OT has since become four million times dimmer and continues to fade. Now, it can be seen easily with only a large telescope. The diffuse object above is of particular interest because it appears to be the host galaxy of GRB 990123. This distant galaxy seems to have a normal brightness but an irregular shape. This discovery increases the evidence that most OTs do occur in galaxies. Are all host galaxies this strange? "
Copyright 1997 Dr. Sten Odenwald
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