Gamma Ray Bursts are same as they seem like... the detection of high-energy gamma rays, coming from a point in the sky, that start and then go away. There is no usual repetition, they just show up and then go away. Their energy is usually pretty strong, and that so many come from a very small area indicates a single source. They usually come from all directions, but when so many come in such a short burst from a seeming point-source, it makes scientists sit up and notice.
It takes a lot of energy to produce a gamma ray. The number/types of events that can make a lot of them are few (a supernova, for example), and as far as we know, these things are coming from outside our galaxy. So whatever event that produces one has to be huge and very energetic. Many theories, but not much good evidence, as they come and go before any observations can be made.
First detected in the 1960s by satellites designed to detect nuclear weapon test explosions, the CRGO/BATSE satellite data showed that they were spread evenly over the sky. As detection and localization gets better, we are now seeing the “afterglow” of these things, and there are definite indications that they are usually very far away, and associated with very energetic events.
What causes GRBs?
There are several theories - which are, however, difficult to prove or disprove due to the immense distance of the bursts. But we are quite sure that there are different mechanisms for long and short gamma ray bursts.
Long gamma ray bursts (lasting minutes): Commonly accepted theory is a hypernova explosion— the supernova of an extremely massive star. After the core of such a hypernova collapsed to a black hole, additional material falling on the black hole is creating jets which emit particles at near light-speed. This theory is supported by the positions of long gamma ray bursts and observed supernovae shortly after an observed gamma ray burst.
Short gamma ray bursts: Short gamma-ray bursts appear to be an exception. The currently preferred model is the merger of two compact objects: two neutron stars, or a neutron star and a black hole.
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