<P> The true nature of these objects was initially unknown , and the leading hypothesis was that they originated from the mergers of binary neutron stars or a neutron star with a black hole . Such mergers were theorized to produce kilonovae , and evidence for a kilonova associated with GRB 130603B was seen . The mean duration of these events of 0.2 seconds suggests ( because of causality ) a source of very small physical diameter in stellar terms ; less than 0.2 light - seconds ( about 60,000 km or 37,000 miles -- four times the Earth 's diameter ) . This further suggests a very compact object as the source . The observation of minutes to hours of X-ray flashes after a short gamma - ray burst is consistent with small particles of a primary object like a neutron star initially swallowed by a black hole in less than two seconds , followed by some hours of lesser energy events , as remaining fragments of tidally disrupted neutron star material ( no longer neutronium ) remain in orbit to spiral into the black hole , over a longer period of time . A small fraction of short gamma - ray bursts are probably produced by giant flares from soft gamma repeaters in nearby galaxies . </P>
<P> The true nature of these objects was initially unknown , and the leading hypothesis was that they originated from the mergers of binary neutron stars or a neutron star with a black hole . Such mergers were theorized to produce kilonovae , and evidence for a kilonova associated with GRB 130603B was seen . The mean duration of these events of 0.2 seconds suggests ( because of causality ) a source of very small physical diameter in stellar terms ; less than 0.2 light - seconds ( about 60,000 km or 37,000 miles -- four times the Earth 's diameter ) . This further suggests a very compact object as the source . The observation of minutes to hours of X-ray flashes after a short gamma - ray burst is consistent with small particles of a primary object like a neutron star initially swallowed by a black hole in less than two seconds , followed by some hours of lesser energy events , as remaining fragments of tidally disrupted neutron star material ( no longer neutronium ) remain in orbit to spiral into the black hole , over a longer period of time . A small fraction of short gamma - ray bursts are probably produced by giant flares from soft gamma repeaters in nearby galaxies . </P>
short duration gamma-ray bursts are thought to be caused by
short duration gamma-ray bursts are thought to be caused by
mergers of binary neutron stars or a neutron star with a black hole
mergers of binary neutron stars or a neutron star with a black hole