Gamma Ray Bursts and their host galaxies


Credit: NASA/Swift/Cruz deWilde


Gamma-ray Bursts (GRBs) are the most violent explosions in the universe after the Big Bang. They are divided into two categories based on their duration: the short GRBs (SGRBs) with duration shorter than 2 seconds and the long GRBs (LGRBs) with longer durations. The LGRBs are possibly powered by the collapse of rapidly rotating massive stars while the SGRBs are widely believed to be from mergers of binary compact objects that involve at least one neutron star. Another characteristic of SGRBs is that they have a broad range of spatial offsets from their host galaxies.

The study of the properties of the host galaxies of GRBs became feasible after the launch of the BeppoSAX satellite. The data BeppoSAX provided to astronomers showed indications that the spatial offsets of SGRBs from their host galaxies depends on the BRGs progenitors, i.e. whether the binary objects that generate GRBs are Black HoleNeutron Star or Neutron Star – Neutron Star. If this is correct then it has implications on the detection of Gravitational Waves (GW).

Recently a team of astrophysicists used a sample of 18 SGRBs to test the above hypothesis. Their results suggest that there is no correlation between the spatial offset of GRBS and their progenitors, in contradiction with some of the previous studies. More data are therefore required to answer the question of why GRBs present such a wide range of spatial offset from their host galaxies.


Publication: Zhang et al. 2017