Astrophysicists pin down jet from merging neutron stars

Avatar By Le Williams | 2 years ago

Computer simulations by astrophysicists Davide Lazzati of Oregon State University and colleagues in the US and Italy have discovered short gamma-ray burst (GRB) that followed gravitational waves from the GW170817 neutron star merger was created in an astrophysical jet pointing 30° away from Earth

The simulations of the merger offer an additional explanation for why the short GRB was much weaker than understood.

Typically lasting for less than 2 s, short GRBs and their origins have puzzled astronomers for decades. An important clue came in 2005 when X-rays and visible light were detected from the sources of two short bursts. This provided evidence that a short GRB can be created by the merger of two neutron stars to form a black hole.

The concept stems from evidence that the merger creates two astrophysical jets of fast-moving material that flow out in opposite directions from the poles of the rapidly spinning black hole. Violent interactions that occur within the jet just after the merger create a short GRB. As the jet moves outward and slows down, a radiation afterglow at longer wavelengths is emitted.

This model was supported by the GW170817 event, in which a short GRB was observed at the same time as the gravitational waves from two merging neutron stars.

Contrarily, the GW170817 experiments did not match what astrophysicists assumed from a neutron-star merger.

The short GRB was much dimmer than predicted by theory. The afterglow observed in the days and weeks after the short GRB increased in brightness over time.