Observational consequences of structured jets from neutron star mergers in the local Universe

Understand

The recent multi-messenger discovery of binary neutron star (BNS) merger GW170817 showed that $\gamma$-ray emission in short GRBs is wider than the central energetic narrow cone, and weakly expands out to tens of degrees.

• Here we explore some of the observational consequences of this structured emission, taking the reconstructed angular emission profile of gamma-ray burst GRB170817A to be typical.
• We calculate the expected fraction of gravitational-wave observations from BNS mergers that will have an observed GRB counterpart to be $\sim30\%$, implying that joint gravitational-wave and GRB observations will be common.
• Further, we find that $\sim10\%$ of observed short GRBs occur within 200 Mpc.