The Delay Time of Gravitational Wave -- Gamma-Ray Burst Associations

Understand

The first gravitational wave (GW) - gamma-ray burst (GRB) association, GW170817/GRB 170817A, had an offset in time, with the GRB trigger time delayed by $\sim$1.7 s with respect to the merger time of the GW signal.

• We generally discuss the astrophysical origin of the delay time, $\Delta t$, of GW-GRB associations within the context of compact binary coalescence (CBC) -- short GRB (sGRB) associations and GW burst -- long GRB (lGRB) associations.
• In general, the delay time should include three terms, the time to launch a clean (relativistic) jet, $\Delta t_{\rm jet}$; the time for the jet to break out from the surrounding medium, $\Delta t_{\rm bo}$; and the time for the jet to reach the energy dissipation and GRB emission site, $\Delta t_{\rm GRB}$.
• For CBC-sGRB associations, $\Delta t_{\rm jet}$ and $\Delta t_{\rm bo}$ are correlated, and the final delay can be from 10 ms to a few seconds.