3D magnetised jet break-out from neutron-star binary merger ejecta: afterglow emission from the jet and the ejecta

Understand

We perform three-dimensional (3D) general-relativistic magnetohydrodynamic simulations to model the jet break-out from the ejecta expected to be produced in a binary neutron-star merger.

• The structure of the relativistic outflow from the 3D simulation confirms our previous results from 2D simulations, namely, that a relativistic magnetized outflow breaking out from the merger ejecta exhibits a hollow core of $\theta_{\rm core}\approx4^{\circ}$, an opening angle of $\theta_{\rm jet}\gtrsim10^{\circ}$, and is accompanied by a wind of ejected matter that will contribute to the kilonova emission.
• We also compute the non-thermal afterglow emission of the relativistic outflow and fit it to the panchromatic afterglow from GRB170817A, together with the superluminal motion reported from VLBI observations.
• In this way, we deduce an observer angle of $\theta_{\rm obs}= 35.7^{\circ \,\,+1.8}_{\phantom{\circ \,\,}-2.2}$.