EM counterparts of structured jets from 3D GRMHD simulations

TL;DR

This study uses 3D GRMHD simulations to demonstrate that black hole accretion systems naturally produce structured jets, explaining observed features of GW170817/GRB170817A's prompt and afterglow emissions.

Contribution

It provides the first self-consistent simulation of a relativistic magnetized jet from a black hole accretion system, linking jet structure to accretion physics.

Findings

Structured jets naturally emerge from the simulations.

Jet collimation by disk wind results in a 10-degree opening angle.

Simulated jet emission matches observed GRB170817A features.

Abstract

GW170817/GRB170817A has offered unprecedented insight into binary neutron star post-merger systems. Its Prompt and afterglow emission imply the presence of a tightly collimated relativistic jet with a smooth transverse structure. However, it remains unclear whether and how the central engine can produce such structured jets. Here, we utilize 3D GRMHD simulations starting with a black hole surrounded by a magnetized torus with properties typically expected of a post-merger system. We follow the jet, as it is self-consistently launched, from the scale of the compact object out to more than 3 orders of magnitude in distance. We find that this naturally results in a structured jet, which is collimated by the disk wind into a half-opening angle of roughly 10 degrees, its emission can explain features of both the prompt and afterglow emission of GRB170817A for a 30 degree observing angle. Our work is the first to compute the afterglow, in the context of a binary merger, from a relativistic magnetized jet self-consistently generated by an accreting black hole, with the jet's transverse structure determined by the accretion physics and not prescribed at any point.