EM counterparts of structured jets from 3D GRMHD simulations

• Published in: Monthly notices of the Royal Astronomical Society. Letters Vol. 484; no. 1; pp. L98 - L103
• Main Authors: Kathirgamaraju, Adithan, Tchekhovskoy, Alexander, Giannios, Dimitrios, Barniol Duran, Rodolfo
• Format: Journal Article
• Language: English
• Published: United Kingdom Oxford University Press 21.03.2019
• Subjects: radiation mechanisms: non-thermal; MHD; methods: numerical; gamma-ray burst: individual:170817A
• ISSN: 1745-3925; 1745-3933
• DOI: 10.1093/mnrasl/slz012

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 general relativistic magnetohydrodynamic 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 three orders of magnitude in distance. We find that this naturally results in a structured jet, which is collimated by the disc wind into a half-opening angle of roughly 10°; its emission can explain features of both the prompt and afterglow emission of GRB170817A for a 30° 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.