Role of injection parameters in jet propagation through realistic binary neutron star merger environments

TL;DR

This study uses 3D RMHD simulations to investigate how injection parameters and realistic merger environments influence jet propagation in binary neutron star mergers, highlighting environment impact on jet success.

Contribution

First comprehensive 3D RMHD simulation suite examining how injection parameters and realistic merger environments jointly affect jet evolution in BNS mergers.

Findings

Jet fate depends on environment properties even with identical injection parameters.

Realistic environments cause significant differences in jet breakout compared to simplified models.

Environment plays a central role in shaping jet evolution and success.

Abstract

After the first multi-messenger observation of a binary neutron star (BNS) merger powering a short-duration gamma-ray burst (GRB), GW170817-GRB 170817A, remarkable effort is ongoing to unravel the evolution of the collimated, relativistic outflow (or jet) that was launched during the merger and fed the GRB event, imprinting its angular structure onto the follow-up afterglow signal. Current theoretical models, based on relativistic magneto-hydrodynamic (RMHD) simulations, offer detailed insights into the launch and propagation processes that govern jet evolution. Notably, these simulations point out that jet injection parameters, such as luminosity, magnetization, power decay time scale, and launch time relative to merger, play a crucial role. However, the impact of these parameters is typically investigated within simplified jet propagation environments, lacking a direct connection with a realistic BNS merger aftermath. In this work, we present the first suite of 3D RMHD simulations exploring the influence of such parameters on the propagation of magnetized incipient GRB jets injected into magnetized environments directly imported from the outcome of a general-relativistic MHD BNS merger simulation. Our results demonstrate that, alongside the injection parameters, the BNS merger environment has a central role in shaping the overall jet evolution. Specifically, under identical jet parameters, the fate of an incipient jet (whether it successfully breaks out or becomes choked) depends strongly on the properties of such an environment. Further quantitative comparison between realistic and simplified environments reveals major differences, emphasizing the importance of incorporating the former for accurate modeling.