Dynamics of a relativistic jet through magnetized media

TL;DR

This study uses 2.5D RMHD simulations to explore how magnetized environments influence the evolution and stability of relativistic jets from neutron star mergers, impacting gamma-ray burst emissions.

Contribution

It introduces new simulations of relativistic jets in magnetized media, revealing how ambient magnetization suppresses instabilities and affects jet dynamics and emission properties.

Findings

Magnetized media suppress jet instabilities.

Suppression of collimation shocks reduces internal shock efficiency.

Jet-head velocity remains largely unaffected by ambient magnetization.

Abstract

The merger of two neutron stars (NSs) produces the emission of gravitational waves, the formation of a compact object surrounded by a dense and magnetized environment, and the launching of a collimated and relativistic jet, which will eventually produce a short gamma-ray burst (SGRB). The interaction of the jet with the environment has been shown to play a major role in shaping the structure of the outflow that eventually powers the gamma-ray emission. In this paper, we present a set of 2.5 dimensional RMHD simulations that follow the evolution of a relativistic non-magnetized jet through a medium with different magnetization levels, as produced after the merger of two NSs. We find that the predominant consequence of a magnetized ambient medium is that of suppressing instabilities within the jet, and preventing the formation of a series of collimation shocks. One implication of this is that internal shocks lose efficiency, causing bursts with low-luminosity prompt emission. On the other hand, the jet-head velocity and the induced magnetization within the jet are fairly independent from the magnetization of the ambient medium. Future numerical studies with a larger domain are necessary to obtain light curves and spectra in order to better understand the role of magnetized media.