The MRI imprint on the Short-GRB Jets

TL;DR

This paper uses general relativistic MHD simulations to study the structure, evolution, and variability of jets in short gamma-ray bursts resulting from neutron star mergers, focusing on magnetic collimation and jet Lorentz factors.

Contribution

It provides new insights into the formation and variability of short GRB jets through axisymmetric simulations of accreting plasma and magnetic fields.

Findings

Jet variability linked to magneto-rotational instability.

Estimated maximum Lorentz factor of jets.

Magnetic fields influence jet collimation and structure.

Abstract

Short gamma ray bursts are presumably results of binary neutron star mergers, which lead to the formation of a stellar mass black hole, surrounded by a remnant matter. The strong magnetic fields help collimate jets of plasma, launched along the axis of the black hole rotation. We study the structure and evolution of the accreting plasma in the short GRBs and we model the formation of the base of a relativistic, Poynting-dominated jets. Our numerical models are based on the general relativistic MHD, axisymmetric simulations. We discuss the origin of variability in the GRB jet emission, which timescales are related to the action of the magneto-rotational instability in the accreting plasma. We also estimate the value of a maximum achievable Lorentz factor in the jets produced by our simulations, and reached at the large distances, where the gamma ray emission is produced.