Understanding of GRB-SN Connection by General Relativistic MHD Simulations

TL;DR

This paper uses general relativistic MHD simulations to explore the connection between gamma-ray bursts and supernovae, revealing jet launching mechanisms and nucleosynthesis outcomes in collapsar models.

Contribution

It introduces two numerical codes for collapsar simulations, demonstrating jet formation via GRMHD and analyzing nucleosynthesis, advancing understanding of GRB-SN connections.

Findings

Jets are launched mainly by toroidal magnetic fields.

GRMHD simulations show jets with high energy flux and potential for high Lorentz factors.

Nucleosynthesis results indicate sensitivity of 56Ni production to energy deposition.

Abstract

I have developed two numerical codes to investigate the dynamics of collapsars. One is two-dimensional MHD code that are performed using the Newtonian (ZEUS-2D) code where realistic equation of state, neutrino cooling and heating processes are taken into account. The other one is two-dimensional general relativistic magnetohydrodynamic (GRMHD) code. I have performed numerical simulations of collapsars using these codes and realistic progenitor models. In the Newtonian code, it is found that neutrino heating processes are not efficient enough to launch a jet in this study. It is also found that a jet is launched mainly by toroidal fields that are amplified by the winding-up effect. However, since the ratio of total energy relative to the rest-mass energy in the jet is not as high as several hundred, we conclude that the jets seen in this study are not GRB jets. In the GRMHD simulation, it is shown that a jet is launched from the center of the progenitor. We also find that the mass accretion rate after the launch of the jet shows rapid time variability that resembles to a typical time profile of a GRB. We find that the energy flux per unit rest-mass flux is as high as 10^2 at the bottom of the jet. Thus we conclude that the bulk Lorentz factor of the jet can be potentially high when it propagates outward. We also performed two-dimensional relativistic hydrodynamic simulations of the collapsar model to investigate the explosive nucleosynthesis happened there. It is found that the amount of 56Ni is very sensitive to the energy deposition rate. Thus the synthesized 56Ni can be little even if the total explosion energy is as large as 10^52 erg. We conclude that some GRBs can associate with faint supernovae.