Central engines of Gamma Ray Bursts. Magnetic mechanism in the collapsar model

TL;DR

This paper investigates the magnetic mechanisms driving gamma-ray bursts in the collapsar model by simulating the collapse of massive stars onto black holes, highlighting jet formation via the Blandford-Znajek process.

Contribution

It extends previous work by modeling the collapse with detailed magnetohydrodynamics, realistic physics, and analyzing jet formation and explosion criteria in the collapsar scenario.

Findings

Strong Poynting-dominated jets can be produced with powers up to 12×10^{51} erg/s.

Jets originate from the black hole and are powered by the Blandford-Znajek mechanism.

A provisional criterion for explosion is proposed.

Abstract

In this study we explore the magnetic mechanism of hypernovae and relativistic jets of long duration gamma ray bursts within the collapsar scenario. This is an extension of our earlier work [1]. We track the collapse of massive rotating stars onto a rotating central black hole using axisymmetric general relativistic magnetohydrodynamic code that utilizes a realistic equation of state and takes into account the cooling associated with emission of neutrinos and the energy losses due to dissociation of nuclei. The neutrino heating is not included. We describe solutions with different black hole rotation, mass accretion rate, and strength of progenitor's magnetic field. Some of them exhibits strong explosions driven by Poynting-dominated jets with power up to $12\times10^{51} {erg s}^{-1}$. These jets originate from the black hole and powered via the Blandford-Znajek mechanism. A provisional criterion for explosion is derived. A number of simulation movies can be downloaded from http://www.maths.leeds.ac.uk/~serguei/research/movies/anim.html