The Dependence of Gamma-Ray Burst Jet Collimation on Black Hole Spin

TL;DR

This paper explores how the spin of black holes influences the collimation of gamma-ray burst jets, suggesting higher spins lead to narrower jets, which may explain observed correlations with redshift.

Contribution

It introduces the first investigation of black hole spin effects on jet collimation using 3D GRRMHD simulations, revealing a link between spin and jet narrowing.

Findings

Higher black hole spins produce narrower jets.

Simulation results support the spin's role in jet collimation.

Potential explanation for jet angle-redshift correlation.

Abstract

Gamma-Ray Bursts are the most luminous events in the Universe, and are excellent laboratories to study extreme physical phenomena in the cosmos. Despite a long trajectory of progress in understanding these highly energetic events, there are still many observed features that are yet to be fully explained. Observations of the jet opening angle of long gamma-ray bursts (LGRBs) suggest that LGRB jets are narrower for those GRBs at higher redshift. This phenomenon has been explained in the context of collimation by the stellar envelope, with denser (lower metallicity) stars at higher redshifts able to collimate the jet more effectively. However, until now, the dependence of jet opening angle on the properties of the central engine has not been explored. We investigate the effect of black hole spin on the jet collimation angle for a magnetically launched jet, using the General Relativistic Radiation Magnetohydrodynamical (GRRMHD) code \nubhlight. We present 3D results for a range of spin values. The simulations show that higher spinning black holes tend to create narrower jets. If indeed LGRB progenitors in the early universe are able to produce black hole central engines with higher spin, this could account for at least some of the observed jet opening angle-redshift correlation.