Accretion induced black hole spin up in magnetized collapsars

TL;DR

This paper investigates how magnetized stellar collapses can spin up black holes by combining semi-analytical models with numerical GRMHD simulations to understand the evolution of black hole parameters.

Contribution

It introduces a combined semi-analytical and numerical approach to study black hole spin-up during collapsar events with magnetic fields.

Findings

Black hole spin increases during magnetized collapse.

Progenitor rotation influences final black hole parameters.

Constraints on black hole spin and mass from different progenitor models.

Abstract

We study the gravitational collapse and formation of the Kerr black hole from the rotating progenitor star. We follow the evolution of black hole spin, coupled with its increasing mass. We study the effect of different level of rotation endowed in the progenitor's envelope, and we out some constraints on the final black hole parameters. Our method is based on semi-analytical computations that involve stellar-evolution models of different progenitors. We also follow numerically the black hole evolution and spacetime metric changes during the collapse, via General Relativistic MHD modeling. (abridged)