General Relativistic Simulations of the Collapsar Scenario

TL;DR

This paper uses advanced general relativistic hydrodynamic simulations to investigate the collapsar model for gamma-ray bursts, focusing on core collapse, black hole formation, and the effects of rotation and metallicity.

Contribution

It introduces a comprehensive simulation framework with a new neutrino leakage scheme to study collapsar scenarios in 1D and 2D, highlighting the role of rotation in black hole formation.

Findings

Fast rotating cores lead to Kerr black holes.

Neutrino cooling enables the formation of a metastable neutron star.

Fallback matter can cause black hole formation despite supernova shocks.

Abstract

We are exploring the viability of the collapsar model for long-soft gamma-ray bursts. For this we perform state-of-the-art general relativistic hydrodynamic simulations in a dynamically evolving space-time with the CoCoNuT code. We start from massive low metallicity stellar models evolved up to core gravitational instability, and then follow the subsequent evolution until the system collapses forming a compact remnant. A preliminary study of the collapse outcome is performed by varying the typical parameters of the scenario, such as the initial stellar mass, metallicity, and rotational profile of the stellar progenitor. 1D models (without rotation) have been used to test our newly developed neutrino leakage scheme. This is a fundamental piece of our approach as it allows the central remnant (in all cases considered, a metastable high-mass neutron star) to cool down, eventually collapsing to a black hole. In two dimensions, we show that sufficiently fast rotating cores lead to the formation of Kerr black holes, due to the fall-back of matter surrounding the compact remnant, which has not been successfully unbounded by a precedent supernova shock.