GRB 090618: The First Example of a Neutron Star Gravitational Collapse to a Black Hole Induced by a Type Ib/c Supernova

TL;DR

This paper proposes a model where a neutron star collapses into a black hole due to accretion from a Type Ib/c supernova, explaining the temporal coincidence of GRB 090618 with a supernova event.

Contribution

It introduces a novel scenario linking neutron star collapse to black hole formation triggered by a supernova, specifically applied to GRB 090618.

Findings

Neutron star reaches critical mass in seconds leading to collapse.

Mass ranges for neutron star and supernova progenitor are identified.

The model explains the timing of GRB 090618 with associated supernova.

Abstract

A novel concept has been recently proposed for explaining the temporal coincidence of some Gamma Ray Bursts (GRBs) with an associated Supernova (SN) in terms of the gravitational collapse of a neutron star (NS) to a Black Hole (BH), induced by a type Ib/c SN explosion. We apply these considerations to the exceptional case of GRB 090618, for which there is evidence of a SN $\sim 10$ days after the GRB occurrence. We calculate the accretion rate and total accreted mass onto a NS from a SN Ib/c originated from a companion evolved star. It is shown that the NS reaches in a few seconds the critical mass and undergoes gravitational collapse to a BH leading to the emission of a GRB. We find for the mass of the NS companion, $M_{\rm NS}$, and for the SN core progenitor, $M_{\rm core}$, the following mass ranges: $1.8\lesssim M_{NS}/M_\odot \lesssim 2.1$ and $3\leq M_{\rm core}/M_\odot \leq 8$. Finally, we discuss the complementarity of these considerations to alternative processes explaining long and short GRBs.