# On the role of the Kerr-Newman black hole in the GeV emission of long gamma-ray bursts

## TL;DR

This paper investigates the role of Kerr-Newman black holes in the GeV emission of long gamma-ray bursts, proposing a model linking BH properties to observed high-energy emissions and their geometrical distribution.

## Contribution

It introduces a new asymmetric emission model for BdHNe, connecting BH spin and mass to GeV emission and revealing a cone-shaped emission geometry similar to AGN.

## Key findings

- GeV emission is absent in XRFs, present in some BdHNe, and blocked by SN ejecta in others.
- The emission occurs within a cone of approximately 60° half-opening angle.
- The GeV luminosity follows a universal power-law decay, enabling BH spin-down estimation.

## Abstract

X-ray Flashes (XRFs), binary-driven hypernovae (BdHNe) are long GRB subclasses with progenitor a CO$_{\rm core}$, undergoing a supernova (SN) explosion and hypercritically accreting in a tight binary system onto a companion neutron star (NS) or black hole (BH). In XRFs the NS does not reach by accretion the critical mass and no BH is formed. In BdHNe I, with shorter binary periods, the NS gravitationally collapses and leads to a new born BH. In BdHNe II the accretion on an already formed BH leads to a more massive BH. We assume that the GeV emission observed by \textit{Fermi}-LAT originates from the rotational energy of the BH. Consequently, we verify that, as expected, in XRFs no GeV emission is observed. In $16$ BdHNe I and $5$ BdHNe II, within the boresight angle of LAT, the integrated GeV emission allows to estimate the initial mass and spin of the BH. In the remaining $27$ sources in the plane of the binary system no GeV emission occurs, hampered by the presence of the HN ejecta. From the ratio, $21/48$, we infer a new asymmetric morphology for the BdHNe reminiscent of the one observed in active galactic nuclei (AGN): the GeV emission occurs within a cone of half-opening angle $\approx 60^{\circ}$ from the normal to the orbital plane of the binary progenitor. The transparency condition requires a Lorentz factor $\Gamma \sim 1500$ on the source of GeV emission. The GeV luminosity in the rest-frame of the source follows a universal power-law with index of $-1.20 \pm 0.04$, allowing to estimate the spin-down rate of the BH