Neutrino-cooled accretion and GRB variability

TL;DR

This paper explores how the transition from advection-dominated to neutrino-cooled accretion disks around black holes affects gamma-ray burst (GRB) emissions, linking disk physics to observable spectral features.

Contribution

It demonstrates that small increases in accretion rate during the transition significantly enhance Poynting luminosity and alter GRB spectra, providing a physical explanation for observed spectral variations.

Findings

Enhanced Poynting luminosity during transition

Decreased baryon loading in GRB flows

Explanation for spectral narrowing with energy

Abstract

For accretion rates Mdot~0.1 Msun/s to a few solar mass black hole the inner part of the disk is expected to make a transition from advection dominance to neutrino cooling. This transition is characterized by sharp changes of the disk properties. I argue here that during this transition, a modest increase of the accretion rate leads to powerful enhancement of the Poynting luminosity of the GRB flow and decrease of its baryon loading. These changes of the characteristics of the GRB flow translate into changing gamma-ray spectra from the photosphere of the flow. The photospheric interpretation of the GRB emission explains the observed narrowing of GRB pulses with increasing photon energy and the luminosity-spectral peak relation within and among bursts.