Opaque or Transparent? A Link between Neutrino Optical Depths and the Characteristic Duration of Short Gamma-Ray Bursts

Abstract

Cosmological gamma-ray bursts (GRBs) are thought to occur as a result of violent hypercritical accretion onto stellar mass black holes, following either core collapse in massive stars or compact binary mergers. This dichotomy may be reflected in the two classes of bursts having different durations. Dynamical calculations of the evolution of these systems are essential if one is to establish characteristic relevant timescales. We show here for the first time the result of dynamical simulations, lasting approximately 1 s, of postmerger accretion disks around black holes, using a realistic equation of state and considering neutrino emission processes. We find that the inclusion of neutrino optical depth effects produces important qualitative temporal and spatial transitions in the evolution and structure of the disk, which may directly reflect on the duration and variability of short GRBs.