Hadronic supercriticality as a trigger for GRB emission

Abstract

We explore a one-zone hadronic model that may be able to reproduce $\gamma$-ray burst (GRB) prompt emission with a minimum of free parameters. Assuming only that GRBs are efficient high-energy proton accelerators and without the presence of an ab initio photon field, we investigate the conditions under which the system becomes supercritical, i.e. there is a fast, non-linear transfer of energy from protons to secondary particles initiated by the spontaneous quenching of proton-produced $\gamma$-rays. We first show analytically that the transition to supercriticality occurs whenever the proton injection compactness exceeds a critical value, which favours high proton injection luminosities and a wide range of bulk Lorentz factors. The properties of supercriticality are then studied with a time-dependent numerical code that solves concurrently the coupled equations of proton, photon, electron, neutron and neutrino distributions. For conditions that drive the system deep into the supercriticality we find that the photon spectra obtain a Band-like shape due to Comptonization by cooled pairs and that the energy transfer efficiency from protons to $\gamma$-rays and neutrinos is high reaching $\sim 0.3$. Although some questions concerning its full adaptability to the GRB prompt emission remain open, supercriticality is found to be a promising process in that regard.

15 pages, 10 figures, 1 table, accepted by MNRAS

References in corpus (11)

• Gamma-Ray Bursts: Progress, Problems & Prospects
• Modeling the Emission Processes in Blazars
• Prompt emission spectra from the photosphere of a GRB
• Synchrotron emission in small scale magnetic field as possible explanation for prompt emission spectra of gamma-ray bursts
• Prompt GeV-TeV Emission of Gamma-Ray Bursts Due to High-Energy Protons, Muons and Electron-Positron Pairs
• Ultra-high energy cosmic rays, cascade gamma-rays, and high-energy neutrinos from gamma-ray bursts
• GRB Energetics in the Swift Era
• Magnetic Field and Flavor Effects on the Gamma-Ray Burst Neutrino Flux
• UHECR escape mechanisms for protons and neutrons from GRBs, and the cosmic ray-neutrino connection
• The role of hadronic cascades in GRB models of efficient neutrino production
• The Supercritical Pile GRB Model: The Prompt to Afterglow Evolution