High-energy emission as a test of the prior emission model for gamma-ray burst afterglows

TL;DR

This paper investigates high-energy gamma-ray emission from gamma-ray bursts within the prior emission model, predicting detectable signals around the end of the X-ray plateau phase, which can be tested with current and future telescopes.

Contribution

It provides a detailed prediction of high-energy gamma-ray signals from GRBs in the prior emission model, linking X-ray plateau features to gamma-ray observables.

Findings

Peak gamma-ray energy around 10-100 GeV at plateau end

Detectability of signals by Cherenkov telescopes like MAGIC, VERITAS, CTA

External inverse-Compton emission may produce delayed GeV-TeV signals

Abstract

We study high-energy gamma-ray afterglow emission from gamma-ray bursts (GRBs) in the prior emission model, which is proposed to explain the plateau phase of the X-ray afterglow. This model predicts the high-energy gamma-ray emission when the prompt GRB photons from the main flow are up-scattered by relativistic electrons accelerated at the external shock due to the prior flow. The expected spectrum has the peak of 10-100 GeV at around the end time of the plateau phase for typical GRBs, and high-energy gamma rays from nearby and/or energetic GRBs can be detected by current and future Cherenkov telescopes such as MAGIC, VERITAS, CTA, and possibly Fermi. Multi-wavelength observations by ground-based optical telescopes as well as Fermi and/or Swift sattelites are important to constrain the model. Such external inverse-Compton emission may even lead to GeV-TeV gamma-ray signals with the delay time of 10-100 s, only if the plateau phase is short-lived.