External Shocks, UHECRs, and the Early Afterglow of GRBs

TL;DR

This paper explores how external shocks in gamma-ray bursts can produce ultra-high-energy cosmic rays and explain rapid X-ray declines, suggesting a link between cosmic ray acceleration and GRB afterglow features.

Contribution

It proposes that external shocks in GRBs can accelerate UHECRs and cause rapid afterglow declines, challenging the central engine activity paradigm.

Findings

External shocks can accelerate cosmic rays to 10^{20} eV.

Hadronic energy escape affects GRB blast wave deceleration.

External shocks may explain rapid X-ray declines in Swift GRBs.

Abstract

Highly variable gamma-ray pulses and X-ray flares in GRB light curves can result from external shocks rather than central engine activity under the assumption that the GRB blast-wave shell does not spread. Acceleration of cosmic rays to 10^{20} eV energies can take place in the external shocks of GRBs. Escape of hadronic energy in the form of UHECRs leads to a rapidly decelerating GRB blast wave, which may account for the rapid X-ray declines observed in Swift GRBs.