GeV Emission from neutron-rich internal shocks of some long Gamma-ray Bursts

TL;DR

This paper proposes that in long gamma-ray bursts, neutron decay and subsequent interactions produce GeV gamma-ray emission, which could be detected by future space telescopes like GLAST.

Contribution

It introduces a model linking neutron-rich internal shocks in long GRBs to observable GeV emission via electron acceleration and decay processes.

Findings

GeV emission is expected in some long GRBs due to neutron decay interactions.

The emission is detectable by upcoming satellite GLAST.

The model explains the origin of high-energy gamma rays in long GRBs.

Abstract

In the neutron-rich internal shocks model for gamma-ray bursts (GRBs), the Lorentz factors (LFs) of ion shells are variable, and so are the LFs of accompanying neutron shells. For slow neutron shells with a typical LF of approximate tens, the typical $\beta$-decay radius is $\sim 10^{14}-10^{15}$ cm. As GRBs last long enough [$T_{90}>14(1+z)$ s], one earlier but slower ejected neutron shell will be swept successively by later ejected ion shells in the range $\sim10^{13}-10^{15}$ cm, where slow neutrons have decayed significantly. Part of the thermal energy released in the interaction will be given to the electrons. These accelerated electrons will be mainly cooled by the prompt soft $\gamma-$rays and give rise to GeV emission. This kind of GeV emission is particularly important for some very long GRBs and is detectable for the upcoming satellite {\it Gamma-Ray Large Area Space Telescope} (GLAST).