Gamma-Ray Burst high energy emission from Internal Shocks

TL;DR

This study models synchrotron and SSC emissions from internal shocks in GRBs to evaluate their role in prompt and flare emissions and assess high-energy detectability with satellites.

Contribution

It provides a detailed analysis of internal shock parameters that can produce observed GRB flares and predicts high-energy emission detectability with specific satellite configurations.

Findings

High Lorentz factors enhance SSC detectability during prompt emission.

X-ray flares with lower Lorentz factors lack high-energy counterparts.

Substructure in flare light curves can indicate internal shock origins.

Abstract

In this paper we study synchrotron and synchrotron self Compton (SSC) emission from internal shocks (IS) during the prompt and X-ray flare phases of Gamma-Ray Bursts (GRBs). The aim is to test the IS model for the flare emission and for whether GRBs can be GeV sources. We determine the parameters for which the IS model can account for the observed prompt and X-ray flares emission, and study the detectability of the high energy SSC emission by the AGILE and GLAST satellites. We find that the detectability of the SSC emission during the prompt phase of GRBs improves for higher values of the fireball Lorentz factor and of the temporal variability. If IS is the mechanism responsible of the flare emission, and the Lorentz factor of the shells producing the flare is of the order of 100, the flare light curves are expected to present some substructures with temporal variability of 10-100 ms which are much smaller than the average duration of flares, and similar to those observed during the prompt phase of GRBs. If one assumes lower Lorentz factors, such as 10-25, then a larger temporal variaibility of 40 s can also account for the observed flare properties. However in this case we predict that X-ray flares do not have a counterpart at very high energies (MeV-GeV). An investigation on the substructures of the X-ray flares light curves, and simultaneous X-ray and high energy observations, will allow us to corroborate the hypothesis that late IS are responsible of the X-ray flares.