Gamma-ray Burst Prompt Emission Spectrum and $E_p$ Evolution Patterns in the ICMART Model

TL;DR

This study uses simulations within the ICMART model to reproduce GRB prompt emission spectra and $E_p$ evolution patterns, showing that complex observed behaviors can arise from multiple ICMART events driven by central engine activity.

Contribution

It demonstrates that the ICMART model can produce realistic GRB spectra and $E_p$ evolution patterns, including mixed behaviors, supporting its viability for explaining GRB prompt emission.

Findings

ICMART can generate Band-shaped spectra matching observations.

$E_p$ evolution in a single ICMART event is always hard-to-soft.

Combined ICMART events can produce diverse $E_p$ evolution patterns.

Abstract

In this paper, we simulate the gamma-ray bursts (GRBs) prompt emission light curve, spectrum and $E_p$ evolution patterns within the framework of the Internal-Collision-induced MAgnetic Reconnection and Turbulence (ICMART) model. We show that this model can produce a Band shape spectrum, whose parameters ($E_p$, $\alpha$, $\beta$) could distribute in the typical distribution from GRB observations, as long as the magnetic field and the electron acceleration process in the emission region are under appropriate conditions. On the other hand, we show that for one ICMART event, $E_p$ evolution is always a hard-to-soft pattern. However, a GRB light curve is usually composed of multiple ICMART events that are fundamentally driven by the erratic GRB central engine activity. In this case, we find that if one individual broad pulse in the GRB light curve is composed of multiple ICMART events, the overall $E_p$ evolution could be disguised as the intense-tracking pattern. Therefore, mixed $E_p$ evolution patterns can coexist in the same burst, with a variety of combined patterns. Our results support the ICMART model to be a competitive model to explain the main properties of GRB prompt emission. The possible challenges faced by the ICMART model are also discussed in details.