Modeling Spectral Variability of Prompt GRB Emission within the Jitter Radiation Paradigm

TL;DR

This paper models the spectral variability of prompt gamma-ray burst emission using jitter radiation, explaining observed spectral features and correlations through anisotropic radiation patterns and relativistic effects.

Contribution

It introduces a novel application of jitter radiation to explain spectral variability and correlations in GRB prompt emission, supported by implementation results.

Findings

Reproduces spectral softening within pulses

Explains flux-spectral parameter correlations

Predicts hard spectra at spike onset

Abstract

The origin of rapid spectral variability and certain spectral correlations of the prompt gamma-ray burst emission remains an intriguing question. The recently proposed theoretical model of the prompt emission is build upon unique spectral properties of jitter radiation -- the radiation from small-scale magnetic fields generated at a site of strong energy release (e.g., a relativistic collisionless shock in baryonic or pair-dominated ejecta, or a reconnection site in a magnetically-dominated outflow). Here we present the results of implementation of the model. We show that anisotropy of the jitter radiation pattern and relativistic shell kinematics altogether produce effects commonly observed in time-resolved spectra of the prompt emission, e.g., the softening of the spectrum below the peak energy within individual pulses in the prompt light-curve, the so-called "tracking" behavior (correlation of the observed flux with other spectral parameters), the emergence of hard, synchrotron-violating spectra at the beginning of individual spikes. Several observational predictions of the model are discussed.