GRB Spectra in the complex of synchrotron and Compton processes

TL;DR

This paper models GRB spectra considering synchrotron and Compton processes, revealing broken power laws, phase transitions, and correlations between flux and peak energy, providing insights into electron acceleration and shock models.

Contribution

It introduces a detailed electron spectrum model under complex radiation processes and analyzes spectral indices and phase transitions in GRBs, addressing the $eta o -1$ problem.

Findings

GRB spectra follow a broken power law in different phases.

Strong correlations between spectral indices and peak energy are observed.

The complex scenario challenges existing electron acceleration mechanisms.

Abstract

Under the steady state condition, the spectrum of electrons is investigated by solving the continuity equation under the complex radiation of both the synchrotron and Compton processes. The resulted GRB spectrum is a broken power law in both the fast and slow cooling phases. On the basis of this electron spectrum, the spectral indices of the Band function in four different phases are presented. In the complex radiation frame, the detail investigation on physical parameters reveals that both the reverse shock photosphere model and the forward shock with strong coupling model can answer the $\alpha \sim -1$ problem. A possible marginal to fast cooling phase transition in GRB 080916C is discussed. The time resolved spectra in different pulses of GRB 100724B, GRB 100826A and GRB 130606B are investigated. We found that the flux is proportional to the peak energy in almost all pulses. The phases for different pulses are determined according to the spectral index revolution. We found the strong correlations between spectral indices and the peak energy in GRB 100826A, which can be explained by the Compton effect in the fast cooling phase. However, the complex scenario predicts a steeper index for the injected electrons, which challenges the acceleration mechanism in GRBs.