Bayesian Time-Resolved Spectroscopy of GRB Pulses: $\alpha$-Intensity Correlation

TL;DR

This paper employs Bayesian analysis to study time-resolved spectra of GRB pulses, revealing a systematic correlation between the low-energy spectral index and energy flux, interpreted within the photospheric emission framework.

Contribution

It introduces a Bayesian method for fitting GRB spectra and uncovers a consistent $oldsymbol{ extit{ extbf{alpha}}}$-energy flux correlation in long GRB pulses, advancing understanding of spectral evolution.

Findings

Identified a systematic $oldsymbol{ extit{ extbf{alpha}}}$-energy flux correlation.

Interpreted the correlation within the photospheric emission model.

Analyzed 9 years of Fermi/GBM data for long GRB pulses.

Abstract

Gamma-ray bursts (GRBs) show different behaviours and trends in their spectral evolution. One of the methods used to understand the physical origin of these behaviours is to study correlation between the spectral fit parameters. In this work, we used a Bayesian analysis method to fit time-resolved spectra of GRB pulses that were detected by the \textit{Fermi}/GBM during its first 9 years of mission. We studied single pulsed long bursts ($T_{90}\geq2$ s). Among all the parameter correlations, we found that the correlation between the low-energy power-law index $\alpha$ and the energy flux exhibited a systematic behaviour. We presented the properties of the observed characteristics of this behaviour and interpreted it in the context of the photospheric emission model.