Revisiting the Spectral-Energy Correlations of GRBs with {\it Fermi} Data I: Model-wise Properties

TL;DR

This study analyzes Fermi-GBM GRB data to examine spectral-energy correlations across different spectral models, revealing model-dependent differences and suggesting distinct radiation mechanisms for different burst types.

Contribution

It provides a comprehensive, model-independent catalog of GRBs with detailed spectral analysis, highlighting the model-wise dependence of spectral-energy correlations.

Findings

A tight correlation between $E_{p,z}$ and $E_{γ, m iso}$ for Band-like and CPL-like bursts.

CPL-like bursts do not follow the same correlations as Band-like bursts, indicating different radiation processes.

Spectral-energy correlations are strongly dependent on the spectral model used.

Abstract

Gamma-ray bursts (GRBs) exhibit a diversity of spectra. Several spectral models (e.g., Band, cutoff power-law, and blackbody) and their hybrid versions (e.g., Band+blackbody) have been widely used to fit the observed GRB spectra. Here, we attempt to collect all the bursts detected by {\it Fermi}-GBM with known redshifts from July 2008 to May 2022, motivated to (i) provide a parameter catalog independent from the official \emph{Fermi}/GBM team and (ii) achieve a ``clean" model-based GRB spectral-energy correlation analysis. A nearly complete GRB sample was created, containing 153 such bursts (136 long gamma-ray bursts and 17 short gamma-ray bursts). Using the sample and by performing detailed spectral analysis and model comparisons, we investigate two GRB spectral-energy correlations: the cosmological rest-frame peak energy ($E_{\rm p,z}$) of the $\nu F_\nu$ prompt emission spectrum correlated with (i) the isotropic-bolometric-equivalent emission energy $E_{\gamma, \rm iso}$ (the Amati relation), and (ii) the isotropic-bolometric-equivalent peak luminosity $L_{\rm p, iso}$ (the Yonetoku relation). From a linear regression analysis, a tight correlation between $E_{\rm p,z}$ and $E_{\gamma, \rm iso}$ (and $L_{\gamma,\rm iso}$) is found for both the Band-like and CPL-like bursts. More interestingly, the CPL-like bursts do not fall on the Band-like burst Amati and Yonetoku correlations, suggesting distinct radiation processes, and pointing towards the fact that these spectral-energy correlations are tightly reliant on the model-wise properties.