Hardness as a Spectral Peak Estimator for Gamma-Ray Bursts

TL;DR

This paper demonstrates that a simple hardness ratio effectively estimates the spectral peak energy in Gamma-Ray Bursts, showing a strong, nearly linear correlation across different burst types and enabling spectral peak predictions for a large GRB catalog.

Contribution

It introduces a new spectral peak estimator based on hardness ratios, validated with Bayesian and MCMC methods, applicable across diverse GRB types and extensive datasets.

Findings

High correlation between hardness ratio and spectral peak energy.

The relation is nearly linear over the BATSE energy range.

Predictions for nearly all BATSE GRBs are provided.

Abstract

Simple hardness ratios are found to be a good estimator for the spectral peak energy in Gamma-Ray Bursts (GRBs). Specifically, a high correlation strength is found between the $\nu F_{\nu}$ peak in the spectrum of BATSE GRBs, $\epo$, and the hardness of GRBs, $\hr$, as defined by the fluences in channels 3 and 4, divided by the combined fluences in channels 1 and 2 of the BATSE Large Area Detectors. The correlation is independent of the type of the burst, whether Long-duration GRB (LGRB) or Short-duration (SGRB) and remains almost linear over the wide range of the BATSE energy window (20-2000 KeV). Based on Bayes theorem and Markov Chain Monte Carlo techniques, we also present multivariate analyses of the observational data while accounting for data truncation and sample-incompleteness. Prediction intervals for the proposed \hrep ~relation are derived. Results and further simulations are used to compute $\epo$ estimates for nearly the entire BATSE catalog: 2130 GRBs. These results may be useful for investigating the cosmological utility of the spectral peak in GRBs intrinsic luminosity estimates.