Does the Amati Correlation Exhibit Redshift-Driven Heterogeneity in Long GRBs?

TL;DR

This study investigates whether the Amati correlation in long GRBs varies with redshift, revealing significant heterogeneity that suggests evolution in GRB properties over cosmic time, impacting their use in cosmology.

Contribution

It provides evidence of redshift-dependent heterogeneity in the Amati relation, challenging its assumed universality and highlighting the need for larger, more precise datasets.

Findings

Significant differences in Amati parameters between low and high redshift groups.

Variation in parameters is approximately 2σ at z=1.5 and >1σ at z=2.

Results suggest possible evolution in GRB population with redshift.

Abstract

Long gamma-ray bursts (GRBs) offer significant insights into cosmology due to their high energy emissions and the potential to probe the early universe. The Amati relation, which links the intrinsic peak energy to the isotropic energy, is crucial for understanding their cosmological applications. This study investigates the redshift-driven heterogeneity of the Amati correlation in long GRBs. Analyzing 221 long GRBs with redshifts from 0.034 to 8.2 we divided the dataset based on redshift thresholds of 1.5 and 2. Using Bayesian marginalization and Reichart's likelihood approach, we found significant differences in the Amati parameters between low and high redshift subgroups. These variations, differing by approximately $2\sigma$ at $z = 1.5$ and more than $1\sigma$ at $z = 2$, suggest an evolution in the GRB population with redshift, possibly reflecting changes in host galaxy properties. However, selection effects and instrumental biases may also contribute. Our results challenge the assumption of the Amati relation's universality and underscore the need for larger datasets and more precise measurements from upcoming missions like Transient High-Energy Sky and Early Universe Surveyor (THESEUS) and enhanced X-ray Timing and Polarimetry mission (eXTP) to refine our understanding of GRB physics.