Does the Amati correlation exhibit redshift-driven heterogeneity in long GRBs?

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. We analyzed 221 long GRBs with redshifts from 0.034 to 8.2, dividing them by 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 2σ at $z=1.5$ and more than 1σ at $z=2$, suggest an evolution in the GRB population with redshift, possibly reflecting changes in host galaxy properties. The Akaike and Bayesian Information Criteria also confirm these results. However, selection effects and instrumental biases may also contribute to it. 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.