Investigating the Evolution of Amati Parameters with Redshift

TL;DR

This study examines whether the spectral-energy correlation of Gamma Ray Bursts, known as the Amati relation, evolves with redshift by analyzing a large sample and finding potential intrinsic differences.

Contribution

It provides evidence that the Amati parameters may intrinsically vary with redshift, challenging the assumption of their universality in cosmological applications.

Findings

Amati parameters differ significantly between low and high redshift groups.

Selection effects are unlikely to explain the observed differences.

Results suggest possible intrinsic evolution of GRB properties with redshift.

Abstract

Gamma Ray Bursts (GRB) are among the brightest objects in the Universe and hence can be observed up to a very high redshift. Properly calibrated empirical correlations between intensity and spectral correlations of GRBs can be used to estimate the cosmological parameters. However, the possibility of the evolution of GRBs with the redshift is a long-standing puzzle. In this work, we used 162 long-duration GRBs to determine whether GRBs below and above a certain redshift have different properties. The GRBs are split into two groups, and we fit the Amati relation for each group separately. Our findings demonstrate that estimations of the Amati parameters for the two groups are substantially dissimilar. We perform simulations to investigate whether the selection effects could cause the difference. Our analysis shows that the differences may be intrinsic, and the selection effects are not their true origin.