The Observed Luminosity Correlations of Gamma-Ray Bursts and Their Applications

TL;DR

This paper reviews empirical luminosity correlations in gamma-ray bursts, discusses their theoretical interpretations, and explores their potential for cosmological applications despite calibration challenges.

Contribution

It provides a comprehensive overview of GRB parameter correlations, their theoretical basis, and methods to calibrate them for cosmological use, addressing the circularity problem.

Findings

Various GRB parameter correlations are identified and discussed.

Calibration efforts aim to overcome the circularity problem.

Potential of certain correlations as redshift indicators is highlighted.

Abstract

Gamma-ray bursts (GRBs) are among the most luminous electromagnetic transients in the universe, providing unique insights into extreme astrophysical processes and serving as promising probes for cosmology. Unlike Type Ia supernovae, which have a unified explosion mechanism, GRBs cannot directly act as standard candles for tracing cosmic evolution at high redshifts due to significant uncertainties in their underlying physical origins. Empirical correlations derived from statistical analyses involving various GRB parameters provide valuable information regarding their intrinsic properties. In this brief review, we describe various correlations among GRB parameters involving the prompt and afterglow phases, discussing possible theoretical interpretations behind them. The scarcity of low-redshift GRBs poses a major obstacle to the application of GRB empirical correlations in cosmology, referred to as the circularity problem. We present various efforts aiming at calibrating GRBs to address this challenge and leveraging established empirical correlations to constrain cosmological parameters. The pivotal role of GRB sample quality in advancing cosmological research is underscored. Some correlations that could potentially be utilized as redshift indicators are also introduced.