The luminosity of GRB afterglows as distance estimator

TL;DR

This paper explores how clustering in GRB afterglow light curves at X-ray and optical wavelengths can be used to estimate their distances, offering a new method for redshift determination based on early afterglow observations.

Contribution

It introduces a novel approach to estimate GRB redshifts using early afterglow fluxes and properties, linking clustering patterns to physical parameters of the fireball.

Findings

Clustering correlates with fireball energy and environment.

Method accurately estimates redshift for tested GRBs.

Supports using early afterglow data for distance measurement.

Abstract

We investigate the clustering of afterglow light curves observed at X-ray and optical wavelengths. We have constructed a sample of 61 bursts with known distance and X-ray afterglow. GRB sources can be divided in three classes, namely optical and X-ray bright afterglows, optical and X-ray dim one s, and optically bright -X-ray dim ones. We argue that this clustering is related to the fireball total energy, the external medium density, the fraction of fireball energy going in relativistic electrons and magnetic fields. We propose a method for the estimation of the GRB source redshift based on the observe d X-ray flux one day after the burst and optical properties. We tested this method on three recently detected SWIFT GRBs with known redshift, and found it i n good agreement with the reported distance from optical spectroscopy.