Study of possible systematics in the L*X - Ta* correlation of Gamma Ray Bursts

TL;DR

This study investigates the L*X - Ta* correlation in Gamma Ray Bursts to identify potential systematics and assess its use as a redshift estimator, confirming the correlation's physical basis but noting significant uncertainties.

Contribution

It provides a systematic analysis of the L*X - Ta* correlation in GRBs, confirming its physical origin and evaluating its potential as a cosmological tool.

Findings

No systematic bias found in the correlation

Confirmation of physical GRB subclasses

Limited utility of the correlation as a redshift estimator due to scatter

Abstract

Gamma Ray Bursts (GRBs) are the most energetic sources in the universe and among the farthest known astrophysical sources. These features make them appealing candidates as standard candles for cosmological applications so that studying the physical mechanisms for the origin of the emission and correlations among their observable properties is an interesting task. We consider here the luminosity L*X - break time Ta* (hereafter LT) correlation and investigate whether there are systematics induced by selection effects or redshift dependent calibra- tion. We perform this analysis both for the full sample of 77 GRBs with known redshift and for the subsample of GRBs having canonical X-ray light curves, hereafter called U0095 sample. We do not find any systematic bias thus con- firming the existence of physical GRB subclasses revealed by tight correlations of their afterglow properties. Furthermore, we study the possibility of applying the LT correlation as a redshift estimator both for the full distribution and for the canonical lightcurves. The large uncertainties and the non negligible intrin- sic scatter make the results not so encouraging, but there are nevertheless some hints motivating a further analysis with an increased U0095 sample.