Determination of the intrinsic Luminosity Time Correlation in the X-ray Afterglows of GRBs

Author: Maria Dainotti

Abstract: Gamma-ray bursts (GRBs), which have been observed up to redshifts z ≈ 9.5 can be good probes of the early universe and have the potential of testing cosmological models. The analysis by Dainotti of afterglows lightcurves of GRBs with known redshifts and definite X-ray plateau shows an anti-correlation between the rest frame time when the plateau ends (the plateau end time) and the calculated luminosity at that time (or approximately an anti-correlation between plateau duration and luminosity). We here present an update of this correlation with a larger data sample of 100 GRBs with good lightcurves. Since some of this correlation could result from the redshift dependences of these parameters and/or their cosmological evolution we use the Efron-Petrosian method to reveal the intrinsic nature of this correlation. We find that the correlation is mostly intrinsic and describe how we recover it and how this can be used to constrain physical models of the plateau emission, whose origin is still unknown. We also present here the luminosity function and the GRB formation rate evolution. The present result could help clarifying the debated issue about the nature of the plateau emission and the relation between GRB and star formation rates.