A possible redshift evolution of the time-lag and variability luminosity relations for long gamma-ray bursts Original Research Article

Several luminosity relations currently exist for long gamma-ray bursts (GRBs). Some were derived from the light curves; others were obtained from the spectra. In this study, we consider two of these luminosity relations: the time-lag, image, relation and the variability, V, relation and investigate their possible dependence on (or “evolution” with) the redshift, z. The data we use are taken from Schaefer’s literature (Schaefer et al., 2007) in which 69 long gamma-ray bursts were analyzed. The method consists of binning the data by redshift interval, then writing the time-lag relation in the form image and extracting the fit parameters A and B for each redshift bin; likewise, for the variability relation, which we write in the form image. The objective is then to see whether the fitting parameters A and B evolve in any systematic way with the redshift. Our analysis indicates that both the A and B parameters do evolve with z in a systematic way for the lag-relation but not for the variability relation. A flat universe with image, and image is assumed.