The LGRBs Redshift and Jet Opening Angle Distributions and the Hubble Constant H 0

Using the Swift-Perley sample, Le, Ratke, & Mehta performed a study of the rate density of LGRBs with an assumed broken power-law GRB spectrum. They obtained a GRB-burst-rate functional form that fits the preSwift and Swift redshift cumulative distributions at all redshifts with an assumed Hubble constant of H 0 = 72, km, s-1, Mpc-1. Further analysis indicated that the cumulative redshift distribution is weakly sensitive to variations in the Hubble constant H 0, whereas the corresponding differential burst-rate distribution exhibits greater sensitivity. In this paper, we extend this analysis by comparing model predictions for different values of H 0 with the observed cumulative and differential redshift and jet-opening angle distributions, while adopting the same GRB framework and observational samples. We find that both the cumulative and differential distributions depend only weakly on variations in H 0, and the model predictions using H 0 about 68 - 80, km, s-1, Mpc-1 provide agreement with the observed LGRB distributions.