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

Abstract 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 H0 = 72 km s−1 Mpc−1. Further analysis indicated that the cumulative redshift distribution is weakly sensitive to variations in the Hubble constant H0, 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 H0 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 H0, and the model predictions using H0 ≈ 68 − 80 km s−1 Mpc−1 provide agreement with the observed LGRB distributions.