Analysis of the observed and intrinsic durations of $Swift$/BAT gamma-ray bursts

TL;DR

This study analyzes the duration distribution of 947 Swift/BAT gamma-ray bursts, finding that a two-Gaussian model best describes the data and that the intermediate-duration class is unlikely to exist.

Contribution

It provides a statistical analysis of GRB durations, demonstrating that a two-Gaussian model suffices and challenging the existence of an intermediate class.

Findings

Two-Gaussian model fits the data better than three-Gaussian.

Intermediate-duration class is unlikely to be present.

Duration distributions differ between observed and rest frames.

Abstract

The duration distribution of 947 GRBs observed by $Swift$/BAT, as well as its subsample of 347 events with measured redshift, allowing to examine the durations in both the observer and rest frames, are examined. Using a maximum log-likelihood method, mixtures of two and three standard Gaussians are fitted to each sample, and the adequate model is chosen based on the value of the difference in the log-likelihoods, Akaike information criterion and Bayesian information criterion. It is found that a two-Gaussian is a better description than a three-Gaussian, and that the presumed intermediate-duration class is unlikely to be present in the $Swift$ duration data.