  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.

High Energy Astrophysical Phenomena;Cosmology and Nongalactic Astrophysics;High Energy Physics - Phenomenology;Space Physics