Brightness-independent measurements of GRB durations

We present measurements of T90 and T50 durations of BATSE gamma-ray bursts in the 3B catalog, based on an automated algorithm designed to reduce brightness bias effects by scaling burst peak intensities and variances to those of the dimmest burst in the sample. A multi-scale threshold is applied to estimate the beginning and end of burst activity. T90 and T50 measures indicate an observed time-dilation factor of order 2 between average durations of bright and dim bursts. We also estimate the dependence of duration measure on energy band, and find that an increase of order 10–25% would be required if the actual cosmological time-dilation factor were 2–3.