The spectral lag distribution of Swift gamma-ray bursts

Swift has detected 350 GRBs from its launch in November 2004 up to August 2008. Approximately one third of these bursts have a measured redshift. We present the spectral lag distributions of long and short-duration Swift GRBs. The spectral lags are determined using a cross-correlation analysis between lightcurves in the 15-25 and 50-100 keV BAT energy channels. The proposed relationship between spectral lag and isotropic peak luminosity is investigated for the GRBs with known redshift. The sensitivity of BAT does not allow the lags of very faint bursts to be measured and so a correlation between faint, long-lag Swift GRBs and the supergalactic plane cannot be confirmed using this sample.