Spectral lag , the time difference between the arrival of high-energy and low-energy photons , is a common feature in Gamma-ray Bursts ( GRBs ) .
Norris et al .
2000 reported a correlation between the spectral lag and the isotropic peak luminosity of GRBs based on a limited sample .
More recently , a number of authors have provided further support for this correlation using arbitrary energy bands of various instruments .
In this paper we report on a systematic extraction of spectral lags based on the largest Swift sample to date of 31 GRBs with measured redshifts .
We extracted the spectral lags for all combinations of the standard Swift hard x-ray energy bands : 15-25 keV , 25-50 keV , 50-100 keV and 100-200 keV and plotted the time dilation corrected lag as a function of isotropic peak luminosity .
The mean value of the correlation coefficient for various channel combinations is -0.68 with a chance probability of \sim 0.7 \times 10 ^ { -3 } .
In addition , the mean value of the power-law index is 1.4 \pm 0.3 .
Hence , our study lends support for the existence of a lag-luminosity correlation , albeit with large scatter .