Time and spectral study of the internal structure of long GRBs with z close to 1

We investigated the internal structure of a sample of 5 long GRBs detected by Swift satellite with z close to one. First, we determined the spectral lag applying an exponential model (Norris model, 2005) [2]. We fitted the pulses with Norris model according to the sensitivity of the BAT detector (15-150 KeV). We concluded that high energy photons arrived before low energy photons in 88% of lags. Moreover, spectral analysis in regions of 1 second width was performed, and the temporal evolution of spectral parameters such as photon index and energy peak, additionally we determined that the contribution of the synchrotron radiation inside the burst is important for the 45% of sample. Finally, we investigated correlation between spectral lag and photon index or luminosity. We concluded that spectral lag and luminosity are anticorrelated, nevertheless spectral lag and photon index are not correlated. We used three spectral models: power law, cut-o_ power law and Band model.