The peak luminosity – peak energy correlation in GRBs

We derive the peak luminosity–peak energy (Liso–Epeak) correlation using 22 long Gamma– Ray Bursts (GRBs) with firm redshift measurements. We find that its slope is similar to the correlation between the time integrated isotropic emitted energy Eiso and Epeak (Amati et al. 2002). For the 15 GRBs in our sample with estimated jet opening angle we compute the collimation corrected peak luminosity Lγ , and find that it correlates with Epeak. This has, however, a scatter larger than the correlation between Epeak and Eγ (the time integrated emitted energy, corrected for collimation; Ghirlanda et al. 2004), which we ascribe to the fact that the opening angle is estimated through the global energetics. We have then selected a large sample of 442 GRBs with pseudo–redshifts, derived through the lag–luminosity relation, to test the existence of the Liso–Epeak correlation. With this sample we also explore the possibility of a correlation between time resolved quantities, namely Lpiso and the peak energy at the peak of emission E peak.