Properties of Multi Pulsed GRBs seen by HETE‐2

It is claimed by many authors that there are tight correlations between the spectral peak energy Ep, and the “brightness” such as isotropic energy Erad, collimation‐corrected energy Eγ, or peak luminosity Lp. In many long GRBs, their light curves consist of several pulses or humps, and each pulse has a different spectrum. Using data of multi pulsed GRBs observed by HETE‐2, we investigated these relations for each pulse and found it looked to have some correlations. This may imply that each pulse could behave as a single burst. Considering that the GRB rate follow the star formation rate of the Universe, we should have already detected a number of distant GRBs. Some methods are proposed to estimate a redshift by applying the above mentioned correlations. Extending the previous studies, we apply the redshift estimations using Ep‐Erad correlation for an individual pulse.