The time resolved Ep-L correlation in GRBs: characterization and implications

Our understanding of the GRB phenomenon is still affected by several open issues including the prompt emission physics, the problem related to the trigger of the GRB activity, the classification of different classes of GRBs and the degree of collimation of their emission. All of these issues have strong implications for a full comprehension of the nature of GRBs progenitors. In addition, their huge luminosity and their redshift distribution up to the early Universe make GRBs very promising as cosmological tools. The most investigated way for using them to measure cosmological parameters and the properties and evolution of dark energy is the correlation between the radiated energy and the photon energy at which the spectrum peaks Ep. This work aims at a further investigation of the time-resolved Ep - L correlation, based on large data sets from the BATSE/CGRO and Fermi/GBM experiments, and its application to cosmology. This is an innovative approach leading to a significant improvement in the estimates of cosmological parameters w/r to previous time integrated analysis. Indeed, in time-resolved analysis we can use the correlation between flux and Ep existing in individual GRBs allowing a cosmology independent and unbiased calibration of the slope and of the extra-statistical scatter of the correlation. The results of my thesis also provide important inputs for discriminating among different emission models of the prompt emission of GRBs and the comparison between the dispersion of the time-resolved correlation and that obtained through the averaged spectra provides an estimate of the dispersion of jet opening angles, with strong implications regarding the nature of GRB progenitors. Finally, my research activity includes also the fit of time-resolved spectra of some GRBs with both empirical models and a physical Comptonization model recently delevoped and simulations of the expected contribution by spectral measurements of GRBs through the Chinese satellite HXMT.