Rest-frame properties of gamma-ray bursts observed by the Fermi Gamma-Ray Burst Monitor

Abstract

In this talk I present the main spectral and temporal properties of Fermi/GBM gamma-ray bursts (GRBs) with known redshift. Key properties of these GRBs in the rest-frame of the progenitor are investigated to better understand the intrinsic nature of these events. The sample comprises 47 GRBs with measured redshift that were observed by GBM until May 2012. 39 sources belong to the long-duration population and 8 events were classified as short bursts. For all of these events we derive, where possible, the intrinsic peak energy in the {\nu}F{\nu} spectrum (Ep,rest), the duration in the rest-frame, defined as the time in which 90% of the burst counts were observed (T90,rest) and the isotropic equivalent bolometric energy (Eiso). We confirm the tight correlation between Ep,rest and Eiso (Amati relation) with a larger scatter than previously reported. We also confirm the relation between Ep,rest and the 1-s peak luminosity (Lp) (Yonetoku relation). Short GRB 080905A, whose host galaxy was identified at redshift z = 0.1218 is a peculiar outlier of this relation. Moreover, an intriguing, but preliminary, cosmic evolution of Ep,rest was observed, while no such evolution is evident for T90,rest.