The updated Epeak-Eγ correlation in GRBs

The recently discovered correlation between the rest frame GRB peak spectral energy Epeak and the collimation corrected energy Eγ in long GRBs is potentially very important, yet awaits confirmation from an independent sample. It may help to shed light on the radiation mechanism of the prompt GRB phase and on the way-and in which form- the energy is released from the central engine. Here are presented some additional evidence for the correlation (two new bursts) and rederive the best-fit parameters. The tightness of the correlation is confirmed (σ = 0.1 dex). It is shown that this correlation allows, for the first time, to use GRBs as cosmological probes to constrain the expansion history of the universe