A cosmological test for shock-powered GRBs

We calculate the pattern of correlated behavior expected in GRB shock models for νFν peak photon energies Ep and peak intensities Ip. The Ep−Ip correlation expected in synchrotron shock models of GRB emission with a changing magnetic field is qualitatively similar to the redshift-dimming effect induced by cosmology. However, we show that the cosmologically-driven and magnetically-driven mechanisms of GRB emission lead to quite distinct patterns of the Ep−Ip correlation. Future studies focussed on individual GRB pulses and their corresponding Ip and Ep may reveal the true nature of the apparent Ep−Ip correlation.