Recent observations by the Fermi Gamma-ray Space Telescope have confirmed the existence of thermal and non-thermal components in the prompt photon spectra of some Gamma-ray bursts (GRBs). Through an analysis of six bright Fermi GRBs, we have discovered a correlation between the observed photospheric and non-thermal γ-ray emission components of several GRBs using a physical model that has previously been shown to be a good fit to the Fermi data. From the spectral parameters of these fits we find that the characteristic energies, Ep and kT, of these two components are correlated via the relation Ep∝Tα which varies from GRB to GRB. We present an interpretation in which the value of index α indicates whether the jet is dominated by kinetic or magnetic energy. To date, this jet composition parameter has been assumed in the modeling of GRB outflows rather than derived from the data.
@article{arxiv.1403.0374,
title = {An Observed Correlation Between Thermal and Non-Thermal Emission in Gamma-Ray Bursts},
author = {J. Michael Burgess and Robert D. Preece and Felix Ryde and Peter Veres and Peter Meszaros and Valerie Connaughton and Michael Briggs and Asaf Pe'er and Shabnam Iyyani and Adam Goldstein and Magnus Axelsson and Matthew G. Baring and P. N. Bhat and David Byrne and Gerard Fitzpatrick and Suzanne Foley and Daniel Kocevski and Nicola Omodei and William S. Paciesas and Veronique Pelassa and Chryssa Kouveliotou and Shaolin Xiong and Hoi-Fung Yu and Binbin Zhang and Sylvia Zhu},
journal= {arXiv preprint arXiv:1403.0374},
year = {2015}
}