The extremely high peak energy of GRB 110721A in the context of a dissipative photosphere synchrotron emission model

The Fermi observations of GRB 110721A (Axelsson et al. 2012) have revealed an unusually high peak energy ~ 15 MeV in the first time bin of the prompt emission. We find that an interpretation is unlikely in terms of internal shock models, and confirm that a standard black-body photospheric model also falls short. We show that dissipative photospheric synchrotron models ranging from extreme magnetically dominated to baryon dominated dynamics, on the other hand, are able to accommodate such high peak values.