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

The Fermi observations of GRB 110721A 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 blackbody photospheric model also falls short. On the other hand, we show that dissipative photospheric synchrotron models ranging from extreme magnetically dominated to baryon dominated dynamics are able to accommodate such high peak values.