Is magnetically dominated outflow required to explain GRBs?

ABSTRACT The composition of relativistic outflows producing gamma-ray bursts is a long-standing open question. One the main arguments in favour magnetically dominated absence photospheric component their broad-band time-resolved spectra, with such notable example as GRB 080916C. Here, we perform analysis this burst and confirm previous detection an additional spectral component. We show that subdominant consistent photosphere ultrarelativistic baryonic outflow, deep coasting regime. argue that, contrary to statements, magnetic dominance outflow not required for interpretation GRB. Moreover, simultaneous high-energy emission its prompt phase requires departure from one-zone model.