Photodisintegrated gamma rays and neutrinos from heavy nuclei in the gamma-ray burst jet of GRB 130427A

Detection of ~0.1-70 GeV prompt γ-ray emission from the exceptionally bright gamma-ray burst (GRB) 130427A by the Fermi-Large Area Telescope provides an opportunity to explore the physical processes of GeV γ-ray emission from the GRB jets. In this work, we discuss interactions of Iron and Oxygen nuclei with observed keV-MeV photons in the jet of GRB 130427A in order to explain an additional, hard spectral component observed during 11.5-33 s after trigger. The photodisintegration time-scale for Iron nuclei is comparable to or shorter than this duration.We find that γ rays resulting from the Iron nuclei disintegration can account for the hard power-law component of the spectra in the ~1-70 GeV range, before the γγ →e± pair production with low-energy photons severely attenuates emission of higher energy photons. Electron antineutrinos from the secondary neutron decay, on the other hand, can be emitted with energies up to ~2 TeV. The flux of these neutrinos is low and consistent with non-detection of GRB 130427A by the IceCube Neutrino Observatory. The required total energy in the Iron nuclei for this hadronic model for GeV emission is ≲10 times the observed total energy released in the prompt keV-MeV emission.