2017ApJ...844...56T

The origin of the prompt high-energy ( 100 MeV) emission of gamma-ray bursts (GRBs), detected by the Large Area Telescope (LAT) on board the Fermi Gamma-ray Space Telescope, for which both an external shock origin and internal dissipation origin have been suggested, is still under debate. In the internal dissipation scenario, the high-energy emission is expected to exhibit significant temporal variability, tracking the keV/MeV fast variable behavior. Here, we report a detailed analysis of the Fermi data of GRB 170214A, which is sufficiently bright in high energies to enable a quantitative analysis of the correlation between high-energy emission and keV/MeV emission with high statistics. Our result shows a clear temporal correlation between high-energy and keV/MeV emission in the whole prompt emission phase as well as in two decomposed short time intervals. Such a correlation is also found in some other bright LAT GRBs, e.g., GRB 080916C, 090902B, and 090926A. For these GRBs as well as GRB 090510, we also find rapid temporal variability in the high-energy emission. We thus conclude that the prompt high-energy emission in these bright LAT GRBs should be due to an internal origin.