GRB 080916C: ON THE RADIATION ORIGIN OF THE PROMPT EMISSION FROM keV/MeV TO GeV
- Department of Astronomy, Nanjing University, Nanjing 210093 (China)
- Department of Astronomy, Peking University, Beijing 100871 (China)
- Department of Astronomy and Astrophysics, Pennsylvania State University, University Park, PA 16802 (United States)
Fermi observations of high-energy gamma-ray emission from GRB 080916C shows that its spectrum is consistent with the band function from MeV to tens of GeV. Assuming one single emission mechanism dominates in the whole energy range, we show that this spectrum is consistent with synchrotron origin by shock-accelerated electrons. The simple electron inverse-Compton model and the hadronic model are found to be less viable. In the synchrotron scenario, the synchrotron self-Compton scattering is likely to be in the Klein-Nishina (KN) regime and therefore the resulting high-energy emission is subdominant, even though the magnetic field energy density is lower than that in relativistic electrons. The KN inverse-Compton cooling may also affect the low-energy electron number distribution and hence results in a low-energy synchrotron photon spectrum n({nu}) {proportional_to} {nu}{sup -1} below the peak energy. Under the framework of the electron synchrotron interpretation, we constrain the shock microphysical parameters and derive a lower limit of the upstream magnetic fields. The detection of synchrotron emission extending to about 70 GeV in the source frame in GRB 080916C favors the Bohm diffusive shock acceleration if the bulk Lorentz factor of the relativistic outflow is not significantly greater than thousands.
- OSTI ID:
- 21307775
- Journal Information:
- Astrophysical Journal (Online), Vol. 698, Issue 2; Other Information: DOI: 10.1088/0004-637X/698/2/L98; Country of input: International Atomic Energy Agency (IAEA); ISSN 1538-4357
- Country of Publication:
- United States
- Language:
- English
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