Spectrum and duration of delayed mev-gev emission of gamma-ray bursts in cosmic background radiation fields
Mar, 20025 pages
Published in:
- Astrophys.J. 580 (2002) 1013-1016
e-Print:
- astro-ph/0203084 [astro-ph]
DOI:
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Abstract: (arXiv)
We generally analyze prompt high-energy emission above a few hundreds of GeV due to synchrotron self-Compton scattering in internal shocks. However, such photons cannot be detected because they may collide with cosmic infrared background photons, leading to electron/positron pair production. Inverse-Compton scattering of the resulting electron/positron pairs off cosmic microwave background photons will produce delayed MeV-GeV emission, which may be much stronger than a typical high-energy afterglow in the external shock model. We expand on the Cheng & Cheng model by deriving the emission spectrum and duration in the standard fireball shock model. A typical duration of the emission is ~ 10^3 seconds, and the time-integrated scattered photon spectrum is nu^{-(p+6)/4}, where p is the index of the electron energy distribution behind internal shocks. This is slightly harder than the synchrotron photon spectrum, nu^{-(p+2)/2}. The lower energy property of the scattered photon spectrum is dependent on the spectral energy distribution of the cosmic infrared background radiation. Therefore, future observations on such delayed MeV-GeV emission and the higher-energy spectral cutoff by the Gamma-Ray Large Area Space Telescope (GLAST) would provide a probe of the cosmic infrared background radiation.- gamma ray: burst
- synchrotron radiation: Compton scattering
- photon: cosmic radiation
- cosmic background radiation
- electron: pair production
- fireball: shock waves
- photon: energy spectrum
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