We investigate two high-energy radiation mechanisms, the proton-synchrotron and the electron inverse Compton emission, and explore their possible signatures in the broadband spectra and in the keV-GeV light curves of gamma-ray burst afterglows. We develop a simple analytical approach, also allowing for the effects of photon-photon pair production, and explore the conditions under which one or the other of these components dominates. We identify three parameter-space regions in which different spectral components dominate: (1) a region where the proton-synchrotron and other hadron-related emission components dominate, which is small; (2) a region in which the electron inverse Compton component dominates, which is substantial; and (3) a third substantial region in which electron-synchrotron emission dominates. We discuss the prospects and astrophysical implications of directly detecting the inverse Compton and the proton high-energy components in various bands, in particular, in the GeV band, with future missions such as the Gamma-Ray Large Area Space Telescope (GLAST) and in the X-ray band with Chandra. We find that regime II parameter space is the most favorable regime for high-energy emission. The inverse Compton component is detectable by GLAST within hours for bursts at typical cosmological distances and by Chandra within days if the ambient density is high.
All Science Journal Classification (ASJC) codes
- Astronomy and Astrophysics
- Space and Planetary Science