GeV emission from gamma-ray burst afterglows
Abstract
We calculate the GeV afterglow emission expected from a few mechanisms related to gamma-ray bursts (GRBs) and their afterglows. Given the brightness of the early X-ray afterglow emission measured by Swift/X-Ray Telescope, Gamma-ray Large Area Space Telescope (GLAST)/Large Area Telescope (LAT) should detect the self-Compton emission from the forward shock driven by the GRB ejecta into the circumburst medium. Novel features discovered by Swift in X-ray afterglows (plateaus and chromatic light-curve breaks) indicate the existence of a pair-enriched, relativistic outflow located behind the forward shock. Bulk and inverse-Compton upscattering of the prompt GRB emission by such outflows provide another source of GeV afterglow emission detectable by LAT. The large-angle burst emission and synchrotron forward-shock emission are, most likely, too dim at high photon energy to be observed by LAT. The spectral slope of the high-energy afterglow emission and its decay rate (if it can be measured) allow the identification of the mechanism producing the GeV transient emission following GRBs.
- Publication:
-
Monthly Notices of the Royal Astronomical Society
- Pub Date:
- April 2008
- DOI:
- 10.1111/j.1365-2966.2008.12950.x
- arXiv:
- arXiv:0712.1536
- Bibcode:
- 2008MNRAS.385.1628P
- Keywords:
-
- radiation mechanisms: non-thermal;
- shock waves;
- gamma-rays: bursts;
- Astrophysics
- E-Print:
- 8 pages, accepted by MNRAS