Interpretation of the unprecedentedly long-lived high-energy emission of GRB 130427A

TL;DR

This paper explains the long-lasting high-energy emission of GRB 130427A as synchrotron-self Compton emission from the afterglow, accounting for >10 GeV photons observed up to 30,000 seconds post-burst.

Contribution

It demonstrates that the hard spectral component in GRB 130427A's afterglow originates from SSC emission, providing a new interpretation for high-energy photon production in GRBs.

Findings

High-energy photons up to 30,000 seconds post-burst are explained by SSC emission.

The multi-wavelength afterglow data fit well with the SSC model.

Implications for the circumburst environment are discussed.

Abstract

High energy photons (>100 MeV) are detected by the Fermi/LAT from GRB 130427A up to almost one day after the burst, with an extra hard spectral component being discovered in the high-energy afterglow. We show that this hard spectral component arises from afterglow synchrotron-self Compton emission. This scenario can explain the origin of >10 GeV photons detected up to ~30000s after the burst, which would be difficult to be explained by synchrotron radiation due to the limited maximum synchrotron photon energy. The lower energy multi-wavelength afterglow data can be fitted simultaneously by the afterglow synchrotron emission. The implication of detecting the SSC emission for the circumburst environment is discussed.