Observational Signatures of High-Energy Emission during the Shallow Decay Phase of GRB X-Ray Afterglows

Understand

The widely existing shallow decay phase of the X-ray afterglows of gamma-ray bursts (GRBs) is generally accepted to be due to long-lasting energy injection.

• The outflows carrying the injecting energy, based on the component that is dominative in energy, fall into two possible types: baryon-dominated and lepton-dominated ones.
• The former type of outflow could be ejecta that is ejected during the prompt phase of a GRB and consists of a series of baryonic shells with a distribution of Lorentz factors, and the latter type could be an electron-positron-pair wind that is driven by the post-burst central engine.
• We here provide a unified description for the dynamics of fireballs based on these two types of energy injection, and calculate the corresponding high-energy photon emission by considering synchrotron radiation and inverse Compton scattering (including synchrotron self-Compton and combined inverse-Compton) of electrons.