External Inverse-Compton Emission from Low-luminosity Gamma-Ray Bursts: Application to GRB 190829A

• Published in: The Astrophysical journal Vol. 920; no. 1; pp. 55 - 64
• Main Authors: Zhang, B. Theodore, Murase, Kohta, Veres, Péter, Mészáros, Péter
• Format: Journal Article
• Language: English
• Published: Philadelphia The American Astronomical Society 01.10.2021; IOP Publishing
• Subjects: Astrophysics; Emission; Energy dissipation; Gamma ray bursts; Gamma rays; Gamma-ray bursters; Kinetic energy; Lorentz factor; Luminosity; Non-thermal radiation sources; Particle acceleration; Particle astrophysics; Radio sources; Relativistic particles; Stellar jets; Telescopes; X-ray sources
• ISSN: 0004-637X; 1538-4357
• DOI: 10.3847/1538-4357/ac0cfc

Abstract The detection of TeV gamma-ray bursts (GRBs) brought new opportunities for studying the physics of particle acceleration at relativistic shocks. The High Energy Stereoscopic System (H.E.S.S.) telescopes recently observed very-high-energy (VHE) emission from a nearby low-luminosity GRB, GRB 190829A. Follow-up observations with, e.g., Swift-XRT, revealed unusual flare activities at ∼10 3 s, which can be caused by a long-lasting central engine. We show that the VHE emission during the H.E.S.S. observation time is naturally produced in the external inverse-Compton (EIC) scenario, where seed photons supplied by the flares or other late-time dissipations are upscattered to VHE energies by the nonthermal electrons accelerated at the external forward shock. Our calculations show that the EIC flare nearly coincides with the late-prompt flare, but extends ∼3–4 times longer than the duration of the late-prompt flare. The preferred kinetic energy and initial Lorentz factor used in our model are ∼10 52 erg and ∼20, respectively. Understanding the mechanisms of the VHE emission from low-luminosity GRBs will help us constrain the properties of the outflow and the central engine activities, as well as the particle acceleration mechanism.