Synchrotron Self-Compton Emission in the Two-Component Jet Model for Gamma-Ray Bursts

Abstract

Gamma-ray bursts (GRBs) are intense bursts of high-energy photons (prompt emissions) caused by relativistic jets. After the emissions, multi-wavelength afterglows, from radio to very-high-energy (VHE) gamma-ray, last for more than a few days. In the past three years, the VHE gamma-ray photons from four GRBs (GRBs 180720B, 190114C, 190829A and 201216C) were detected by ground-based Imaging Atmospheric Cherenkov Telescopes, such as the Major Atmospheric Gamma Imaging Cherenkov (MAGIC) telescopes and the High Energy Stereoscopic System (H.E.S.S.). One of them, GRB 190829A, had some peculiar features of showing achromatic peaks in X-ray and optical bands at $1.4\times 10^3$ s and being classified as low-luminosity GRBs. Previously, we proposed a two-component jet model, which has `narrow jet' with a small initial opening half-angle ${\theta }_0=0.015$ rad and large bulk Lorentz factor ${\Gamma }_0=350$, and `wide jet' with ${\theta }_0=0.1$ rad and ${\Gamma }_0=20$. The narrow jet explained the early X-ray and optical emissions and apparently small isotropic gamma-ray energy and peak energy in the off-axis viewing case. Furthermore, the late X-ray and radio (1.3 and 15.5 GHz) afterglows were emitted from the wide jet. Here, we calculate the VHE gamma-ray flux by the synchrotron self-Compton (SSC) emission. The multi-wavelength afterglows of GRB 190829A including the VHE gamma-ray emission are well explained by our two-component jet model. The afterglow emissions from our two-component jet are also consistent with the observational results of GRBs 180720B, 190114C and 201216C, when the jets are viewed on-axis. Furthermore, we discuss the detectability of off-axis orphan afterglows by the Cherenkov Telescope Array (CTA).

16 pages, 9 figures, 3 tables, JHEAp, in press

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• Two-component jet model for the afterglow emission of GRB 201216C and GRB 221009A and implications for jet structure of very-high-energy gamma-ray bursts
• GRB 221009A: Observations with LST-1 of CTAO and Implications for Structured Jets in Long Gamma-Ray Bursts
• Modelling multiwavelength afterglows of the VHE-GRB population
• Jets in a Gamma-Ray Burst During its Prompt Emission: Evolution of Lorentz Factor
• Catching TeV emission from GRB 221009A and alike with LHAASO, LACT and SWGO
• Gravitational Wave Memory from Accelerating Relativistic Jets in Multiple Thick Shell Scenarios
• Modeling the imprints of large-scale magnetized structures on $\gamma$-rays from extragalactic transients