Very High Energy Emission and Cascade Radiation of Gamma-Ray Burst Afterglows: Homogeneous Versus Wind External Media

Abstract

Recent detection of sub-TeV emission from gamma-ray bursts (GRBs) represents a breakthrough in the GRB study. The multi-wavelength data of the afterglows of GRB 190114C support the synchrotron self-Compton (SSC) origin for its sub-TeV emission. We present a comparative analysis on the SSC emission of GRB afterglows in the homogeneous and wind environment in the framework of the forward shock model. The $\gamma \gamma$ absorption of very high-energy photons due to pair production within the source and the Klein-Nishina effect on the inverse-Compton scattering are considered. Generally a higher SSC flux is expected for a larger circum-burst density due to a larger Compton parameter, but meanwhile the internal $\gamma \gamma$ absorption is more severer for sub-TeV emission. The flux ratio between the SSC component and the synchrotron component decreases more quickly with time in the wind medium case than that in the homogenous-density medium case. The light curves of the SSC emission are also different for the two types of media. We also calculate the cascade emission resulted from the absorbed high-energy photons. In the ISM environment with $n>1\mathrm{c}{\mathrm{m}}^{-3}$, the cascade synchrotron emission could be comparable to the synchrotron emission of the primary electrons in the optical band, which may flatten the optical afterglow light curve at early time ($t<1$ h). In the wind medium with $A_{\ast }>0.1$, the cascade emission in the eV-GeV band is comparable or even larger than the emission of the primary electrons at early time.

9 pages, 6 figures, accepted for publication in ApJ

References in corpus (11)

• A very-high-energy component deep in the Gamma-ray Burst afterglow
• Observation of inverse Compton emission from a long $\gamma$-ray burst
• Klein-Nishina Effects on Optically Thin Synchrotron and Synchrotron Self-Compton Spectrum
• Formation of hard VHE gamma-ray spectra of blazars due to internal photon-photon absorption
• High Energy Afterglow from Gamma-ray Bursts
• Analysis and modelling of the multi-wavelength observations of the luminous GRB 190114C
• Detectability of Pair Echos from Gamma-Ray Bursts and Intergalactic Magnetic Fields
• GRB Fermi-LAT afterglows: explaining flares, breaks, and energetic photons
• Understanding the TeV emission from a distant blazar PKS 1424+240 in a lepto-hadronic jet model
• The Effect of Pair Cascades on the High-Energy Spectral Cutoff in Gamma-Ray Bursts
• Properties of the Intergalactic Magnetic Field Constrained by Gamma-ray Observations of Gamma-Ray Bursts

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• Prospects for the detection of the prompt very-high-energy emission from $\gamma$-ray bursts with the High Altitude Detection of Astronomical Radiation experiment
• Radio Loud vs. Radio Quiet Gamma-ray Bursts: the Role of Binary Progenitors
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