Simulations of gamma-ray burst afterglows with a relativistic kinetic code

Abstract

This paper introduces a kinetic code that simulates gamma-ray burst (GRB) afterglow emission from the external forward shock and presents examples of some of its applications. One interesting research topic discussed in the paper is the high-energy radiation produced by Compton scattering of the prompt GRB photons against the shock-accelerated electrons. The difference between the forward shock emission in a wind-type and a constant-density medium is also studied, and the emission due to Maxwellian electron injection is compared to the case with pure power-law electrons. The code calculates the time-evolving photon and electron distributions in the emission region by solving the relativistic kinetic equations for each particle species. For the first time, the full relativistic equations for synchrotron emission/absorption, Compton scattering, and pair production/annihilation were applied to model the forward shock emission. The synchrotron self-absorption thermalization mechanism, which shapes the low-energy end of the electron distribution, was also included in the electron equation. The simulation results indicate that inverse Compton scattering of the prompt GRB photons can produce a luminous TeV emission component, even when pair production in the emission region is taken into account. This very high-energy radiation may be observable in low-redshift GRBs. The test simulations also show that the low-energy end of a pure power-law distribution of electrons can thermalize owing to synchrotron self-absorption in a wind-type environment, but without an observable impact on the radiation spectrum. Moreover, a flattening in the forward shock X-ray light curve may be expected when the electron injection function is assumed to be purely Maxwellian instead of a power law.

16 pages, 11 figures, accepted for publication in A&A

References in corpus (14)

• Particle acceleration in relativistic collisionless shocks: Fermi process at last?
• The Dynamics and Afterglow Radiation of Gamma-Ray Bursts. I. Constant Density Medium
• On the Mechanism of Gamma-Ray Burst Afterglows
• Can the early X-ray afterglow of GRBs be explained by a contribution from the reverse shock?
• "Late prompt" emission in Gamma Ray Bursts?
• Properties of Gamma-Ray Burst Progenitor Stars
• Hot accretion flow in black hole binaries: a link connecting X-rays to the infrared
• Deceleration of arbitrarily magnetized GRB ejecta: the complete evolution
• MAGIC upper limits on the very high energy emission from GRBs
• Prior Emission Model for X-ray Plateau Phase of Gamma-Ray Burst Afterglows
• On the Implications of Late Internal Dissipation for Shallow-Decay Afterglow Emission and Associated High-Energy Gamma-Ray Signals
• AMRVAC and Relativistic Hydrodynamic simulations for GRB afterglow phases
• GRB 090902B: afterglow observations and implications
• The full curvature effect expected in early X-ray afterglow emission of gamma-ray bursts

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• Nonlinear particle acceleration and thermal particles in GRB afterglows
• Temporal Evolution of the Gamma-ray Burst Afterglow Spectrum for an Observer: GeV--TeV Synchrotron Self-Compton Light Curve
• MAGIC detection of GRB 201216C at $z=1.1$
• Subsequent Nonthermal Emission due to the Kilonova Ejecta in GW 170817