Particle Acceleration in Gamma-Ray Burst Jets

Abstract

Gradual shear acceleration of energetic particles in gamma-ray burst (GRB) jets is considered. Special emphasis is given to the analysis of universal structured jets, and characteristic acceleration timescales are determined for a power-law and a Gaussian evolution of the bulk flow Lorentz factor ${\gamma }_b$ with angle $\varphi$ from the jet axis. The results suggest that local power-law particle distributions may be generated and that higher energy particles are generally concentrated closer to the jet axis. Taking several constraints into account we show that efficient electron acceleration in gradual shear flows, with maximum particle energy successively decreasing with time, may be possible on scales larger than $r\sim 10^{15}$ cm, provided the jet magnetic field becomes sufficiently weak and/or decreases rapidly enough with distance, while efficient acceleration of protons to ultra-high energies $>10^{20}$ eV may be possible under a wide range of conditions.

11 pages, 3 figures; ApJ Letters accepted; final version: small typos corrected in order to match published version

References in corpus (4)

• The Physics of Gamma-Ray Bursts
• Shear acceleration in relativistic astrophysical jets
• Evolution of the polarization of the optical afterglow of the gamma-ray burst GRB 030329
• Particle acceleration in astrophysical shear flows

Cited by in corpus (13)

• Gamma-Ray Bursts
• The Astrophysics of Ultrahigh Energy Cosmic Rays
• The microphysics of collisionless shock waves
• Fermi acceleration in astrophysical jets
• UHECRs from magnetic reconnection in relativistic jets
• An Introduction to Particle Acceleration in Shearing Flows
• A microscopic analysis of shear acceleration
• Generalized Fermi acceleration
• On the maximum energy of shock-accelerated cosmic rays at ultra-relativistic shocks
• H.E.S.S. follow-up observations of GRB221009A
• The implications of TeV detected GRB afterglows for acceleration at relativistic shocks
• Shear Acceleration in Expanding Flows
• Acceleration and propagation of ultrahigh energy cosmic rays