On particle acceleration and very high energy gamma-ray emission in Crab-like pulsars

TL;DR

This paper models particle acceleration in Crab-like pulsars, showing electrons can reach energies producing detectable TeV gamma-ray emission, primarily in young pulsars, through inverse Compton and curvature radiation processes.

Contribution

It introduces a toy model analyzing centrifugal particle acceleration near the light surface in pulsar magnetospheres, estimating maximum energies and gamma-ray outputs for Crab-like pulsars.

Findings

Electrons can reach Lorentz factors up to ~10^7 in Crab-like pulsars.

Inverse Compton scattering can produce TeV gamma-ray emission with luminosity ~10^31 erg/s.

Curvature radiation results in GeV emission up to 10^35 erg/s, decreasing at higher energies.

Abstract

The origin of very energetic charged particles and the production of very high-energy (VHE) gamma-ray emission remains still a challenging issue in modern pulsar physics. By applying a toy model, we explore the acceleration of co-rotating charged particles close to the light surface in a plasma-rich pulsar magnetosphere and study their interactions with magnetic and photon fields under conditions appropriate for Crab-type pulsars. Centrifugal acceleration of particles in a monopol-like magnetic field geometry is analyzed and the efficiency constraints, imposed by corotation, inverse Compton interactions and curvature radiation reaction are determined. We derive expressions for the maximum particle energy and provide estimates for the corresponding high-energy curvature and inverse Compton power outputs. It is shown that for Crab-like pulsars, electron Lorentz factor up to $\gamma \sim 10^7$ can be achieved, allowing inverse Compton (Klein-Nishina) up-scattering of thermal photons to TeV energies with a maximum luminosity output of $\sim10^{31}$ erg/s. Curvature radiation, on the other hand, will result in a strong GeV emission output of up to $\sim(10^{34}-10^{35})$ erg/s, quasi-exponentially decreasing towards higher energies for photon energies below $\sim 50$ GeV. Accordingly to the results presented only young pulsars are expected to be sites of detectable VHE $\gamma$-ray emission.