Resonant cyclotron scattering in pulsar magnetospheres and its application to isolated neutron stars

TL;DR

This paper investigates resonant cyclotron scattering in pulsar magnetospheres, deriving a photon diffusion model, and explores its implications for the spectra of isolated neutron stars, including explaining their optical/UV excess and low pulsation amplitudes.

Contribution

The paper develops a 3D model of RCS, derives the photon diffusion equation, and applies it to explain spectral features of isolated neutron stars, including down scattering effects.

Findings

RCS can cause both up and down scattering depending on parameters

The model explains the optical/UV excess in INSs

INSs may be normal neutron stars with low pulsation amplitudes

Abstract

Resonant cyclotron scattering (RCS) in pulsar magnetospheres is considered. The photon diffusion equation (Kompaneets equation) for RCS is derived. The photon system is modeled three dimensionally. Numerical calculations show that there exist not only up scattering but also down scattering of RCS, depending on the parameter space. RCS's possible applications to the spectra energy distributions of magnetar candidates and radio quiet isolated neutron stars (INSs) are point out. The optical/UV excess of INSs may caused by the down scattering of RCS. The calculations for RX J1856.5-3754 and RX J0720.4-3125 are presented and compared with their observational data. In our model, the INSs are proposed to be normal neutron stars, although the quark star hypothesis is still possible. The low pulsation amplitude of INSs is a natural consequence in the RCS model.