General-relativistic pulsar radio and high-energy emission

TL;DR

This paper introduces a new method to simulate how a neutron star's gravitational field influences its pulsar emission, revealing significant effects on observed light curves and phase delays, especially due to the Shapiro time delay.

Contribution

The study develops a numerical approach to incorporate general relativity into pulsar emission modeling, improving understanding of gravitational impacts on observed signals.

Findings

Shapiro time delay significantly affects phase delays in light curves.

General relativity alters the timing and shape of pulsar emission profiles.

Newtonian models are less accurate compared to general-relativistic simulations.

Abstract

According to current pulsar emission models, photons are produced within their magnetosphere or inside the current sheet outside the light-cylinder. Radio emission is favoured in the vicinity of the polar caps whereas the high-energy counterpart is presumably enhanced in regions around the light-cylinder, magnetosphere or/and wind. However, gravitational impacts on light-curves and their spectral properties have only been sparsely touched. In this paper, we present a new method to simulate the influence of the neutron star gravitational field on its emission according to general relativity. We numerically compute photon trajectories assuming a background Schwarzschild metric, applying our method to neutron star radiation mechanisms, like thermal emission from hot spots and non-thermal magnetospheric emission by curvature radiation. We detail the general-relativistic impacts onto observations made by a distant observer. Sky maps are computed using the vacuum electromagnetic field of a general-relativistic rotating dipole. We compare Newtonian results to their general-relativistic counterpart. For magnetospheric emission, we show that, more importantly than the aberration and the curvature of the trajectory of the photons, the Shapiro time delay significantly affected the phase delay between radio and high-energy light curves although the characteristic pulse profile that defines pulsar emission is kept.