Polarized Emission of Intrabinary Shocks in Spider Pulsars from Global 3D Kinetic Simulations

TL;DR

This study presents the first global 3D kinetic simulations of intrabinary shocks in spider pulsars, predicting their polarized emission properties and providing insights into particle acceleration and emission mechanisms.

Contribution

It introduces the first comprehensive 3D kinetic simulation framework for spider pulsar shocks, enabling detailed predictions of spectra, light curves, and polarization.

Findings

Reproduces observed double-peaked light curves at 90° inclination.

Predicts polarization degree exceeding 15%, increasing with magnetic field strength.

Provides testable predictions for upcoming X-ray polarization observations.

Abstract

In spider pulsar systems, a relativistic intrabinary shock forms when the pulsar wind collides with the massive outflow driven off the pulsar's low-mass stellar companion. The shock is a site of non-thermal particle acceleration, likely via shock-driven magnetic reconnection, and produces synchrotron emission. These shocks are among the few systems in which global scales can be reasonably captured with kinetic simulations, enabling first-principles particle acceleration and emission studies. We perform the first global 3D kinetic simulations of spider pulsar intrabinary shocks and predict their polarized emission properties. We report emission spectra, light curves, and polarization patterns as a function of the stripe-averaged magnetic field, cooling strength, and viewing inclination. At $90^\circ$ inclination and for a low stripe-averaged magnetic field, we reproduce the double peaked light curve observed in spider systems. We predict a significant polarization degree $\gtrsim15\%$, which monotonically increases with the stripe-averaged field strength. Our results can be applied to and tested by forthcoming X-ray polarization observations of spider pulsars.