X-ray polarization from accreting white dwarfs and associated systems

TL;DR

This study uses Monte-Carlo simulations to analyze X-ray polarization in accreting white dwarf systems, revealing higher polarization levels than previous models and distinguishing between different binary system models.

Contribution

It provides the first realistic density and velocity structure simulations of polarized X-ray emission, improving upon previous simplified models.

Findings

X-ray polarization can reach about 8% in high accretion rate systems.

Negligible polarization in unipolar-inductor binary models.

Direct-impact accretor models may produce polarization similar to magnetic cataclysmic variables.

Abstract

We present our results of Monte-Carlo simulations of polarized Compton X-rays from magnetic cataclysmic variables, with realistic density, temperature and velocity structures in the accretion flow. Our study has shown that the X-ray linear polarization may reach about 8% for systems with high accretion rates viewed at a high viewing inclination angle. This value is roughly twice the maximum value obtained by previous studies which assumed a cold, static emission region with a uniform density. We also investigate the X-ray polarization properties of ultra-compact double-degenerate binaries for the unipolar-inductor and direct-impact accretor models. Our study has shown negligible X-ray polarization for the unipolar-induction model. However, the direct-impact accretor model may give X-ray polarization levels similar to that predicted for the magnetic cataclysmic variables.