Strongly Magnetized Sources: QED and X-ray Polarization

TL;DR

This paper explores how quantum electrodynamics predicts vacuum birefringence in strong magnetic fields, affecting X-ray polarization from astrophysical sources like magnetars and pulsars, with implications for understanding their magnetic environments.

Contribution

It provides a first-principles derivation of vacuum birefringence effects and applies these to predict polarization signatures in astrophysical observations.

Findings

Vacuum birefringence causes polarization-dependent light speed differences.

Predicted polarization levels for magnetars and X-ray pulsars.

Quantitative calculations of polarization signatures in strong magnetic fields.

Abstract

Radiative corrections of quantum electrodynamics cause a vacuum threaded by magnetic field to be birefringent. This means that radiation of different polarizations travels at different speeds. Even in the strong magnetic fields of astrophysical sources the difference in speed is small; however, it has profound consequences for the extent of polarization expected from strongly magnetized sources. We demonstrate how the birefringence arises from first principles, show how birefringence affects the polarization state of radiation and present recent calculations for the expected polarization from magnetars and X-ray pulsars.