Probing the gravitational Faraday rotation using quasar X-ray microlensing

TL;DR

This paper proposes a novel method to detect gravitational Faraday rotation by analyzing X-ray polarization variations in microlensed quasars, which could provide new tests of general relativity in strong gravity regimes.

Contribution

It introduces the first simulation of quasar X-ray microlensing polarization light curves to detect gravitational Faraday rotation.

Findings

Rapid, concurrent variations in X-ray polarization and flux during caustic-crossing events.

Potential to confirm strong gravity effects in quasar X-ray emission.

Feasibility of measuring gravitational Faraday rotation through polarization monitoring.

Abstract

The effect of gravitational Faraday rotation was predicted in the 1950s, but there is currently no practical method for measuring this effect. Measuring this effect is important because it will provide new evidence for correctness of general relativity, in particular, in the strong field limit. We predict that the observed degree and angle of the X-ray polarization of a cosmologically distant quasar microlensed by the random star field in a foreground galaxy or cluster lens vary rapidly and concurrently with flux during caustic-crossing events using the first simulation of quasar X-ray microlensing polarization light curves. Therefore, it is possible to detect gravitational Faraday rotation by monitoring the X-ray polarization of gravitationally microlensed quasars. Detecting this effect will also confirm the strong gravity nature of quasar X-ray emission.