Axion-plasmon or magnetized plasma effect on an observable shadow and gravitational lensing of a Schwarzschild black hole

TL;DR

This study investigates how axion-plasmon interactions in a plasma medium influence the observable features of a Schwarzschild black hole, such as shadow size and gravitational lensing, potentially enabling detection of axion effects.

Contribution

It introduces the impact of axion-plasmon coupling on black hole optics, extending previous models and suggesting observable signatures in black hole shadows and lensing phenomena.

Findings

Black hole shadow size decreases with increasing axion-plasmon coupling.

Photon trajectories and gravitational lensing are affected by axion-plasmon parameters.

Potential observational signatures for axion detection in black hole imaging.

Abstract

In this paper, we study the influence of the axion-plasmon, as proposed in (Phys. Rev. Lett. 120, 181803 (2018)) on the optical properties of the Schwarzschild black hole. Our aim is to provide a test to detect the effects of a fixed axion background using black holes. To accomplish our goal, we explore the effect of the axion-plasmon coupling on the motion of photons around the Schwarzschild black hole and check the possibility of observing those effects upon the black hole shadow, the gravitational deflection angle, Einstein rings and shadow images obtained by radially infalling gas on a black hole within a plasma medium. We find that these quantities are indeed affected by the axion-plasmon coupling parameters which consequently generalize some of the well-known results in the literature. It is shown that the size of the black hole shadow decreases with increasing axion-plasmon if observed from sufficiently large distance.