Gravitational Lensing by Transparent Janis-Newman-Winicour Naked Singularities

TL;DR

This paper studies gravitational lensing effects caused by Janis-Newman-Winicour naked singularities, revealing unique image formations that could help detect such exotic objects.

Contribution

It demonstrates how photons behave near JNW naked singularities and introduces lensing signatures that distinguish them from black holes.

Findings

Photons converge to the singularity in finite coordinate time.

Regularization allows photons to traverse the singularity.

New images appear within the critical curve due to lensing.

Abstract

The Janis-Newman-Winicour (JNW) spacetime can describe a naked singularity with a photon sphere that smoothly transforms into a Schwarzschild black hole. Our analysis reveals that photons, upon entering the photon sphere, converge to the singularity in a finite coordinate time. Furthermore, if the singularity is subjected to some regularization, these photons can traverse the regularized singularity. Subsequently, we investigate the gravitational lensing of distant sources and show that new images emerge within the critical curve formed by light rays escaping from the photon sphere. These newfound images offer a powerful tool for the detection and study of JNW naked singularities.