Retrolensing by light rays slightly inside and outside of a photon sphere around a Reissner-Nordstr\"{o}m naked singularity

TL;DR

This paper studies how light rays near a Reissner-Nordström naked singularity can produce brighter retrolensing effects than black holes, due to reflections near photon and antiphoton spheres.

Contribution

It demonstrates that retrolensing brightness can be enhanced by potential barriers around naked singularities, extending previous black hole retrolensing models.

Findings

Retrolensing brightness is higher around Reissner-Nordström naked singularities.

Reflections by potential barriers influence the retrolensing signals.

Brighter retrolensing can occur due to rays reflected near antiphoton spheres.

Abstract

We investigate retrolensing of sunlights reflected by a photon sphere and by a potential barrier near an antiphoton sphere around a Reissner-Nordstr\"{o}m naked singularity. We apply the deflection angles of light rays in strong deflection limits to the retrolensing. We show that the retrolensing by the photon sphere around the Reissner-Nordstr\"{o}m naked singularity can be brighter than the one around a Reissner-Nordstr\"{o}m black hole because of the existence of the rays which reflected by the potential barrier.