Strong field limit analysis of gravitational retro-lensing

TL;DR

This paper develops a comprehensive analysis of gravitational retro-lensing in the strong field limit for static spherically symmetric objects, comparing it with ordinary lensing and applying it to black holes in different astrophysical contexts.

Contribution

It introduces a formalism for strong field retro-lensing analysis and applies it to black holes using Schwarzschild and Reissner-Nordstrom geometries, expanding understanding of lensing phenomena.

Findings

Retro-lensing effects differ from ordinary lensing in strong fields.

Black holes can act as retro-lenses in astrophysical scenarios.

The formalism applies to both supermassive and stellar mass black holes.

Abstract

We present a complete treatment in the strong field limit of gravitational retro-lensing by a static spherically symmetric compact object having a photon sphere. The results are compared with those corresponding to ordinary lensing in similar strong field situations. As examples of application of the formalism, a supermassive black hole at the galactic center and a stellar mass black hole in the galactic halo are studied as retro-lenses, in both cases using the Schwarzschild and Reissner-Nordstrom geometries.