Gravitational Lensing of a star by a rotating black hole

TL;DR

This paper numerically models the gravitational lensing effects on a star orbiting a rotating black hole, predicting observable phenomena like image positions and flux variations, relevant for future space interferometry missions.

Contribution

It provides detailed numerical calculations of star lensing by a Kerr black hole, including light echoes and flux changes, advancing understanding of strong gravity lensing effects.

Findings

Calculated star image positions and flux variations over time

Predicted first and second light echoes from the black hole lensing

Identified observational requirements for detecting such lensing phenomena

Abstract

The gravitational lensing of a finite star moving around a rotating Kerr black hole has been numerically calculated. Calculations for the direct image of the star and for the first and second light echoes have been performed for the star moving with an orbital period of 3.22 h around the supermassive black hole SgrA* at the Galactic Center. Time dependences for the observed star position on the celestial sphere, radiation flux from the star, frequency of detected radiation, major and minor semiaxes of the lensed star image have been calculated and plotted. The detailed observation of such lensing requires a space interferometer such as the Russian Millimetron project.