Gravitational lensing of stars orbiting the Massive Black Hole in the Galactic Center

TL;DR

This paper analyzes gravitational lensing effects on stars orbiting the Milky Way's central black hole, predicting secondary images and their properties for 28 stars, with implications for observational astronomy.

Contribution

It extends previous gravitational lensing analysis to a new set of stars near Sgr A*, calculating their secondary images' properties for the first time.

Findings

Star S6's secondary image peaks at K=20.8 magnitude.

S6's secondary image is 0.3 mas from the black hole.

Predicted secondary images are near current instrument resolution limits.

Abstract

The existence of a massive black hole in the center of the Milky Way, coinciding with the radio source Sgr A*, is being established on more and more solid ground. In principle, this black hole, acting as a gravitational lens, is able to bend the light emitted by stars moving within its neighborhood, eventually generating secondary images. Extending a previous analysis of the gravitational lensing phenomenology to a new set of 28 stars, whose orbits have been well determined by recent observations, we have calculated all the properties of their secondary images, including time and magnitude of their luminosity peaks and their angular distances from the central black hole. The best lensing candidate is represented by the star S6, since the magnitude of its secondary image at the peak reaches K=20.8, with an angular separation of 0.3 mas from the central black hole, that is just at the borders of the resolution limit in the K band of incoming astronomical instruments.