The impact of gravitational lensing in the reconstruction of stellar orbits around Sgr A*

Abstract

After the amazing discoveries by the GRAVITY collaboration in the last few years on the star S2 orbiting the black hole Sgr A* in the center of the Milky Way, we present a detailed investigation of the impact of gravitational lensing on the reconstruction of stellar orbits around this massive black hole. We evaluate the lensing astrometric effects on the stars S2, S38 and S55 and how these systematically affect the derived orbital parameters. The effect is below current uncertainties, but not negligible. With the addition of more observations on these stars, it will be possible to let the astrometric shift by lensing emerge from the statistical noise and be finally detected. By repeating the analysis on a smaller semimajor axis $a$ and various inclinations $i$, we are able to quantify the lensing effects on a broader range of parameters. As expected, for smaller semimajor axes and for nearly edge-on orbits lensing effects increase by about an order of magnitude.

arXiv comment21 pages, 9 figures

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• Gravitational lensing of a Schwarzschild-like black hole in Kalb-Ramond gravity
• Gravitational lens effect of a holonomy corrected Schwarzschild black hole
• The Influence of Uniform Magnetic Fields on Strong Field Gravitational Lensing by Kerr Black Holes
• Probing a Lorentz-violating parameter from orbital precession of the S2 star around the galactic centre supermassive black hole
• Constraints on the $\gamma$-parameter for the vacuum solution of Cotton gravity with geodesics and shadows
• Detecting Lorentz-violation induced by a tensor field with S-star's motion around Sgr A*