Orbital precession of the S2 star in Scalar-Tensor-Vector-Gravity

TL;DR

This study constrains the parameters of Scalar-Tensor-Vector-Gravity using S2-star orbital data, finding no significant deviation from General Relativity and limiting the theory's additional parameter.

Contribution

First constraint on Scalar-Tensor-Vector-Gravity parameters using S2-star orbital data around the Milky Way's black hole.

Findings

Parameter alpha constrained to alpha < 0.410 at 99.7% confidence

No significant tension with General Relativity found

Orbital precession measurements used to test gravity theory

Abstract

We have obtained the first constraint of the parameter space of Scalar-Tensor-Vector-Gravity using the motion of the S2-star around the supermassive black hole at the centre of the Milky Way, and we did not find any serious tension with General Relativity. We used the Schwarzschild-like metric of Scalar-Tensor-Vector-Gravity to predict the orbital motion of S2-star, and to compare it with the publicly available astrometric data, which include 145 measurements of the positions, 44 measurements of the radial velocities of S2-star along its orbit, and the recent measurement of the orbital precession. We employed a Monte Carlo Markov Chain algorithm to explore the parameter space, and constrained the only one additional parameter of Scalar-Tensor-Vector-Gravity to $\alpha \lesssim 0.410$ at 99,7$\%$ confidence level, where $\alpha=0$ reduces this modified theory of gravity to General Relativity.