Observations of Sgr A*'s shadow and the S2 star's orbit constrain the Hernquist-type environmental halo compactness to below about 10^-4, while its radial scale stays bimodally degenerate.
Orbital precession of the S2 star in Scalar-Tensor-Vector-Gravity
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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.
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Multiscale probing of a Hernquist-type environmental black hole spacetime with the Sgr A* shadow and S2 orbital dynamics
Observations of Sgr A*'s shadow and the S2 star's orbit constrain the Hernquist-type environmental halo compactness to below about 10^-4, while its radial scale stays bimodally degenerate.