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arXiv · 2601.06491

Probing a Lorentz-violating parameter from orbital precession of the S2 star around the galactic centre supermassive black hole

Qi Qi·Yu Sang·Xiao-Mei Kuang
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Abstract

Testing Lorentz symmetry in strong gravitational fields provides a promising probe of extensions to general relativity. The supermassive black hole Sgr~A* and the orbit of the S-stars offer a laboratory for such tests in a regime beyond weak field limit. We analyze the S2 orbital data focusing on the Schwarzschild-like black hole within bumblebee gravity, where deviations from general relativity are encoded in a single Lorentz-violating parameter $\ell$. Using a full 14-dimensional Markov Chain Monte Carlo analysis under uniform and Gaussian priors, we obtain $\ell = {-8.01 \times 10^{-5}}^{+2.77 \times 10^{-4}}_{-2.09 \times 10^{-4}} $ and $\ell = {1.00 \times 10^{-5}}^{+2.90 \times 10^{-4}}_{-2.91 \times 10^{-4}} $ at $1\sigma$ confidence level, respectively. These constraints are about three orders of magnitude tighter than those from Event Horizon Telescope imaging of Sgr~A*.

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Qi Qi, Yu Sang, Xiao-Mei Kuang. 2026-01-10. Probing a Lorentz-violating parameter from orbital precession of the S2 star around the galactic centre supermassive black hole. https://doi.org/10.1007/s11433-026-2960-1

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