Exploring the presence of a fifth force at the Galactic Center

Aims: The presence of a Yukawa-like correction to Newtonian gravity is investigated at the Galactic Center, leading to a new upper limit for the intensity of such a correction. Methods: We perform a Markov Chain Monte Carlo analysis using the astrometric and spectroscopic data of star S$2$ collected at the Very Large Telescope by GRAVITY, NACO and SINFONI instruments, covering the period from $1992$ to $2022$. Results: The precision of the GRAVITY instrument allows us to derive the most stringent upper limit at the Galactic Center for the intensity of the Yukawa contribution ($\propto , αe^{- λr}$) to be $|α| < 0.003$ for a scale length $λ= 3 \cdot 10^{13}, \rm m, (\sim 200 , \rm AU)$. This improves by roughly one order of magnitude all estimates obtained in previous works.

💡 Research Summary

The paper investigates whether a Yukawa‑type correction to Newtonian gravity—characterized by a strength parameter α and a range λ—can be detected in the strong‑field environment of the Galactic Center (GC). The authors use a comprehensive data set of the star S2, which orbits the supermassive black hole Sagittarius A* (Sgr A*), collected over three decades (1992–2022) with the Very Large Telescope (VLT). The astrometric component consists of 128 positional measurements from the SHARP camera (1992‑2002) and the NACO imager (2002‑2019), plus 76 ultra‑precise GRAVITY interferometric points (2016‑2022) with typical uncertainties of ~50 µas. Spectroscopic data comprise 102 radial‑velocity measurements from SINFONI (2000‑2022) and two points from NIRC2, with typical errors of 10‑15 km s⁻¹.

The theoretical model adds a Yukawa term to the Newtonian potential:
U = −GM/r