Improving constraints on the Yukawa correction at the Galactic Center with multiple stellar orbits

We investigate the presence of a Yukawa-like correction (proportional to, αe- r/λ) to Newtonian gravity at the Galactic Center, using a multi-star fitting code, including the newly discovered star S 301, to improve the constraints obtained using S 2 orbit alone. We perform a Markov Chain Monte Carlo analysis using the astrometric and spectroscopic data of stars S 2, S 55, S 29, S 38 and S 301 collected by GRAVITY, GRAVITY+, NACO and SINFONI instruments, covering the period from 1992 to 2025. Compared to GRAVITY Collaboration 2025 (Paper I), in which only S 2 was fitted, the tightest bound on the Yukawa coupling is again reached at λ= 3 times10 13, m (about 200,AU), where we find α < 6 times10-4, an improvement of roughly a factor five. The addition of S 301 extends the constraint to short ranges that were inaccessible to S 2, yielding α < 0.004 at λ=10 12, m and α < 0.006 at λ=5 times 10 11, m, while S 29, with its larger apoapsis, gives α < 0.1 at λ about 2 times10 15, m. The latter two represent the tightest limits at these scale lengths on a Yukawa correction obtained to date around a supermassive black hole.