Testing General Relativity with stellar orbits around the supermassive black hole in our Galactic center

Hees, A.; Do, T.; Ghez, A. M.; Martinez, G. D.; Naoz, S.; Becklin, E. E.; Boehle, A.; Chappell, S.; Chu, D.; Dehghanfar, A.; Kosmo, K.; Lu, J. R.; Matthews, K.; Morris, M. R.; Sakai, S.; Schödel, R.; Witzel, G.
eprint arXiv:1705.07902


In this Letter, we demonstrate that short-period stars orbiting around the supermassive black hole in our Galactic Center can successfully be used to probe the gravitational theory in a strong regime. We use 19 years of observations of the two best measured short-period stars orbiting our Galactic Center to constrain a hypothetical fifth force that arises in various scenarios motivated by the development of a unification theory or in some models of dark matter and dark energy. No deviation from General Relativity is reported and the fifth force strength is restricted to an upper 95% confidence limit of $\left|\alpha\right| < 0.016$ at a length scale of $\lambda=$ 150 astronomical units. We also derive a 95% confidence upper limit on a linear drift of the argument of periastron of the short-period star S0-2 of $\left|\dot \omega_\textrm{S0-2} \right|< 1.6 \times 10^{-3}$ rad/yr, which can be used to constrain various gravitational and astrophysical theories. This analysis provides the first fully self-consistent test of the gravitational theory using orbital dynamic in a strong gravitational regime, that of a supermassive black hole. A sensitivity analysis for future measurements is also presented.