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Paper: Testing Fundamental Physics With Stellar Orbits at the Galactic Center
Volume: 528, New Horizons in Galactic Center Astronomy and Beyond
Page: 249
Authors: Do, T.; Hees, A.; Ghez, A.; Martinez, G. D.; Chu, D. S.; Jia, S.; Sakai, S.; Lu, J. R.; Gautam, A. K.; O'Neil, K. K.; Becklin, E. E.; Morris, M. R.; Matthews, K.; Nishiyama, S.; Campbell, R.; Chappell, S.; Chen, Z.; Ciurlo, A.; Witzel, A.; Gallego-Cano, E.; Kerzendorf, W. E.; Lyke, J. E.; Naoz, S.; Saida, H.; Schödel, R.; Takahashi, M.; Takamori, Y.; Witzel, G.; Wizinowich, P.; Roberts, B. M.
Abstract: The closest approach of the star S0-2 to the supermassive black hole Sgr A* in 2018 opened a new era of tests of gravity with stellar orbits at the Galactic Center. Using radial velocity and astrometry measurements from 24 years of data, including data from 2018, we are able to measure the relativistic redshift from S0-2. In addition, the stars in orbit around Sgr A* can be used to search for variations in the fundamental constants of nature around a supermassive black hole. Using the spectral features of late-type giants in orbit around the black hole, we present limits on the variation of fine structure constant in the gravitational field of a supermassive black hole. Both the relativistic redshift measurement and the limits on the fine structure constant allows us to test Einstein's Equivalence Principle, a fundamental component of General Relativity. We find that both of these tests are consistent with the predictions of GR. Improvements in stellar orbital measurements as well as high spectral-resolution measurements will significantly improve the power of these tests in the future.
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