Investigating the Relativistic Motion of the Stars Near the Supermassive Black Hole in the Galactic Center
Abstract
The Sstar cluster in the Galactic center allows us to study the physics close to a supermassive black hole, including distinctive dynamical tests of general relativity. Our best estimates for the mass of and the distance to Sgr A* using the three stars with the shortest period (S2, S38, and S55/S0102) and Newtonian models are M _{BH} = (4.15 ± 0.13 ± 0.57) × 10^{6} M _{⊙} and R _{0} = 8.19 ± 0.11 ± 0.34 kpc. Additionally, we aim at a new and practical method to investigate the relativistic orbits of stars in the gravitational field near Sgr A*. We use a firstorder postNewtonian approximation to calculate the stellar orbits with a broad range of periapse distance r _{ p }. We present a method that employs the changes in orbital elements derived from elliptical fits to different sections of the orbit. These changes are correlated with the relativistic parameter defined as ϒ ≡ r _{ s }/r _{ p } (with r _{ s } being the Schwarzschild radius) and can be used to derive ϒ from observational data. For S2 we find a value of ϒ = 0.00088 ± 0.00080, which is consistent, within the uncertainty, with the expected value of ϒ = 0.00065 derived from M _{BH} and the orbit of S2. We argue that the derived quantity is unlikely to be dominated by perturbing influences such as noise on the derived stellar positions, field rotation, and drifts in black hole mass.
 Publication:

The Astrophysical Journal
 Pub Date:
 August 2017
 DOI:
 10.3847/15384357/aa7bf0
 arXiv:
 arXiv:1708.03507
 Bibcode:
 2017ApJ...845...22P
 Keywords:

 astrometry;
 black hole physics;
 Galaxy: center;
 infrared: stars;
 Astrophysics  Astrophysics of Galaxies
 EPrint:
 27 pages, 24 figures