Relativistic dynamics of stars near a supermassive black hole
Abstract
General relativistic precession limits the ability of gravitational encounters to increase the eccentricity e of orbits near a supermassive black hole (SBH). This `Schwarzschild barrier' (SB) has been shown to play an important role in the orbital evolution of stars like the Galactic Centre Sstars. However, the evolution of orbits below the SB, e > e_{SB}, is not well understood; the main current limitation is the computational complexity of detailed simulations. Here, we present an Nbody algorithm that allows us to efficiently integrate orbits of test stars around an SBH including general relativistic corrections to the equations of motion and interactions with a large (≳10^{3}) number of field stars. We apply our algorithm to the Sstars and extract diffusion coefficients describing the evolution in angular momentum L. We identify three angularmomentum regimes, in which the diffusion coefficients depend in functionally different ways on L. Regimes of lowest and highest L are well described in terms of nonresonant relaxation and resonant relaxation, respectively. In addition, we find a new regime of `anomalous relaxation'. We present analytic expressions, in terms of physical parameters, that describe the diffusion coefficients in all three regimes, and propose a new, empirical criterion for the location of the SB in terms of the Ldependence of the diffusion coefficients. Subsequently, we apply our results to obtain the steadystate distribution of angular momentum for orbits near an SBH.
 Publication:

Monthly Notices of the Royal Astronomical Society
 Pub Date:
 September 2014
 DOI:
 10.1093/mnras/stu1126
 arXiv:
 arXiv:1406.2846
 Bibcode:
 2014MNRAS.443..355H
 Keywords:

 gravitation;
 relativistic processes;
 Galaxy: centre;
 galaxies: nuclei;
 Astrophysics  Astrophysics of Galaxies
 EPrint:
 Accepted for publication in MNRAS. 34 pages, 32 figures