David Merritt


Also archived in: arXiv:astro-ph/0012264 v2 21 Mar 2001 AND Rutgers Astrophysics Preprint Series No. 296 The dynamical friction and diffusion coefficients are derived for a massive binary that moves against a uniform background of stars. The random impulses exerted on the binary’s center of mass by the field stars are greater than those exerted on a point particle due to inelastic scattering. The frictional force acting on the binary is less than that acting on a point particle due to randomization of the trajectories of field stars that pass near the binary. Both effects tend to increase the random motion of a binary compared with that of a point mass. If the maximum effective impact parameter for gravitational encounters is comparable to the radius of gravitational influence of the binary, its Brownian velocity can be increased by a modest factor (<∼ 2) compared with that of a single particle. This condition is probably fulfilled in the case of binary supermassive black holes in galactic nuclei. (Refer to PDF file for exact formulas).

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This work was supported by NSF grants AST 96-17088 and 00-71099 and by NASA grants NAG5-6037 and NAG5-9046.

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Department, Program, or Center

School of Physics and Astronomy (COS)


RIT – Main Campus