Gravitational Encounters and the Evolution of Galactic Nuclei. IV. Captures Mediated by Gravitational-Wave Energy Loss

Understand

Direct numerical integrations of the two-dimensional Fokker-Planck equation are carried out for compact objects orbiting a supermassive black hole (SBH) at the center of a galaxy.

• As in Papers I-III, the diffusion coefficients incorporate the effects of the lowest-order post-Newtonian corrections to the equations of motion.
• In addition, terms describing the loss of orbital energy and angular momentum due to the 5/2-order post-Newtonian terms are included.
• In the steady state, captures are found to occur in two regimes that are clearly differentiated in terms of energy, or semimajor axis; these two regimes are naturally characterized as "plunges" (low binding energy) and "EMRIs," or extreme-mass-ratio inspirals (high binding energy).