2008/04/12 by Hyosun Kim, Woong-Tae Kim, Woong‐Tae Kim +2
Physics and Astronomy · #Astrophysical Phenomena and Observations #Experimental and Theoretical Physics Studies #Pulsars and Gravitational Waves Research #astro-ph
paper · pdf · doi:10.1086/589149
4 pages, 3 figures, accepted for publication in ApJL
arxiv created 2008/04/12 · openalex publication_date 2008/04/22 · arxiv updated 2009/12/01 · openalex created_date 2025/10/10 · openalex updated_date 2026/07/31
In many astrophysical situations, as in the coalescence of supermassive black hole pairs at gas-rich galactic nuclei, the dynamical friction experienced by an object is a combination of its own wake as well as the wakes of its companion. Using a semianalytic approach, we investigate the composite wake due to, and the resulting drag forces on, double perturbers that are placed at the opposite sides of the orbital center and move on a circular orbit in a uniform gaseous medium. The circular orbit makes the wake of each perturber asymmetric, creating an overdense tail at the trailing side. The tail not only drags the perturber backward but it also exerts a positive torque on the companion. For equal-mass perturbers, the positive torque created by the companion wake is, on average, a fraction ~40%-50% of the negative torque created by its own wake, but this fraction may be even larger for perturbers moving subsonically. This suggests that the orbital decay of a perturber in a double system, especially in the subsonic regime, can take considerably longer than in isolation. We provide the fitting formulae for the forces due to the companion wake and discuss our results in light of recent numerical simulations of mergers of binary black holes.