http://arxiv.org/abs/2203.09646
Close encounters between two bodies in a disk often result in a single orbital deflection. However, within their Jacobi volumes, where the gravitational forces between the two bodies and the central body become competitive, temporary captures with multiple close encounters become possible outcomes: a Jacobi capture. We perform 3-body simulations in order to characterise the dynamics of Jacobi captures in the plane. We find that the phase space structure resembles a Cantor set with a fractal dimension of 0.4. The lifetime distribution decreases exponentially, while the distribution of the closest separation follows a power law with index 0.5. In our first application, we consider the Jacobi capture of the Moon. We demonstrate that both tidal captures and giant impacts are possible outcomes. Their respective 1D cross sections differ within an order of magnitude, evaluated at a heliocentric distance of 1 AU. The impact speed is well approximated by a parabolic encounter, while the impact angles follow that of a uniform beam on a circular target. In our second application, we find that Jacobi captures with gravitational wave dissipation can result in the formation of binary black holes in galactic nuclei. The eccentricity distribution is approximately super-thermal and includes both prograde and retrograde orientations. We estimate a cosmic rate density of 0.083 < R < 14 Gpc^-3 yr^-1. We conclude that dissipative Jacobi captures form an efficient channel for binary formation, which motivates further research into establishing the universality of Jacobi captures across multiple astrophysical scales.
T. Boekholt, C. Rowan and B. Kocsis
Mon, 21 Mar 22
8/60
Comments: Submitted to MNRAS. 18 pages, 16 figures