Analytical solution of spinning, eccentric binary black hole dynamics at the second post-Newtonian order
Phys. Rev. D 114, 064051 – Published 10 September, 2026
DOI: https://doi.org/10.1103/tr9z-qky6
Abstract
Recent gravitational wave (GW) detections showing signatures of eccentricity and spin precession underscore the need to model binary black holes (BBHs) possessing these features simultaneously. Most efforts over the past fifteen years to model spinning BBHs and their corresponding GWs have relied on heuristically twisting waveforms from nonprecessing systems. This approach is based on empirical observations rather than first principles. This article aims to model the dynamics of spinning and eccentric BBHs from a first-principles approach using the post-Newtonian (PN) approximation within general relativity. Building on the already-existing 1.5PN solution, we construct an analytical solution for the time evolution of the relative separation vector, the individual black hole spin vectors, and the orbital angular momentum vector at 2PN order for BBHs with arbitrary spins and eccentricity. Such a solution is not fully 2PN accurate in that the tiny orbital timescale fluctuations in the solutions for the spins are only leading 1.5PN order accurate, instead of 2PN. However, it is shown that our new 2PN solution is still an order of magnitude improvement over the earlier 1.5PN solution, underlining the subdominant nature of the neglected next-to-leading-order oscillations in the spin solutions.
