Analytical Solution of Spinning, Eccentric Binary Black Hole Dynamics at the Second Post-Newtonian Order

TL;DR

This paper develops an analytical 2PN order solution for spinning, eccentric binary black hole dynamics, improving upon previous 1.5PN models and aiding gravitational wave modeling from such systems.

Contribution

It provides the first-principles 2PN analytical solution for the evolution of spins, orbits, and eccentricity in binary black holes with arbitrary spins.

Findings

The 2PN solution is an order of magnitude more accurate than the 1.5PN model.

Neglected 2PN order oscillations in spins are sub-dominant.

The solution models GW sources with combined spin precession and eccentricity.

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 non-precessing systems. This approach is based on empirical observations rather than first principles. This article aims to model the GWs from spinning and eccentric BBHs from a first-principles approach within general relativity and post-Newtonian (PN) approximation. Building on the already-existing 1.5 PN 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 sub-dominant nature of the neglected next-to-leading-order oscillations in the spin solutions.