Spin precession effects in the phasing formula of eccentric compact binary inspirals up to the second post-Newtonian order

TL;DR

This paper derives analytic gravitational wave phasing formulas for eccentric, precessing binary systems up to second post-Newtonian order, improving waveform modeling efficiency and accuracy for data analysis.

Contribution

It introduces a novel analytic framework that incorporates eccentricity and spin precession effects into gravitational waveform phasing up to second PN order.

Findings

Derived closed form solutions for eccentricity evolution and GW phase up to eighth order in initial eccentricity.

Generalized TaylorT2 approximant to include spin precession effects.

Implemented a resummation technique to enhance accuracy for moderate to high eccentricities.

Abstract

Compact binary systems emitting gravitational waves (GWs) can exhibit orbital eccentricity, along with generic spin orientations, leading to the precession of the orbital angular momentum, individual spins, and the orbital plane. While eccentric binaries with aligned spins are well studied, closed form post Newtonian (PN) expressions that simultaneously include eccentricity and precessing spin effects have remained unavailable. Eccentricity complicates orbital evolution because solving the coupled differential equations typically requires numerical integration, which slows down the generation of waveforms. We exploit the separation of timescales between orbital motion, spin precession, and radiation reaction, applying the precession averaging method of Morras et al. (2025) to remove explicit time dependence from the spin orbit and spin spin dynamics through the second PN order. Using this framework, we derive analytic phasing formulae from the evolution equations for orbital frequency and eccentricity, treating eccentricity as a small parameter. Closed form solutions for the eccentricity evolution and GW phase are obtained up to eighth order in the initial eccentricity. We also generalize the TaylorT2 approximant to include spin precession effects and compute the orbital phase in both time and frequency domains. To improve accuracy for moderate to high initial eccentricities, we perform a resummation of the TaylorT2 phasing. These results offer efficient, closed form phasing expressions that capture the coupled dynamics of eccentricity and precession, enabling more accurate and computationally tractable GW waveform modeling for data analysis.