Exploiting Newton-factorized, 2PN-accurate, waveform multipoles in effective-one-body models for spin-aligned noncircularized binaries

TL;DR

This paper introduces a new factorization and resummation method for gravitational waveforms from spin-aligned, noncircular binaries within the effective-one-body framework, improving accuracy especially for high-eccentricity inspirals.

Contribution

It develops a novel multipolar waveform factorization that includes noncircular effects resummed with Padé approximants, validated against numerical waveforms for eccentric inspirals and dynamical captures.

Findings

Resummation of noncircular tail is crucial for high-eccentricity accuracy.

Achieves excellent agreement with numerical waveforms up to eccentricity 0.9.

Maximal unfaithfulness around 10^{-3} for eccentricities up to 0.3.

Abstract

We present a new approach to factorize and resum the post-Newtonian (PN) waveform for generic equatorial motion to be used within effective-one-body (EOB) based waveform models. The new multipolar waveform factorization improves previous prescriptions in that: (i) the generic Newtonian contribution is factored out from each multipole; (ii) the circular part is factored out and resummed using standard EOB methods and (iii) the residual, 2PN-accurate, noncircular part, and in particular the tail contribution, is additionally resummed using Pad\'e approximants. The resulting waveform is validated in the extreme-mass-ratio limit by comparisons with nine (mostly nonspinning) numerical waveforms either from eccentric inspirals, with eccentricities up to $e=0.9$, or dynamical captures . The resummation of the noncircular tail contribution is found essential to obtain excellent (${\lesssim}0.05$~rad at periastron for $e=0.9$) analytical/numerical agreement and to considerably improve the prescription with just the Newtonian prefactor. In the comparable mass case, the new 2PN waveform shows only a marginal improvement over the previous Newtonian factorization, though yielding maximal unfaithfulness $\simeq 10^{-3}$ with the 28 publicly available numerical relativity simulations with eccentricity up to $\sim 0.3$ (except for a single outlier that grazes $10^{-2}$). We finally use test-particle data to validate the waveform factorization proposed by Khalil et al.~[Phys.~Rev.~104 (2021) 2, 024046] and conclude that its amplitude can be considered reliable (though less accurate, $\sim 6\%$ fractional difference versus $1.5\%$ of our method) only up to eccentricities $\sim 0.3$.