Adding higher-order spherical harmonics in non-spinning eccentric binary black hole merger waveform models

TL;DR

This paper introduces a framework that enhances gravitational wave models by incorporating higher-order spherical harmonics for eccentric binary black hole mergers, improving accuracy and modularity in waveform predictions.

Contribution

The paper develops and demonstrates a modular framework, gwNRHME, to incorporate higher-order spherical harmonics into eccentric binary black hole waveform models, validated with numerical relativity data.

Findings

Model predictions agree well with NR simulations (relative L2 errors ~0.01).

Framework effectively combines different waveform models for eccentric mergers.

Models are publicly available through the gwModels package.

Abstract

gwNRHME is a recently developed framework that seamlessly converts a multi-modal (i.e with several spherical harmonic modes) quasi-circular waveform into multi-modal eccentric waveform if the quadrupolar eccentric waveform is known. Here, we employ the gwNRHME framework to combine a multi-modal quasi-circular waveform model NRHybSur3dq8 and quadrupolar non-spinning eccentric waveform model EccentricIMR to construct multi-modal non-spinning eccentric model NRHybSur3dq8-gwNRHME. Using a total of 35 eccentric numerical relativity (NR) simulations obtained from the SXS and RIT catalogs, we demonstrate that NRHybSur3dq8-gwNRHME model predictions agree well with NR (with typical relative $L_2$ errors of ~0.01 for the dominant quadrupolar mode) for mass ratios $ 1 \leq q \leq 4$ and eccentricities up to ~0.2 measured about 10 cycles before the merger. To demonstrate the modularity of the gwNRHME framework, we further combine EccentricIMR with BHPTNRSur1dq1e4 model and develop a non-spinning eccentric models named BHPTNRSur1dq1e4-gwNRHME. Finally, we develop a different variant of these models by replacing EccentricIMR with EccentricTD. Both the gwNRHME framework and associated models are available through the gwModels package.