Waveform models for the gravitational-wave memory effect: III. Phenomenological frequency-domain model for nonspinning binaries

Abstract

We present a phenomenological frequency-domain model for the gravitational-wave (GW) memory signal from nonspinning binary-black-hole mergers on quasicircular orbits. We develop separate amplitude and phase models for the dominant $(l,m)=(2,0)$ spherical-harmonic mode of the GW memory signal. The amplitude and phase models are built from superpositions of elementary and transcendental functions, which can be evaluated efficiently. Both portions of the model are calibrated against a numerical-relativity surrogate model over mass ratios from one to eight. Their accuracy is assessed by computing their mismatch with the numerical-relativity models using the Advanced LIGO sensitivity curve from the fourth observing run. The mismatches are of the order $10^{-4}\unicode{x2013}10^{-3}$ over the parameter space of total mass covered by LIGO. The resulting frequency-domain model is a more computationally efficient waveform model for the GW memory signal than a related time-domain model earlier produced by the authors. An open-access implementation of both the time-domain and frequency-domain models is provided in the Python package GWMemoryModel, which can be used for relevant analyses of nonspinning binary black holes.