High-accuracy waveforms for black hole-neutron star systems with spinning black holes

Abstract

The availability of accurate numerical waveforms is an important requirement for the creation and calibration of reliable waveform models for gravitational wave astrophysics. For black hole-neutron star binaries (BHNS), very few accurate waveforms are however publicly available. Most recent models are calibrated to a large number of older simulations with good parameter space coverage for low-spin nonprecessing binaries but limited accuracy, and a much smaller number of longer, more recent simulations limited to nonspinning black holes. In this paper, we present long, accurate numerical waveforms for three new systems that include rapidly spinning black holes, and one precessing configuration. We study in detail the accuracy of the simulations, and in particular perform for the first time in the context of BHNS binaries a detailed comparison of waveform extrapolation methods to the results of Cauchy characteristic extraction. The new waveforms have <0.1  rad phase errors during inspiral, rising to ∼(0.2–0.4)  rad errors at merger, and ≲1% error in their amplitude. We compute the faithfulness of recent analytical models to these numerical results for the late inspiral and merger phases covered by the numerical simulations, and find that models specifically designed for BHNS binaries perform well (faithfulness F > 0.99) for binaries seen face on. For edge-on observations, particularly for precessing systems, disagreements between models and simulations increase, and models that include precession and/or higher-order modes start to perform better than BHNS models that currently lack these features.