Gravitational waveforms from SpEC simulations : neutron star-neutron star and low-mass black hole-neutron star binaries

Gravitational waveformsfrom numerical simulations are a critical tool to test and analytically calibrate the waveformmodels used to study the properties of merging compact objects. In this paper, we present a series of high-accuracy waveformsproduced with the SpECcode for systems involving at least one neutron star. We provide for the first time waveformswith sub- radianaccuracy over more than twenty cycles for low-mass black hole- neutron starbinaries, including binaries with non-spinning objects, and binaries with rapidly spinning neutron starsthat maximize the impact on the gravitational wave signal of the near-resonant growth of the fundamental excitation mode of the neutron star(f-mode). We also provide for the first time with SpECa high-accuracy neutron star-neutron star waveform. These waveformsare made publicly available as part of the SxS catalogue. We compare our results to analytical waveformmodels currently implemented in data analysis pipelines. For most simulations, the models lie outside of the predicted numerical errorsin the last few orbits before merger, but do not show systematic deviations from the numerical results: comparing different models appears to provide reasonable estimates of the modeling errors. The sole exception is the equal-mass simulation using a rapidly counter-rotating neutron starto maximize the impact of the excitation of the f-mode, for which all models perform poorly. This is however expected, as even the single model that takes f-mode excitation into account ignores the significant impact of the neutron starspin on the f-mode excitation frequency.