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General Relativity and Quantum Cosmology, gr-qc
Abstract:
After the discovery of gravitational waves from binary black holes (BBHs) and
binary neutron stars (BNSs) with the LIGO and Virgo detectors,
neutron-star--black-holes (NSBHs) are the natural next class of binary systems
to be observed. In this work, we develop a waveform model for aligned-spin
neutron-star--black-holes (NSBHs) combining a binary black-hole baseline
waveform (available in the effective-one-body approach) with a phenomenological
description of tidal effects (extracted from numerical-relativity simulations),
and correcting the amplitude during the late inspiral, merger and ringdown to
account for the NS's tidal disruption. In particular, we calibrate the
amplitude corrections using NSBH waveforms obtained with the
numerical-relativity spectral Einstein code (SpEC) and the SACRA code. Based on
the simulations used, and on checking that sensible waveforms are produced, we
recommend our model to be employed with NS's mass in the range $1-3 M_\odot$,
tidal deformability $0\mbox{-}5000$, and (dimensionless) BH's spin magnitude up
to $0.9$. We also validate our model against two new, highly accurate NSBH
waveforms with BH's spin 0.9 and mass ratios 3 and 4, characterized by tidal
disruption, produced with SpEC, and find very good agreement. Furthermore, we
compute the unfaithfulness between waveforms from NSBH, BBH, and BNS systems,
finding that it will be challenging for the advanced LIGO-Virgo--detector
network at design sensitivity to distinguish different source classes. We
perform a Bayesian parameter-estimation analysis on a synthetic
numerical-relativity signal in zero noise to study parameter biases. Finally,
we reanalyze GW170817, with the hypothesis that it is a NSBH. We do not find
evidence to distinguish the BNS and NSBH hypotheses, however the posterior for
the mass ratio is shifted to less equal masses under the NSBH hypothesis.
