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Abstract

We identify various contributors of systematic effects in the measurement of
the neutron star (NS) tidal deformability and quantify their magnitude for
several types of neutron star - black hole (NSBH) binaries. Gravitational waves
from NSBH mergers contain information about the components' masses and spins as
well as the NS equation of state. Extracting this information requires
comparison of the signal in noisy detector data with theoretical templates
derived from some combination of post-Newtonian (PN) approximants, effective
one-body (EOB) models and %analytic fits to numerical relativity (NR)
simulations. The accuracy of these templates is limited by errors in the NR
simulations, by the approximate nature of the PN/EOB waveforms, and by the
hybridization procedure used to combine them. In this paper, we estimate the
impact of these errors by constructing and comparing a set of PN-NR hybrid
waveforms, for the first time with NR waveforms from two different codes,
namely, SpEC and SACRA, for such systems. We then attempt to recover the
parameters of the binary using two non-precessing template approximants. We
find that systematic errors are too large for tidal effects to be accurately
characterized for any realistic NS equation of state model. We conclude that
NSBH waveform models must be significantly improved if they are to be useful
for the extraction of NS equation of state information or even for
distinguishing NSBH systems from binary black holes.