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General Relativity and Quantum Cosmology, gr-qc,Astrophysics, Cosmology and Extragalactic Astrophysics, astro-ph.CO
Abstract:
The first direct detection of neutron-star-black-hole binaries will likely be
made with gravitational-wave observatories. Advanced LIGO and Advanced Virgo
will be able to observe neutron-star-black-hole mergers at a maximum distance
of 900Mpc. To acheive this sensitivity, gravitational-wave searches will rely
on using a bank of filter waveforms that accurately model the expected
gravitational-wave signal. The angular momentum of the black hole is expected
to be comparable to the orbital angular momentum. This angular momentum will
affect the dynamics of the inspiralling system and alter the phase evolution of
the emitted gravitational-wave signal. In addition, if the black hole's angular
momentum is not aligned with the orbital angular momentum it will cause the
orbital plane of the system to precess. In this work we demonstrate that if the
effect of the black hole's angular momentum is neglected in the waveform models
used in gravitational-wave searches, the detection rate of $(10+1.4)M_{\odot}$
neutron-star--black-hole systems would be reduced by $33 - 37%$. The error in
this measurement is due to uncertainty in the Post-Newtonian approximations
that are used to model the gravitational-wave signal of neutron-star-black-hole
inspiralling binaries. We describe a new method for creating a bank of filter
waveforms where the black hole has non-zero angular momentum, but is aligned
with the orbital angular momentum. With this bank we find that the detection
rate of $(10+1.4)M_{\odot}$ neutron-star-black-hole systems would be reduced by
$26-33%$. Systems that will not be detected are ones where the precession of
the orbital plane causes the gravitational-wave signal to match poorly with
non-precessing filter waveforms. We identify the regions of parameter space
where such systems occur and suggest methods for searching for highly
precessing neutron-star-black-hole binaries.
