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Abstract

Gravitational waves from binary neutron star (BNS) and black hole/neutron
star (BHNS) inspirals are primary sources for detection by the Advanced Laser
Interferometer Gravitational-Wave Observatory. The tidal forces acting on the
neutron stars induce changes in the phase evolution of the gravitational
waveform, and these changes can be used to constrain the nuclear equation of
state. Current methods of generating BNS and BHNS waveforms rely on either
computationally challenging full 3D hydrodynamical simulations or approximate
analytic solutions. We introduce a new method for computing inspiral waveforms
for BNS/BHNS systems by adding the post-Newtonian (PN) tidal effects to full
numerical simulations of binary black holes (BBHs), effectively replacing the
nontidal terms in the PN expansion with BBH results. Comparing a waveform
generated with this method against a full hydrodynamical simulation of a BNS
inspiral yields a phase difference of $<1$ radian over $\sim 15$ orbits. The
numerical phase accuracy required of BNS simulations to measure the accuracy of
the method we present here is estimated as a function of the tidal
deformability parameter ${\lambda}$.