Gravitational waveforms for neutron star binaries from binary black hole simulations

TL;DR

This paper presents a new method to generate gravitational waveforms for neutron star binaries by combining post-Newtonian tidal effects with binary black hole simulations, achieving high phase accuracy with less computational effort.

Contribution

The authors introduce a novel approach that integrates PN tidal effects into BBH simulations to efficiently produce accurate BNS and BHNS waveforms.

Findings

Phase difference of <1 radian over ~15 orbits compared to full hydrodynamical simulations

Method effectively replaces nontidal PN terms with BBH results

Accuracy depends on the tidal deformability parameter λ

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 ${\lambda}$.