Gravitational waves from nonspinning black hole-neutron star binaries: Dependence on equations of state

Koutarou Kyutoku, Masaru Shibata, and Keisuke Taniguchi
Phys. Rev. D 82, 044049 – Published 30 August 2010; Erratum Phys. Rev. D 84, 049902 (2011)

Abstract

We report results of a numerical-relativity simulation for the merger of a black hole-neutron star binary with a variety of equations of state (EOSs) modeled by piecewise polytropes. We focus, in particular, on the dependence of the gravitational waveform at the merger stage on the EOSs. The initial conditions are computed in the moving-puncture framework, assuming that the black hole is nonspinning and the neutron star has an irrotational velocity field. For a small mass ratio of the binaries (e.g., MBH/MNS=2, where MBH and MNS are the masses of the black hole and neutron star, respectively), the neutron star is tidally disrupted before it is swallowed by the black hole irrespective of the EOS. Especially for less-compact neutron stars, the tidal disruption occurs at a more distant orbit. The tidal disruption is reflected in a cutoff frequency of the gravitational-wave spectrum, above which the spectrum amplitude exponentially decreases. A clear relation is found between the cutoff frequency of the gravitational-wave spectrum and the compactness of the neutron star. This relation also depends weakly on the stiffness of the EOS in the core region of the neutron star, suggesting that not only the compactness but also the EOS at high density is reflected in gravitational waveforms. The mass of the disk formed after the merger shows a similar correlation with the EOS, whereas the spin of the remnant black hole depends primarily on the mass ratio of the binary, and only weakly on the EOS. Properties of the remnant disks are also analyzed.

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  • Received 7 June 2010

DOI:https://doi.org/10.1103/PhysRevD.82.044049

© 2010 The American Physical Society

Erratum

Authors & Affiliations

Koutarou Kyutoku and Masaru Shibata

  • Yukawa Institute for Theoretical Physics, Kyoto University, Kyoto 606-8502, Japan

Keisuke Taniguchi

  • Graduate School of Arts and Sciences, University of Tokyo, Komaba, Meguro, Tokyo 153-8902, Japan

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Issue

Vol. 82, Iss. 4 — 15 August 2010

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