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Phys. Rev. D 79, 124018 (2009) [13 pages]

Quasiequilibrium states of black hole-neutron star binaries in the moving-puncture framework

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Koutarou Kyutoku and Masaru Shibata
Yukawa Institute for Theoretical Physics, Kyoto University, Kyoto, 606-8502, Japan

Keisuke Taniguchi
Department of Physics, University of Wisconsin-Milwaukee, P.O. Box 413, Milwaukee, Wisconsin 53201, USA

Received 18 March 2009; published 12 June 2009

General relativistic quasiequilibrium states of black hole-neutron star binaries are computed in the moving-puncture framework. We propose three conditions for determining the quasiequilibrium states and compare the numerical results with those obtained in the excision framework. We find that the results obtained in the moving-puncture framework agree with those in the excision framework and with those in the third post-Newtonian approximation for the cases that (i) the mass ratio of the binary is close to unity irrespective of the orbital separation, and (ii) the orbital separation is large enough (m0Ω≲0.02, where m0 and Ω are the total mass and the orbital angular velocity, respectively) irrespective of the mass ratio. For m0Ω≳0.03, both of the results in the moving-puncture and excision frameworks deviate, more or less, from those in the third post-Newtonian approximation. Thus the numerical results do not provide a quasicircular state, rather they seem to have a non-negligible eccentricity of order 0.01–0.1. We show by numerical simulation that a method in the moving-puncture framework can provide approximately quasicircular states in which the eccentricity is by a factor of ∼2 smaller than those in quasiequilibrium given by other approaches.

© 2009 The American Physical Society

URL:
http://link.aps.org/doi/10.1103/PhysRevD.79.124018
DOI:
10.1103/PhysRevD.79.124018
PACS:
04.25.D−, 04.30.−w, 04.40.Dg