Quasiequilibrium sequences of synchronously rotating binary neutron stars with constant rest masses in general relativity: Another approach without using the conformally flat condition

Fumihiko Usui and Yoshiharu Eriguchi
Phys. Rev. D 65, 064030 – Published 28 February 2002
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Abstract

We compute quasiequilibrium sequences of synchronously rotating compact binary star systems with constant rest masses. This computation is carried out by using a numerical scheme which is different from the scheme based on the conformally flat assumption about the space. Stars are assumed to be polytropes with polytropic indices of N=0.5, N=1.0, and N=1.5. Since we compute binary star sequences with a constant rest mass, they provide approximate evolutionary tracks of binary star systems. For relatively stiff equations of state (N<1.0), there appear turning points along the quasiequilibrium sequences plotted in the angular momentum—angular velocity plane. Consequently a secular instability against exciting internal motion sets in at those points. Qualitatively, these results agree with those of Baumgarte et al. who employed the conformally flat condition. We further discuss the effect of different equations of state and a different strength of gravity by introducing two kinds of dimensionless quantities which represent the angular momentum and the angular velocity. The strength of gravity is renormalized in these quantities so that the quantities are transformed to values around unity. Therefore we can clearly see relations among quasiequilibrium sequences for a wide variety of strength of gravity and for different compressibility.

  • Received 12 November 2001

DOI:https://doi.org/10.1103/PhysRevD.65.064030

©2002 American Physical Society

Authors & Affiliations

Fumihiko Usui* and Yoshiharu Eriguchi

  • Department of Earth Science and Astronomy, Graduate School of Arts and Sciences, University of Tokyo, Komaba 3-8-1, Meguro, Tokyo 153-8902, Japan

  • *Electronic address: usui@provence.c.u-tokyo.ac.jp
  • Electronic address: eriguchi@valis.c.u-tokyo.ac.jp

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Vol. 65, Iss. 6 — 15 March 2002

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