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We present the extension of our \cocal~- Compact Object CALculator - code to compute general-relativistic initial data for binary compact-star systems. In particular, we construct quasiequilibrium initial data for equal-mass binaries with…

General Relativity and Quantum Cosmology · Physics 2015-06-04 Antonios Tsokaros , Koji Uryu , Luciano Rezzolla

Using an energy variational method, we calculate quasi-equilibrium configurations of binary neutron stars modeled as compressible triaxial ellipsoids obeying a polytropic equation of state. Our energy functional includes terms both for the…

Astrophysics · Physics 2009-10-30 James C. Lombardi , Frederic A. Rasio , Stuart L. Shapiro

In this paper we have examined numerically exact configurations of close binary systems composed of incompressible fluids with internal flows. Component stars of binary systems are assumed to be circularly orbiting each other but rotating…

Astrophysics · Physics 2009-10-30 Koji Uryu , Yoshiharu Eriguchi

We model two mergers of orbiting binary neutron stars, the first forming a black hole and the second a differentially rotating neutron star. We extract gravitational waveforms in the wave zone. Comparisons to a post-Newtonian analysis allow…

General Relativity and Quantum Cosmology · Physics 2008-11-26 Matthew Anderson , Eric W. Hirschmann , Luis Lehner , Steven L. Liebling , Patrick M. Motl , David Neilsen , Carlos Palenzuela , Joel E. Tohline

We report on numerical results from an independent formalism to describe the quasi-equilibrium structure of nonsynchronous binary neutron stars in general relativity. This is an important independent test of controversial numerical…

General Relativity and Quantum Cosmology · Physics 2009-10-31 P. Marronetti , G. J. Mathews , J. R. Wilson

We report on numerical results from an independent formalism to describe the quasi-equilibrium structure of nonsynchronous binary neutron stars in general relativity. This is an important independent test of controversial numerical…

General Relativity and Quantum Cosmology · Physics 2007-05-23 Pedro Marronetti , Grant J. Mathews , James R. Wilson

We present a numerical method to compute quasiequilibrium configurations of close binary neutron stars in the pre-coalescing stage. A hydrodynamical treatment is performed under the assumption that the flow is either rigidly rotating or…

General Relativity and Quantum Cosmology · Physics 2009-10-31 E. Gourgoulhon , P. Grandclement , K. Taniguchi , J. -A. Marck , S. Bonazzola

We present the first computations of quasiequilibrium binary neutron stars with different mass components in general relativity, within the Isenberg-Wilson-Mathews approximation. We consider both cases of synchronized rotation and…

General Relativity and Quantum Cosmology · Physics 2009-11-07 Keisuke Taniguchi , Eric Gourgoulhon

Quasiequilibrium sequences of binary neutron stars are numerically calculated in the framework of the Isenberg-Wilson-Mathews (IWM) approximation of general relativity. The results are presented for both rotation states of synchronized…

General Relativity and Quantum Cosmology · Physics 2009-11-10 Keisuke Taniguchi , Eric Gourgoulhon

Two relations, the virial relation $M_{\rm ADM}=M_{\rm K}$ and the first law in the form $\delta M_{\rm ADM}=\Omega \delta J$, should be satisfied by a solution and a sequence of solutions describing binary compact objects in…

General Relativity and Quantum Cosmology · Physics 2014-11-17 Masaru Shibata , Koji Uryu , John L. Friedman

For isentropic fluids, dynamical evolution of a binary system conserves the baryonic mass and circulation; therefore, sequences of constant rest mass and constant circulation are of particular importance. In this work, we present the…

General Relativity and Quantum Cosmology · Physics 2019-01-01 Antonios Tsokaros , Koji Uryu , Milton Ruiz , Stuart L. Shapiro

A new method is described for constructing initial data for a binary neutron-star (BNS) system in quasi-equilibrium circular orbit. Two formulations for non-conformally flat data, waveless (WL) and near-zone helically symmetric (NHS), are…

General Relativity and Quantum Cosmology · Physics 2013-05-29 Koji Uryu , Francois Limousin , John L. Friedman , Eric Gourgoulhon , Masaru Shibata

We have computed quasiequilibrium sequences of synchronously rotating compact binary star systems with constant rest masses. This computation has been carried out by using the numerical scheme which is different from the scheme based on the…

Astrophysics · Physics 2009-11-07 Fumihiko Usui , Yoshiharu Eriguchi

With an increasing number of expected gravitational-wave detections of binary neutron star mergers, it is essential that gravitational-wave models employed for the analysis of observational data are able to describe generic compact binary…

General Relativity and Quantum Cosmology · Physics 2022-04-06 Reetika Dudi , Tim Dietrich , Alireza Rashti , Bernd Bruegmann , Jan Steinhoff , Wolfgang Tichy

We study equilibrium sequences of close binary systems composed of identical polytropic stars in Newtonian gravity. The solving method is a multi-domain spectral method which we have recently developed. An improvement is introduced here for…

General Relativity and Quantum Cosmology · Physics 2009-11-07 Keisuke Taniguchi , Eric Gourgoulhon , Silvano Bonazzola

Information about the last stages of a binary neutron star inspiral and the final merger can be extracted from quasi-equilibrium configurations and dynamical evolutions. In this article, we construct quasi-equilibrium configurations for…

A general relativistic version of the Euler equation for perfect fluid hydrodynamics is applied to a system of two neutron stars orbiting each other. In the quasi-equilibrium phase of the evolution of this system, a first integral of motion…

General Relativity and Quantum Cosmology · Physics 2009-10-30 S. Bonazzola , E. Gourgoulhon , J. -A. Marck

Gravitational waves from binary neutron stars in quasiequilibrium circular orbits are computed using an approximate method which we propose in this paper. In the first step of this method, we prepare general relativistic irrotational binary…

General Relativity and Quantum Cosmology · Physics 2009-11-07 Masaru Shibata , Koji Uryu

Binary boson stars can be used to model the nonlinear dynamics and gravitational wave signals of merging ultracompact, but horizonless, objects. However, doing so requires initial data satisfying the Hamiltonian and momentum constraints of…

General Relativity and Quantum Cosmology · Physics 2023-12-05 Nils Siemonsen , William E. East

We study equilibrium sequences of close binary systems on circular orbits and composed of different mass stars with polytropic equation of state in Newtonian gravity. The solving method is a multidomain spectral method which we have…

Astrophysics · Physics 2009-11-07 Keisuke Taniguchi , Eric Gourgoulhon