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We investigate close binary neutron stars in quasiequilibrium states in a general relativistic framework. We assume conformal flatness for the spatial metric and irrotational velocity field for the neutron stars. We adopt the polytropic…

General Relativity and Quantum Cosmology · Physics 2009-10-31 Koji Uryu , Masaru Shibata , Yoshiharu Eriguchi

Neutron star binaries offer a rich phenomenology in terms of gravitational waves and merger remnants. However, most general relativistic studies have been performed for nearly circular binaries, with the exception of head-on collisions. We…

General Relativity and Quantum Cosmology · Physics 2013-01-10 Roman Gold , Sebastiano Bernuzzi , Marcus Thierfelder , Bernd Bruegmann , Frans Pretorius

We analyze the stability of relativistic, quasi-equilibrium binary neutron stars in synchronous circular orbit. We explore stability against radial collapse to black holes prior to merger, and against orbital plunge. We apply theorems based…

General Relativity and Quantum Cosmology · Physics 2009-10-30 T. W. Baumgarte , G. B. Cook , M. A. Scheel , S. L. Shapiro , S. A. Teukolsky

Rapid uniform rotation of newborn neutron stars (protoneutron stars) is studied for a range of internal temperatures and entropies per baryon predicted by the existing numerical simulations. Calculations are performed using general…

Astrophysics · Physics 2008-11-26 J-O. Goussard , P. Haensel , J. L. Zdunik

Outcomes of numerical relativity simulations of massive core collapses or binary neutron star mergers with moderate masses suggest formations of rapidly and differentially rotating neutron stars. Subsequent fall back accretion may also…

High Energy Astrophysical Phenomena · Physics 2017-11-29 Koji Uryu , Antonios Tsokaros , Luca Baiotti , Filippo Galeazzi , Keisuke Taniguchi , Shin'ichirou Yoshida

Binary neutron star mergers are studied using nonlinear 3+1 numerical relativity simulations and the analytical effective-one-body (EOB) model. The EOB model predicts quasiuniversal relations between the mass-rescaled gravitational wave…

General Relativity and Quantum Cosmology · Physics 2015-04-15 Sebastiano Bernuzzi , Alessandro Nagar , Simone Balmelli , Tim Dietrich , Maximiliano Ujevic

We present a new numerical method for the construction of quasiequilibrium models of black hole-neutron star binaries. We solve the constraint equations of general relativity, decomposed in the conformal thin-sandwich formalism, together…

General Relativity and Quantum Cosmology · Physics 2009-11-10 Thomas W. Baumgarte , Monica L. Skoge , Stuart L. Shapiro

We investigate fundamental quasiradial oscillations in slow-rotation approximation of pure and hybrid neutron stars, employing equations of state of nuclear matter from Brueckner-Hartree-Fock theory or the relativistic mean field model, and…

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

Binary neutron stars in circular orbits can be modeled as helically symmetric, i.e., stationary in a rotating frame. This symmetry gives rise to a first integral of the Euler equation, often employed for constructing equilibrium solutions…

General Relativity and Quantum Cosmology · Physics 2014-10-31 Niclas Moldenhauer , Charalampos M. Markakis , Nathan K. Johnson-McDaniel , Wolfgang Tichy , Bernd Bruegmann

In the last few decades, lots of universal relations between different global physical quantities of neutron stars have been proposed to constrain the unobservable or hard to be observed properties of neutron stars. But few of them are…

General Relativity and Quantum Cosmology · Physics 2020-08-10 Wenjie Sun , Dehua Wen , Jue Wang

Recently discovered quasi periodic oscillations in the X-ray brightness of low mass X-ray binaries are used to derive constraints on the mass of the neutron star component and the equation of state of neutron star matter. The observations…

Astrophysics · Physics 2009-10-31 Christoph Schaab , Manfred K. Weigel

Most numerical models of binary stars - in particular neutron stars in compact binaries - assume the companions to be either corotational or irrotational. Either one of these assumptions leads to a significant simplification in the…

General Relativity and Quantum Cosmology · Physics 2009-10-02 Thomas W. Baumgarte , Stuart L. Shapiro

This work introduces the Elliptica pseudo-spectral code for generating initial data of binary neutron star systems. Building upon the recent Elliptica code update, we can now construct initial data using not only piecewise polytropic…

General Relativity and Quantum Cosmology · Physics 2024-11-20 Alireza Rashti , Andrew Noe

We present our study of stability of differentially rotating, axisymmetric neutron stars described by a polytropic equation of state with $\Gamma = 2$. We focus on quasi-toroidal solutions with a degree of differential rotation $\widetilde…

High Energy Astrophysical Phenomena · Physics 2024-02-29 Paweł Szewczyk , Dorota Gondek-Rosińska , Pablo Cerdá-Durán

We construct quasiequilibrium sequences of black hole-neutron star binaries for arbitrary mass ratios by solving the constraint equations of general relativity in the conformal thin-sandwich decomposition. We model the neutron star as a…

General Relativity and Quantum Cosmology · Physics 2009-11-11 Keisuke Taniguchi , Thomas W. Baumgarte , Joshua A. Faber , Stuart L. Shapiro

The numerical modeling of binary neutron star mergers has become a subject of much interest in recent years. While a full and accurate model of this phenomenon would require the evolution of the equations of relativistic hydrodynamics along…

Astrophysics · Physics 2009-10-31 F. Douglas Swesty , Edward Y. M. Wang , Alan C. Calder

A complete formalism for constructing initial data representing black-hole binaries in quasi-equilibrium is developed. Radiation reaction prohibits, in general, true equilibrium binary configurations. However, when the timescale for orbital…

General Relativity and Quantum Cosmology · Physics 2009-11-07 Gregory B. Cook

We report on the first calculations of fully relativistic binary circular orbits to span a range of separation distances from the innermost stable circular orbit (ISCO), deeply inside the strong field regime, to a distance ($\sim$ 200 km)…

General Relativity and Quantum Cosmology · Physics 2011-07-19 P. Marronetti , G. J. Mathews , J. R. Wilson

We present results of numerical computations of quasiequilibrium sequences of binary neutron stars with zero vorticity, in the general relativistic framework. The Einstein equations are solved under the assumption of a conformally flat…

General Relativity and Quantum Cosmology · Physics 2007-05-23 S. Bonazzola , E. Gourgoulhon , J. -A. Marck