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We perform 3D numerical simulations in full general relativity to study the stability of rapidly rotating, supramassive neutron stars at the mass-shedding limit to dynamical collapse. We adopt an adiabatic equation of state with $\Gamma =…

Astrophysics · Physics 2009-10-31 Masaru Shibata , Thomas W. Baumgarte , Stuart L. Shapiro

We demonstrate how observables of slowly rotating neutron stars can be used to constrain the nuclear equation of state. By building a Bayesian framework we demonstrate how combining different types of neutron star measurements, motivated by…

General Relativity and Quantum Cosmology · Physics 2022-07-20 Sebastian H. Völkel , Christian J. Krüger

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

In this work we provide a framework that connects the co-rotating and counter rotating $f$-mode frequencies of rotating neutron stars with their stellar structure. The accurate computation of these modes for realistic equations of state has…

General Relativity and Quantum Cosmology · Physics 2021-04-21 Sebastian H. Völkel , Christian J. Krüger , Kostas D. Kokkotas

The paper considers the spectrum of axial perturbations of slowly uniformly rotating general relativistic stars in the framework of Y. Kojima. In a first step towards a full analysis only the evolution equations are treated but not the…

General Relativity and Quantum Cosmology · Physics 2007-05-23 Horst R. Beyer

We present the field equations governing the equilibrium of rapidly rotating neutron stars in scalar-tensor theories of gravity, as well as representative numerical solutions. The conditions for the presence of a nontrivial scalar field and…

General Relativity and Quantum Cosmology · Physics 2014-02-25 Daniela D. Doneva , Stoytcho S. Yazadjiev , Nikolaos Stergioulas , Kostas D. Kokkotas

We study torsional oscillations of neutron stars in the scalar-tensor theory of gravity using the relativistic Cowling approximation. We compute unperturbed neutron star models adopting realistic equations of state for the neutron star's…

General Relativity and Quantum Cosmology · Physics 2014-12-24 Hector O. Silva , Hajime Sotani , Emanuele Berti , Michael Horbatsch

Violent astrophysical events, including core-collapse supernovae and binary neutron star mergers, can result in rotating neutron stars with diverse degrees of differential rotation. Oscillation modes of these neutron stars could be excited…

High Energy Astrophysical Phenomena · Physics 2025-10-02 Anson Ka Long Yip , Patrick Chi-Kit Cheong , Tjonnie Guang Feng Li

We present a brief review of general results about non-rotating neutron stars in simple R-square gravity and its extension with a scalar axion field. Modified Einstein equations are presented for metrics in isotropical coordinates. The…

General Relativity and Quantum Cosmology · Physics 2020-07-08 Artyom V. Astashenok , Sergei D. Odintsov

We propose a new method to study the quasi-normal modes of rotating relativistic stars. Oscillations are treated as perturbations in the frequency domain of the stationary, axisymmetric background describing a rotating star. The perturbed…

General Relativity and Quantum Cosmology · Physics 2008-11-26 V. Ferrari , L. Gualtieri , S. Marassi

A set of theoretical mass-radius relations for rigidly rotating neutron stars with exotic cores, obtained in various theories of dense matter, is reviewed. Two basic observational constraints are used: the largest measured rotation…

High Energy Astrophysical Phenomena · Physics 2016-04-20 P. Haensel , M. Bejger , M. Fortin , J. L. Zdunik

We investigate the radial stability of neutron stars under conditions where their composition may or may not remain in chemical equilibrium during oscillations. Using different equations of state that include nucleons, hyperons, and/or…

High Energy Astrophysical Phenomena · Physics 2024-12-31 Martin O. Canullan-Pascual , German Lugones , Milva G. Orsaria , Ignacio F. Ranea-Sandoval

We discuss the stability and construct dynamical configurations describing the gravitational collapse of unstable neutron stars with realistic equations of state compatible with the recent LIGO-Virgo constraints. Unlike other works that…

General Relativity and Quantum Cosmology · Physics 2020-06-17 J. M. Z. Pretel , M. F. A. da Silva

The remnants of binary neutron star mergers are expected to be massive, rapidly rotating stars whose oscillations produce gravitational waves in the kilohertz band. The degree of differential rotation and the rotation profiles strongly…

General Relativity and Quantum Cosmology · Physics 2026-04-01 Santiago Jaraba , Jérôme Novak , Micaela Oertel

We investigate equilibrium configurations of uniformly rotating neutron stars in $R^2$ gravity with axion scalar field for GM1 equation of state (EoS) for nuclear matter. The mass-radius diagram, mass-central energy density are presented…

General Relativity and Quantum Cosmology · Physics 2020-09-09 Artyom V. Astashenok , Sergey D. Odintsov

We present new results on instabilities in rapidly and differentially rotating neutron stars. We model the stars in full general relativity and describe the stellar matter adopting a cold realistic equation of state based on the unified SLy…

General Relativity and Quantum Cosmology · Physics 2010-06-01 Giovanni Corvino , Luciano Rezzolla , Sebastiano Bernuzzi , Roberto De Pietri , Bruno Giacomazzo

We study slowly-rotating neutron stars in ghost-free massive bigravity. This theory modifies General Relativity by introducing a second, auxiliary but dynamical tensor field that couples to matter through the physical metric tensor through…

General Relativity and Quantum Cosmology · Physics 2018-02-14 Andrew Sullivan , Nicolas Yunes

A brief review of the stability of rotating relativistic stars is followed by a more detailed discussion of recent work on an instability of r-modes, modes of rotating stars that have axial parity in the slow-rotation limit. These modes may…

General Relativity and Quantum Cosmology · Physics 2008-11-26 John L. Friedman , Keith H. Lockitch

Relativistic Cowling approximation in which all metric perturbations are omitted is applied to non-axisymmetric infinitesimal oscillations of uniformly rotating general relativistic polytropes. Frequencies of lower order f-modes which are…

Astrophysics · Physics 2009-10-30 Shin'ichirou Yoshida , Yoshiharu Eriguchi

We investigate f-mode oscillations of static anisotropic stable neutron stars within the framework of full general relativity. We present equations governing unperturbed stellar structures and oscillations with an ansatz to account for the…

General Relativity and Quantum Cosmology · Physics 2025-02-25 Sushovan Mondal , Manjari Bagchi