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The evolution of a nonaxisymmetric bar-mode perturbation of rapidly rotating stars due to a secular instability induced by gravitational wave emission is studied in post-Newtonian simulations taking into account gravitational radiation…

Astrophysics · Physics 2010-11-19 Masaru Shibata , Sigeyuki Karino

Axial oscillations relevant to the r-mode instability are studied with slow rotation formalism in general relativity. The approximate equation governing the oscillations is derived with second-order rotational corrections. The equation…

General Relativity and Quantum Cosmology · Physics 2009-10-31 Yasufumi Kojima , Masayasu Hosonuma

Newly born neutron stars can present differential rotation, even if later it should be suppressed by viscosity or a sufficiently strong magnetic field. And in this early stage of its life, a neutron star is expected to have a strong…

General Relativity and Quantum Cosmology · Physics 2013-02-22 Cecilia Chirenti , Jozef Skakala , Shin'ichirou Yoshida

We investigate the effects of general relativity upon the non-axisymmetric ``bar'' mode secular instability of rapidly rotating stars, i.e. the relativistic and compressible analog of the transition from Maclaurin spheroids to Jacobi…

General Relativity and Quantum Cosmology · Physics 2009-10-28 S. Bonazzola , J. Frieben , E. Gourgoulhon

We present an asymptotic theory that describes regular frequency spacings of pressure modes in rapidly rotating stars. We use an asymptotic method based on an approximate solution of the pressure wave equation constructed from a stable…

Solar and Stellar Astrophysics · Physics 2012-09-27 Michael Pasek , François Lignières , Bertrand Georgeot , Daniel R. Reese

Linear perturbation theory is appropriate to describe small oscillations of stars, while a mild non-linearity is still tractable perturbatively but requires to consider mode coupling. It is natural to start to look at this problem by…

General Relativity and Quantum Cosmology · Physics 2009-11-10 Andrea Passamonti , Marco Bruni , Leonardo Gualtieri , Carlos F. Sopuerta

Strong magnetic fields in relativistic stars can be a cause of crust fracturing, resulting in the excitation of global torsional oscillations. Such oscillations could become observable in gravitational waves or in high-energy radiation,…

Astrophysics · Physics 2009-11-06 Neophytos Messios , Demetrios B. Papadopoulos , Nikolaos Stergioulas

We investigate the non-linear coupling between radial and non-radial oscillations of static spherically symmetric neutron stars as a possible mechanism for the generation of gravitational waves that may lead to observable signatures. In…

General Relativity and Quantum Cosmology · Physics 2009-11-11 A. Passamonti , M. Bruni , L. Gualtieri , A. Nagar , C. F. Sopuerta

We study low-amplitude crustal oscillations of slowly rotating relativistic stars consisting of a central fluid core and an outer thin solid crust. We estimate the effect of rotation on the torsional toroidal modes and on the interfacial…

General Relativity and Quantum Cosmology · Physics 2009-11-13 M. Vavoulidis , K. D. Kokkotas , A. Stavridis

This is a progress report on our study of the coupling of first-order radial and non-radial relativistic perturbations of a static spherical star. Our goal is to investigate the effects of this coupling on the gravitational wave signal of…

General Relativity and Quantum Cosmology · Physics 2007-05-23 Andrea Passamonti , Marco Bruni , Leonardo Gualtieri , Carlos F. Sopuerta

Exact models of uniformly rotating strange stars, built of self bound quark matter, are calculated within the framework of general relativity. This is made possible thanks to a new numerical technique capable to handle the strong density…

Astrophysics · Physics 2010-11-19 E. Gourgoulhon , P. Haensel , R. Livine , E. Paluch , S. Bonazzola , J. A. Marck

The excitation of the axial quasi-normal modes of a relativistic star by scattered particles is studied by evolving the time dependent perturbation equations. This work is the first step towards the understanding of more complicated…

General Relativity and Quantum Cosmology · Physics 2009-10-31 V. Ferrari , K. D. Kokkotas

The non-linear behaviour of oscillation modes in compact stars is a topic of considerable current interest. Accurate numerical studies of such phenomena are likely to require powerful new approaches to both fluid and spacetime computations.…

Astrophysics · Physics 2007-05-23 Uli Sperhake , Philippos Papadopoulos , Nils Andersson

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

We calculate non-axisymmetric oscillations of uniformly rotating polytropes magnetized with a purely toroidal magnetic field, taking account of the effects of the deformation due to the magnetic field. As for rotation, we consider only the…

Solar and Stellar Astrophysics · Physics 2015-06-24 Hidetaka Asai , Umin Lee , Shijun Yoshida

The first direct detection of gravitational waves has opened a new window to study the Universe and would probably start a new era: the gravitational wave Astronomy. Gravitational waves emitted by compact objects like neutron stars could…

High Energy Astrophysical Phenomena · Physics 2018-12-26 Ignacio F. Ranea-Sandoval , Octavio M. Guilera , Mauro Mariani , Milva G. Orsaria

An inconsistency between the theoretical analysis and numerical calculations of the relativistic $r$-modes puzzles the neutron star community since the Kojima's finding of the continuous part in the $r$-mode oscillation spectrum in 1997. In…

High Energy Astrophysical Phenomena · Physics 2022-11-16 Kirill Y. Kraav , Mikhail E. Gusakov , Elena M. Kantor

Rotating relativistic stars have been studied extensively in recent years, both theoretically and observationally, because of the information they might yield about the equation of state of matter at extremely high densities and because…

High Energy Astrophysical Phenomena · Physics 2017-12-01 Vasileios Paschalidis , Nikolaos Stergioulas

We present a new survey of the radial oscillation modes of neutron stars. This study complements and corrects earlier studies of radial oscillations. We present an extensive list of frequencies for the most common equations of state and…

General Relativity and Quantum Cosmology · Physics 2011-05-23 Kostas. D. Kokkotas , Johannes Ruoff

We study the inertial modes of slowly rotating, fully relativistic compact stars. The equations that govern perturbations of both barotropic and non-barotropic models are discussed, but we present numerical results only for the barotropic…

General Relativity and Quantum Cosmology · Physics 2009-11-07 K. H. Lockitch , J. L. Friedman , N. Andersson