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We calculate non-axisymmetric oscillations of neutron stars magnetized by purely poloidal magnetic fields. We use polytropes of index $n=1$ and 1.5 as a background model, where we ignore the equilibrium deformation due to the magnetic…

High Energy Astrophysical Phenomena · Physics 2015-12-16 Hidetaka Asai , Umin Lee , Shijun Yoshida

In the present paper we study the oscillations of fast rotating neutron stars with realistic equations of state (EoS) within the Cowling approximation. We derive improved empirical relations for gravitational wave asteroseismology with…

Solar and Stellar Astrophysics · Physics 2013-09-04 Daniela D. Doneva , Erich Gaertig , Kostas D. Kokkotas , Christian Krüger

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 continue our studies on stellar latitudinal differential rotation. The presented work is a sequel of the work of Reiners et al. who studied the spectral line broadening profile of hundreds of stars of spectral types A through G at high…

Solar and Stellar Astrophysics · Physics 2010-10-29 Matthias~Ammler von Eiff , Ansgar Reiners

An understanding of the dynamics of differentially rotating systems is key to many areas of astrophysics. We investigate the oscillations of a simple system exhibiting differential rotation, and discuss issues concerning the role of…

Astrophysics · Physics 2009-01-09 Anna L. Watts , Nils Andersson , Horst Beyer , Bernard F. Schutz

We have succeeded in obtaining exact configurations of irrotational binary systems for compressible (polytropic) equations of state. Our models correspond to binaries of equal mass neutron star systems in the viscosity free limit. By using…

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

Internal gravity waves propagate in stellar radiative zones and transport angular momentum throughout the evolution of stars, shaping the internal rotation pro le of these regions. We use the analytical study of Andre\'e et al. (2018) to…

Solar and Stellar Astrophysics · Physics 2019-01-23 Q. André , S. Mathis , L. Amard

A newly discovered instability in rotating neutron stars, driven by gravitational radiation reaction acting on the stars' $r$-modes, is shown here to set an upper limit on the spin rate of young neutron stars. We calculate the timescales…

Astrophysics · Physics 2009-10-30 Nils Andersson , Kostas Kokkotas , Bernard F. Schutz

We study the fully non-adiabatic tidal response of a uniformly rotating unevolved 20 Msun star to the dominant l=m=2 component of the companion's perturbing potential. This is done numerically with a 2D implicit finite difference scheme. We…

Astrophysics · Physics 2015-06-24 G. J. Savonije , J. C. Papaloizou

We consider the spin evolution of highly magnetized neutron stars in a hypercritical inflow just after their birth in supernovae. Presence of a strong magnetic field could deform the star and if the symmetry axis of the field is misaligned…

Astrophysics · Physics 2009-11-07 Shin Yoshida

We present an analytic description of the $r$-mode instability in newly-born neutron stars, using the approximation of uniform density. Our computation is consistently accurate to second order in the angular velocity of the star. We obtain…

Astrophysics · Physics 2011-05-23 K. D. Kokkotas , N. Stergioulas

Neutron stars may experience differential rotation on short, dynamical timescales following extreme astrophysical events like binary neutron star mergers. In this work, the masses and radii of differentially rotating neutron star models are…

Nuclear Theory · Physics 2023-11-16 Delaney Farrell , Fridolin Weber , Jia Jie Li , Armen Sedrakian

We perform nonlinear general relativistic ideal magnetohydrodynamic simulations of poloidal magnetic fields in rotating polytropic neutron stars. We have three primary goals: i) to understand the nature of magnetohydrodynamic instabilities…

Solar and Stellar Astrophysics · Physics 2012-03-19 Paul D. Lasky , Burkhard Zink , Kostas D. Kokkotas

Recent discoveries by the Rossi X-Ray Timing Explorer indicate that most of the rapidly accreting and weakly magnetic neutron stars in the Galaxy are rotating at spin frequencies greater than 250 Hz. Remarkably, they all rotate in a narrow…

Astrophysics · Physics 2010-11-19 Lars Bildsten

Space missions like CoRoT and Kepler have provided numerous new observations of stellar oscillations in a multitude of stars by high precision photometry. This work compares the observed rich oscillation spectrum of the rapidly rotating B3…

Solar and Stellar Astrophysics · Physics 2015-06-17 G. J. Savonije

Context: With the launch of space missions devoted to asteroseismology (like COROT), the scientific community will soon have accurate measurements of pulsation frequencies in many rapidly rotating stars. Aims: The present work focuses on…

Astrophysics · Physics 2008-11-26 D. Reese , F. Lignières , M. Rieutord

In this review article, we present the main results from our most recent research concerning the oscillations of fast rotating neutron stars. We derive a set of time evolution equations for the investigation of non-axisymmetric oscillations…

General Relativity and Quantum Cosmology · Physics 2021-10-04 Christian J. Krüger , Kostas D. Kokkotas , Praveen Manoharan , Sebastian H. Völkel

We compute zero-frequency (neutral) quasi-normal f-modes of fully relativistic and rapidly rotating neutron stars, using several realistic equations of state (EOSs) for neutron star matter. The zero-frequency modes signal the onset of the…

General Relativity and Quantum Cosmology · Physics 2014-11-17 Sharon M. Morsink , Nikolaos Stergioulas , Steve R. Blattnig

To date, asteroseismology has provided core to surface differential rotation measurements in eight main-sequence stars. These stars, ranging in mass from $\sim$1.5-9$M_\odot$, show rotation profiles ranging from uniform to counter-rotation.…

Solar and Stellar Astrophysics · Physics 2015-12-23 T. M. Rogers

We study how the frequencies and damping times of oscillations of a newly born, hot proto-neutron star depend on the physical quantities which characterize the star quasi-stationary evolution which follows the bounce. Stellar configurations…

Solar and Stellar Astrophysics · Physics 2011-08-12 G. F. Burgio , V. Ferrari , L. Gualtieri , H. J. Schulze