Nonlinear evolution of the r-modes in neutron stars.
TL;DR: The evolution of a neutron-star r-mode driven unstable by gravitational radiation is studied here using numerical solutions of the full nonlinear fluid equations to study the nonlinear evolution of the mode.
Abstract: The evolution of a neutron-star $r$-mode driven unstable by gravitational radiation is studied here using numerical solutions of the full nonlinear fluid equations. The dimensionless amplitude of the mode grows to order unity before strong shocks develop which quickly damp the mode. In this simulation the star loses about $40%$ of its initial angular momentum and $50%$ of its rotational kinetic energy before the mode is damped. The nonlinear evolution causes the fluid to develop strong differential rotation which is concentrated near the surface and poles of the star.
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TL;DR: In this article, the saturation amplitudes of a rotating neutron star are determined by nonlinear mode-mode coupling, and analytic values for the shear damping and mode normalization are presented.
Abstract: R-modes of a rotating neutron star are unstable because of the emission of gravitational radiation. We explore the saturation amplitudes of these modes determined by nonlinear mode-mode coupling. Modelling the star as incompressible allows the analytic computation of the coupling coefficients. All couplings up to $n=30$ are obtained, and analytic values for the shear damping and mode normalization are presented. In a subsequent paper we perform numerical simulations of a large set of coupled modes.
31 citations
TL;DR: In this paper, the authors proposed an alternative explanation to the rapid cooling of a neutron star in Cas A. It is suggested that the star experiences the recovery period following the r-mode heating process assuming the star is differentially rotating.
Abstract: We proposed an alternative explanation to the rapid cooling of neutron star in Cas A. It is suggested that the star experiences the recovery period following the r-mode heating process assuming the star is differentially rotating. Like the neutron-superfluidity-triggering model, our model predicts that the rapid cooling will continue for several decades. However, the behavior of the two models has slight differences, and they might be distinguished by observations in the near future.
31 citations
Cites background from "Nonlinear evolution of the r-modes ..."
...As an important nonlinear effect, differential rotation induced by r -modes was studied extensively (Rezzolla et al. 2000, 2001a,b; Stergioulas & Font 2001; Lindblom et al. 2001, Sá 2004)....
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TL;DR: In this article, the authors modeled the nonlinear development of the bar-mode instability that is driven by gravitational radiation reaction (GRR) forces in rotating neutron stars, and determined the gravitational waveforms generated by such an event.
Abstract: We have modeled the nonlinear development of the secular bar-mode instability that is driven by gravitational radiation reaction (GRR) forces in rotating neutron stars. In the absence of any competing viscous effects, an initially uniformly rotating axisymmetricn ¼ 1=2polytropic star with a ratio of rotational to gravitational potential energy T = W jj ¼0:181 is driven by GRR forces to a barlike structure, as predicted by linear theory. The pattern frequencyofthebarslowstonearlyzero,thatis,thebarbecomesalmoststationaryasviewedfromaninertialframe ofreferenceasGRRremovesenergyandangularmomentumfromthestar.Inthis‘‘Dedekind-like’’state,rotational energyisstoredasmotionofthefluidinhighlynoncircularorbitsinsidethebar.However,inlessthan10dynamical timesafteritsformationthe bar losesitsinitially coherent structure astheorderedflow insidethe baris disruptedby what appears to be a purely hydrodynamic short-wavelength ‘‘shearing’’-type instability. The gravitational waveforms generated by such an event are determined, and an estimate of the detectability of these waves is presented. Subject headingg gravitational waves — hydrodynamics — instabilities — stars: neutron
31 citations
Cites methods from "Nonlinear evolution of the r-modes ..."
...…time derivative were evaluated using the expressions D22 ¼ ffiffiffiffiffiffiffiffi 15 32 r Z $2e 2i d3x; ð6Þ D (1) 22 ¼ ffiffiffiffiffiffi 15 8 r Z $ v$ iv e 2i d3x: ð7Þ Following Lindblom et al. (2001, 2002) we have assumed that the quadrupole moment has a time dependence of the form D22 / e i!...
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...This is the same technique that was successfully employed by Lindblom et al. (2001, 2002) in an earlier investigation of the r-mode instability in young neutron stars....
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TL;DR: In this paper, the authors provided explanations for solar topics ranging from the multiple personality disorder of neutrinos to cannibalism of CMEs (coronal mass ejections) and extra-solar topics including quivering stars, out-of-phase gaseous media, black holes of all sizes (too large, too small, and too medium), and the existence of the universe.
Abstract: During the year, astronomers provided explanations for solar topics ranging from the multiple personality disorder of neutrinos to cannibalism of CMEs (coronal mass ejections) and extra-solar topics including quivering stars, out-of-phase gaseous media, black holes of all sizes (too large, too small, and too medium), and the existence of the universe. Some of these explanations are probably possibly true, though the authors are not betting large sums on any one. The data ought to remain true forever, though this requires a careful definition of "data" (think of the Martian canals).
30 citations
TL;DR: In this paper, the authors investigate the oscillations of a simple system exhibiting differential rotation and discuss issues concerning the role of corotation points and the emergence of dynamical instabilities, which is of particular relevance to the emission of gravitational waves from oscillating neutron stars.
Abstract: 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 corotation points and the emergence of dynamical instabilities. This problem is of particular relevance to the emission of gravitational waves from oscillating neutron stars, which are expected to possess significant differential rotation immediately after birth or binary merger.
29 citations