Gravitational waves from instabilities in relativistic stars

Andersson, Nils

doi:10.1088/0264-9381/20/7/201

Cited by 207 publications

(369 citation statements)

References 152 publications

(263 reference statements)

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“…Fig. 5 in Andersson 2003). When a mode has a negative (positive) pattern speed, it is retrograde (prograde) with respect to the star.…”

Section: The F-modementioning

confidence: 99%

The intimate relation between the low T/W instability and the corotation point

Passamonti

Andersson

2014

Monthly Notices of the Royal Astronomical Society

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We study the low T/W instability associated with the f-mode of differentially rotating stars. Our stellar models are described by a polytropic equation of state and the rotation profile is given by the standard j-constant law. The properties of the relevant oscillation modes, including the instability growth time, are determined from time evolutions of the linearised dynamical equations in Newtonian gravity. In order to analyse the instability we monitor also the canonical energy and angular momentum. Our results demonstrate that the l = m = 2 f-mode becomes unstable as soon as a co-rotation point develops inside the star (i.e. whenever there is a point where the mode's pattern speed matches the bulk angular velocity). Considering various degrees of differential rotation, we show that the instability grows faster deep inside the corotation region and deduce an empirical relation that correlates the mode frequency and the star's parameters, which captures the main features of the l = m = 2 f-mode growth time. This function is proportional to the product of the kinetic to gravitational energy ratio and the gradient of the star's spin, strengthening further the relationship between the co-rotation point and the low T/W instability. We briefly consider also the l = m = 2 r-mode and demonstrate that it never moves far inside the co-rotation region even for significant differential rotation.

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“…Fig. 5 in Andersson 2003). When a mode has a negative (positive) pattern speed, it is retrograde (prograde) with respect to the star.…”

Section: The F-modementioning

confidence: 99%

The intimate relation between the low T/W instability and the corotation point

Passamonti

Andersson

2014

Monthly Notices of the Royal Astronomical Society

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“…Once excited -e.g. during the birth of a neutron star, via an accretion process, or through tidal interactions with a bound compact object -it may grow to sufficient strength to be detected by an earth-bound gravitational wave detector [4]. This mechanism, the so-called CFS instability [5], may cause the fundamental pressure mode (f -mode) of a neutron star to become unstable as well.…”

Section: Introductionmentioning

confidence: 99%

Eigenmode frequency distribution of rapidly rotating neutron stars

Boutloukos

Nollert

2007

Phys. Rev. D

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We use perturbation theory and the relativistic Cowling approximation to numerically compute characteristic oscillation modes of rapidly rotating relativistic stars which consist of a perfect fluid obeying a polytropic equation of state. We present a code that allows the computation of modes of arbitrary order. We focus here on the overall distribution of frequencies. As expected, we find an infinite pressure mode spectrum extending to infinite frequency. In addition we obtain an infinite number of inertial mode solutions confined to a finite, well-defined frequency range which depends on the compactness and the rotation frequency of the star. For non-axisymmetric modes we observe how this range is shifted with respect to the axisymmetric ones, moving towards negative frequencies and thus making all m > 2 modes unstable. We discuss whether our results indicate that the star's spectrum must have a continuous part, as opposed to simply containing an infinite number of discrete modes.

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“…Stars in nature are usually rotating and subject to nonaxisymmetric rotational instabilities (see [1], [2], [3] or [4] for recent reviews). An exact treatment of these instabilities exists only for incompressible equilibrium fluids in Newtonian gravity, (e.g.…”

Section: Introductionmentioning

confidence: 99%

Viscosity driven instability in rotating relativistic stars

Saijo

Gourgoulhon

2006

Phys. Rev. D

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We investigate the viscosity driven instability in rotating relativistic stars by means of an iterative approach. We focus on polytropic rotating equilibrium stars and impose an m = 2 perturbation in the lapse. We vary both the stiffness of the equation of state and the compactness of the star to study those effects on the value of the threshold. For a uniformly rotating star, the criterion T /W , where T is the rotational kinetic energy and W is the gravitational binding energy, mainly depends on the compactness of the star and takes values around 0.13 ∼ 0.16, which differ slightly from that of Newtonian incompressible stars (∼ 0.14). For differentially rotating stars, the critical value of T /W is found to span the range 0.17 − 0.25. This is significantly larger than the uniformly rotating case with the same compactness of the star. Finally we discuss a possibility of detecting gravitational waves from viscosity driven instability with ground-based interferometers.

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Gravitational waves from instabilities in relativistic stars

Cited by 207 publications

References 152 publications

The intimate relation between the low T/W instability and the corotation point

The intimate relation between the low T/W instability and the corotation point

Eigenmode frequency distribution of rapidly rotating neutron stars

Viscosity driven instability in rotating relativistic stars

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