Rotational modes of relativistic stars: Numerical results

Lockitch, Keith H.; Friedman, John L.; Andersson, Nils

doi:10.1103/physrevd.68.124010

Cited by 72 publications

(142 citation statements)

References 62 publications

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“…This trend, which was already known for κ 0 , is to be expected because both the gravitational redshift and the frame dragging will act to decrease the oscillation frequencies as measured by a comoving observer (see eq. (30) in [19]). …”

Section: A Fast Rotationmentioning

confidence: 98%

R -mode frequencies of rapidly and differentially rotating relativistic neutron stars

Jasiulek

Chirenti

2017

Phys. Rev. D

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R-modes of neutron stars could be a source of gravitational waves for ground based detectors. If the precise frequency σ is known, guided gravitational wave searches with enhanced detectability are possible. Because of its physical importance many authors have calculated the r-mode frequency. For the dominant mode, the associated gravitational wave frequency is 4/3 times the angular velocity of the star Ω, subject to various corrections of which relativistic and rotational corrections are the most important. This has led several authors to investigate the dependence of the r-mode frequency on factors such as the relativistic compactness parameter (M/R) and the angular velocity of stars with different equations of state. The results found so far, however, are almost independent of the equation of state. Here we investigate the effect of rapid rotation and differential rotation on σ. We evolve the perturbation equations using the Cowling approximation by applying finite differencing methods to compute the r-mode frequency for a series of rotating neutron stars with polytropic equations of state. We find that rotational effects in the r-mode frequency can be larger than relativistic effects for rapidly spinning stars with low compactness, reducing the observed frequency. Differential rotation also acts to decrease σ, but its effect inscreases with the compactness. The results presented here are relevant to the design of gravitational wave and electromagnetic r-mode searches.

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Section: A Fast Rotationmentioning

confidence: 98%

R -mode frequencies of rapidly and differentially rotating relativistic neutron stars

Jasiulek

Chirenti

2017

Phys. Rev. D

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“…In case of general relativity oscillation equations become much more complicated (see Ruoff & Kokkotas 2002;Lockitch, Friedman & Andersson 2003, for example). Furthermore, Lockitch, Andersson & Friedman (2000) demonstrate fully relativistic equations for r-modes in NSs with barotropic and nonbarotropic equations of state to be qualitatively different.…”

Section: R-modes In Nonmagnetized Nsmentioning

confidence: 99%

Differential rotation and r-modes in magnetized neutron stars

Chugunov

2015

Monthly Notices of the Royal Astronomical Society

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] draw attention to the second order secular drift associated with r-modes and claimed that it should lead to magnetic field enhancement and suppression of r-mode instability in magnetized neutron stars. We critically revise these results. We present a particular second order r-mode solution with vanishing secular drift, thus refuting a widely believed statement that secular drift is an unavoidable feature of r-modes. This non-drifting solution is not affected by magnetic field B, if B ≪ B crit ≈ 10 17 (ν/600 Hz) G (ν is a spin frequency) and does not lead to secular evolution of magnetic field. For general second order r-mode solution the drift does not necessarily vanish, but the solution can be presented as a superposition of two solutions: one describes evolution of differential rotation in nonoscillating star (which describes secular drift; for nonmagnetized star it is arbitrary stationary rotation stratified on cylinders; for magnetized star differential rotation evolves on the Alfvén timescale and may lead to magnetic energy enhancement), and another one is non-drifting r-mode solution mentioned above. This representation allows us to conclude that enhancement of magnetic field energy is limited by initial energy of differential rotation, which is much less (for a factor ∝ α 2 , where α is mode amplitude) than the total energy of r-mode. Hence, magnetic field enhancement by drift cannot suppress r-mode instability. Results can be generalized for any oscillation mode in any medium, if this mode has non-drifting solution for B = 0.

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“…The growth times for the inertial modes of a canonical 1.4M ⊙ relativistic barotropic (uniform density) star. The data is for the modes that correspond to the first few l = m r-modes in the Newtonian limit (M/R → 0) [95].…”

Section: The Cfs Instabilitymentioning

confidence: 99%

Gravitational waves from instabilities in relativistic stars

Andersson

2003

Class. Quantum Grav.

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207

356

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Abstract. This article provides an overview of stellar instabilities as sources of gravitational waves. The aim is to put recent work on secular and dynamical instabilities in compact stars in context, and to summarize the current thinking about the detectability of gravitational waves from various scenarios. As a new generation of kilometer length interferometric detectors are now coming online this is a highly topical theme. The review is motivated by two key questions for future gravitationalwave astronomy: Are the gravitational waves from various instabilities detectable? If so, what can these gravitational-wave signals teach us about neutron star physics? Even though we may not have clear answers to these questions, recent studies of the dynamical bar-mode instability and the secular r-mode instability have provided new insights into many of the difficult issues involved in modelling unstable stars as gravitational-wave sources.

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Rotational modes of relativistic stars: Numerical results

Cited by 72 publications

References 62 publications

R -mode frequencies of rapidly and differentially rotating relativistic neutron stars

R -mode frequencies of rapidly and differentially rotating relativistic neutron stars

Differential rotation and r-modes in magnetized neutron stars

Gravitational waves from instabilities in relativistic stars

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