Gravitational Radiation from Nonaxisymmetric Spherical Couette Flow in a Neutron Star

Peralta, C.; Melatos, A.; Giacobello, Matteo; Ooi, Andrew

doi:10.1086/505422

Cited by 36 publications

(66 citation statements)

References 51 publications

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“…The cross-correlation algorithm in Section III A must be accompanied by a parameterized model for the phase and frequency of the signal as functions of time, in terms of which we express the factors ∆Φ IJ and ν(T I ) − ν(T J ) in equations (5) (4) . As noted in Section II B, N total is suppressed strongly by the factor ξ 10 , with ξ 10 1 for SNR 1987A.…”

Section: B Astrophysical Phase Modelmentioning

confidence: 99%

“…Second, less time has passed in young objects for their crusts and interiors to settle down and erase historical nonaxisymmetries frozen-in at birth. Third, young objects spin down rapidly, driving crust-superfluid differential rotation which can excite nonaxisymmetric flows in the high-Reynolds-number interior [4][5][6]. For a review of gravitational wave generation mechanisms in neutron stars, see Ref.…”

Section: Introductionmentioning

confidence: 99%

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Cross-correlation search for continuous gravitational waves from a compact object in SNR 1987A in LIGO Science run 5

et al. 2016

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We present the results of a cross-correlation search for gravitational waves from SNR 1987A using the second year of LIGO Science Run 5 data. The frequency band 75-450 Hz is searched. No evidence of gravitational waves is found. A 90% confidence upper limit of h0 ≤ 3.8 × 10 −25 is placed on the gravitational wave strain at the most sensitive frequency near 150 Hz. This corresponds to an ellipticity of ≤ 8.2 × 10 −4 and improves on previously published strain upper limits by a factor ≈ 4. We perform a comprehensive suite of validations of the search algorithm and identify several computational savings which marginally sacrifice sensitivity in order to streamline the parameter space being searched. We estimate detection thresholds and sensitivities through Monte-Carlo simulations.PACS numbers: 95.85.Sz, 97.60.Jd

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Section: B Astrophysical Phase Modelmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Cross-correlation search for continuous gravitational waves from a compact object in SNR 1987A in LIGO Science run 5

et al. 2016

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“…Prima facie, therefore, the lower bound implied by (11), with T 1 year obs » and S f ( ) 9 h »1 0 Hz 48 1 --for Advanced LIGO, 9 is potentially detectable and deserves careful consideration. One advantage is that the vortices pin to the crust, so the radio ephemeris (which tracks the crust) should be phase locked to the gravitational wave signal, which is not always true for other emission mechanisms, e.g., superfluid wave modes (Peralta et al 2006a;Sidery et al 2010). Previous directed coherent searches for known pulsars in data from LIGO Science Run 5, guided by a known radio or X-ray ephemeris, have reported 95% confidence upper bounds of h 7.2 10 0 26 -⩽ (median of 116 objects) and h 2.3 10 0 26 -⩽ (minimum; PSR J1603-7202), approaching the indirect spin-down limit in certain objects (Abbott et al 2010).…”

Section: Detectabilitymentioning

confidence: 99%

Persistent Gravitational Radiation From Glitching Pulsars

Melatos

Douglass

Simula

2015

ApJ

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Quantum mechanical simulations of neutron star rotational glitches, triggered by vortex avalanches in the superfluid stellar interior, reveal that vortices pin nonaxisymmetrically to the crust during the intervals between glitches. Hence a glitching neutron star emits a persistent current quadrupole gravitational wave signal at the star's rotation frequency, whose interglitch amplitude is constant and determined by the avalanche history since birth. The signal can be detected in principle by coherent searches planned for the Laser Interferometer Gravitational Wave Observatory (LIGO), whether or not a glitch occurs during the observation, if the power-law distribution of glitch sizes extends up to D 10 ( ) ( 10 rad s ) ( 1 kpc)in the targeted object, where max DW and f D are the largest angular velocity jump and avalanche opening angle, respectively, to have occurred in a glitch since birth, Ω is the angular velocity at present, η is the crustal fraction of the moment of inertia, and D is the distance from the Earth. A major caveat concerning detectability is whether the nonaxisymmetries observed in existing simulations with 10 3  vortices extrapolate to realistic neutron stars with 10 15  vortices. The arguments for and against extrapolation are discussed critically in the context of avalanche dynamics in self-organized critical systems, but the issue cannot be resolved without larger simulations and tighter observational limits on max h f D DW from future LIGO (non)detections and radio timing campaigns.

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“…In old neutron stars, the presence of a solid crust plays an important role in the balance between the growth of the r-mode amplitude due to the CFS instability and its dissipation [12][13][14][15][16][17]. One simple, but useful, model assumes a perfectly rigid crust [12][13][14].…”

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confidence: 99%

Sensitivity of the neutron starr-mode instability window to the density dependence of the nuclear symmetry energy

Wang

Newton

2012

Phys. Rev. C

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Using a simple model of a neutron star with a perfectly rigid crust constructed with a set of crust and core equations of state that span the range of nuclear experimental uncertainty in the symmetry energy, we calculate the instability window for the onset of the Chandrasekhar-Friedmann-Schutz (CFS) instability in r-mode oscillations for canonical neutron stars (1.4M⊙) and massive neutron stars (2.0M⊙). In these models the crust-core transition density, and thus crustal thickness, is calculated consistently with the core equation of state (EOS). The EOSs are calculated using a simple model for the energy density of nuclear matter and probe the dependence on the symmetry energy by varying the slope of the symmetry energy at saturation density L from 25 MeV (soft symmetry energy and EOS) to 115 MeV (stiff symmetry energy and EOS) while keeping the EOS of symmetric nuclear matter fixed. For the canonical neutron star, the lower bound of the r-mode instability window is reduced in frequency by ≈ 150 Hz from the softest to the stiffest symmetry energy used, independent of mass and temperature. The instability window also drops by ≈ 100 Hz independent of EOS when the mass is raised from 1.4M⊙ to 2.0M⊙. Where temperature estimates are available, the observed neutron stars in low mass X-ray binaries (LMXBs) have frequencies below the instability window for the 1.4M⊙ models, while some LMXBs fall within the instability window for 2.0M⊙ stars if the symmetry energy is relatively stiff, indicating that a softer symmetry energy is more consistent with observations within this model. Thus we conclude that smaller values of L help stabilize neutron stars against runaway r-mode oscillations. The critical temperature, below which no star can reach the instability window without exceeding its Kepler frequency, varies by nearly an order of magnitude from soft to stiff symmetry energies. When the crust thickness and core EOS are treated consistently, a thicker crust corresponds to a lower critical temperature, the opposite result to previous studies in which the transition density was independent of the core EOS.

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Gravitational Radiation from Nonaxisymmetric Spherical Couette Flow in a Neutron Star

Cited by 36 publications

References 51 publications

Cross-correlation search for continuous gravitational waves from a compact object in SNR 1987A in LIGO Science run 5

Cross-correlation search for continuous gravitational waves from a compact object in SNR 1987A in LIGO Science run 5

Persistent Gravitational Radiation From Glitching Pulsars

Sensitivity of the neutron starr-mode instability window to the density dependence of the nuclear symmetry energy

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