Saturation amplitude of the f-mode instability

Journal Article · Mon Nov 15 00:00:00 EST 2010 · Physical Review. D, Particles Fields

DOI:https://doi.org/10.1103/PHYSREVD.82.104036· OSTI ID:21503637

Kastaun, Wolfgang; Willburger, Beatrix; Kokkotas, Kostas D ^[1]

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1. International School for Advanced Studies (SISSA) and National Institute of Nuclear Physics (INFN), via Bonomea 265, Trieste 34136 (Italy) and Theoretical Astrophysics, Eberhard -Karls University of Tuebingen, Tuebingen 72076 (Germany)

We investigate strong nonlinear damping effects which occur during high amplitude oscillations of neutron stars, and the gravitational waves they produce. For this, we use a general relativistic nonlinear hydrodynamics code in conjunction with a fixed spacetime (Cowling approximation) and a polytropic equation of state (EOS). Gravitational waves are estimated using the quadrupole formula. Our main interest are l=m=2 f modes subject to the CFS (Chandrasekhar, Friedman, Schutz) instability, but we also investigate axisymmetric and quasiradial modes. We study various models to determine the influence of rotation rate and EOS. We find that axisymmetric oscillations at high amplitudes are predominantly damped by shock formation, while the nonaxisymmetric f modes are mainly damped by wave breaking and, for rapidly rotating models, coupling to nonaxisymmetric inertial modes. From the observed nonlinear damping, we derive upper limits for the saturation amplitude of CFS-unstable f modes. Finally, we estimate that the corresponding gravitational waves for an oscillation amplitude at the upper limit should be detectable with the advanced LIGO (Laser Interferometer Gravitational Wave Observatory) and VIRGO interferometers at distances above 10 Mpc. This strongly depends on the stellar model, in particular, on the mode frequency.

• OSTI ID: 21503637
• Journal Information: Physical Review. D, Particles Fields, Vol. 82, Issue 10; Other Information: DOI: 10.1103/PhysRevD.82.104036; (c) 2010 American Institute of Physics; ISSN 0556-2821
• Country of Publication: United States
• Language: English

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71 CLASSICAL AND QUANTUM MECHANICS
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AXIAL SYMMETRY
COUPLING
EQUATIONS OF STATE
GRAVITATIONAL WAVES
HYDRODYNAMICS
INSTABILITY
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MEASURING INSTRUMENTS
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