关于f模不稳定性的饱和振幅
On the saturation amplitude of the f-mode instability
摘要：
我们研究了中子星高振幅振荡过程中的强非线性阻尼效应及其产生的引力波。为此，我们使用一个广义相对论非线性流体动力学代码结合一个固定的时空（考林近似）和多方状态方程（EOS）。引力波的估计使用四极公式。我们的主要兴趣是l=m=2 f模式的CFS（Eschrasekhar，Friedman，Schutz）不稳定性，但我们也调查轴对称和准径向模式。我们研究了各种模型，以确定旋转速率和EOS的影响。我们发现，在高振幅的轴对称振荡主要是由激波形成阻尼，而非轴对称f模式主要是由波破碎阻尼，并为快速旋转的模型，耦合到非轴对称惯性模式。从所观察到的非线性阻尼，我们推导出上限的CFS不稳定f模式的饱和振幅。最后，我们估计，相应的引力波的振荡幅度在上限应该是可检测的先进的LIGO和VIRGO干涉仪在10 MPc以上的距离。这在很大程度上取决于恒星模型，特别是模式频率。
英文摘要：
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 and VIRGO interferometers at distances above 10 MPc. This strongly depends on the stellar model, in particular on the mode frequency.
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