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arXiv 0911.1609astro-ph.HEgr-qc
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差转中子星中流体动力学Turbulence的引力辐射

Gravitational Radiation from Hydrodynamic Turbulence in a Differentially Rotating Neutron Star

A. Melatos, C. Peralta

摘要:

(节录)本文分析计算了在高雷诺数湍流中的均方电流四极矩,以及由此产生的随机引力波信号的振幅和退相干时间。该计算解决了信号是否由最小或最大的湍流涡旋主导的微妙问题:对于在超流球形Couette模拟中观察到的Kolmogorov样功率谱,波应变由最大的涡旋控制,并且退相干时间近似等于最大涡旋周转时间。对于自旋频率为$ν_s$、罗斯比数为$Ro$的中子星,在距离地球为$d$处,均方根波应变达到$h_{RMS} \approx 3\times 10^{-24} Ro^3 (ν_s / 30 Hz)^3 (d/1 kpc)^{-1}$。互相关搜索原则上可以检测到这样的源,因为信号在时间尺度$τ_c \approx 10^{-3} Ro^{-1} (ν_s / 30 Hz)^{-1} s$上去相干,这是由现有的长基线干涉仪充分采样的。因此,流体动力学湍流对中子星的引力波观测施加了一个基本的噪声基底,尽管它的污染效应可能会被百赫兹波段的部分退相干所减弱,目前的连续波搜索集中在最高频率(因此也是最强大的)源上。

英文摘要:

(Abridged.) The mean-square current quadrupole moment associated with vorticity fluctuations in high-Reynolds-number turbulence in a differentially rotating neutron star is calculated analytically, as are the amplitude and decoherence time of the resulting, stochastic gravitational wave signal. The calculation resolves the subtle question of whether the signal is dominated by the smallest or largest turbulent eddies: for the Kolmogorov-like power spectrum observed in superfluid spherical Couette simulations, the wave strain is controlled by the largest eddies, and the decoherence time approximately equals the maximum eddy turnover time. For a neutron star with spin frequency $ν_s$ and Rossby number $Ro$, at a distance $d$ from Earth, the root-mean-square wave strain reaches $h_{RMS} \approx 3\times 10^{-24} Ro^3 (ν_s / 30 Hz)^3 (d/1 kpc)^{-1}$. A cross-correlation search can detect such a source in principle, because the signal decoheres over the time-scale $τ_c \approx 10^{-3} Ro^{-1} (ν_s / 30 Hz)^{-1} s$, which is adequately sampled by existing long-baseline interferometers. Hence hydrodynamic turbulence imposes a fundamental noise floor on gravitational wave observations of neutron stars, although its polluting effect may be muted by partial decoherence in the hectohertz band, where current continuous-wave searches are concentrated, for the highest frequency (and hence most powerful) sources.

机构、总结、中文摘要均由AI分析而来,可能存在错误,请以论文正文为准。

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