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arXiv 1302.6033astro-ph.HEastro-ph.COgr-qc
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差速旋转中子星流体动力学turbulence的随机引力波背景

Stochastic gravitational wave background from hydrodynamic turbulence in differentially rotating neutron stars

Paul D. Lasky, Mark F. Bennett, Andrew Melatos

摘要:

由壳核差异旋转驱动的流体动力学湍流对中子星的引力波观测施加了基本的噪声基底。引力波的发射峰值位于柯尔莫哥洛夫退相干频率处,对于壳核切变的合理值ΔΩ,该频率出现在地基长基线干涉仪频带的最敏感部分附近。我们计算的能量密度谱的随机引力波背景的宇宙学人口的湍流中子星概括以前的计算个别来源。该谱类似于分段幂律,Ω_{gw}(ν)=Ω_αν^α,其中α分别在退相干频率上下为-1和7,其归一化标度为Ω_α \propto(ΔΩ)^{7}。初始LIGO未检测到随机信号意味着ΔΩ的上限,因此也意味着地壳和地核进入同向旋转的内部弛豫时间尺度,τ_{d}=ΔΩ/ \dot Ω,其中\dot Ω是观测到的电磁自旋下降速率,其中毫秒双星的吸积时间τ_{d} \lesssim 10^{7}年,射电强双星的吸积时间τ_{d} \lesssim 10^{5}年。对未来的探测器,即先进的LIGO和爱因斯坦望远镜的τ_{d}的目标限制也进行了估计,并发现天体物理学有趣。

英文摘要:

Hydrodynamic turbulence driven by crust-core differential rotation imposes a fundamental noise floor on gravitational wave observations of neutron stars. The gravitational wave emission peaks at the Kolmogorov decoherence frequency which, for reasonable values of the crust-core shear, ΔΩ, occurs near the most sensitive part of the frequency band for ground-based, long-baseline interferometers. We calculate the energy density spectrum of the stochastic gravitational wave background from a cosmological population of turbulent neutron stars generalising previous calculations for individual sources. The spectrum resembles a piecewise power law, Ω_{gw}(ν)=Ω_αν^α, with α=-1 and 7 above and below the decoherence frequency respectively, and its normalisation scales as Ω_α\propto(ΔΩ)^{7}. Non-detection of a stochastic signal by Initial LIGO implies an upper limit on ΔΩand hence by implication on the internal relaxation time-scale for the crust and core to come into co-rotation, τ_{d}=ΔΩ/\dotΩ, where \dotΩ is the observed electromagnetic spin-down rate, with τ_{d}\lesssim 10^{7} yr for accreting millisecond pulsars and τ_{d}\lesssim 10^{5} yr for radio-loud pulsars. Target limits on τ_{d} are also estimated for future detectors, namely Advanced LIGO and the Einstein Telescope, and are found to be astrophysically interesting.

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