Beyond the linear tide: impact of the non-linear tidal response of neutron stars on gravitational waveforms from binary inspirals
Beyond the linear tide: impact of the non-linear tidal response of neutron stars on gravitational waveforms from binary inspirals
复制标题
超越线性潮汐：中子星非线性潮汐响应对双星螺旋引力波形的影响
DOI：
10.1093/mnras/stac3614
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发表时间：
2022
影响因子：
4.8
通讯作者：
Venumadhav, Tejaswi
中科院分区：
文献类型：
--
作者：
Yu, Hang;Weinberg, Nevin N.;Arras, Phil;Kwon, James;Venumadhav, Tejaswi
合并双中子星中的潮汐相互作用改变了激励动力学，因此以额外相移的形式在它们的引力波（GW）信号上留下了一个特征。为了从观测中约束超核状态方程，我们需要精确的潮汐相移模型。在以往的研究中，通常将潮汐视为扰动潮场的线性响应来构建GW波形模型。在这项工作中，我们结合了由于水动力三模和四模相互作用而产生的非线性修正，并展示了它们如何提高波形模型的准确性和解释力。建立了轨道与模态的耦合微分方程并进行了数值求解，解析导出了系统平衡位形的解。我们的解析解与数值解一致，直到合并，并且只涉及代数关系，允许在大参数空间上对不同的状态方程进行快速相移和波形评估。我们发现，在牛顿阶下，非线性流体效应可以在1000 Hz的GW频率上增强潮汐相移，对应于对线性理论的修正。合并附近额外相移的规模与数值相对论和只考虑线性潮汐的理论预测之间的差异是一致的。因此，非线性流体效应在解释数值相对论的结果以及为当前和未来的GW探测器构建波形模型时非常重要。
Tidal interactions in coalescing binary neutron stars modify the dynamics of the inspiral and hence imprint a signature on their gravitational wave (GW) signals in the form of an extra phase shift. We need accurate models for the tidal phase shift in order to constrain the supranuclear equation of state from observations. In previous studies, GW waveform models were typically constructed by treating the tide as a linear response to a perturbing tidal field. In this work, we incorporate non-linear corrections due to hydrodynamic three- and four-mode interactions and show how they can improve the accuracy and explanatory power of waveform models. We set up and numerically solve the coupled differential equations for the orbit and the modes and analytically derive solutions of the system’s equilibrium configuration. Our analytical solutions agree well with the numerical ones up to the merger and involve only algebraic relations, allowing for fast phase shift and waveform evaluations for different equations of state over a large parameter space. We find that, at Newtonian order, non-linear fluid effects can enhance the tidal phase shift byat a GW frequency of 1000 Hz, corresponding to acorrection to the linear theory. The scale of the additional phase shift near the merger is consistent with the difference between numerical relativity and theoretical predictions that account only for the linear tide. Non-linear fluid effects are thus important when interpreting the results of numerical relativity and in the construction of waveform models for current and future GW detectors.