Equation of State Dependence of Nonlinear Mode-tide Coupling in Coalescing Binary Neutron Stars
Equation of State Dependence of Nonlinear Mode-tide Coupling in Coalescing Binary Neutron Stars
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DOI：
10.3847/1538-4357/aa906e
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发表时间：
2017-11
期刊：
影响因子：
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通讯作者：
Yixiao Zhou;Fan Zhang
中科院分区：
文献类型：
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作者：
Yixiao Zhou;Fan Zhang
最近，人们较为详细地研究了潮汐变形中子星在聚结双星中由于p-模和g-模的非线性耦合而产生的不稳定性。这一结果意义重大，因为它可以影响激发态，并在依赖于中子星状态方程(EOS)的引力波信号上留下印记。由于它的潜在重要性，应该进一步阐明这种不稳定性的细节，并研究它对状态方程的敏感性。为此，我们用六个有代表性的EOS对静态和非静态潮汐进行了数值分析。我们证实了在静潮汐下不存在p-g不稳定性以及在非静态潮汐下p-g不稳定性的返回是整个EOS的普遍现象，并进一步揭示了它的一个新的贡献，这对中高阶p-g对(以前的研究集中在很高阶模)来说变得重要，其相关的耦合强度可以随状态方程的不同而变化∼10-100倍。我们发现，对于具有较硬EOSS和较小浮力频率的恒星，不稳定开始时间较早，且不稳定模式增长较快。这些结果表明，不稳定性对引力波信号的影响可能对中子星状态方程很敏感。为了充分评估这一前景，未来的研究将需要调查其饱和度作为状态方程和二元参数的函数。
Recently, an instability due to the nonlinear coupling of p-modes to g-modes in tidally deformed neutron stars in coalescing binaries has been studied in some detail. The result is significant because it could influence the inspiral and leave an imprint on the gravitational wave signal that depends on the neutron star equation of state (EOS). Because of its potential importance, the details of the instability should be further elucidated and its sensitivity to the EOS should be investigated. To this end, we carry out a numerical analysis with six representative EOSs for both static and non-static tides. We confirm that the absence of the p-g instability under static tides, as well as its return under non-static tides, is generic across EOSs, and further reveal a new contribution to it that becomes important for moderately high-order p-g pairs (previous studies concentrated on very high order modes), whose associated coupling strength can vary by factors of ∼10–100 depending on the EOS. We find that, for stars with stiffer EOSs and smaller buoyancy frequencies, the instability onsets earlier in the inspiral and the unstable modes grow faster. These results suggest that the instability’s impact on the gravitational wave signal might be sensitive to the neutron star EOS. To fully assess this prospect, future studies will need to investigate its saturation as a function of the EOS and the binary parameters.