Excitation of f -modes during mergers of spinning binary neutron star
Excitation of f -modes during mergers of spinning binary neutron star
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DOI：
10.1103/physrevd.101.123020
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发表时间：
2020-03
影响因子：
5
通讯作者：
Sizheng Ma;Hang Yu;Yanbei Chen
中科院分区：
文献类型：
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作者：
Sizheng Ma;Hang Yu;Yanbei Chen
在涉及中子星（NSs）的双星合并的最后阶段，潮汐效应对发射的引力波（GWs）有重要的影响。当NS振荡与轨道运动发生共振时，动态潮汐可能是显著的；了解这一过程对于从这些二进制中准确地模拟GW发射以及从GW数据中提取NS信息非常重要。本文采用半解析方法系统地研究了聚并双星中自旋NSs的基本模式（f模式）的潮汐激发，重点研究了NSs自旋与轨道角动量反对准时最可能发生潮汐共振的情况。我们首先将NS振荡扩展为恒星本征模，然后得到一个控制潮汐耦合轨道模演化的哈密顿量。（我们的处理是牛顿级的，包括四极级的重力辐射反应。）然后，我们发现了一个新的近似，它可以导致潮汐激励的解析表达式具有很高的精度，并且在二元演化的所有制度：绝热，共振和后共振有效。利用模拟轨道的方法，得到了轨道演化和GW发射的半解析近似；它们与数值结果的一致性使我们对系统动力学的理解有了信心。特别地，我们恢复了平均共振后演化，它不同于共振前点粒子轨道的轨道能量和角动量的变化，以及潮汐运动驱动的瞬时扰动。最后，利用Fisher矩阵技术研究了动态潮汐对参数估计的影响。我们发现，对于100 Mpc时组分质量为（1.4,1.4）M_⊙的系统，当自旋频率高达500 Hz时，对牛顿阶（2,2）模的有效Love数的约束可以提高3 ~ 4倍。宇宙探索者的相对误差为0.7 ~ 0.8，后牛顿效应可能会进一步改善。对f模频率和自旋频率的约束分别提高了5 ~ 6倍和19 ~ 27倍。在Cosmic Explorer中，相对误差分别为0.2 ~ 0.4和0.7 ~ 1.0。因此，动态潮汐可能为研究纳米粒子的物理特性提供了一个额外的途径。本文提出的方法具有通用性，不局限于f模；它也可以应用于其他类型的潮汐。
Tidal effects have important imprints on gravitational waves (GWs) emitted during the final stage of the coalescence of binaries that involve neutron stars (NSs). Dynamical tides can be significant when NS oscillations become resonant with orbital motion; understanding this process is important for accurately modeling GW emission from these binaries and for extracting NS information from GW data. In this paper, we use semianalytic methods to carry out a systematic study on the tidal excitation of fundamental modes (f-modes) of spinning NSs in coalescencing binaries, focusing on the case when the NS spin is antialigned with the orbital angular momentum—where the tidal resonance is most likely to take place. We first expand NS oscillations into stellar eigenmodes, and then obtain a Hamiltonian that governs the tidally coupled orbit-mode evolution. (Our treatment is at Newtonian order, including a gravitational radiation reaction at quadrupole order.) We then find a new approximation that can lead to analytic expressions of tidal excitations to a high accuracy, and are valid in all regimes of the binary evolution: adiabatic, resonant, and postresonance. Using the method of osculating orbits, we obtain semianalytic approximations to the orbital evolution and GW emission; their agreements with numerical results give us confidence in our understanding of the system’s dynamics. In particular, we recover both the averaged postresonance evolution, which differs from the preresonance point-particle orbit by shifts in orbital energy and angular momentum, as well as instantaneous perturbations driven by the tidal motion. Finally, we use the Fisher matrix technique to study the effect of dynamical tides on parameter estimation. We find that, for a system with component masses of (1.4,1.4) M_⊙ at 100 Mpc, the constraints on the effective Love number of the (2,2) mode at Newtonian order can be improved by a factor of 3 ∼ 4 if spin frequency is as high as 500 Hz. The relative errors are 0.7 ∼ 0.8 in the Cosmic Explorer, and they might be further improved by post-Newtonian effects. The constraints on the f-mode frequency and the spin frequency are improved by factors of 5 ∼ 6 and 19 ∼ 27, respectively. In the Cosmic Explorer case, the relative errors are 0.2 ∼ 0.4 and 0.7 ∼ 1.0, respectively. Hence, the dynamical tides may potentially provide an additional channel to study the physics of NSs. The method presented in this paper is generic and not restricted to f-mode; it can also be applied to other types of tides.