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arXiv 2102.05668astro-ph.SR
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共振锁定双星的潮汐循环I:前主序星的重要性

Tidal Circularization of Binaries by Resonance Locking I: The Importance of the Pre-Main-Sequence

J. J. Zanazzi, Yanqin Wu

摘要:

虽然双星系统的潮汐耗散已经被研究了一个多世纪,但理论预测还没有与观测到的双星系统的特性相匹配。这项工作定量研究最近的建议,潮汐循环共振锁定,其中潮汐耗散产生的共振之间的恒星的自然振荡频率和谐波的轨道频率,共振“锁定”的时间延长,由于并发恒星演化。我们专注于潮汐共振与轴对称的重力模式,并检查从一到两个太阳质量的主要质量的双星。我们发现,通过共振锁定的轨道演化主要发生在恒星的前主序星阶段,与主序星阶段的贡献可以忽略不计。共振锁定,忽略非线性,可以循环双星与周边中心距离$\sim 10$恒星半径,对应的圆形周期$\sim 4-6$天。然而,我们发现共振激发的引力模将成为非线性的恒星核心,这将阻止他们达到其完整的,线性的振幅。我们估计,这样一个“饱和共振锁”减少了约三分之一的循环周期,但共振锁定仍然比平衡潮汐的累积作用更有效。在一篇配套论文中,我们研究了最近的二进制数据,以与理论进行比较。

英文摘要:

Although tidal dissipation in binary stars has been studied for over a century, theoretical predictions have yet to match the observed properties of binary populations. This work quantitatively examines the recent proposal of tidal circularization by resonance locking, where tidal dissipation arises from resonances between the star's natural oscillation frequencies and harmonics of the orbital frequency, and where resonances are `locked' for an extended period of time due to concurrent stellar evolution. We focus on tidal resonances with axi-symmetric gravity-modes, and examine binaries with primary masses from one to two solar masses. We find that orbital evolution via resonance locking occurs primarily during the star's pre-main-sequence phase, with the main-sequence phase contributing negligibly. Resonance locking, ignoring non-linearity, can circularize binaries with peri-centre distances out to $\sim 10$ stellar radii, corresponding to circular periods of $\sim 4-6$ days. However, we find resonantly excited gravity-modes will become nonlinear in stellar cores, which prevents them from reaching their full, linear amplitudes. We estimate that such a `saturated resonance lock' reduces the circularization period by about a third, but resonance locking remains much more effective than the cumulative actions of equilibrium tides. In a companion paper, we examine recent binary data to compare against theory.

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