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arXiv 2407.04261astro-ph.EPastro-ph.SR
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星团内双行星的动力学

Dynamics of Binary Planets within Star Clusters

Yukun Huang, Wei Zhu, Eiichiro Kokubo

AI总结:

本研究通过分析工具和三体模拟,揭示了星团内双行星的轨道稳定性主要取决于轨道周期,并提出了改进的临界飞越判据,应用于JWST发现的JuMBOs,表明其可能形成于星团核心附近的紧密双星。

摘要:

我们开发了分析工具并进行了三体模拟,以研究星团内双行星的轨道演化和动力学稳定性。我们的分析结果表明,行星质量双星对抗掠过恒星的轨道稳定性主要与其轨道周期有关。临界飞越,定义为能量冲击与双星结合能相当的恒星遭遇,可以有效地从原始紧密的JuMBOs主导群体中产生广泛的半长轴($a$)和偏心率($e$)范围。我们推导的临界飞越判据相对于常用的潮汐半径判据有所改进,特别是在高速恒星遭遇中。将我们的结果应用于詹姆斯·韦布空间望远镜(JWST)最近发现的木星质量双天体(JuMBOs),我们的模拟表明,为了匹配观测到的约9%的宽双星比例,初始半长轴$a_0 \sim$ 10-20 au和密度加权驻留时间$\chi\gtrsim 10^4$ Myr pc$^{-3}$是受青睐的。这些结果暗示JWST JuMBOs可能是在星团核心附近形成的紧密双星。

英文摘要:

We develop analytical tools and perform three-body simulations to investigate the orbital evolution and dynamical stability of binary planets within star clusters. Our analytical results show that the orbital stability of a planetary-mass binary against passing stars is mainly related to its orbital period. Critical flybys, defined as stellar encounters with energy kicks comparable to the binary binding energy, can efficiently produce a wide range of semimajor axes ($a$) and eccentricities ($e$) from a dominant population of primordially tight JuMBOs. The critical flyby criterion we derived offers an improvement over the commonly used tidal radius criterion, particularly in high-speed stellar encounters. Applying our results to the recently discovered Jupiter-Mass Binary Objects (JuMBOs) by the James Webb Space Telescope (JWST), our simulations suggest that to match the observed $\sim$9% wide binary fraction, an initial semimajor axis of $a_0 \sim$ 10-20 au and a density-weighted residence time of $χ\gtrsim 10^4$ Myr pc$^{-3}$ are favored. These results imply that the JWST JuMBOs probably formed as tight binaries near the cluster core.

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