恒星相遇期间对星际物体的捕获
Capture of interstellar objects during stellar encounters
AI总结：
研究恒星相遇时对星际物体的捕获，用N体和蒙特卡罗模拟，发现太阳历史上少量此类捕获，估计捕获约10⁴个类似‘奥陌陌’的物体，占奥尔特云总数10⁻⁸±¹，多数恒星有此类捕获形成的稀疏奥尔特云，大质量恒星捕获效率更高。
AI中文摘要：
当恒星在星系中运行时，会穿过大量星际物体（ISOs）。本文利用N体模拟表明，在距离太阳约1秒差距（其潮汐半径）内的一部分ISOs可能在另一颗恒星飞越时被捕获，此机制无需行星。当飞越产生的冲量与最宽稳定轨道处的逃逸速度相当（太阳约为0.1 km/s）时捕获效率最高。ISO捕获由少数高冲量恒星飞越主导，多数被捕获在奥尔特云外部，半长轴大于约50,000天文单位。通过蒙特卡罗模拟发现太阳在其历史中仅有少量ISO捕获飞越。利用特定人口模型估计太阳可能捕获了约10⁴个类似‘奥陌陌’大小的ISOs，这仅占奥尔特云总数的10⁻⁸±¹，但所含当前捕获的ISOs数量与木星辅助捕获相当。鉴于飞越在星系中不可避免，多数恒星在任何时刻都应有由恒星飞越捕获的ISOs构成的稀疏奥尔特云。大质量恒星既是捕获的主要驱动力，且比低质量恒星更能有效捕获周围的ISOs。
英文摘要：
As they orbit within the Galaxy, stars swim through a vast population of interstellar objects (ISOs). In this paper, we use N-body simulations to show that a fraction of ISOs within $\sim$1 pc of the Sun (its tidal radius) may be captured during the flyby of another star -- a mechanism that requires no planets. Capture is most efficient when the impulse imparted by the flyby is comparable to the escape speed at the widest stable orbit, which is roughly 0.1 km/s for the Sun. ISO capture is dominated by the few highest-impulse stellar flybys, typically involving relatively slow encounters with massive stars. Most ISOs are captured in the outer parts of the Oort cloud, with semimajor axes greater than $\sim$50,000 au. Using Monte Carlo simulations, we show that the Sun underwent only a small number of ISO-capturing flybys in its history (median [mean] of 1 [1.7]). Using the {Ō}tautahi-Oxford population model, we estimate that a few times $\sim$$10^{4}$ `Oumuamua-sized ISOs were likely captured by the Sun. This only represents a $\sim$$10^{-8\pm1}$ contribution to the total Oort cloud population, yet it contains roughly as many present-day captured ISOs as Jupiter-assisted capture provides. Given that flybys are unavoidable in the Galactic field, most stars should host sparse Oort clouds populated with ISOs captured during stellar flybys. Massive stars are both the main drivers of capture when they fly by a given star, and more efficient at capturing ISOs around themselves than low-mass stars.
