发现UBC 63的一个无束缚飞掠伴星：在近距离相遇的直接后果中
Discovery of an Unbound Flyby Companion of UBC 63: In the Immediate Aftermath of a Close Encounter
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中文总结 AI 辅助
研究利用盖亚DR3数据重新研究UBC 63，通过高斯混合模型分解等方法发现它是双星系候选者，分析了两星团年龄、间距等，经模拟预测其未来发散情况，揭示其引力无束缚及存在强烈瞬态潮汐相互作用。
中文摘要 AI 辅助
我们使用盖亚DR3数据重新研究疏散星团UBC 63，发现它并非如先前分类的单一星团，而是正经历无束缚飞掠相互作用的双星系有力候选者。在五维天体测量空间进行的高斯混合模型分解揭示了两个统计上不同的成分，即UBC 63A（98个成员，年龄 = 21 ± 4 Myr）和UBC 63B（148个成员，年龄 = 562 ± 43 Myr）。星团间显著的年龄差ΔAge = 541 ± 43 Myr排除了同时形成的可能性。它们在较年轻星团诞生时的三维间距为60 ± 29 pc，表明可能起源于同一分子云复合体。目前，该系统三维间距为26 ± 8 pc，相对速度为3.60 ± 1.80 km s⁻¹。轨道积分和N体模拟表明，该系统曾有过近距离相遇，仅在约600万年前间距达到7 ± 2 pc，并预测在未来约1亿年内将迅速发散至491 ± 213 pc。与相对三维速度相比，该系统较低的逃逸速度（Vesc = 0.51 ± 0.12 km s⁻¹）表明它们在引力上是无束缚的。其低潮汐因子、拉长结构和超出雅可比半径的星族可能反映了星团间强烈的瞬态潮汐相互作用。
英文摘要
We re-investigate the open cluster UBC 63 using the Gaia DR3 data and show that, rather than being a single cluster as previously classified, it is a compelling candidate for a double cluster undergoing an unbound flyby interaction. A GMM decomposition performed in the 5D astrometric space reveals the two statistically distinct components, namely UBC 63A (98 members, Age = 21 $\pm$ 4 Myr) and UBC 63B (148 members, Age = 562 $\pm$ 43 Myr). A significant age difference of $Δ\mathrm{Age} = 541 \pm 43$ Myr between the clusters, rules out coeval formation. Their 3D separation of $60 \pm 29$ pc at the birth-epoch of the younger cluster, indicates that the clusters might have originated from the same molecular cloud complex. At present, the system exhibits a 3D separation of $26 \pm 8$ pc, with a relative velocity of $3.60 \pm 1.80$ km s$^{-1}$. Orbital integrations and \textit{N}-body simulations of the pair suggest that the systems had a close encounter, reaching a separation of $7 \pm 2$ pc only $\sim$~6 Myr ago and predict a rapid divergence to a separation of $491 \pm 213$ pc within the next $\sim$100 Myr. The low escape velocity ($V_{\rm esc} = 0.51 \pm 0.12$ km s$^{-1}$) of the system compared to the relative 3D velocity indicates that they are gravitationally unbound. Their low tidal factors, elongated structures and populations extending beyond the Jacobi radii may reflect a strong transient tidal interaction between the clusters.
