论文标题
Collinder 135和UBC 7：一对实体群集
Collinder 135 and UBC 7: A Physical Pair of Open Clusters
论文作者
论文摘要
鉴于在天空上两个开放簇Cr 135和UBC 7的接近度，我们研究了两个簇在物理上相关的可能性。我们的目标是在开放群集Collinder 135和UBC 7（来自太阳的300 pc）中恢复当今的恒星成员资格，以限制其运动学参数，年龄和质量，并恢复其原始相位空间配置。选择了最可靠的群集成员，并使用我们的传统方法修改了用于使用Gaia DR2数据的方法。数值模拟使用我们的原始高阶Hermite4 Code \ pgrape及时使用群集轨迹的集成。我们限制了簇的年龄，空间坐标和速度，半径和质量。我们估计集群中心的实际分离等于24 pc。轨道整合表明，如果群集当前的视线速度非常相似，并且总质量大于确定最可靠的成员的质量大于7倍以上，则这些群集的质量大于7倍以上。我们得出的结论是，两个簇Cr 135和UBC 7很可能基于观察性证据和数值模拟形成了一对生理对。机会重合的可能性仅为$ 2 \％$。
Given the closeness of the two open clusters Cr 135 and UBC 7 on the sky, we investigate the possibility of the two clusters to be physically related. We aim to recover the present-day stellar membership in the open clusters Collinder 135 and UBC 7 (300 pc from the Sun), to constrain their kinematic parameters, ages and masses, and to restore their primordial phase space configuration. The most reliable cluster members are selected with our traditional method modified for the use of Gaia DR2 data. Numerical simulations use the integration of cluster trajectories backwards in time with our original high order Hermite4 code \PGRAPE. We constrain the age, spatial coordinates and velocities, radii and masses of the clusters. We estimate the actual separation of the cluster centres equal to 24 pc. The orbital integration shows that the clusters were much closer in the past if their current line-of-sight velocities are very similar and the total mass is more than 7 times larger the mass of the determined most reliable members. We conclude that the two clusters Cr 135 and UBC 7 might very well have formed a physial pair, based on the observational evidence as well as numerical simulations. The probability of a chance coincidence is only about $2\%$.
