Ruprecht 147：一个正在溶解的星团范例
Ruprecht 147: a paradigm of dissolving star cluster
摘要：
利用最近的Gaia/DR 2观测资料，研究了近星系（300 pc）、老星系（2.5 Gyr）的疏散星团Ruprecht~147的动力学状态。我们发现了沿着星团轨道的显著的恒星的前导和拖尾，这表明Ruprecht~147正在快速地失去恒星。恒星计数表明星团的核心半径为33.3弧分，潮汐半径为137.5弧分。该星系团还具有一个扩展的日冕，这是一个简单的King模型无法再现的。我们用它的光度和质量函数计算了现在的星团质量，并得出了234 $\pm$ 52 $M_{\odot}$的估计。我们还估计了集群的原始质量，使用从N体模拟中提取的可用配方，获得出生时的质量为50000 $\pm$ 6500 $M_{\odot}$。因此，主要由银河系与潮汐相互作用引起的动力学质量损失使星团质量减少了约99%。然后，我们得出结论，Ruprecht~147正在迅速溶解到银河系的一般盘。
英文摘要：
We employed recent Gaia/DR2 data to investigate the dynamical status of the nearby (300 pc), old (2.5 Gyr) open cluster Ruprecht~147. We found prominent leading and trailing tails of stars along the cluster orbit, which demonstrates that Ruprecht~147 is losing stars at fast pace. Star counts indicate the cluster has a core radius of 33.3 arcmin, and a tidal radius of 137.5 arcmin. The cluster also possesses an extended corona, which cannot be reproduced by a simple King model. We computed the present-day cluster mass using its luminosity and mass function, and derived an estimate of 234$\pm$52 $M_{\odot}$. We also estimated the cluster original mass using available recipes extracted from N-body simulations obtaining a mass at birth of 50000$\pm$6500 $M_{\odot}$. Therefore dynamical mass loss, mostly caused by tidal interaction with the Milky Way, reduced the cluster mass by about 99\%. We then conclude that Ruprecht~147 is rapidly dissolving into the general Galactic disc.
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