标题： 球状星团恒星种群中的双星发生率 显示英文标题

标题： The incidence of binaries in Globular Cluster stellar populations

摘要： 二进制分数和轨道特征提供了关于恒星形成条件的指示，因为它们揭示了它们诞生的环境。 多星系统在低密度环境中比在高密度环境中更为常见。 在关于球状星团及其多代恒星形成的当前争论中，研究它们所宿主恒星群体中的二进制出现率，为了解它们的诞生环境和随后的动力学演化提供了关键信息。 通过使用VLT上的FLAMES进行多年的观测活动，我们监测了10个银河系球状星团中位于半光半径附近的968颗红巨星的视向速度。 我们总共发现了21个视向速度变星，被识别为{\it 真实的}二进制恒星，二进制分数为2.2%$\pm$0.5%。 当将样本分为第一代和第二代恒星时，我们发现二进制分数分别为4.9%$\pm$1.3%和1.2%$\pm$0.4%。 通过考虑在两个群体中检测视向速度变化可能的偏差来源的模拟，我们表明这种差异是显著的，并且仅受到这些效应的轻微影响。 这种不同的二进制分数强烈表明第一代和第二代恒星的形成和演化环境存在差异，后者是在一个更密集的环境中形成的。 因此，我们的结果强烈支持这样的观点，即第二代恒星是在松散分布的第一代恒星中心的一个密集子系统中形成的，在那里（松散）双星被有效地破坏。 显示英文摘要

摘要： Binary fraction and orbital characteristics provide indications on the conditions of star formation, as they shed light on the environment they were born in. Multiple systems are more common in low density environments rather than in higher density ones. In the current debate about the formation of Globular Clusters and their multiple populations, studying the binary incidence in the populations they host offers a crucial piece of information on the environment of their birth and their subsequent dynamical evolution. Through a multi-year observational campaign using FLAMES at VLT, we monitored the radial velocity of 968 Red-Giant Branch stars located around the half-light radii in a sample of 10 Galactic Globular Clusters. We found a total of 21 radial velocity variables identified as {\it bona fide} binary stars, for a binary fraction of 2.2%$\pm$0.5%. When separating the sample into first generation and second generation stars, we find a binary fraction of 4.9%$\pm$1.3% and 1.2%$\pm$0.4% respectively. Through simulations that take into account possible sources of bias in detecting radial velocity variations in the two populations, we show that the difference is significant and only marginally affected by such effects. Such a different binary fraction strongly suggests different conditions in the environment of formation and evolution of first and second generations stars, with the latter being born in a much denser environment. Our result hence strongly supports the idea that the second generation forms in a dense subsystem at the center of the loosely distributed first generation, where (loose) binaries are efficiently destroyed.