AI 中文总结
研究六个银河系球状星团双星分数径向分布，用哈勃太空望远镜和地面数据测量，发现其非单调下降，呈双峰分布，最小值与弛豫时间尺度及星团动态年龄指标相关，数值模拟显示源于双星破坏和质量分离综合效应。
AI 中文摘要
我们首次对六个银河系球状星团（GCs）的双星分数径向分布进行了均匀研究，这些星团跨越了从动态年轻系统到核心坍缩星团的广泛动态年龄范围。我们使用深度光学哈勃太空望远镜（HST）观测和宽视场地面数据的组合来测量双星分数的径向变化。首次有证据表明，球状星团中的双星分数并非如通常假设的那样随半径单调下降，而是呈现出一种双峰分布，其特征是外部区域过剩。具体而言，双星分数显示出一个中心峰值，随后在中间半径处出现最小值，并在大约1 - 2个半光半径之外有一个上升分支。这个最小值的位置与星团弛豫时间尺度相关，表明它是由驱动双星演化、分离和破坏的双体弛豫的长期动力学效应塑造的。最小半径还与从蓝离散星的径向分布导出的A +参数相关，这是星团动态年龄的一个经验指标，进一步支持了这一特征是由于内部动力学过程的解释。在一篇配套论文中给出的数值模拟表明，这种双峰分布自然地源于星团中双星破坏和幸存双星的质量分离的综合效应。
英文摘要
We present the first homogeneous study of the radial distribution of the binary fraction across the full extent of six Galactic globular clusters (GCs) spanning a wide range of dynamical ages, from dynamically young systems to core-collapsed clusters. We measured the radial variation of the binary fraction using a combination of deep optical HST observations and wide-field ground-based data. For the first time, we provide evidence that the binary fraction in GCs does not decrease monotonically with radius, as commonly assumed, but instead exhibits a bimodal distribution characterized by an excess in the outer regions. Specifically, the binary fraction displays a central peak, followed by a minimum at intermediate radii and a rising branch beyond approximately 1-2 half-light radii. The position of this minimum correlates with the cluster relaxation timescale, indicating that it is shaped by long-term dynamical effects of two-body relaxation driving the binary evolution, segregation, and disruption. The minimum radius also correlates with the A+ parameter derived from the radial distribution of blue straggler stars, an empirical indicator of the cluster dynamical age, further supporting the interpretation that this feature is due to internal dynamical processes. Numerical simulations presented in a companion paper show that such bimodal distributions naturally arise from the combined effects of binary disruption and mass segregation of the surviving binaries in clusters.
CommentsAccepted for publication by A&A
