Collaborative Research: Deep Astrometric and Radial Velocity Studies of Old Open Clusters

AST0406615PI MathieuOpen星团是年龄和组成相似的恒星的集合，因此为许多恒星天体物理和恒星动力学提供了重要的观测基础。进入这些天体物理实验室的关键是了解星系团的成员资格，因为星系团前面或后面的恒星似乎都在它里面。由于所有受引力约束的星团都以非常相似的速度和方向移动，识别星团成员的途径是通过自行和径向速度确定在星团边界内可见的所有恒星的速度。该项目正在对五个丰富的古老疏散星团中的恒星和双星群进行异常全面和可靠的普查。通过完整描述星团质量函数、双星频率和双星轨道元素作为半径的函数，探索恒星演化和恒星动力学之间的界面，从而允许与包括动力学和恒星演化的n体数值模拟进行详细比较。通过详细描述主序转折点的形态，正在探索恒星核心内辐射和流体动力学过程之间的复杂相互作用。更广泛的影响：该项目通过整合研究生论文、本科生论文和其他本科生的研究经验，提高未来科学家的研究和教学技能。这项工作与威斯康星大学的NSF研究、教学和学习整合中心有关。台湾-波罗的海三方合作帮助最近处于不利地位的国家的学生进行培训和教育。

AST 0406615PI MathieuOpen clusters are collections of stars with similar ages and compositions, and as such provide a vital observational foundation for much of stellar astrophysics and stellar dynamics. The key for entry into these astrophysical laboratories is knowledge of the cluster membership, for stars in front of or behind a cluster appear to be within it. Since all stars gravitationally bound to a cluster move with very similar speed and direction, the path to identifying the members of a cluster is to measure the velocities for all stars visible within the cluster boundaries through proper motion and radial velocity determinations. This project is carrying out an exceptionally comprehensive and reliable census of the stellar and binary star populations in five rich old open clusters. The interface between stellar evolution and stellar dynamics is being explored through complete descriptions of the cluster mass functions, binary frequencies, and binary orbital elements as a function of radius, permitting detailed comparisons with n-body numerical simulations that include both dynamical and stellar evolution. The complex interplay between radiative and hydrodynamical processes within stellar cores is being explored through detailing the morphologies of main-sequence turnoff points. Broader Impacts: This project is enhancing the research and teaching skills of future scientists by integrating graduate student dissertations, undergraduate theses, and research experiences for other undergraduate students. This work is associated with the NSF Center for the Integration of Research, Teaching, and Learning at the University of Wisconsin. A trilateral Taiwan-Baltic collaboration assists in the training and education of students in recently disadvantaged countries.