Alternative Pathways of Stellar Evolution in Open Clusters

我们对单个恒星生命周期的理解是上个世纪最伟大的智力成就之一。然而，像我们的太阳这样的恒星有一半是在轨道上与伴星一起形成的。仅仅了解单个明星就像研究人类的生活，而不包括夫妻之间的人。这项研究的目标是通过跟踪在数千颗恒星星团中出生、生活和死亡的恒星，了解这些不同的恒星生命故事。当两颗恒星围绕彼此的轨道运行时，就会产生另一种生命路径。他们的生活故事可能包括他们之间交换材料，两者慢慢融合为一个，甚至是激烈的恒星碰撞。将对单星的研究与对星团中恒星的新理解相结合，将产生对所有恒星生命的完整图景。这项工作也将增加STEM中代表性不足的学生的参与。研究小组将为威斯康星州麦迪逊社区中心的学生开发课外项目。这些项目建立在天文视频游戏的基础上，以激发和培养人们对STEM的兴趣。该团队还将在威斯康星大学和麦迪逊学院的天文学和物理课程中增加基于游戏的学习。最后，该团队将为未被充分代表的本科生和研究生提供和指导研究经验。这项研究试图通过包括星团中恒星的相互作用来改变我们对恒星生命周期的看法。这项计划中的研究基于NSF资助的WIYN开放星团研究研究，该研究全面定义了6个丰富的较老(1.6 Gyr t 8 Gyr)开放星团中的替代恒星演化产物，以及它们形成的近距离双星群体。第一个目标是使用两个数值模拟程序，称为MESA和TWINE，在理论上再现所有6个星系团内的可选恒星演化路径。特别是，带有探测到的白矮星伴星的蓝色散星将允许对从前身双星到当前蓝散双星的质量传递演化进行直接、详细的建模。第二个目标是模拟星团中恒星的自转分布，作为有效温度的函数。主序单星的自转趋势不成立，实际的自转分布尚不清楚。第三个目标是将角动量的变化建模为质量的函数。他们将使用恒星当前自转速度的模型来限制恒星形成事件中自旋事件的规模。

Our understanding of the life cycle of individual stars is one of the great intellectual accomplishments of the past century. However, half of stars like our Sun form in orbit with companion stars. Going no further than understanding individual stars would be like studying human lives without including people who are in couples. The goal of this research is to understand these alternative stellar life stories, by following stars that are born, live and die in clusters of thousands of stars. The alternative life paths result when two stars orbit near each other. Their life stories can include exchanging material between them, the two slowly merging into one, or even violent stellar collisions. Combining the studies single stars with new understanding of stars in clusters will yield a complete picture of lives of all stars.This work also will increase participation of students underrepresented in STEM. The research team will develop after-school programs for students at community centers in Madison WI. These programs build on astronomy video games to excite and nurture interest in STEM. The team also will add game-based learning to astronomy and physics classes at the University of Wisconsin and at Madison College. Finally, the team will provide and mentor research experiences for underrepresented undergraduate and graduate students. This research seeks to transform our view of stellar life cycles by including the interactions of stars in clusters. The planned research rests upon NSF-funded WIYN Open Cluster Study research that comprehensively defines alternative stellar evolution products, and the close binary populations from which they form, in 6 rich older (1.6 Gyr t 8 Gyr) open clusters. The first objective is to theoretically reproduce alternative stellar evolution pathways within all 6 clusters using two numerical modeling codes, called MESA and TWIN. In particular, blue stragglers with detected white-dwarf companions will permit direct, detailed modeling of mass-transfer evolution from progenitor binaries to current blue-straggler binaries. The second objective is to simulate the rotation distributions of stars in clusters, as a function of effective temperature. The rotation trends of main-sequence single stars do not hold, and the actual rotation distributions of not yet known. The third objective is to model angular momentum changes as a function of mass. They will use models of current spin-down rates of stars to constrain the magnitude of spin-up events in stellar formation events.