Stellar Rotation and the Chronology of the Galaxy

我们对周围宇宙如何随时间变化的理解受到我们测量恒星年龄的能力的限制。与其他基本性质不同，这不是我们能够直接衡量的东西。至少在统计学意义上，我们对一些恒星--特别是那些在“星团”中聚集在一起的恒星--有一些有限的概念。我们还开发了复杂的计算机模型，可以预测其他观测到的属性如何随时间变化，我们可以将其与对真实恒星的观测进行比较。恒星形成时自转速度很快，但随着时间的推移，自转速度会变慢。为了更好地理解这一现象是如何发生的，人们付出了大量的努力。“回转年代学”的目标是能够通过测量恒星的自转速度来推断它的年龄，同时仔细考虑它的其他可测量特性(并非所有自转速度相同的恒星都有相同的年龄)。该项目将试图通过仔细比较描述恒星如何自转的理论模型、使用开普勒航天器史无前例的数据库测量长周期自转(数十天)以及地面观测站的后续观测来解决许多不确定因素。拟议的活动将直接有助于对研究生进行观测和理论天体物理学以及高级统计分析方面的培训。它还将为本科生提供研究机会。PI还将领导将俄亥俄州立大学的新天文馆作为数据可视化实验室的努力。COPIS将与一名研究生和两名使用开普勒数据库的专家合作者一起进行仔细的观测和理论研究，目标是为场星建立一个校准良好的自转-年龄关系。这将基于对星团恒星性质的更仔细的分析，使用开普勒数据和基特峰MDM天文台的后续观测对较长周期的测量，以及恒星角动量损失的详细模型。它将受益于该团队在星震学和统计方面的专业知识。回转年代学被应用于从行星到银河系外的一系列天体物理问题，但在自转速度和年龄之间建立单值函数涉及到严重的复杂问题。这个团队已经确定了所有的复杂情况，并制定了一项计划，可能会导致一项受到很好限制、广泛适用于外场恒星的回转年代学定律。

Our understanding of how the universe around us changes with time is limited by our ability to measure ages of stars. Unlike other fundamental properties, this is not something that we are able to measure directly. We have some limited idea, at least in a statistical sense, for some stars - particularly those all formed together in "clusters". We have also developed sophisticated computer models that predict how other observed properties change in time, which we can compare to observations of real stars. Stars spin rapidly when they are formed, but their spin slows with time. A lot of effort is going into developing a better understanding of how this happens. The goal of "gyrochronology" is to be able to infer the age of a star by measuring how fast it spins, with careful consideration of its other measureable properties (not all stars with the same spin rate have the same age). This project will attempt to resolve many of the uncertainties through a careful comparison of theoretical models describing how stars spin down, measurements of long-period rotators (tens of days) using the unprecedented database from the Kepler spacecraft, and follow-up observations from ground-based observatories. The proposed activities will directly contribute to the training of a graduate student in observational and theoretical astrophysics, as well as advanced statistical analysis. It will also provide research opportunities for undergraduate students. The PI will also lead efforts to use the new Planetarium at Ohio State as a laboratory for data visualization.The CoPIs, along with a graduate student and two collaborators who are experts using the Kepler database, will conduct a careful observational and theoretical study with the goal of producing a well-calibrated rotation-age relation for field stars. This will be based on a more careful analysis of the properties of cluster stars, measurements of longer periods using Kepler data with follow-up observations at the MDM observatory at Kitt Peak, and detailed models of angular momentum loss in stars. It will benefit from the team's expertise in asteroseismology and statistics. Gyrochronology is being applied to a vast array of astrophysical problems, from planetary to extragalactic, yet there are serious complications involved in establishing a single-valued function between rotation rate and age. This team has identified all of the complications and laid out a plan that could lead to a well-constrained and widely-applicable gyrochronology law for field stars.