Monte Carlo Stellar Evolution Models and Isochrones

从确定系外行星宿主恒星的半径，单个恒星的年龄，到遥远的原星系的年龄，恒星演化模型的使用在天体物理学中无处不在。恒星模型需要使用各种物理参数（如核反应速率和不透明度），并做出各种假设（如对流的性质）。首席研究员和他在达特茅斯学院的学生将使用现有的最佳数据来测试和改进恒星模型。他们的蒙特卡罗方法将提供与恒星模型相关的不确定性的估计。建议的研究将构成学生博士论文的核心。通过达特茅斯大学的女性参与科学项目，由PI和研究生共同指导的一年级本科生将被雇用来协助该项目。PI开发了一个天文学外国研究项目，该项目将达特茅斯学院的学生带到南非进行为期10周的天文学密集介绍，并对南非的文化、历史和科学研究进行了丰富的介绍。该项目将测试和改进恒星模型，将预测的恒星模型的颜色和绝对星等与相对本地的恒星进行比较，这些恒星具有盖亚卫星在其最新数据发布（DR3）中获得的精确视差距离。了解与恒星模型和等时线有关的不确定性是很重要的。将使用蒙特卡罗方法，而不是生成一组基于对恒星演化模型的各种输入参数的最佳估计的恒星模型和等时线。对于每个恒星物理参数（质量和化学成分），将通过随机抽样用于生成模型的各种输入参数（不透明度、核反应速率等）中的不确定性，生成一套1000个恒星演化模型。这套恒星演化模型将用于生成一套等时线，从这些等时线中，用户不仅可以提取给定数量（如半径、光度或恒星年龄）的最佳估计值，还可以提取相关的68%和95%置信限。这些不确定性估计可以被那些使用恒星模型和等时线的人纳入到后续的分析中，以确保导出量（如年龄）的不确定性不仅反映了观测的不确定性，而且反映了与理论模型相关的不确定性。该奖项反映了美国国家科学基金会的法定使命，并通过使用基金会的知识价值和更广泛的影响审查标准进行评估，被认为值得支持。

From determining the radius of exoplanet hosting stars, the ages of individual stars, to the age of distant protogalaxies, the use of stellar evolution models is ubiquitous in astrophysics. Stellar models require the use of a variety of physical parameters (such as nuclear reaction rates and opacities) and make a variety of assumptions (such as the nature of convection). The Principal Investigator and his students at Dartmouth College will use the best data available to test and improve stellar models. Their Monte Carlo approach will provide an estimate of the uncertainties associated with stellar modeling. The proposed research will form the core of student's PhD thesis. Through Dartmouth’s Women in Science Project, first year undergraduate women, jointly mentored by the PI and the graduate student, will be employed to assist in the project. The PI has developed an astronomy foreign studies program, which takes Dartmouth students to South Africa for an intensive 10-week introduction to astronomy and a rich introduction to South African culture, history, and scientific research.This project will test and improve stellar models by comparing the predicted colors and absolute magnitudes of the stellar models to relatively local stars which have accurate parallax distances obtained by the Gaia satellite in its most recent data release (DR3). It is important to have an understanding of the uncertainties associated with stellar models and isochrones. Instead of generating a single set of stellar models and isochrones which are based upon the best estimates for the various input parameters to stellar evolution models, a Monte Carlo approach will be used. For each physical stellar parameter (mass and chemical composition), a suite of a 1000 stellar evolution models will be generated by randomly sampling the uncertainties in the various input parameters (opacity, nuclear reaction rates, etc.) used to generate the models. This suite of stellar evolution models will be used to generate a suite of isochrones, and from these the user will be able to extract not just the best estimate for a given quantity (such as the radius, luminosity or age of a star), but also their associated 68% and 95% confidence limits. These uncertainty estimates can be incorporated into subsequent analysis by those who use the stellar models and isochrones to ensure that the uncertainty in derived quantities (such as age) reflect not just observational uncertainties, but also uncertainties associated with the theoretical models.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.