Nonlinear Nonradial Pulsations of Cepheids and RR Lyrae

在过去的几年里，观测和理论证据积累表明，在天琴座RR星和造父变星的脉动中，非径向模式比传统预期的更重要，也许在长周期变星中也是如此。所有这些恒星在天文学和宇宙学中都扮演着至关重要的角色，因此彻底了解它们的特性是必不可少的。在这里，将开发一个二维和三维数值流体动力学代码，对这些恒星的全振幅非径向脉动进行数值模拟，目的是解释最近的观测数据。尽管这种新颖的数值模拟具有复杂的性质，但时机已经成熟，而且必要的计算能力也已经具备。预计这项研究也将为长期存在的天琴座RR恒星的Blazhko效应问题提供新的线索。这里将采用的技术预计在其他研究领域也非常有用，从天文学到非线性动力学再到医学。最终的数字代码将在彻底测试后公开。本项目将资助一名本科生参与科学研究，一名博士后研究员将接受多维流体动力学模拟方面的培训。本研究也将透过Buchler博士的教学活动，带入通识教育课堂。

Over the last few years observational as well as theoretical evidence has accumulated that nonradial modes are more important than traditionally expected in the pulsations of RR Lyrae stars and Cepheids, and perhaps in the Long Period Variables as well. All these stars play a vital role in Astronomy and Cosmology and a thorough understanding of their properties is therefore imperative. Here, a 2 and 3-dimensional numerical hydrodynamics code will be developed to make numerical simulations of full amplitude nonradial pulsations of these stars with the goal of explaining the recent observational data. The time is ripe for such novel numerical simulations despite their complicated nature, and the necessary computing power is available. It is anticipated that this study will also shed new light on the long standing problem of the Blazhko effect in RR Lyrae stars. The techniques that will be employed here are expected to be very useful in other research areas as well, ranging from astronomy to nonlinear dynamics to medicine. The final numerical codes will be made publicly available after thorough testing. Support is included here for an undergraduate student who will be exposed to scientific research through this project and a postdoctoral research associate will be trained in multidimensional hydrodynamic simulations. This research will also be brought into the general education classroom through Dr. Buchler's teaching activities.