Nonlinear Stellar Pulsations

很可能所有的恒星都有脉动，尽管大多数恒星的脉动很小，而且恒星又很遥远，所以很难探测到脉动。例如，以太阳为例，直到最近才用新开发的仪器检测到脉动，从而产生了“日震学”这门科学。然而，有些恒星的脉动相当强烈。这些恒星明显地变亮变暗，它们膨胀和收缩。有些恒星的周期相当规律，比如造父变星和天琴座RR星；其他恒星的脉动非常不稳定，比如金牛座RV星。首席研究员（PI）建议继续他目前由美国国家科学基金会资助的所有类型的脉动恒星的理论和数值研究，从造父变星和天琴座RR星到半正规星和金牛座RV星。计算方法将由“半解析振幅方程形式和数值流体力学的明智混合”组成。目标将是发展脉动恒星模型的单参数族，而不是研究特定的观测恒星。为了支持这项研究，PI建议扩展他目前的计算机代码，使它们更真实，并根据混沌理论解释恒星脉动。

Quite possibly all stars pulsate, though in most stars the pulsations are so small and the stars are so distant that the pulsations are very difficult to detect. For example, in the case of the sun, pulsations have been detected only recently with newly developed instrumentation, giving rise to the science of "helioseismology." Ther are, however, stars that pulsate rather strongly. These stars grow visibly brighter and dimmer, and they expand and contract. Some do so with rather regular periods, as for example the Cepeheid and RR Lyra stars; others are quite erratic in their pulsations, such as the RV Tauri stars. The Principal Investigator (PI) proposes to continue with his current NSF funded theoretical and numerical study of pulsating stars of all types, from Cepeheids and RR Lyra stars to Semi- Regulars and the RV Tauri stars. The computing method will consist of a "judicious mixture of semi-analytical amplitude equation formalism and of numerical hydrodynamics." The goal will be to develop one-parameter families of pulsating star models, rather than to study specific observed stars. In support of this study, the PI proposes to expand his current computer codes to make them more realistic and to interpret stellar pulsation in terms of chaos theory.