论文标题
混合模式分离和耦合的半分析表达式
Semi-analytic Expressions for the Isolation and Coupling of Mixed Modes
论文作者
论文摘要
在巨型恒星的振荡光谱中，可以看到非放射模式经历避免的横梁，在其各自的echelle图中产生了原本均匀的渐近P-和G模式模式的特征性“模式颠簸”。相对于典型的观察误差，避免过境的发展非常快，因此在确定恒星的精确年龄时非常有用，尤其是在亚巨星中。这种现象是由彼此几乎共振的P和G模式之间的模式之间的耦合引起的。这些模式腔之间耦合的大多数理论分析都依赖于JWKB方法，这对于在子巨星中观察到的低阶G模式或在非常进化的红色巨人中看到的低阶P模型而言，这严格来说是不适用的。我们提出了用于隔离两个模式腔的非沉积处方，以及它们之间的耦合的扰动（也是非扰动）的描述，在这些物理情况下，我们表明对低阶G和P模型保持有益。最后，我们讨论如何将这些结果应用于建模恒星并确定其从振荡频率中确定其全局特性。我们还为所有这些计算公开提供了代码。
In the oscillation spectra of giant stars, nonradial modes may be seen to undergo avoided crossings, which produce a characteristic "mode bumping" of the otherwise uniform asymptotic p- and g-mode patterns in their respective echelle diagrams. Avoided crossings evolve very quickly relative to typical observational errors, and are therefore extremely useful in determining precise ages of stars, particularly in subgiants. This phenomenon is caused by coupling between modes in the p- and g-mode cavities that are near resonance with each other. Most theoretical analyses of the coupling between these mode cavities rely on the JWKB approach, which is strictly speaking inapplicable for the low-order g-modes observed in subgiants, or the low-order p-modes seen in very evolved red giants. We present both a nonasymptotic prescription for isolating the two mode cavities, as well as a perturbative (and also nonasymptotic) description of the coupling between them, which we show to hold good for the low-order g- and p-modes in these physical situations. Finally, we discuss how these results may be applied to modelling subgiant stars and determining their global properties from oscillation frequencies. We also make our code for all of these computations publicly available.
