A new class of pulsating binary stars was recently discovered, whose pulsation amplitudes are strongly modulated with orbital phase. Stars in close binaries are tidally distorted, so we examine how a star's tidally induced asphericity affects its oscillation mode frequencies and eigenfunctions. We explain the pulsation amplitude modulation via tidal mode coupling such that the pulsations are effectively confined to certain regions of the star, e.g., the tidal pole or the tidal equator. In addition to a rigorous mathematical formalism to compute this coupling, we provide a more intuitive semi-analytic description of the process. We discuss three resulting effects: 1. Tidal alignment, i.e., the alignment of oscillation modes about the tidal axis rather than the rotation axis; 2. Tidal trapping, e.g., the confinement of oscillations near the tidal poles or the tidal equator; 3. Tidal amplification, i.e., increased flux perturbations near the tidal poles where acoustic modes can propagate closer to the surface of the star. Together, these phenomena can account for the pulsation amplitude and phase modulation of the recently discovered class of "tidally tilted pulsators." We compare our theory to the three tidally tilted pulsators HD 74423, CO Cam, and TIC 63328020, finding that tidally trapped modes that are axisymmetric about the tidal axis can largely explain the first two, while a non-axisymmetric tidally aligned mode is present in the latter. Finally, we discuss implications and limitations of the theory, and we make predictions for the many new tidally tilted pulsators likely to be discovered in the near future.

中文翻译：

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双星中的潮汐捕获脉动

最近发现了一类新的脉动双星，其脉动幅度受到轨道相位的强烈调制。近距离双星中的恒星会发生潮汐畸变，因此我们研究了恒星的潮汐引起的非球面性如何影响其振荡模式频率和本征函数。我们通过潮汐模式耦合来解释脉动幅度调制，这样脉动被有效地限制在恒星的某些区域，例如潮汐极或潮汐赤道。除了计算这种耦合的严格数学形式之外，我们还提供了对过程的更直观的半分析描述。我们讨论了三种由此产生的影响： 1. 潮汐排列，即振荡模式围绕潮汐轴而不是旋转轴排列；2. 潮汐诱捕，例如，潮汐两极或潮汐赤道附近振荡的限制；3. 潮汐放大，即在潮汐极附近增加通量扰动，在那里声波模式可以传播到更靠近恒星表面的地方。总之，这些现象可以解释最近发现的一类“潮汐倾斜波轮”的脉动幅度和相位调制。我们将我们的理论与三个潮汐倾斜波轮 HD 74423、CO Cam 和 TIC 63328020 进行比较，发现关于潮汐轴轴对称的潮汐捕获模式可以在很大程度上解释前两个，而非轴对称潮汐对齐模式存在于后者。最后，我们讨论了该理论的含义和局限性，并对可能在不久的将来发现的许多新的潮汐倾斜脉动器进行了预测。