Non-adiabatic tidal oscillations induced by a planetary companion
Non-adiabatic tidal oscillations induced by a planetary companion
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由行星伴星引起的非绝热潮汐振荡
DOI：
10.1093/mnras/stz2561
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发表时间：
2019
影响因子：
4.8
通讯作者：
Bunting A
中科院分区：
文献类型：
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作者：
Bunting A
我们计算了 1 和 1.4 M⊙ 的非旋转恒星上的近邻行星伴星引起的动力潮汐。使用 Henyey 方法，我们求解整个恒星的完全非绝热方程。研究发现，在恒星表面附近的薄层区域，水平拉格朗日位移比平衡潮汐值大 10-100 倍。这是因为非绝热效应在对流区外缘以下一直延伸到恒星表面的区域中占主导地位，而平衡潮汐近似与非绝热性不一致。虽然这种近似通常适用于低频极限，但它也不适用于对流区中强迫频率较小但大于布伦特-维萨拉频率的部分。我们得出的分析估计可以很好地近似地表水平位移和径向位移之比的数值。相对表面通量扰动也很显着，对于以 51 Pegasi b 为模型的系统而言，扰动约为 0.1%。因此，受水平位移影响的观测可能比之前想象的更容易实现，并且亮度扰动可能是通量扰动的结果，而不是径向位移造成的。我们讨论了这对检测此类潮汐激发振荡的可能性的影响，包括利用大水平运动观测诸如 51 Pegasi 等系统的前景。
We calculate the dynamical tides raised by a close planetary companion on non-rotating stars of 1 and 1.4 M⊙. Using the Henyey method, we solve the fully non-adiabatic equations throughout the star. The horizontal Lagrangian displacement is found to be 10–100 times larger than the equilibrium tide value in a thin region near the surface of the star. This is because non-adiabatic effects dominate in a region that extends from below the outer edge of the convection zone up to the stellar surface, and the equilibrium tide approximation is inconsistent with non-adiabaticity. Although this approximation generally applies in the low frequency limit, it also fails in the parts of the convection zone where the forcing frequency is small but larger than the Brunt–Väisälä frequency. We derive analytical estimates that give a good approximation to the numerical values of the magnitude of the ratio of the horizontal and radial displacements at the surface. The relative surface flux perturbation is also significant, of the order of 0.1 per cent for a system modelled on 51 Pegasi b. Observations affected by the horizontal displacement may therefore be more achievable than previously thought, and brightness perturbations may be the result of flux perturbations rather than due to the radial displacement. We discuss the implication of this on the possibility of detecting such tidally excited oscillations, including the prospect of utilizing the large horizontal motion for observations of systems such as 51 Pegasi.