A new window to tidal asteroseismology: non-linearly excited stellar eigenmodes and the period spacing pattern in KOI-54
A new window to tidal asteroseismology: non-linearly excited stellar eigenmodes and the period spacing pattern in KOI-54
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潮汐星震学的新窗口：KOI-54 中的非线性激发恒星本征模和周期间隔模式
DOI：
10.1093/mnras/stac2611
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发表时间：
2022
影响因子：
4.8
通讯作者：
Sun, Meng
中科院分区：
文献类型：
--
作者：
Guo, Zhao;Ogilvie, Gordon I.;Li, Gang;Townsend, Richard H. D.;Sun, Meng
我们重新审视了A型主序偏心双星KOI-54（心跳星的原型）中的潮汐激发振荡（TEO）。虽然星星的线性潮汐响应是一系列轨道谐波频率，这不是恒星的本征频率，我们表明，非线性激发的非轨道谐波TEO是本征模式。通过仔细选择满足模式耦合选择规则的模式，可以在傅里叶谱中识别出周期间隔（ΔP）为2520-2535 s的四极重力模式，其检测显著性水平为.推断的周期间隔值同意非常好的理论所有= 2，m= 0 g模式从恒星模型与测量的质量，半径和有效温度。我们还发现，在N = 90，91谐波处的两个最大振幅的TEO与l = 2，m= 0本征模的共振非常接近，可能来自不同的恒星。以往的潮汐振荡研究主要集中在对TEO振幅和相位的模拟上，由于TEO振幅对频率失谐（潮汐强迫频率减去最近的恒星本征频率）的高度敏感性，需要非常密集的恒星模型网格，这使得我们很难对恒星物理参数进行约束。这项工作，但是，打开了窗口的真实的潮汐星震学使用的本征频率推断的星星的非线性TEO和可能非常接近共振的线性TEO。我们的地震模型，这些确定的本征g-模式表明，最匹配的恒星模型（M <$2.20，2.35 M <$）和超太阳的金属丰度，与以前的测量结果很好地吻合。
We revisit the tidally excited oscillations (TEOs) in the A-type main-sequence eccentric binary KOI-54, the prototype of heartbeat stars. Although the linear tidal response of the star is a series of orbital-harmonic frequencies which are not stellar eigenfrequencies, we show that the non-linearly excited non-orbital-harmonic TEOs are eigenmodes. By carefully choosing the modes which satisfy the mode-coupling selection rules, a period spacing (ΔP) pattern of quadrupole gravity modes (ΔP≈ 2520–2535 s) can be discerned in the Fourier spectrum, with a detection significance level of. The inferred period spacing value agrees remarkably well with the theoreticall= 2,m= 0 g modes from a stellar model with the measured mass, radius, and effective temperature. We also find that the two largest-amplitude TEOs atN= 90, 91 harmonics are very close to resonance withl= 2,m= 0 eigenmodes, and likely come from different stars. Previous works on tidal oscillations primarily focus on the modelling of TEO amplitudes and phases, the high sensitivity of TEO amplitude to the frequency detuning (tidal forcing frequency minus the closest stellar eigenfrequency) requires extremely dense grids of stellar models and prevents us from constraining the stellar physical parameters easily. This work, however, opens the window of real tidal asteroseismology by using the eigenfrequencies of the star inferred from the non-linear TEOs and possibly very-close-to-resonance linear TEOs. Our seismic modelling of these identified eigen g-modes shows that the best-matching stellar models have (M≈ 2.20, 2.35 M⊙) and super-solar metallicity, in good agreement with previous measurements.