Low frequencies in Kepler δ Scuti stars
Low frequencies in Kepler δ Scuti stars
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DOI：
10.1093/mnras/stt1981
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发表时间：
2014-01
影响因子：
4.8
通讯作者：
L. Balona
中科院分区：
文献类型：
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作者：
L. Balona
我们用开普勒光度法研究了A星的低频振荡特性。我们发现，在0-5 d−1的范围内，几乎所有的δScuti恒星都有多个峰值，甚至那些远离γDoradus不稳定带蓝色边缘的恒星也是如此。所有δ单细胞移植明星基本上都是δ单细胞移植/γDOR混血儿。地面观测没有发现这一事实的原因是，低频在γDOR不稳定带蓝边附近达到最大幅度。没有δ星体温度脉动高频特征的恒星也不具有低频率。低频的幅度与δ单层螺旋CT脉动的幅度相关。低频具有与δ单细胞转换模式类似的长寿命。因此，他们对随机机制并不感到兴奋。我们发现，低频不能解释为δ单层模式的非线性组合。通过将观测到的频率分布与δ单层螺旋CT模型的频率分布进行比较，我们发现低频峰值不能解释为高频δ单层螺旋CT模式旋转微扰的结果。我们发现低频峰的数目随着转动的增加而增加，但可以排除Rossby和Kelvin模作为可能的候选者。如果对流阻塞机制即使在最热的A星上也继续活跃，那么A星中低频的存在就可以解释了。
We useKeplerphotometry to examine the properties of low-frequency oscillations in A stars. We find that multiple peaks in the range 0–5 d−1are found in nearly all δ Scuti stars, even those well outside the blue edge of the γ Doradus instability strip. All δ Sct stars are essentially δ Sct/γ Dor hybrids. The reason why this fact was not recognized from ground-based observations is due to the fact that the low frequencies reach maximum amplitude close to the blue edge of the γ Dor instability strip. Stars which do not have high frequencies characteristic of δ Sct pulsations also do not have low frequencies. The amplitudes of the low frequencies correlate with the amplitudes of the δ Sct pulsations. The low frequencies have long lifetimes similar to those of the δ Sct modes. They are therefore not excited by a stochastic mechanism. We show that the low frequencies cannot be explained as non-linear combinations of δ Sct modes. By comparing the observed distribution of frequencies with those from δ Sct models, we show that low-frequency peaks cannot be explained as a result of rotational perturbation of high-frequency δ Sct modes. We find that the number of low-frequency peaks increases with rotation, but Rossby and Kelvin modes can be ruled out as possible candidates. The presence of low frequencies in A stars would be explained if the convective blocking mechanism continues to be active even in the hottest A stars.