K2 observations of the rapidly oscillating Ap star 33 Lib (HD 137949): new frequencies and unique non-linear interactions
K2 observations of the rapidly oscillating Ap star 33 Lib (HD 137949): new frequencies and unique non-linear interactions
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DOI：
10.1093/mnras/sty2053
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发表时间：
2018-07
影响因子：
4.8
通讯作者：
D. Holdsworth;M. Cunha;H. Shibahashi;D. Kurtz;D. Bowman
中科院分区：
文献类型：
--
作者：
D. Holdsworth;M. Cunha;H. Shibahashi;D. Kurtz;D. Bowman
本文分析了天秤座33（HD 137949）快速振荡Ap（roAp）星星的K2短步频数据。与之前报道的三种脉动模式相比，K2数据的精度使我们能够识别出这颗星星中至少11种脉动模式。这些模式之间的重复分离使我们提出了78.9 µHz的大频率分离，是文献报道的两倍。我们检测到的其他频率分离可能代表小的频率分离δν，但由于频率的磁扰动，这在这个阶段是不确定的。由于33 Lib中的高度非线性脉动，我们识别出四倍于主频率的谐波。此外，我们注意到一个独特的发生的非线性相互作用的11个识别的艾德模式。主频率附近的模式的频率分离在第一谐波周围被复制，与第二谐波也有一些相互作用。这种现象以前在roAp星中从未见过。在修正了恒星参数的情况下，33 Lib的线性非绝热模型表明，脉动不大于声截止频率，κ机制可以激发观测到的模式。我们的观察结果与文献中所提出的33 Lib的旋转周期远大于88 d是一致的。
We present the analysis of K2 short cadence data of the rapidly oscillating Ap (roAp) star, 33 Librae (HD 137949). The precision afforded to the K2 data allow us to identify at least 11 pulsation modes in this star, compared to the three previously reported. Reoccurring separations between these modes leads us to suggest a large frequency separation, ∆ν, of 78.9 µHz, twice that reported in the literature. Other frequency separations we detect may represent the small frequency separation, δν, but this is inconclusive at this stage due to magnetic perturbation of the frequencies. Due to the highly non-linear pulsation in 33 Lib, we identify harmonics to four times the principal frequency. Furthermore, we note a unique occurrence of non-linear interactions of the 11 identified modes. The frequency separations of the modes around the principal frequency are replicated around the first harmonic, with some interaction with the second harmonic also. Such a phenomenon has not been seen in roAp stars before. With revised stellar parameters, linear non-adiabatic modelling of 33 Lib shows that the pulsations are not greater than the acoustic cutoff frequency, and that the κ-mechanism can excite the observed modes. Our observations are consistent with 33 Lib having a rotation period much larger than 88 d as presented in the literature.