The Rotational Shear Layer inside the Early Red-giant Star KIC 4448777
The Rotational Shear Layer inside the Early Red-giant Star KIC 4448777
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DOI：
10.3847/1538-4357/aac7c4
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发表时间：
2018-05
期刊：
影响因子：
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通讯作者：
M. D. Di Mauro;R. Ventura;E. Corsaro;Bruno Lustosa de Moura
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文献类型：
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作者：
M. D. Di Mauro;R. Ventura;E. Corsaro;Bruno Lustosa de Moura
我们提出了早期红巨星星星KIC 4448777的星震研究，补充和整合以前的工作，旨在通过分析开普勒卫星在其第一次标称使命的四年中收集的整体数据集来表征其内部的动态。我们采用贝叶斯推理程序钻石的峰值装袋分析和星震分裂反演方法来获得星星的内部旋转轮廓。新的混合模式分裂的检测，这是更集中在非常内部的氦核心部分，使我们能够重建角速度剖面更深入到内部的星星和解开的细节比在论文一：氦核几乎刚性地旋转，大约比对流包层快6倍，而氢壳层的一部分似乎以比He核低1.15倍的恒定速度旋转。特别是，我们研究了快速旋转的辐射内部和缓慢的对流区之间的内部剪切层，我们发现，它部分位于氢壳层内r = 0.05R以上，并延伸到整个核心包络边界。最后，我们从理论上探讨了未来探测红巨星对流包层的可能性，并得出结论，即使假设有大量的模式，一组只有低调和度l ≤ 3的分裂的反演也不允许我们详细地解决这个区域的旋转轮廓。
We present the asteroseismic study of the early red-giant star KIC 4448777, complementing and integrating a previous work, aimed at characterizing the dynamics of its interior by analyzing the overall set of data collected by the Kepler satellite during the four years of its first nominal mission. We adopted the Bayesian inference code diamonds for the peak bagging analysis and asteroseismic splitting inversion methods to derive the internal rotational profile of the star. The detection of new splittings of mixed modes, which are more concentrated in the very inner part of the helium core, allowed us to reconstruct the angular velocity profile deeper into the interior of the star and to disentangle the details better than in Paper I: the helium core rotates almost rigidly about 6 times faster than the convective envelope, while part of the hydrogen shell seems to rotate at a constant velocity about 1.15 times lower than the He core. In particular, we studied the internal shear layer between the fast-rotating radiative interior and the slow convective zone and we found that it lies partially inside the hydrogen shell above r ≃ 0.05R and extends across the core–envelope boundary. Finally, we theoretically explored the possibility for the future capabilty to sound the convective envelope in the red-giant stars and we concluded that the inversion of a set of splittings with only low-harmonic degree l ≤ 3, even supposing a very large number of modes, will not allow us to resolve the rotational profile of this region in detail.