Asteroseismology of the dip structure in period-spacings of rapidly rotating γ Doradus stars caused by the coupling between core and envelope oscillations
Asteroseismology of the dip structure in period-spacings of rapidly rotating γ Doradus stars caused by the coupling between core and envelope oscillations
复制标题
由核心和包络振荡耦合引起的快速旋转 γ 剑鱼座星周期间距倾角结构的星震学
DOI：
10.1093/mnras/stac1492
复制
发表时间：
2022
影响因子：
4.8
通讯作者：
Masao
中科院分区：
文献类型：
--
作者：
Tokuno;Takato ; Takata;Masao
最近由开普勒太空任务进行的恒星地震观测揭示了快速旋转的γ剑鱼座恒星的周期间隔与周期图中的倾角精细结构。在前人通过数值计算成功再现倾角结构的基础上，本文提出了辐射包层中的重力惯性波与对流核中的纯惯性波相互作用形成倾角的物理机制。我们解析地描述了辐射包络和对流核心中的波解，并在界面上匹配它们来构造本征模。通过分析我们发现：倾角结构主要受一个与界面Brunt-VäisäLä频率成反比的参数控制；倾角的深度和宽度随着参数的增大而变浅和变宽；倾角的形状可以用洛伦兹函数来近似；倾角中心位置的周期等于或略小于对流核心中所涉及的纯惯性模的周期。根据主序星的演化模型，我们还了解到，该参数与对流核心边界的化学成分梯度成反比。因此，DIP结构将提供关于对流核心和辐射包层之间边界周围的扩散、对流超射和旋转混合等鲜为人知的物理过程的信息。
Recent asteroseismic observations by theKeplerspace mission have revealed the dip fine structure in the period-spacing versus period diagram of rapidly rotating γ Doradus stars. Following the successful reproduction of the dip structure by numerical calculations in previous studies, we present in this paper the physical mechanism of how the dip is formed as a result of the interaction between the gravito-inertial waves in the radiative envelope and the pure inertial waves in the convective core. We analytically describe the wave solutions in both of the radiative envelope and the convective core, and match them at the interface to construct an eigenmode. We have found from the analysis the following points: the dip structure is mainly controlled by a parameter that has an inverse correlation with Brunt–Väisälä frequency at the interface; the depth and the width of the dip is shallower and larger, respectively, as the parameter gets large; the shape of the dip can be approximated by the Lorentzian function; the period at the central position of the dip is equal to or slightly smaller than that of the involved pure inertial mode in the convective core. We have also understood based on the evolutionary models of main-sequence stars that the parameter is inversely correlated with the chemical composition gradient at the convective-core boundary. The dip structure thus would provide information about the poorly-understood physical processes, such as diffusion, convective overshooting and rotational mixing, around the boundary between the convective core and the radiative envelope.