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arXiv 2104.04531astro-ph.SR
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探测具有重力惯性模的恒星核边界层中的温度梯度:KIC $\,$ 7760680的情况

Probing the temperature gradient in the core boundary layer of stars with gravito-inertial modes: the case of KIC$\,$7760680

M. Michielsen, C. Aerts, D. M. Bowman

摘要:

目的:利用重力惯性模研究具有对流核的恒星近核区的热结构和化学结构。我们这样做是通过确定不同的小行星地震观测和拟合方法的探测功率。我们集中在B型恒星KIC $\,$ 7760680的情况下,旋转的四分之一的临界转速。研究方法:我们计算网格的一维恒星结构和演化模型的两个不同处方的温度梯度和混合剖面在近核心区域。我们根据KIC $\,$ 7760680的4年$\textit{Kepler}$光度测定中检测到的双极模式确定这些处方中的哪一种是首选。我们考虑不同的一套asteroseismic观测值和比较结果的回归问题的$χ^2$和Mahalanobis距离的价值函数,后者考虑到现实的不确定性的理论预测和前者没有。结果如下:连续径向顺序的模式的周期间隔提供了一个更好的诊断比模式周期或模式频率的asteroseismic模拟的恒星只揭示高阶重力惯性模式。我们发现KIC $\,$ 7760680揭示了对流边界混合模型中的辐射温度梯度,但不太复杂的模型,没有这种混合统计上的首选旋转星,揭示了极低的垂直信封混合。结论:我们的研究结果强烈建议使用连续径向顺序的模式作为asteroseisic诊断恒星建模的B-型的重力惯性模式的embritator的测量的个人周期间隔值。

英文摘要:

Aims: We investigate the thermal and chemical structure in the near-core region of stars with a convective core by means of gravito-inertial modes. We do so by determining the probing power of different asteroseismic observables and fitting methodologies. We focus on the case of the B-type star KIC$\,$7760680, rotating at a quarter of its critical rotation velocity. Methods: We compute grids of 1D stellar structure and evolution models for two different prescriptions of the temperature gradient and mixing profile in the near-core region. We determine which of these prescriptions is preferred according to the prograde dipole modes detected in 4-yr $\textit{Kepler}$ photometry of KIC$\,$7760680. We consider different sets of asteroseismic observables and compare the outcomes of the regression problem for a $χ^2$ and Mahalanobis Distance merit function, where the latter takes into account realistic uncertainties for the theoretical predictions and the former does not. Results: Period spacings of modes with consecutive radial order offer a better diagnostic than mode periods or mode frequencies for asteroseismic modelling of stars revealing only high-order gravito-inertial modes. We find KIC$\,$7760680 to reveal a radiative temperature gradient in models with convective boundary mixing, but less complex models without such mixing are statistically preferred for this rotating star, revealing extremely low vertical envelope mixing. Conclusions: Our results strongly suggest the use of measured individual period spacing values for modes of consecutive radial order as an asteroseismic diagnostic for stellar modelling of B-type pulsators with gravito-inertial modes.

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