恒星大气超绝热层中渐近熵跃变的标度
Scaling of the asymptotic entropy jump in the superadiabatic layers of stellar atmospheres
摘要：
恒星结构计算能够精确预测恒星演化过程中的性质。然而，对流仍然是模拟的混合长度理论，因此，光学表面附近的上边界条件不同意与asteroseisic观测。我们希望改进恒星结构计算中确定外边界条件的方法。我们研究现实的3D恒星大气模型，以找到替代属性。我们发现，渐近熵运行的超绝热对流表面层表现出明显的普遍分层时，归一化的熵最小值和跳跃。归一化熵可以非常精确地由5阶多项式表示，并且3阶多项式也产生精确的系数。这种通用的熵分层或太阳分层，当缩放的熵跳跃和最小值，可以用来改善模拟的超绝热表面层的恒星结构计算。此外，这一发现表明，表面对流对所有冷恒星的作用方式都是相同的，但需要进一步研究，以提高我们对恒星大气的理解。
英文摘要：
Stellar structure calculations are able to predict precisely the properties of stars during their evolution. However, convection is still modelled by the mixing length theory; therefore, the upper boundary conditions near the optical surface do not agree with asteroseismic observations. We want to improve how the outer boundary conditions are determined in stellar structure calculations. We study realistic 3D stellar atmosphere models to find alternative properties. We find that the asymptotic entropy run of the superadiabatic convective surface layers exhibit a distinct universal stratification when normalised by the entropy minimum and jump. The normalised entropy can be represented by a 5th order polynomial very accurately, and a 3rd order polynomial also yields accurate coefficients. This generic entropy stratification or the solar stratification, when scaled by the entropy jump and minimum, can be used to improve the modelling of superadiabatic surface layers in stellar structure calculations. Furthermore, this finding indicates that surface convection operates in the same way for all cool stars, but requires further scrutiny in order to improve our understanding of stellar atmospheres.
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