The Impact of Metallicity on the Evolution of the Rotation and Magnetic Activity of Sun-like Stars
The Impact of Metallicity on the Evolution of the Rotation and Magnetic Activity of Sun-like Stars
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DOI：
10.3847/1538-4357/ab6173
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发表时间：
2020-02-01
影响因子：
4.9
通讯作者：
Matt, Sean P.
中科院分区：
文献类型：
--
作者：
Amard, LouisY;Matt, Sean P.
已知类太阳和低质量（小于或接近1.4 M）主序星的自转速率和磁活动会随时间而下降，现在有几种模型可以解释自转和活动的演化。然而，化学成分在恒星自旋下降过程中所起的作用尚未被探索。在这项工作中，我们使用结构演化代码来计算三种不同质量（0.7，1.0和1.3 M）和六种不同金属丰度的恒星的旋转演化，范围从[Fe/H] = -1.0到[Fe/H] =+0.5。我们还实施了文献中的三种不同的风制动公式（两种现代公式和一种经典公式），并比较了它们对旋转演化的预测。金属丰度对恒星结构性质的影响，特别是对流周转时间尺度，导致两个现代风制动配方预测的扭矩金属丰度的强烈依赖。因此，他们预测富含金属的恒星在晚期（大于或接近1 Gyr）比缺乏金属的恒星更有效地自旋下降，并且这种影响足够大，可以用现有的观测设施检测到。例如，该公式预测，一颗[Fe/H] = -0.3的类太阳（太阳质量和太阳年龄）星星的自转周期将小于20天。尽管老的、贫金属的恒星被预测在给定的年龄旋转得更快，但它们有更大的罗斯比数，因此预计具有更低的磁活动水平。最后，不同的风制动公式预测恒星旋转的金属丰度依赖的定量差异，这可能是用来测试它们。
The rotation rates and magnetic activity of Sun-like and low-mass (less than or similar to 1.4M) main-sequence stars are known to decline with time, and there now exist several models for the evolution of rotation and activity. However, the role that chemical composition plays during stellar spin-down has not yet been explored. In this work, we use a structural evolution code to compute the rotational evolution of stars with three different masses (0.7, 1.0, and 1.3 M) and six different metallicities, ranging from [Fe/H] = -1.0 to [Fe/H] = +0.5. We also implement three different wind-braking formulations from the literature (two modern and one classical) and compare their predictions for rotational evolution. The effect that metallicity has on stellar structural properties, and in particular the convective turnover timescale, leads the two modern wind-braking formulations to predict a strong dependence of the torque on metallicity. Consequently, they predict that metal-rich stars spin down more effectively at late ages (greater than or similar to 1 Gyr) than metal-poor stars, and the effect is large enough to be detectable with current observing facilities. For example, the formulations predict that a Sun-like (solar-mass and solar-aged) star with [Fe/H] = -0.3 will have a rotation period of less than 20 days. Even though old, metal-poor stars are predicted to rotate more rapidly at a given age, they have larger Rossby numbers and are thus expected to have lower magnetic activity levels. Finally, the different wind-braking formulations predict quantitative differences in the metallicity dependence of stellar rotation, which may be used to test them.