The effects of surface fossil magnetic fields on massive star evolution – II. Implementation of magnetic braking in mesa and implications for the evolution of surface rotation in OB stars
The effects of surface fossil magnetic fields on massive star evolution – II. Implementation of magnetic braking in mesa and implications for the evolution of surface rotation in OB stars
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DOI：
10.1093/mnras/staa237
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发表时间：
2020-01
影响因子：
4.8
通讯作者：
Z. Keszthelyi;Z. Keszthelyi;Z. Keszthelyi;G. Meynet;M. Shultz;A. David-Uraz;A. ud-Doula;R. Townse
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作者：
Z. Keszthelyi;Z. Keszthelyi;Z. Keszthelyi;G. Meynet;M. Shultz;A. David-Uraz;A. ud-Doula;R. Townse
大质量恒星的角动量和表面自转的时间演化受化石磁场通过磁制动的强烈影响。我们提出了一个新的模块，在恒星天体物理实验(MESA)软件仪器的模块中，包含了一个简单、全面的大质量恒星表面场的实现。我们测试了磁制动的两种限制方案：第一种情况下，角动量损失分布在整个恒星上，第二种情况下，将角动量损失限制在表面储存库中。我们用表面磁场(M⋆=5-60M⊙，Ω/ΩCRIT=0.2-1.0，BP=1-2 0 kg)的OB星模型网格系统地研究了自转演化。然后，我们使用具有代表性的B型恒星模型网格(M⋆=5，10，15M⊙，Ω/ΩCrit=0.2，0.5，0.8，BP=1，3，10，30 kg)来与最近对已知磁性B型恒星样本的自洽分析的结果进行比较。我们推断，磁性大质量恒星到达零年龄主序列(ZAMS)时，自转速度是一定范围的，而不是一个共同值。特别是，一些恒星被要求在ZAMS进行接近临界的自转。然而，磁制动产生的表面自转速度收敛到一个常见的低值，这使得很难推断进化中的缓慢自转恒星的初始自转速度。
The time evolution of angular momentum and surface rotation of massive stars are strongly influenced by fossil magnetic fields via magnetic braking. We present a new module containing a simple, comprehensive implementation of such a field at the surface of a massive star within the Modules for Experiments in Stellar Astrophysics (mesa) software instrument. We test two limiting scenarios for magnetic braking: distributing the angular momentum loss throughout the star in the first case, and restricting the angular momentum loss to a surface reservoir in the second case. We perform a systematic investigation of the rotational evolution using a grid of OB star models with surface magnetic fields (M⋆ = 5–60 M⊙, Ω/Ωcrit = 0.2–1.0, Bp = 1–20 kG). We then employ a representative grid of B-type star models (M⋆ = 5, 10, 15 M⊙, Ω/Ωcrit = 0.2, 0.5, 0.8, Bp = 1, 3, 10, 30 kG) to compare to the results of a recent self-consistent analysis of the sample of known magnetic B-type stars. We infer that magnetic massive stars arrive at the zero-age main sequence (ZAMS) with a range of rotation rates, rather than with one common value. In particular, some stars are required to have close-to-critical rotation at the ZAMS. However, magnetic braking yields surface rotation rates converging to a common low value, making it difficult to infer the initial rotation rates of evolved, slowly rotating stars.