THE ROLE OF THE MAGNETOROTATIONAL INSTABILITY IN MASSIVE STARS
THE ROLE OF THE MAGNETOROTATIONAL INSTABILITY IN MASSIVE STARS
复制标题
磁旋转不稳定性在大质量恒星中的作用
DOI：
10.1088/0004-637x/799/1/85
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发表时间：
2014
期刊：
影响因子：
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通讯作者：
E. Chatzopoulos
中科院分区：
文献类型：
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作者：
J. Wheeler;D. Kagan;E. Chatzopoulos
磁旋转不稳定性（MRI）是吸积盘物理学的关键，并被广泛认为在大规模星核塌陷中发挥了一定作用。旋转大质量恒星的模型自然会在成分边界处产生非常强的剪切力，这是 MRI 不稳定的必要条件，并且 MRI 在辐射区域会受到三重扩散不稳定效应的影响。我们使用 MESA 恒星演化代码来计算大质量恒星模型样本中由 Spruit-Tayler (ST) 机制和 MRI 引起的磁效应，分别或一起计算。我们发现 MRI 在大质量恒星演化的后期阶段可能很活跃，从而导致忽略 MRI 的模型中无法捕捉到的混合效应。 MRI和相关的磁旋转效应可以将给定的零年龄主序质量模型跨越“边界”从简并CO核心移动到简并O/Ne/Mg核心，从简并O/Ne/Mg核心移动到铁核心，从而影响最终的演化和核心塌陷的物理过程。单独使用 MRI 可以减缓内核的旋转，与观测到的脉冲星“初始”旋转速率基本一致。 MRI 分析表明，铁芯边界处可能存在约 1012 G 的局部磁场。由于 ST 和 MRI 机制在 20 M☉ 模型中都处于活动状态，我们发现氦壳完全混合到包膜中。增强混合可能会产生一群黄色甚至蓝色超巨星超新星前身，这不是标准的 SN IIP。
The magnetorotational instability (MRI) is key to physics in accretion disks and is widely considered to play some role in massive star core collapse. Models of rotating massive stars naturally develop very strong shear at composition boundaries, a necessary condition for MRI instability, and the MRI is subject to triply diffusive destabilizing effects in radiative regions. We have used the MESA stellar evolution code to compute magnetic effects due to the Spruit–Tayler (ST) mechanism and the MRI, separately and together, in a sample of massive star models. We find that the MRI can be active in the later stages of massive star evolution, leading to mixing effects that are not captured in models that neglect the MRI. The MRI and related magnetorotational effects can move models of given zero-age main sequence mass across “boundaries” from degenerate CO cores to degenerate O/Ne/Mg cores and from degenerate O/Ne/Mg cores to iron cores, thus affecting the final evolution and the physics of core collapse. The MRI acting alone can slow the rotation of the inner core in general agreement with the observed “initial” rotation rates of pulsars. The MRI analysis suggests that localized fields ∼1012 G may exist at the boundary of the iron core. With both the ST and MRI mechanisms active in the 20 M☉ model, we find that the helium shell mixes entirely out into the envelope. Enhanced mixing could yield a population of yellow or even blue supergiant supernova progenitors that would not be standard SN IIP.