发表机构
Kavli Institute for Theoretical Physics, University of California, Santa Barbara; Department of Astrophysical Sciences, Princeton University; Department of Physics, University of California, Santa Barbara; Center for Computational Astrophysics, Flatiron Institute（加州大学圣塔芭芭拉分校卡弗里理论物理研究所; 普林斯顿大学天体科学系; 加州大学圣塔芭芭拉分校物理系; 西蒙斯平顿研究所计算天体物理中心）
机构由 AI 辅助整理，请以论文原文为准。AI 中文总结
通过三维辐射流体动力学模拟，发现蓝超巨星外包层对流直接延伸至光球层，产生与观测一致的宏观湍流速度场及随机低频光度变化。
AI 中文摘要
我们首次对蓝超巨星的外包层进行了三维辐射流体动力学模拟。这些位于赫氏空隙中接近爱丁顿极限的大质量恒星表现出显著的光度变化，其光谱线宽显示出无法解释的大尺度湍流速度场。我们的Athena++模拟发现，与铁的不透明度峰值相关的对流直接延伸到光球层，这与先前对大质量主序星的三维模拟结果一致。与一维恒星模型不同，这个单一对流区域产生的速度场与光谱学中的宏观湍流模型相符。此外，最外层中的对流导致如此大的密度变化，使得逃逸辐射在大幅度（≲10%）和短时间尺度（约数天）上变化。这导致了随机低频（SLF）光度变化，其振幅和功率谱与观测结果大致相符。
英文摘要
We present the first 3D radiation hydrodynamical simulation of the outer envelope of a blue supergiant. These near Eddington limited massive stars in the Hertzsprung gap exhibit substantial photometric variability and have spectroscopic line widths indicating unexplained macroturbulent velocity fields. Our Athena++ simulations find that the convection associated with the opacity peak from iron directly extends to the photosphere, as found in previous 3D simulations of massive main sequence stars. Unlike 1D stellar models, this single convecting region imprints a velocity field that is consistent with spectroscopic models of macroturbulence. In addition, the convection in the outermost layer leads to such large density variations that the exiting radiation varies on large ($\lesssim 10 \% $) amplitudes and short ($\sim$ days) timescales. This leads to stochastic low frequency (SLF) photometric variability, with amplitudes and power spectra broadly consistent with observations.
CommentsSubmitted to ApJ. For a cool movie, see https://www.astro.princeton.edu/~lm2265/movies/bsg.mp4
