The structured winds of single massive stars can be classified into two broad groups: stochastic structure and organized structure. While the former is typically identified with clumping, the latter is typically associated with rotational modulations, particularly the paradigm of Co-rotating Interaction Regions (CIRs). While CIRs have been explored extensively in the UV band, and moderately in the X-ray and optical, here we evaluate radio variability from CIR structures assuming free-free opacity in a dense wind. Our goal is to conduct a broad parameter study to assess the observational feasibility, and to this end, we adopt a phenomenological model for a CIR that threads an otherwise spherical wind. We find that under reasonable assumptions, it is possible to obtain radio variability at the 10% level. The detailed structure of the folded light curve depends not only on the curvature of the CIR, the density contrast of the CIR relative to the wind, and viewing inclination, but also on wavelength. Comparing light curves at different wavelengths, we find that the amplitude can change, that there can be phase shifts in the waveform, and the the entire waveform itself can change. These characterstics could be exploited to detect the presence of CIRs in dense, hot winds.

中文翻译：

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来自沃尔夫-拉叶风的共转相互作用区域的无线电变异性

单个大质量恒星的结构风可以分为两大类：随机结构和有组织结构。虽然前者通常与结块有关，但后者通常与旋转调制相关，特别是同向旋转相互作用区域 (CIR) 的范式。虽然 CIR 在 UV 波段中得到了广泛的探索，并且在 X 射线和光学中进行了适度的探索，但我们在这里评估了 CIR 结构的无线电可变性，假设在浓密的风中没有自由不透明度。我们的目标是进行广泛的参数研究，以评估观测可行性，为此，我们采用了 CIR 的现象学模型，该模型将其他球形风穿线。我们发现，在合理的假设下，有可能获得 10% 水平的无线电可变性。折叠光曲线的详细结构不仅取决于 CIR 的曲率、CIR 相对于风的密度对比度和观看倾斜度，还取决于波长。比较不同波长的光变曲线，我们发现幅度可以改变，波形中可以有相移，整个波形本身也可以改变。可以利用这些特征来检测密集热风中 CIR 的存在。