发表机构
College of Charleston; Center for Computational Astrophysics, Flatiron Institute; Lawrence Livermore National Laboratory; University of California, Merced; St. Paul’s School（查尔斯顿学院; 平顿研究所计算天体物理中心; 劳伦斯利弗莫尔国家实验室; 加州大学默塞德分校; 圣保罗学校）
机构由 AI 辅助整理，请以论文原文为准。AI 中文总结
本研究利用Cosmos++模拟磁稳定薄吸积盘的偏振与法拉第旋转，发现其效应适中，可产生≥4%偏振度，并能匹配Cyg X-1的IXPE观测偏振度，但偏振角存在约90°偏差。
AI 中文摘要
我们利用Cosmos++的蒙特卡洛辐射输运能力，探索了一组磁稳定、薄黑洞吸积盘的广义相对论辐射磁流体动力学模拟所发射辐射的偏振和法拉第旋转。核心问题是法拉第旋转是否会使辐射退偏振到与成像X射线偏振探测仪（IXPE）测量的较高偏振度不一致的程度。在首先确认我们的代码能够重现电子云、平面散射大气和活动星系核（AGN）盘的预期偏振结果之后，我们使用带有纯环向磁场的Novikov-Thorne盘展示了偏振和法拉第旋转能力。然后，我们分析了三种不同磁场构型的发光薄吸积盘模拟的时间快照。我们发现，在感兴趣的能量范围内，法拉第旋转的影响通常适中，因为这些模拟中存在的最强磁场（≳10^8 G）大多隐藏在光球之下。对于主要侧向观测的源，我们可以轻松产生≥4%的偏振度。作为一个相关目标的例子，我们将结果与Cyg X-1的IXPE观测进行比较，发现我们可以很好地匹配偏振度，尽管我们的偏振角相对于观测数据旋转了约90°。我们推测了这可能的几种解释。
英文摘要
We utilize the Monte Carlo radiation transport capabilities of Cosmos++ to explore the polarization and Faraday rotation of radiation emitted from a set of general relativistic radiation magnetohydrodynamic simulations of magnetically stabilized, thin, black hole accretion disks. The guiding question is whether or not the Faraday rotation depolarizes the radiation to such a degree as to be inconsistent with the relatively high polarization measurements coming from the Imaging X-ray Polarimetry Explorer (IXPE). After first confirming that our code reproduces expected polarization results for electron clouds, planar scattering atmospheres, and AGN disks, we demonstrate the polarization and Faraday rotation capabilities using a Novikov-Thorne disk threaded with a purely toroidal magnetic field. We then analyze temporal snapshots from three different simulations of luminous, thin accretion disks threaded with different magnetic field configurations. We find that the effects of Faraday rotation are generally modest over the energy range of interest, since the strongest fields present in these simulations ($\gtrsim 10^8$ G) are mostly hidden beneath the photosphere. We can easily produce polarization degrees $\ge 4$\% for sources seen mostly edge-on. As one example of a relevant target, we compare our results to an IXPE observation of Cyg X-1, finding that we can match the polarization degree quite well, though our polarization angle is rotated approximately $90^\circ$ with respect to the observed data. We speculate on a few possible explanations for this.
Comments20 pages, 13 figures, to appear in Astrophysical Journal
