标题： 用X射线反射光谱测量黑洞自转：GRMHD的视角 显示英文标题

标题： Measuring black hole spins with X-ray reflection spectroscopy: A GRMHD outlook

摘要： X射线反射光谱学已成为测量黑洞自旋的领先方法之一。 然而，问题是其测量结果是否受到系统性偏差的影响，尤其是在考虑这种技术推断的自旋与引力波观测结果之间可能存在差异的情况下。 在本研究中，我们使用围绕旋转黑洞的薄吸积盘的广义相对论磁流体动力学（GRMHD）模拟来建模吸积过程，然后模拟NuSTAR观测以测试现代反射模型恢复输入自旋的能力。 首次，我们从GRMHD模拟的盘中建模电子密度和电离度分布。 我们的研究发现，当前的反射模型仅在快速旋转的黑洞上表现良好。 我们将日冕建模为喷流的基底，并发现具有灯柱发射率分布的反射模型无法恢复正确的黑洞自旋。 具有分段幂律发射率分布的反射模型表现更好。 随着模拟模型复杂性的增加，恢复正确输入自旋变得更加困难，这表明需要使用更先进的吸积盘和日冕几何结构来更新我们当前的反射模型。 显示英文摘要

摘要： X-ray reflection spectroscopy has evolved as one of the leading methods to measure black hole spins. However, the question is whether its measurements are subjected to systematic biases, especially considering the possible discrepancy between the spin measurements inferred with this technique and those from gravitational wave observations. In this work, we use general relativistic magnetohydrodynamic (GRMHD) simulations of thin accretion disks around spinning black holes for modeling the accretion process, and then we simulate NuSTAR observations to test the capability of modern reflection models in recovering the input spins. For the first time, we model the electron density and ionization profiles from GRMHD-simulated disks. Our study reveals that current reflection models work well only for fast-rotating black holes. We model the corona as the base of the jet and we find that reflection models with lamppost emissivity profiles fail to recover the correct black hole spins. Reflection models with broken power-law emissivity profiles perform better. As we increase the complexity of the simulated models, it is more difficult to recover the correct input spins, pointing towards the need to update our current reflection models with more advanced accretion disks and coronal geometries.