标题： 使用三维多频磁流体力学模拟研究活动星系核吸积盘紫外辐射区的X射线回波效应 显示英文标题

标题： Simulating X-ray Reverberation in the UV-Emitting Regions of Active Galactic Nuclei Accretion Disks with 3D Multi-Frequency Magnetohydrodynamic Simulations

摘要： 活动星系核（AGN）在不同波段观测到的光变曲线表明，较长波长的光变相对于较短波长的光变存在滞后现象。 测量这些滞后时间，即回声映射，用于测量AGN盘的径向温度分布和范围，通常采用重新处理模型，该模型假设X射线是其他波段光变的主要驱动因素。 为了展示这种重新处理如何在实际吸积盘结构下工作，我们使用三维局部剪切盒多频辐射磁流体力学（MHD）模拟来建模AGN盘的紫外线发射区域，该区域不稳定于磁旋转不稳定性（MRI）和对流。 同时，我们将硬X射线（$>1$keV）注入模拟框以研究X射线照射对湍流局部特性以及由此产生的发射紫外线光变曲线的影响。 我们发现盘湍流足以驱动发射紫外线光变曲线的固有变化，并且对于时间尺度$>5$天，阻尼随机游走（DRW）模型很好地拟合了这一紫外线光变曲线。 同时，注入的X射线几乎不会影响发射紫外线光变曲线的功率谱。 此外，只有当存在时间尺度$>1$天的X射线变异性时，注入的X射线和发射的紫外线光变曲线才相关，在这种情况下，我们发现相关系数为$r=0.52$。 这些结果表明，主要由散射主导的吸收截面的硬X射线很可能不是回声信号的主要驱动因素。 显示英文摘要

摘要： Active galactic nuclei (AGN) light curves observed with different wavebands show that the variability in longer wavelength bands lags the variability in shorter wavelength bands. Measuring these lags, or reverberation mapping, is used to measure the radial temperature profile and extent of AGN disks, typically with a reprocessing model that assumes X-rays are the main driver of the variability in other wavelength bands. To demonstrate how this reprocessing works with realistic accretion disk structures, we use 3D local shearing box multi-frequency radiation magnetohydrodynamic (MHD) simulations to model the UV-emitting region of an AGN disk, which is unstable to the magnetorotational instability (MRI) and convection. At the same time, we inject hard X-rays ($>1$~keV) into the simulation box to study the effects of X-ray irradiation on the local properties of the turbulence and the resulting variability of the emitted UV light curve. We find that disk turbulence is sufficient to drive intrinsic variability in emitted UV light curves and that a damped random walk (DRW) model is a good fit to this UV light curve for timescales $>5$~days. Meanwhile, the injected X-rays have almost no impact on the power spectrum of the emitted UV light curve. In addition, the injected X-ray and emitted UV light curves are only correlated if there is X-ray variability on timescales $>1$~day, in which case we find a correlation coefficient $r=0.52$. These results suggest that hard X-rays with scattering dominated opacity are likely not the main driver of the reverberation signals.