Title: Universality in the Random Walk Structure Function of Luminous Quasi-Stellar Objects Show Chinese title

Title: 发光类星体随机行走结构函数的普遍性

Abstract: Rapidly growing black holes are surrounded by accretion disks that make them the brightest objects in the Universe. Their brightness is known to be variable, but the causes of this are not implied by simple disk models and still debated. Due to the small size of accretion disks and their great distance, there are no resolved images addressing the puzzle. In this work, we study the dependence of their variability on luminosity, wavelength and orbital/thermal timescale. We use over 5,000 of the most luminous such objects with light curves of almost nightly cadence from $>5$ years of observations by the NASA/ATLAS project, which provides 2 billion magnitude pairs for a structure function analysis. When time is expressed in units of orbital or thermal time scale in thin-disk models, we find a universal structure function, independent of luminosity and wavelength, supporting the model of magneto-rotational instabilities as a main cause. Over a $>1$~dex range in time, the fractional variability amplitude follows $\log (A/A_0) \simeq 1/2 \times \log (\Delta t/t_{\rm th})$. Deviations from the universality may hold clues on the structure and orientation of disks. Show Chinese abstract

Abstract: 快速增长的黑洞被吸积盘包围，使它们成为宇宙中最明亮的天体。 它们的亮度已知是变化的，但这种变化的原因并不由简单的盘模型所暗示，仍然存在争议。 由于吸积盘尺寸小且距离遥远，没有解析图像能解决这个谜题。 在本研究中，我们研究了它们的变异性与光度、波长和轨道/热时标之间的依赖关系。 我们使用了超过5000个最明亮的此类天体，这些天体来自NASA/ATLAS项目$>5$年的观测，具有几乎每晚的光曲线，该项目提供了20亿个星等对用于结构函数分析。 当时间以薄盘模型中的轨道或热时标单位表示时，我们发现了一个与光度和波长无关的通用结构函数，支持磁旋转不稳定性作为主要原因的模型。 在时间范围约$>1$个数量级内，分数变异性幅度遵循$\log (A/A_0) \simeq 1/2 \times \log (\Delta t/t_{\rm th})$。 对普遍性的偏离可能揭示了盘结构和取向的线索。