arXiv 2201.089432022-01astro-ph.GA

考察AGN在简单阻尼随机游走之外的紫外/光学变化

Examining AGN UV/optical Variability Beyond the Simple Damped Random Walk

Weixiang Yu, Gordon T. Richards, Michael S. Vogeley, Jackeline Moreno, Matthew J. Graham

备注：: 26 pages, 14 figures, revised after referee report, accepted for publication in ApJ
DOI：: 10.3847/1538-4357/ac8351

摘要：

我们提出了阻尼谐振子（DHO）的光变曲线建模的样本12,714光谱确认类星体在斯隆数字巡天条纹82区域。DHO是一个二阶连续时间自回归移动平均（CARMA）过程，它可以用四个独立的参数完全描述：自然振荡频率（$ω_{0}$）、阻尼比（$ξ$）、特征扰动时标（$τ_{\mathrm{perturb}}$）和扰动白噪声的幅度（$σ_{\mathrmε}$）。DHO过程的渐近变异幅度由$σ_{\mathrm{DHO}}$量化--$ω_{0}$、$ξ$、$τ_{\mathrm{perturb}}$和$σ_{\mathrmε}$的函数。我们发现，无论是$τ_{\mathrm{perturb}}$和$σ_{\mathrmε}$遵循不同的依赖关系与休息帧波长（$λ_{\mathrm{RF}}$）的两侧2500毫微米，而$σ_{\mathrm{DHO}}$遵循单一的幂律关系与$λ_{\mathrm{RF}}$。在校正了波长依赖性之后，$σ_{\mathrm{DHO}}$与爱丁顿比和黑洞质量都表现出反相关性，而$τ_{\mathrm{perturb}}$ --在静止坐标系中具有典型的天数值--与热光度表现出反相关性。将活动星系核变率模拟为DHO提供了对活动星系核中心靠近超大质量黑洞（SMBH）的吸积盘工作的更多了解。新发现的短期可变性（以$τ_{\mathrm{perturb}}$和$σ_{\mathrmε}$为特征）及其与热光度的相关性为新算法铺平了道路，该算法将导出基本属性（例如，爱丁顿比）。

英文摘要：

We present damped harmonic oscillator (DHO) light-curve modeling for a sample of 12,714 spectroscopically confirmed quasars in the Sloan Digital Sky Survey Stripe 82 region. DHO is a second-order continuous-time autoregressive moving-average (CARMA) process, which can be fully described using four independent parameters: a natural oscillation frequency ($ω_{0}$), a damping ratio ($ξ$), a characteristic perturbation timescale ($τ_{\mathrm{perturb}}$), and an amplitude for the perturbing white noise ($σ_{\mathrmε}$). The asymptotic variability amplitude of a DHO process is quantified by $σ_{\mathrm{DHO}}$ -- a function of $ω_{0}$, $ξ$, $τ_{\mathrm{perturb}}$, and $σ_{\mathrmε}$. We find that both $τ_{\mathrm{perturb}}$ and $σ_{\mathrmε}$ follow different dependencies with rest-frame wavelength ($λ_{\mathrm{RF}}$) on either side of 2500 Å, whereas $σ_{\mathrm{DHO}}$ follows a single power-law relation with $λ_{\mathrm{RF}}$. After correcting for wavelength dependence, $σ_{\mathrm{DHO}}$ exhibits anti-correlations with both the Eddington ratio and the black hole mass, while $τ_{\mathrm{perturb}}$ -- with a typical value of days in the rest-frame -- shows an anti-correlation with the bolometric luminosity. Modeling AGN variability as a DHO offers more insight into the workings of accretion disks close to the supermassive black holes (SMBHs) at the center of AGN. The newly discovered short-term variability (characterized by $τ_{\mathrm{perturb}}$ and $σ_{\mathrmε}$) and its correlation with bolometric luminosity pave the way for new algorithms that will derive fundamental properties (e.g., Eddington ratio) of AGN using photometric data alone.

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