活动星系核中超大质量双黑洞的搜寻：连续谱特征与周期性变化
A Population Study for Searching Supermassive Binary Black Holes in Active Galactic Nuclei: Continuum Spectral Features and Periodic Variabilities
AI总结：
本文构建种群模型，通过半解析方法研究活动星系核中超大质量双黑洞的SED缺失与周期性特征，发现联合探测可降低误报，相关巡天或脉冲星计时阵列可识别大量此类黑洞。
AI中文摘要：
活跃的亚pc尺度超大质量双黑洞（SMBBHs）因其独特的吸积动力学与几何结构，预计会呈现多种电磁信号，但对其进行观测识别仍具挑战性。本文采用半解析模型，研究两类特征：一是由吸积盘间隙/空洞引发的系统光谱能量分布（SED）缺失，二是由轨道调制多普勒增强或每个SMBBH组分的吸积率变化引发的光变曲线周期性变化。我们构建了一个种群模型，结合SMBBHs的轨道演化及相关吸积、辐射过程，生成宇宙时间内的SMBBHs样本。通过估算每个模拟系统的连续谱发射及其变化，我们在合理给定的判据下，研究通过SED缺失特征或光变曲线周期性来探测SMBBHs的可行性。研究发现，配备类似中国空间站望远镜或鲁宾/LSST（空间和时间遗产巡天望远镜）滤光片的全天巡天，可通过SED缺失特征识别出约3×10²个SMBBHs，或通过周期性（周期≤5年）识别出约10³个SMBBHs，尽管两种选择均可能面临较高的误报率。未来脉冲星计时阵列以信噪比≥3探测，可能发现数个至十余个SED缺失型SMBBHs，从而实现多信使观测。约20%–53%的SED缺失选择的SMBBHs也可通过周期性变化被探测，约7%–9%的周期性变化选择的SMBBHs可通过SED缺失特征被探测。两种方法联合选择的SMBBHs的误报可忽略不计，凸显了使用联合方法搜寻活跃SMBBH系统的重要性。
英文摘要：
Active sub-pc supermassive binary black holes (SMBBHs) are expected to exhibit various electromagnetic signatures due to unique dynamical and geometric structures of their accretion, but observational identification of them remains challenging. In this paper, we adopt semianalytic models to investigate both deficits in spectral-energy-distributions (SEDs) of these systems induced by gaps/holes in their accretion disks and periodic variations in their light curves induced by either orbital-modulated Doppler boosting or accretion rate variation of each SMBH component. We construct a population model to generate SMBBHs across cosmic time by considering their orbital evolution and associated accretion and radiation processes. By estimating the continuum emission from each mock system and its variation, we investigate the detection of SMBBHs via either SED-deficit signature or light curve periodicity under reasonably given criteria. We find that all-sky surveys with filters similar to those of the China Space Station Telescope or Rubin/LSST could identify up to approximately $3\times 10^2$ SMBBHs via SED-deficit features and/or $10^3$ SMBBHs via periodicity ($\lesssim5$\,yr), although both selections may suffer from a high rate of false positives. A few to a dozen SED-deficit SMBBHs may be detected by future pulsar timing arrays with signal-to-noise ratio $\gtrsim3$, enabling multi-messenger observations. Only $\sim20\%-53\%$ of SED-deficit selected SMBBHs may also be detected via periodic variations, and $\sim7\%-9\%$ of periodic variation selected SMBBHs may be detected via SED-deficit signatures. The false positives for those SMBBHs selected jointly by both methods are negligible, highlighting the importance of searching for active SMBBH systems using joint methods.
