Observations indicate that most massive galaxies contain a supermassive black hole, and theoretical studies suggest that when such galaxies have a major merger, the central black holes will form a binary and eventually coalesce. Here we discuss two spectral signatures of such binaries that may help distinguish them from ordinary AGN. These signatures are expected when the mass ratio between the holes is not extreme and the system is fed by a circumbinary disk. One such signature is a notch in the thermal continuum that has been predicted by other authors; we point out that it should be accompanied by a spectral revival at shorter wavelengths and also discuss its dependence on binary properties such as mass, mass ratio, and separation. In particular, we note that the wavelength $λ_n$ at which the notch occurs depends on these three parameters in such a way as to make the number of systems displaying these notches $\propto λ_n^{16/3}$; longer wavelength searches are therefore strongly favored. A second signature, first discussed here, is hard X-ray emission with a Wien-like spectrum at a characteristic temperature $\sim 100$ keV produced by Compton cooling of the shock generated when streams from the circumbinary disk hit the accretion disks around the individual black holes. We investigate the observability of both signatures. The hard X-ray signal may be particularly valuable as it can provide an indicator of black hole merger a few decades in advance of the event.
Signatures of winds and jets in the environment of supermassive black holes
事件视界望远镜合作组织（EHTC）首次展示了M87和Sgr A * 中黑洞阴影的动态范围有限图像。下一代事件视界望远镜（ngEHT）将提供更高的灵敏度和更高的动态范围的图像（和电影），这两个来源加上图像至少十几个其他$\leq$ 100引力半径分辨率。在这里，我们进行了探索性的研究，风和喷流的外观在这样的未来观测。为了做到这一点，我们使用M87和Sgr A * 作为参考系：我们的目标不是精确地再现它们，而是确定它们的观测图像将如何取决于特定的物理假设。即使在类似或相同的动力学的情况下，图像显着依赖于全球参数，如黑洞质量和质量吸积率。我们的研究结果为解释未来的高分辨率图像提供了指导，特别是如果检测到风或射流。
Signatures of Exploding Supermassive PopIII Stars at High Redshift in JWST, EUCLID and Roman Space Telescope
Max Planck Institute for Gravitational Physics (Albert Einstein Institute)（马克斯·普朗克引力物理研究所（爱因斯坦研究所））；Institute for Cosmic Ray Research, The University of Tokyo（东京大学宇宙射线研究所）；Center for Gravitational Physics and Quantum Information, Yukawa Institute for Theoretical Physics, Kyoto University（京都大学汤川理论物理中心引力物理与量子信息研究中心）；Frontier Research Institute for Interdisciplinary Sciences, Tohoku University（东北大学前沿交叉科学研究所）；Astronomical Institute, Graduate School of Science, Tohoku University（东北大学理学研究科天文学系）
Reading signatures of supermassive binary black holes in pulsar timing array observations
Max Planck Institute for Gravitational Physics (Albert Einstein Institute)（马克斯·普朗克引力物理学研究所（阿尔伯特·爱因斯坦研究所））；IISER Bhopal（印度科学教育研究院博帕尔分校）；FORTH Institute of Astrophysics（基础与研究赫尔茨学会天体物理研究所）；ASTRON, Netherlands Institute for Radio Astronomy（荷兰射电天文研究所）；Shanghai Astronomical Observatory, Chinese Academy of Sciences（中国科学院上海天文台）；Trinity College Dublin（都柏林三一学院）
Multiwavelength periodic microlensing signatures of macrolensed supermassive binary black holes
National Astronomical Observatories, Chinese Academy of Sciences（中国科学院国家天文台）；School of Astronomy and Space Science, University of Chinese Academy of Sciences（中国科学院大学天文学与空间科学学院）
An equal mass ratio supermassive binary black holes in Q J0158-4325 with periodic microlensing signature?
National Astronomical Observatories, Chinese Academy of Sciences（中国科学院国家天文台）；School of Astronomy and Space Science, University of Chinese Academy of Sciences（中国科学院大学天文与空间科学学院）
University of Hertfordshire（赫特福德大学）；Stanford University（斯坦福大学）；Princeton University（普林斯顿大学）；University of Cambridge（剑桥大学）；University of Zurich（苏黎世大学）；University of Birmingham（伯明翰大学）；University of Warwick（华威大学）；University of Maryland, College Park（马里兰大学帕克分校）；Joint Space-Science Institute (JSI)（联合空间科学研究所）
Identifying Observational Signatures of Flux Eruption Events in Supermassive Black Hole Accretion Flows with Machine Learning
Center for Astrophysics | Harvard & Smithsonian（哈佛-史密森天体物理中心）；Black Hole Initiative at Harvard University（哈佛大学黑洞倡议）；Khoury College of Computer Sciences, Northeastern University（东北大学科利计算机学院）；NSF Institute for Artificial Intelligence & Fundamental Interactions (IAIFI), Massachusetts Institute of Technology (MIT)（麻省理工学院美国国家科学基金会人工智能与基础相互作用研究所）；John A. Paulson School of Engineering and Applied Science, Harvard University（哈佛大学约翰·A·保尔森工程与应用科学学院）
Lomb-Scargle periodograms struggle with non-sinusoidal supermassive BH binary signatures in quasar lightcurves
Columbia University（哥伦比亚大学）；Washington State University（华盛顿州立大学）；Institute of Astrophysics, FORTH（FORTH天体物理研究所）；Institute of Science and Technology Austria (ISTA)（奥地利科学与技术研究所）
质量为$>10^5$ M $_\odot$的超大质量恒星（SMS）被认为是在红移$z>6-7$观测到的最极端的超大质量黑洞的可能祖先。在这种情况下（“直接碰撞”），SMS以速率$>0.1$ M $_\odot$ yr $^{-1}$吸积，直到它通过广义相对论（GR）不稳定性坍缩成黑洞。旋转在这种超大质量黑洞种子的形成中起着至关重要的作用。在这种恒星形成的极端情况下，离心屏障显得特别强大。此外，旋转敏感地影响SMSs对GR的稳定性，以及随后的崩溃。特别是，它可能允许黑洞形成时的引力波发射和超长伽马射线暴，这是目前文献中提出的此类物体存在的主要观测特征。在这里，我提出了最新的模型的SMSs帐户吸积和旋转，并讨论了一些开放的问题和未来的前景，在这条研究线。
Probing Boson Clouds with Supermassive Black Hole Binaries
Institute of High Energy Physics, Chinese Academy of Sciences（中国科学院高能物理研究所）；School of Physics Sciences, University of Chinese Academy of Sciences（中国科学院大学物理科学学院）；Center for High Energy Physics, Peking University（北京大学高能物理中心）
Probing the Penrose Process: Images of Split Hotspots and Their Observational Signatures
Beijing Normal University（北京师范大学）；Guangzhou University（广州大学）；Beijing Information Science and Technology University（北京信息科技大学）；Ningbo University（宁波大学）；Peking University（北京大学）
