We present the multi-wavelength and environmental properties of 37 variability-selected active galactic nuclei (AGNs), including 30 low luminosity AGNs (LLAGNs), using a high cadence time-domain survey (ASAS-SN) from a spectroscopic sample of 1218 nearby bright galaxies. We find that high-cadence time-domain surveys uniquely select LLAGNs that do not necessarily satisfy other AGN selection methods, such as X-ray, mid-IR, or BPT methods. In our sample, 3% of them pass the mid-infrared color based AGN selection, 18% pass the X-ray luminosity based AGN selection, and 60% pass the BPT selection. This result is supported by two other LLAGN samples from high-cadence time-domain surveys of TESS and PTF, suggesting that the variability selection method from well-sampled light curves can find AGNs that may not be discovered otherwise. These AGNs can have moderate to small amplitudes of variability from the accretion disk, but, of many of them, with no strong corona, emission lines from the central engine, or accretion power to dominate the mid-IR emission. The X-ray spectra of a sub-sample of bright sources are consistent with a power law model. Upon inspecting the environments of our sample, we find that LLAGNs are more common in denser environments of galaxy clusters in contrast with the trend established in the literature for luminous AGNs at low redshifts, which is broadly consistent with our analysis result for luminous AGNs limited by a smaller sample size. This contrast in environmental properties between LLAGN and luminous AGNs suggests that LLAGNs may have different trigger mechanisms.
Asymmetric torus variability in active galactic nuclei driven by global brightening and dimming
Kavli Institute for Astronomy and Astrophysics, Peking University（北京大学科维理天文与天体物理研究所）；Department of Astronomy and Atmospheric Sciences, Kyungpook National University（庆北大学天文与大气科学系）；Department of Astronomy, Yonsei University（延世大学天文学系）；Department of Astronomy, School of Physics, Peking University（北京大学物理学院天文学系）
NEXUS: Spectral Variability of Little Red Dots and Blue Active Galactic Nuclei at $2 \lesssim z \lesssim 6$
University of Illinois at Urbana-Champaign（伊利诺伊大学厄巴纳-香槟分校）；National Center for Supercomputing Applications, University of Illinois at Urbana-Champaign（美国国家超级计算应用中心）；Princeton University（普林斯顿大学）；University of Michigan（密歇根大学）
Ultraviolet variability in Radio-Loud Active Galactic Nuclei observed by UVIT onboard AstroSat
CHRIST University（克里斯特大学）；Indian Institute of Astrophysics（印度天体物理研究所）；Center for Theoretical Physics of the Polish Academy of Sciences（波兰科学院理论物理中心）；St. Joseph’s University（圣约瑟夫大学）
Dwarf Active Galactic Nuclei from Variability for the Origins of Seeds (DAVOS): Properties of Variability-Selected AGNs in the Dark Energy Survey Deep Fields
DAVOS: Dwarf Active Galactic Nuclei from Variability for the Origins of Seeds: Properties of Variability-Selected Active Galactic Nuclei in the COSMOS Field and Expectations for the Rubin Observatory
Seeing through the dust: Unraveling near-infrared variability in type 2 active galactic nuclei
Instituto de Física y Astronomía, Universidad de Valparaíso（瓦帕拉索大学物理与天文学研究所）；Millennium Nucleus on Transversal Research and Technology to Explore Supermassive Black Holes (TITANS)（探索超大质量黑洞跨学科研究与技术千年核）；Millennium Institute of Astrophysics (MAS)（天体物理学千年研究所）；European Southern Observatory（欧洲南方天文台）；Departamento de Astronomía, Universidad de Chile（智利大学天文学系）；Cosmic Dawn Center (DAWN)（宇宙黎明中心）；Niels Bohr Institute, University of Copenhagen（哥本哈根大学尼尔斯·玻尔研究所）；Department of Physics & Astronomy, Bishop’s University（主教大学物理与天文学系）
Probing the Physical Origin of the Balmer Decrement in the Broad-line Region of Nearby Active Galactic Nuclei via Spectral Variability
Kavli Institute for Astronomy and Astrophysics, Peking University（北京大学科维理天文与天体物理研究所）；Department of Astronomy and Atmospheric Sciences, Kyungpook National University（庆北大学天文与大气科学系）；Department of Astronomy, Yonsei University（延世大学天文系）；Department of Astronomy, School of Physics, Peking University（北京大学物理学院天文系）
Characterizing the origins of gamma-ray variability of the jetted active galactic nuclei observed with the Fermi-LAT
Qujing Normal University（曲靖师范学院）；Nanjing University（南京大学）；Yunnan Observatories, Chinese Academy of Sciences（中国科学院云南天文台）；Anqing Normal University（安庆师范大学）；Kunming University（昆明学院）
The relation between the optical variability timescale, magnetic field of jets and black hole spin in active galactic nuclei
Qujing Normal University（曲靖师范学院）；Nanjing University（南京大学）；Chinese Academy of Sciences（中国科学院）；Anqing Normal University（安庆师范大学）；Kunming University（昆明学院）；Yunnan Normal University（云南师范大学）
Variability-selected low-luminosity active galactic nuclei candidates in the 7 Ms Chandra Deep Field-South
在深X射线巡天中，已经发现了光度范围很广的活动星系核。然而，宇宙学上遥远的低光度活动星系核（LLAGN，$L_{\mathrm{X}} \lesssim 10^{42}$ erg s $^{-1}$）的识别仍然是一个挑战，由于来自宿主星系的显着污染。基于7 Ms Chandra Deep Field-South（CDF-S）调查，迄今为止最长的时间尺度（$\sim 17$ years）的深X射线调查，我们利用X射线可变性选择技术来搜索在CDF-S X射线源中仍然未被识别的LLAGN。我们发现13个变量源从110个未分类的CDF-S X射线源。除了一个可能是超亮X射线源外，其余12个源的变化很可能是由于吸积超大质量黑洞造成的。这12个活动星系核候选者具有较低的本征X射线光度，中值为$7 \times10^{40}$ erg s $^{-1}$。它们通常不会被严重遮蔽，平均有效幂律光子指数为1.8。可变活动星系核在CDF-S中的比例与X射线光度无关，仅受观测到的净计数总数的限制，证实了以前的研究结果，即X射线可变性是活动星系核在很宽的光度范围内几乎无处不在的特性。对于高光度活动星系核，X射线光度与变率振幅之间存在反相关，但当光度下降到$\lesssim 10^{42}$ erg s $^{-1}$时，变率振幅不再依赖于光度。整个观测到的亮度变化趋势可以大致再现的经验AGN可变性模型的基…
The hidden variability of the torus in local Active Galactic Nuclei: 20 years of Chandra, XMM-Newton, and NuSTAR observations
Clemson University（克莱姆森大学）；INAF-Osservatorio Astronomico di Brera（意大利国家天体物理研究所布雷拉天文台）；University of Virginia（弗吉尼亚大学）；GECO fellow（GECO研究员）；Università di Bologna（博洛尼亚大学）；INAF-Osservatorio di Astrofisica e Scienza dello Spazio (OAS)（意大利国家天体物理研究所空间科学天文台）；University of Geneva（日内瓦大学）；Instituto de Estudios Astrofísicos, Facultad de Ingeniería y Ciencias, Universidad Diego Portales（迭戈·波特莱斯大学工程与科学学院天体物理研究所）
Changing-look Active Galactic Nuclei from the Dark Energy Spectroscopic Instrument. V. Dramatic Variability in High-Ionization Broad Emission Lines
Nanjing Normal University（南京师范大学）；National Astronomical Observatories, Chinese Academy of Sciences（中国科学院国家天文台）；Peking University（北京大学）；Yunnan University（云南大学）；University of Chinese Academy of Sciences（中国科学院大学）
Anisotropic Radiation in Super-Eddington Active Galactic Nuclei: The Responsivity of Broad-Line Regions to Continuum Variability
State Key Laboratory of Particle Astrophysics, Institute of High Energy Physics, Chinese Academy of Sciences（高能物理研究所粒子天体物理国家重点实验室）；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）
X-ray Absorption Variability in NGC 1142: Another Constraint on the Nature of the Torus/Broad-Line Region in Active Galactic Nuclei
Clemson University（克莱姆森大学）；University of Virginia（弗吉尼亚大学）；Università degli Studi di Bologna（博洛尼亚大学）；INAF-Osservatorio Astronomico di Bologna（意大利国家天体物理研究所博洛尼亚天文台）；INAF-Osservatorio Astronomico di Brera（意大利国家天体物理研究所布雷拉天文台）；University of Illinois at Urbana-Champaign（伊利诺伊大学厄巴纳-香槟分校）；European Southern Observatory（欧洲南方天文台）
