Discovery of Repeating Transitions in 16 Changing-look Active Galactic Nuclei
Xiamen University（厦门大学）；Quanzhou Normal University（泉州师范学院）；National Astronomical Observatories, Chinese Academy of Sciences（中国科学院国家天文台）；University of Science and Technology of China（中国科学技术大学）；Yunnan Normal University（云南师范大学）
The repeating changing-look active galactic nuclei (RCL AGNs) exhibit multiple appearances and disappearances of broad emission lines (BELs), whose underlying mechanism remains a puzzle. Expanding the sample of RCL AGNs is valuable for constraining the transition timescale and probing the accretion physics driving CL behaviors. This study aims to identify RCL AGNs using the multi-epoch spectroscopic data of confirmed CL AGNs from the Sloan Digital Sky Survey, Large Sky Area Multi-Object Fiber Spectroscopic Telescope, and Dark Energy Spectroscopic Instrument, supplemented with mid-infrared (MIR) light curves. Through selection criteria and visual inspection, we identify 22 RCL AGNs among 299 CL AGNs, corresponding to an occurrence rate of about 7\%, indicating that repeated transitions are not extremely rare in CL AGNs. Among the 22 RCL AGNs, 16 are newly identified, which significantly expands the known RCL AGN sample. Based on the spectra and densely sampled MIR light curves, we derive MIR variability timescales for 18 RCL AGNs, and find no significant correlation between the timescale and the black hole mass.
Extreme line profile variations in the repeating changing-look active galactic nucleus IRAS23226-3843
Northern Kentucky University（北肯塔基大学）；University of Johannesburg（约翰内斯堡大学）；ESA, European Space Astronomy Centre (ESAC)（欧洲空间局，欧洲空间天文中心）；South African Astronomical Observatory（南非天文台）
22 Newly Identified Repeating Changing-look AGNs and Evidence for Extreme Broad-line Region Breathing
Aryabhatta Research Institute of Observational Sciences (ARIES)（阿亚巴塔观测科学研究所）；Yunnan Observatories, Chinese Academy of Sciences（中国科学院云南天文台）；Key Laboratory for the Structure and Evolution of Celestial Objects, Chinese Academy of Sciences（中国科学院天体结构与演化重点实验室）
Are "Changing-Look" Active Galactic Nuclei Special in the Coevolution of Supermassive Black Holes and their Hosts? II. The Case of Changing-Look Narrow-Line Seyfert 1 Galaxies
National Astronomical Observatories, Chinese Academy of Sciences（中国科学院国家天文台）；Guangxi Key Laboratory for Relativistic Astrophysics, School of Physical Science and Technology, Guangxi University（广西大学物理科学与技术学院相对论天体物理广西重点实验室）；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）；Department of Astronomy, University of California, Berkeley（加州大学伯克利分校天文学系）；Max-Planck-Institut für Radioastronomie（马克斯·普朗克射电天文研究所）
Mid-Infrared Outbursts in Nearby Galaxies: Nuclear Obscuration and Connections to Hidden Tidal Disruption Events and Changing-Look Active Galactic Nuclei
Tracing Active Galactic Nuclei Properties Through a Changing-look Event
School of Physics and Astronomy, University of Southampton（南安普顿大学物理与天文学学院）；DARK, Niels Bohr Institute, University of Copenhagen（哥本哈根大学尼尔斯·玻尔研究所DARK）；Astrophysics Research Centre, School of Mathematics and Physics, Queen’s University Belfast（贝尔法斯特女王大学数学与物理学院天体物理学研究中心）；School of Physics, The University of Melbourne（墨尔本大学物理学院）；Department of Astronomy and Astrophysics, University of California, Santa Cruz（加州大学圣克鲁兹分校天文与天体物理系）
Polarization properties of changing-look active galactic nuclei: NGC 1365 and NGC 2992
Foundation for Research and Technology-Hellas (FORTH)（希腊研究与技术基金会）；Instituto de Astrofisica de Canarias（加那利群岛天体物理研究所）；Universidad de La Laguna（拉古纳大学）；National Astronomical Observatory of Japan（日本国立天文台）
Changing-Look Active Galactic Nuclei in SDSS-V: Host-Galaxy Properties and Black-Hole Scaling Relations
Tel Aviv University（特拉维夫大学）；Max-Planck-Institut für extraterrestrische Physik（马克斯·普朗克地外物理研究所）；Excellence Cluster ORIGINS（ORIGINS卓越集群）；The Pennsylvania State University（宾夕法尼亚州立大学）；University of Washington（华盛顿大学）；University of Geneva（日内瓦大学）；Universidad Diego Portales（迭戈·波特莱斯大学）；Peking University（北京大学）
Changing-look Active Galactic Nuclei from SDSS, LAMOST and DESI Surveys
Center for Astrophysics, Guangzhou University（广州大学天体物理中心）；Dipartimento di Fisica e Astronomia “G. Galilei”, Università di Padova（帕多瓦大学伽利略物理与天文系）；Abastumani Observatory（阿巴斯图马尼天文台）；Greater Bay Brand Center of the National Astronomical Data Center（国家天文数据中心大湾区品牌中心）；Astronomy Science and Technology Research Laboratory of Department of Education of Guangdong Province（广东省教育厅天文科学与技术重点实验室）；School of Astronomy and Space Science, Nanjing University（南京大学天文与空间科学学院）
Multi-wavelength properties of changing-state active galactic nuclei: I. the evolution of soft excess and X-ray continuum
Universidad Diego Portales（迭戈·波特莱斯大学）；SRM University-AP（SRM大学安得拉邦校区）；University of Geneva（日内瓦大学）；Peking University（北京大学）；INAF-Osservatorio Astronomico di Roma（意大利国家天文台罗马天文台）；Tel Aviv University（特拉维夫大学）；Max-Planck-Institut für extraterrestrische Physik（马克斯·普朗克地外物理研究所）；Excellence Cluster ORIGINS（ORIGINS卓越集群）；Universidad de Tarapacá（塔拉帕卡大学）；Durham University（杜伦大学）；Eureka Scientific（尤里卡科学公司）；Space Science Institute（太空科学研究所）；Liège Université（列日大学）；Universiteit Gent（根特大学）；National Tsing Hua University（国立清华大学）
OQ~208: A New Fe~II Changing-look Active Galactic Nucleus and Implications for the Nature of the Changing-look Phenomenon
National Astronomical Observatories, Chinese Academy of Sciences（中国科学院国家天文台）；Department of Astronomy, University of California, Berkeley（加州大学伯克利分校天文学系）；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）；Guangxi Key Laboratory for Relativistic Astrophysics, School of Physical Science and Technology, Guangxi University（广西大学物理科学与技术学院相对论天体物理重点实验室）
Identifying Changing-Look AGN Transitions in Light Curve Data with the Zwicky Transient Facility
University of Illinois Urbana-Champaign（伊利诺伊大学厄巴纳-香槟分校）；National Center for Supercomputing Applications（国家超级计算应用中心）；Washington State University（华盛顿州立大学）；Yale University（耶鲁大学）；The Pennsylvania State University（宾夕法尼亚州立大学）
A systematic search for changing-look quasars in SDSS-II using difference spectra
“变像类星体”（CLQ）是活动星系核（AGN），表现出极端的变化，导致从1型转变为2型。这些转变的短时间尺度提出了一个挑战的活动星系核的统一模型和物理过程导致这些转变仍然知之甚少。CLQ的中心辐射几乎完全消失，因此也为AGN宿主星系的研究提供了有趣的样本。以前对CLQ的搜索利用光度变化或SDSS分类变化来系统地识别CLQ，这种方法可能会错过较低光度的CLQ。在本文中，我们的目标是使用光谱数据来评估，如果分析差光谱可以用来检测进一步改变外观的类星体错过了光度搜索。我们搜索SDSS-Ⅱ DR 7重复光谱的来源，表现出要么消失或出现的宽线发射和吸积盘连续发射直接分析两个观测时期之间的差异谱。从24，782个具有不同光谱的天体样本中，我们的搜索在红移范围$0.1 \leq z \leq 0.3$内产生了6个CLQ，包括4个新发现的来源。光谱分析表明，吸积速率的变化可以解释变化的外观行为。虽然尘埃消光的变化符合光谱形状的变化，但观察到的变化的时间尺度太短，无法被环形云遮蔽。利用差谱是一种有效而灵敏的检测CLQ的方法。我们恢复CLQs的光度比光度搜索发现的低一个数量级，并实现更高的完整性比光谱搜索依赖于管道分类。
