Multiple flares and asymmetric broad emission lines in a recurring changing-look active galactic nucleus

¹ National Astronomical Observatories, Chinese Academy of Sciences, 20A Datun Road, Chaoyang District, Beijing 100101, People's Republic of China
² College of Physics and Information Engineering, Quanzhou Normal University, Quanzhou, Fujian 362000, People's Republic of China
³ Special Astrophysical Observatory, Russian Academy of Sciences, Nizhnii Arkhyz, Zelenchukskiy region, Karachai-Cherkessian Republic, 357147, Russia
⁴ Space Research Institute Russian Academy of Sciences, 84/32 Profsouznaya str., Moscow, 117997, Russian Federation
⁵ School of Mathematics, Statistics and Physics, Newcastle University, Newcastle upon Tyne, NE1 7RU, UK
⁶ Key Laboratory for Particle Astrophysics, Institute of High Energy Physics, Chinese Academy of Sciences, 19B Yuquan Road, Beijing 100049, People's Republic of China
⁷ Chinese Academy of Sciences South America Center for Astronomy, National Astronomical Observatories, CAS, Beijing 100101, People's Republic of China
⁸ School of Physics and Technology, Nanjing Normal University, No. 1, Wenyuan Road, Nanjing, 210023, People's Republic of China
⁹ Yunnan Observatories, Chinese Academy of Sciences, Kunming 650011, People's Republic of China
¹⁰ Key Laboratory for the Structure and Evolution of Celestial Objects, Chinese Academy of Sciences, Kunming 650011, People's Republic of China
¹¹ Key Laboratory of Optical Astronomy, National Astronomical Observatories, Chinese Academy of Sciences, Beijing 100012, People's Republic of China
¹² Kavli Institute for Astronomy and Astrophysics, Peking University, Beijing 100871, People's Republic of China
¹³ Department of Astronomy, School of Physics, Peking University, Beijing 100871, People's Republic of China

^⋆ Corresponding authors: guowj@bao.ac.cn; zzx@qztc.edu.cn; zouhu@bao.ac.cn

Received: 24 September 2024
Accepted: 2 May 2025

Abstract

We report a case of a changing-look (CL) active galactic nucleus (AGN) at a redshift of z=0.337, identified as J075947.73+112507.3 (hereafter J0759), which exhibits recurring changing-look (RCL) phenomena accompanied by extreme asymmetry in the broad emission-line profiles. J0759 was discovered through the CL-AGN project conducted with the Dark Energy Spectroscopic Instrument. The most recent CL event was confirmed with new spectroscopic observations obtained using the Big Telescope Alt-azimuthal. Variability trends observed in the optical and mid-infrared light curves reveal multiple flares, indicating four to six potential CL events over time. We decomposed the asymmetric broad Hα emission line into two components, which persist in both high and low states. The RCL events in J0759 are inconsistent with the obscuration model and are more likely driven by variations in the accretion rate. However, the physical mechanism underlying such rapid accretion-rate changes remains unclear.