The changing-look AGN SDSS J101152.98+544206.4 is returning to a type I state

¹ Kavli Institute for Astronomy and Astrophysics, Peking University, Beijing 100871, People’s Republic of China
² Department of Astronomy, School of Physics, Peking University, Beijing 100871, People’s Republic of China
³ Leiden Observatory, Leiden University, P.O. Box 9513 NL-2300 RA Leiden, The Netherlands
⁴ Kapteyn Astronomical Institute, University of Groningen, P.O. Box 800 NL-9700 AV Groningen, The Netherlands
⁵ Department of Astronomy, School of Physics, Huazhong University of Science and Technology, 1037 Luoyu Road, Wuhan 430074, People’s Republic of China
⁶ Shanghai Astronomical Observatory, Chinese Academy of Sciences, 80 Nandan Road, Shanghai 200030, People’s Republic of China
⁷ University of Science and Technology of China, No.96, JinZhai Road Baohe District, Hefei, Anhui 230026, People’s Republic of China
⁸ School of Physics and Electrical Engineering, Liupanshui Normal University, Liupanshui, Guizhou 553004, People’s Republic of China
⁹ Key Laboratory of Optical Astronomy, National Astronomical Observatories, Chinese Academy of Sciences, Beijing 100012, People’s Republic of China
¹⁰ Steward Observatory, University of Arizona, 933 N Cherry Avenue, Tucson, AZ 85721, USA

^⋆ Corresponding authors; lyubing@pku.edu.cn; wuxb@pku.edu.cn

Received: 29 July 2024
Accepted: 10 December 2024

Abstract

Aims. We discovered that the changing-look active galactic nucleus (CLAGN) SDSS J101152.98+544206.4 (J1011+5442 for short) gradually returns to the type I state after a short period between 2014 and 2019 in the faint type 1.9 state.

Methods. Motivated by the rebrightening in the optical and mid-infrared light curves from ZTF and WISE, we obtained new spectroscopic observations with the Xinglong 2.16 m, the Lijiang 2.4 m, and the MMT 6.5 m optical telescopes in 2024.

Results. After changing its optical AGN type from 1 to 1.9 between 2003 and 2015 according to the repeat spectroscopy from the Time Domain Spectroscopic Survey, J1011+5442 returned to its type I state in 2024. We detect the significant and very broad Hβ lines (full width at half maximum of ≳5000 km/s) based on the new spectra, which suggests that J1011+5442 was in the intermediate state between the dim state in 2015 and the bright state in 2003. The long-term optical and mid-infrared light curves also show a brightening trend between 2019 and 2024 as the broad Hβ line appeared. The time lag of about 100 days between the mid-infrared and optical variability is consistent with the prediction of dust reverberation mapping.

Conclusions. The behavior of the photometric and spectroscopic observations of J1011+5442 is consistent with the argument that the repeating changing-look phenomenon is regulated by the variation in the accretion rate.