Reverberation Mapping of Changing-look Active Galactic Nucleus NGC 3516
Hai-Cheng Feng, Chen Hu, Sha-Sha Li, H. T. Liu, J. M. Bai, Li-Feng Xing, Wei-Yang Wang, Zi-Xu Yang, Ming Xiao, Kai-Xing Lu
Abstract
Abstract The changes of broad emission lines should be a crucial issue in understanding the physical properties of changing-look active galactic nuclei (CL-AGNs). Here we present the results of an intensive and homogeneous 6 month long reverberation mapping (RM) monitoring campaign during a low-activity state of the CL-AGN Seyfert galaxy NGC 3516. Photometric and spectroscopic monitoring was carried out during 2018–2019 with the Lijiang 2.4 m telescope. The sampling is 2 days in most nights, and the average sampling is ∼3 days. The rest-frame time lags of H α and H β are and days, respectively. From an rms H β line dispersion of σ line = 1713.3 ± 46.7 km s −1 and a virial factor of f σ = 5.5, the central black hole mass of NGC 3516 is estimated to be , which is in agreement with previous estimates. The velocity-resolved delays show that the time lags increase toward negative velocity for both H α and H β . The velocity-resolved RM of H α is done for the first time. These RM results are consistent with other observations before the spectral-type change, indicating a basically constant broad-line region structure during the CL process. The CL model of changes of accretion rate seems to be favored by long-term H β variability and RM observations of NGC 3516.