Changing-look Active Galactic Nuclei from SDSS, LAMOST and DESI Surveys
Abstract
Results. We identify 45 CLAGNs, of which 40 are newly reported. The sample is dominated by turn-off events, comprising 43 turn-off and 2 turn-on sources. This may be because Type 2 AGNs either lack a detectable broad-line region or have their broad emission lines obscured by circumnuclear dust, making turn-on events more difficult to identify. Using DESI spectra as a third spectroscopic epoch, we identified 12 RCLAGNs. Of the 14 newly identified CLAGNs with three-epoch spectroscopic coverage, 7 objects, i.e. 50%, are confirmed as RCLAGNs. In the previously reported sample, 5 out of 16 objects with available DESI spectra, corresponding to ~31%, exhibit repeating CL behaviour. The relatively high incidence of repeated CL behaviour suggests that CL transitions are associated with recurrent physical processes, such as accretion-rate fluctuations or accretion-disk instabilities. In the logM_BH--log(L_bol/L_Edd) plane, the RCLAGNs display a clear high--low--high accretion-state evolution, indicating a close connection between repeated CL behaviour and recurrent variations in accretion power. The rest-frame upper limits on the transition timescales are ~10 yr for the first transition and 4 yr for the second transition.
Versions
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BibTeX
@misc{chen2026changinglook,
title = {{Changing-look Active Galactic Nuclei from SDSS, LAMOST and DESI Surveys}},
author = {Guohai Chen and Wenxin Yang and Xuhong Ye and Zhiqiang Chen and Zhiyuan Pei and Hubing Xiao and Junhui Fan},
howpublished = {arXiv},
year = {2026},
month = aug,
doi = {10.48550/arxiv.2605.24429},
eprint = {2605.24429},
archivePrefix = {arXiv},
url = {https://arxiv.org/abs/2605.24429},
note = {CC BY 4.0},
}
RIS
TY - UNPB
TI - Changing-look Active Galactic Nuclei from SDSS, LAMOST and DESI Surveys
AU - Guohai Chen
AU - Wenxin Yang
AU - Xuhong Ye
AU - Zhiqiang Chen
AU - Zhiyuan Pei
AU - Hubing Xiao
AU - Junhui Fan
PY - 2026
DA - 2026/08/18
PB - arXiv
DO - 10.48550/arxiv.2605.24429
UR - https://arxiv.org/abs/2605.24429
AB - Results. We identify 45 CLAGNs, of which 40 are newly reported. The sample is dominated by turn-off events, comprising 43 turn-off and 2 turn-on sources. This may be because Type 2 AGNs either lack a detectable broad-line region or have their broad emission lines obscured by circumnuclear dust, making turn-on events more difficult to identify. Using DESI spectra as a third spectroscopic epoch, we identified 12 RCLAGNs. Of the 14 newly identified CLAGNs with three-epoch spectroscopic coverage, 7 objects, i.e. 50%, are confirmed as RCLAGNs. In the previously reported sample, 5 out of 16 objects with available DESI spectra, corresponding to ~31%, exhibit repeating CL behaviour. The relatively high incidence of repeated CL behaviour suggests that CL transitions are associated with recurrent physical processes, such as accretion-rate fluctuations or accretion-disk instabilities. In the logM_BH--log(L_bol/L_Edd) plane, the RCLAGNs display a clear high--low--high accretion-state evolution, indicating a close connection between repeated CL behaviour and recurrent variations in accretion power. The rest-frame upper limits on the transition timescales are ~10 yr for the first transition and 4 yr for the second transition.
ER -