EP J062132.0+623837: A Multi-wavelength Study of a Changing-look Active Galactic Nucleus Discovered by Einstein Probe

@misc{xu2026j0621320623837,
  title = {{EP J062132.0+623837: A Multi-wavelength Study of a Changing-look Active Galactic Nucleus Discovered by Einstein Probe}},
  author = {Lin-Na Xu and Ning Jiang and Tinggui Wang and Shifeng Huang and Yibo Wang and Zhenfeng Sheng and Mingxin Wu and Jiazheng Zhu and Huaqing Cheng and Chichuan Jin and Jun-Jie Jin and Dongyue Li and Yuan Liu and Jianwei Lyu and Jian-Guo Wang and Yun-Fei Xu and Yongquan Xue and Zhen Zhang},
  howpublished = {arXiv},
  year = {2026},
  month = oct,
  doi = {10.48550/arxiv.2610.30959},
  eprint = {2610.30959},
  archivePrefix = {arXiv},
  url = {https://arxiv.org/abs/2610.30959},
  note = {CC BY 4.0},
}

TY  - UNPB
TI  - EP J062132.0+623837: A Multi-wavelength Study of a Changing-look Active Galactic Nucleus Discovered by Einstein Probe
AU  - Lin-Na Xu
AU  - Ning Jiang
AU  - Tinggui Wang
AU  - Shifeng Huang
AU  - Yibo Wang
AU  - Zhenfeng Sheng
AU  - Mingxin Wu
AU  - Jiazheng Zhu
AU  - Huaqing Cheng
AU  - Chichuan Jin
AU  - Jun-Jie Jin
AU  - Dongyue Li
AU  - Yuan Liu
AU  - Jianwei Lyu
AU  - Jian-Guo Wang
AU  - Yun-Fei Xu
AU  - Yongquan Xue
AU  - Zhen Zhang
PY  - 2026
DA  - 2026/10/22
PB  - arXiv
DO  - 10.48550/arxiv.2610.30959
UR  - https://arxiv.org/abs/2610.30959
AB  - EP J062132.0+623837 is a new X-ray source identified in 14-day binned survey data from the Wide-field X-ray Telescope aboard the Einstein Probe (EP). Subsequent X-ray observations with the Follow-up X-ray Telescope (FXT) on board EP localized the source to the central region of the galaxy 2MASX J06213207+6238390 at z=0.084. Here, we present a comprehensive analysis of the multi-wavelength data for this object. During the FXT and Swift/XRT follow-up, the source remained X-ray active, with observed luminosities of (3−9)×10^43 erg s^−1, and its X-ray spectra were well described by power-law models with photon indices of Γ∼1.5. The optical spectrum of the host galaxy clearly reveals a broad-line active galactic nucleus (AGN) exhibiting significantly enhanced broad Balmer emission lines compared to an archival spectrum obtained four years earlier, thereby marking a changing-look transition from Type 1.8 to Type 1.5. Furthermore, long-term optical and mid-infrared light curves indicate that the nucleus underwent dramatic brightening around 2010 and has since shown substantial variability. Given the spatial coincidence and multi-wavelength behavior, we identify EP J062132.0+623837 as a changing-look AGN, initially detected by EP and subsequently confirmed to exhibit large-amplitude variability across multiple bands. This case study demonstrates the great potential of wide-field time-domain X-ray surveys for discovering changing-look AGNs, paving a new avenue for their systematic identification as a powerful complement to ongoing optical surveys.
ER  -