{
  "version": 2,
  "submitter": "Xinglong Observatory at National Astronomical Observatories (NAOC), Chinese Academy of Sciences (CAS) <xinglong@nao.cas.cn>",
  "submittedHow": "web",
  "createdOn": 1791557665560,
  "eventType": [
    "X-ray Transient",
    "Optical Transient"
  ],
  "circularId": 45877,
  "editedOn": 1791574756808,
  "format": "text/plain",
  "body": "Junbo-Zhang (NAOC), Junjie-Jin (NAOC), Rui-Zhu (NAOC), Haiyang-Mu (NAOC), Feng-Xiao (NAOC), Yuguang-Sun (NAOC), Jie-Zheng (NAOC), Dong-Xu (NAOC), Zhou-Fan (NAOC), Hong-Wu (NAOC) report on behalf of a large collaboration\n\nWe performed optical observations of the field of EP261006a (Lao et al., GCN 45826), classified as a possible TDE (Eyles-Ferris et al., GCN 45831; Jiang et al., GCN 45833), in the g, r, and i bands using the 2.16-m telescope located at Xinglong, Hebei, China. In each band, 3 × 300 s exposures were taken, with a median observation time of 2026-10-08T15:35:59, approximately 45.8 hours after the EP-WXT trigger (2026-10-06T17:49:57). We measure preliminary magnitudes of g = 18.49 ± 0.04, r = 19.39 ± 0.15, and i = 19.01 ± 0.08 mag (AB) for the host-subtracted optical counterpart, calibrated against nearby stars from the Pan-STARRS catalog. The stacked g, r, and i images have 5σ limiting magnitudes of ~20.68, 20.41, and 20.10 mag, respectively.\nWe summarize our observation results as follows:\nObs. No. | Time (UTC) | Exposure Time (s) | Filter | Apparent mag (AB) | Telescope Name \n     1   | 2026-10-08T15:14:46 |  3x300 s |    g   |   18.49 ± 0.04    | 2.16-m telescope  \n     2   | 2026-10-08T15:30:51 |  3x300 s |    r   |   19.39 ± 0.15    | 2.16-m telescope   \n     3   | 2026-10-08T15:46:46 |  3x300 s |    i   |   19.01 ± 0.08    | 2.16-m telescope",
  "eventId": "EP261006a",
  "subject": "EP261006a: Xinglong 2.16m/BFOSC optical follow-up observations",
  "editedBy": "Vidushi Sharma at NASA GSFC/UMBC <vidushi.sharma@nasa.gov> on behalf of Xinglong Observatory at National Astronomical Observatories (NAOC), Chinese Academy of Sciences (CAS) <xinglong@nao.cas.cn>"
}