{
  "body": "A. A. Volnova (IKI), A. S. Pozanenko (IKI), A. S. Moskvitin (SAO RAS), E. Klunko (ISTP), V. Rumyantsev (CrAO), M. Krugov (FAI), O. I. Spiridonnova (SAO RAS), N. S. Pankov (IKI) report on behalf of IKI-GRB-FuN:\n\nWe observed the field of the transient  EP251118a (Jiang et al., GCN 42749) detected by the Einstein Probe Wide-field X-ray Telescope (EP WXT), with the AZT-33IK 1.5m telescope of the Sayan Solar Observatory (Mondy) on Nov. 20 and 24 in R filter, with the ZTSH telescope of CrAO on Nov. 20 and 22 in B and R bands, with the AZT-20 1.5m telescope of Assy-Turgen observatory on Nov. 21 in Sloan r filter and Zeiss-1000 of SAO RAS on Nov. 30 in Rc-filter. The optical counterpart (Malesani et al., GCN 42751; Lipunov et al., GCN 42755; An et al., GCN 42756; Belkin et al., GCN 42758; Yadav et al., GCN 42760; Busmann et al., GCN 42763; Francile et al., GCN 42767; Urquijo-Rodríguez et al., GCN 42773; Li et al., GCN 42776; Lee et al., GCN 42780; Moskvitin and Spiridonova, GCN 42785; Gupta et al., GCN 42787; Liu et al., GCN 42793; Aryan et al, GCN 42798; Gupta et al., GCN 42810) is detected in the stacked frame of each epoch.\nHowever the flux of the optical transient might be affected by the nearby red star SDSS J081239.57+105619.8 (r_SDSS = 21.911+/-0.178, g-r ~ 3 mag) located in 2.5 arcsec to the East.\nSome of our preliminary PSF photometry and observational details are the following:\n\nDate        UT start  t-T0       Exp.    Filter  OT     Err.  UL      Site/Instrum\n                     (mid,days)  (n*s)                       (3sigma)\n2025-11-20  18:58:01  2.12539    45*120  R       21.45  0.11  22.4    Mondy/AZT-33IK\n2025-11-20  21:40:22  2.23886    42*120  R       21.29  0.10  23.2    CrAO/ZTSh\n2025-11-20  23:13:01  2.31556    51*120  B       21.02  0.11  23.1    CrAO/ZTSh\n2025-11-21  19:57:19  3.16164    57*60   r       22.39  0.08  23.8    Assy/AZT-20\n2025-11-22  22:55:20  4.29925    48*120  R       21.62  0.17  22.5    CrAO/ZTSh\n2025-11-24  19:51:39  6.15840    36*120  R       23.1   0.4   22.5    Mondy/AZT-33IK\n2025-11-30  01:49:42 11.40863    12*300  Rc      22.90  0.15  24.0    SAO/Zeiss-1000\n\nThe photometry is calibrated using several nearby stars, USNO-B1.0 B2, R2 magnitudes for AZT-33IK, ZTSh and Zeiss-1000 data, and SDSS r magnitudes for AZT-20 data, all magnitudes are not corrected for the Galactic extinction.",
  "submittedHow": "web",
  "submitter": "Alina Volnova at IKI RAS <alinusss@gmail.com>",
  "format": "text/plain",
  "subject": "EP251118a: Mondy, CrAO, Assy and SAO RAS/Zeiss-1000 optical observations",
  "eventId": "EP251118a",
  "createdOn": 1764615582448,
  "circularId": 42926,
  "bibcode": "2025GCN.42926....1V"
}