{
  "createdOn": 1765358365377,
  "bibcode": "2025GCN.43061....1V",
  "body": "A. A. Volnova (IKI), E. Klunko (ISTP), R. Ya. Inasaridze (AbAO), N. S. Pankov (HSE, IKI), A. S. Pozanenko (IKI) report on behalf of IKI-GRB-FuN:\n\nWe continued observations of the field of the X-ray transient EP251130a (Wu et al., GCN 42903; Zhang et al., GCN 42915), also detected by Swift/XRT (Evans et al., GCN 42908) with the AZT-33IK 1.5m telescope of the Sayan Solar Observatory (Mondy), and the AS-32 0.7m telescope of Abastumani Observatory (AbAO) taking several frames in R-band. Further observations at AZT-33IK started on Dec. 01 at 20:11 (~1.4 days after the trigger), then followed by AbAO on Dec. 3 starting at 23:01 UT (~3.5 days after the trigger). The optical counterpart (Dornic et al., GCN 42904; He et al. GCN 42914; Gupta et al. GCN 42916; Zheng et al. GCN 42917; van Dalen et al., GCN 42918; Moskvitin and Spiridonova, GCN 42919; Aryan et al., GCN 42921; Volnova et al., GCN 42922; Ma et al., GCN 42940; Corcoran et al., GCN 42951; Tundidor Rodríguez et al., GCN 42963; Abidkhanov et al., GCN 42969; Fu et al., GCN 42990) is seen in the stacked AZT-33IK frame and is not detected in the stacked frame from AS-32. The 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)\n2025-12-01  20:11:34  1.40888    45*120  R       21.83  0.15  22.5    Mondy/AZT-33IK\n2025-12-03  23:01:52  3.56284    285*30  R       n/d    n/d   21.0    AbAO/AS-32\n\nThe photometry is based on several nearby stars from the USNO-B1 catalogue (R2 magnitudes) and is not corrected for the Galactic extinction.\n\nOur observations together with other published magnitudes confirm the steep decay (Tundidor Rodríguez et al., GCN 42963) after the re-brightening: the R-band light curve slope changed from ~1.3 at 0.06-0.19 days to ~4 at 0.9-1.4 days in the observer frame.",
  "circularId": 43061,
  "format": "text/plain",
  "eventId": "EP251130a",
  "subject": "EP251130a: Mondy and AbAO optical observations",
  "submitter": "Alina Volnova at IKI RAS <alinusss@gmail.com>",
  "submittedHow": "web"
}