GCN Circular 43061
Subject
EP251130a: Mondy and AbAO optical observations
Event
Date
2025-12-10T09:19:25Z (3 hours ago)
From
Alina Volnova at IKI RAS <alinusss@gmail.com>
Via
Web form
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:
We 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:
Date UT start t-T0 Exp. Filter OT Err. UL Site/Instrum
(mid,days) (n*s) (3sigma)
2025-12-01 20:11:34 1.40888 45*120 R 21.83 0.15 22.5 Mondy/AZT-33IK
2025-12-03 23:01:52 3.56284 285*30 R n/d n/d 21.0 AbAO/AS-32
The photometry is based on several nearby stars from the USNO-B1 catalogue (R2 magnitudes) and is not corrected for the Galactic extinction.
Our 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.