GCN Circular 42716
Subject
EP251023a: UAFO and AbAO optical observations
Event
Date
2025-11-17T12:54:12Z (17 hours ago)
Edited On
2025-11-17T16:19:45Z (14 hours ago)
From
Alina Volnova at IKI RAS <alinusss@gmail.com>
Edited By
Judith Racusin at NASA/GSFC <judith.racusin@nasa.gov> on behalf of Alina Volnova at IKI RAS <alinusss@gmail.com>
Via
Web form
A. Volnova (IKI), A. Pozanenko (IKI), A. Kochergin (UAFO IAA), R. Ya. Inasaridze (AbAO) report on behalf of IKI-GRB-FuN:
We observed the field of the EP transient EP251023a (Wu et al., GCN 42388) with the RC-500 (0.5m) telescope of Ussuriysk Astrophysical Observatory (UAFO) on Oct., 23, 2025 starting at (UT) 17:51:51, and the AS-32 0.7m telescope of the Abastumani Observatory (AbAO) on Oct., 24, 2025, starting at (UT) 22:53:36. Several 60-second exposures in R-filter were obtained during each observational epoch. The optical counterpart (Wortley et al., GCN 42387; Li et al., GCN 42389; Liu et al., GCN 42391; Mandarakas et al., GCN 42400; Lipunov et al., GCN 42405; Selezneva et al., GCN 42406; Mohan et al., GCN 42411; Rakotondrainibe et al., GCN 42420; Rajabov et al., GCN 42422; Volnova et al., GCN 42468) is clearly detected in the stacked UAFO image and is not detected in that of the AbAO. The preliminary photometry is the following:
Date UT start t-T0 Exp. Filter OT Err. UL Site/Tel.
(mid,days) (n*s) (3sigma)
2025-10-23 17:51:51 0.67889 100*60 R 19.97 0.22 20.9 UAFO/RC-500
2025-10-24 22:53:36 1.88138 40*60 R n/d n/d 20.5 AbAO/AS-32
The photometry is based on several nearby PS1 stars (Lupton's R-band transformation, Vega system) and is not corrected for the Galactic extinction.