GCN Circular 46003
Subject
EP261015a: AZT-20 Assy-Turgen optical observations
Event
Date
2026-10-21T06:17:24Z (7 hours ago)
From
Nicolai Pankov at IKI <colinsergesen@gmail.com>
Via
Web form
N. Pankov (IKI), M. Krugov (FAI), A. Pozanenko (IKI), A. Moskvitin (SAO RAS), A. Volnova (IKI) report on behalf of IKI-GRB-FuN:
We observed the field of the Einstein Probe fast X-ray transient EP261015a (Li et al., GCN 45956) with the 1.5-m AZT-20 telescope of the Assy-Turgen Observatory. Observations started on 2026-10-19 at 19:20:07 UT, 4.276 days after the EP/WXT trigger. A series of frames was obtained in the r' filter.
We clearly detect the optical counterpart (Corcoran et al., GCNs 45955 and 45972; Li et al., GCNs 45956 and 45969; Méndez et al., GCN 45960; Ma et al., GCN 45963; Mohan et al., GCN 45967; Fortin et al., GCN 45991; Volnova et al., GCN 45997; Pawar et al., GCN 45998; Shivaprasad et al., GCN 46000) at coordinates (J2000) 02:57:19.83, -13:21:17.3. The residual source is detected after subtraction of a DESI Legacy Survey DR10 r-band template. Preliminary photometry of the residual source is given below.
Date UTstart t-T0 Exp. Filter OT Err. UL
(mid, days) (s) (3sigma)
2026-10-19 19:20:07 4.2764 67*60 r' 22.59 0.06 23.8
The photometry was calibrated against nearby Pan-STARRS1 stars
RA (J2000) Dec (J2000) r
02:57:33.73 -13:21:44.6 16.891
02:57:25.43 -13:24:41.2 19.263
and is not corrected for Galactic extinction.
The residual magnitude is consistent with the Legacy Survey-subtracted measurements of Fortin et al. (GCN 45991; r = 22.58 +/- 0.09 at 3.7 d) and Shivaprasad et al. (GCN 46000; r = 22.52 +/- 0.28 at 4.37 d).