GCN Circular 44652
Subject
GRB 260515A: CrAO ZTSh BVRI optical observations
Event
Date
2026-05-16T23:52:00Z (5 months ago)
From
Alexander Moskvitin at SAO RAS <mosk@sao.ru>
Via
Web form
A. Moskvitin (SAO RAS), A. Pozanenko (IKI), V. Rumyantsev (CrAO),
N. Pankov (IKI), A. Volnova (IKI) report on behalf of IKI GRB-FuN.
We observed the field of the GRB 260515A (Brunet et al., GCN 44622;
Wang et al., GCN 44642; Frederiks et al., GCN 44647) with the Shajn
2.6-meter telescope (ZTSh) of the Crimean Astrophysical Observatory
(CrAO). We obtained series of 120 s exposures in BVRI filters
starting on 2026-05-15 22:10:11 UT (about 3 hours after trigger).
The OT (He et al., GCN 44623; Saccardi et al., GCN 44624; Sosnovskij
et al., GCN 44625; He et al., GCN 44626; Wu et al., GCN 44628;
Malesani et al., GCN 44629; Dennefeld et al., GCN 44633; Li et al.,
GCN 44634; Antier et al., GCN 44643; Pérez-Fournon et al., GCN 44645;
Dimple et al., GCN 44646) is clearly detected in the stacked frames.
Details of the photometry is the following.
Start_UT, t_mid-T0, exp, filter, mag, err, UL(3 sigma)
2026-05-15T22:54:33 4.79 15*120 B 21.53 0.04 23.9
2026-05-15T22:56:41 4.75 13*120 V 21.30 0.05 23.7
2026-05-15T22:10:11 3.12 5*120 R 20.56 0.04 23.4
2026-05-15T22:20:40 3.29 5*120 R 20.57 0.04 23.4
2026-05-15T22:31:09 3.46 5*120 R 20.65 0.04 23.5
2026-05-15T22:41:44 3.66 6*120 R 20.64 0.03 23.6
2026-05-15T22:56:41 4.26 7*120 R 20.87 0.03 23.7
2026-05-15T23:58:56 5.35 8*120 R 21.03 0.04 23.4
2026-05-15T23:00:57 4.89 15*120 I 20.75 0.05 22.8
This preliminary photometry is based on nearby SDSS stars
(using Lupton 2005 transformation equations) and not corrected for Galactic extinction.