TITLE:   GCN CIRCULAR
NUMBER:  43132
SUBJECT: GRB 251214B: UAFO optical upper limit
DATE:    25/12/15 18:11:38 GMT
FROM:    Alina Volnova at IKI RAS <alinusss@gmail.com>

N. S. Pankov (HSE, IKI), A. Kochergin (UAFO IAA), A. A. Volnova (IKI), A. S. Pozanenko (IKI)  report on behalf of IKI-GRB-FuN:

We observed the field of the long GRB 251214B detected by Fermi (Fermi team, GCN 43088), Swift (Eyles-Ferris et al., GCN 43089; Evans et al., GCN 43098; Kuin and Eyles-Ferris, GCN 43105; Burrows et al., GCN 43112; Laha et al., GCN 43129), and GECAM-B (Luo et al., GCN 43113) with the RC-500 (0.5m) telescope of Ussuriysk Astrophysical Observatory (UAFO) taking several frames in R-band. The observations started on Dec. 14 at 10:44 UT, i.e., ~ 1.5 hours after the Swift/BAT trigger. In the stacked image we do not detect the optical counterpart reported previously (Eyles-Ferris et al., GCN 43089; Kang et al., GCN 43093; Gress et al., GCN 43095; Fu et al., GCN 43097; Gupta et al., GCN 43100; Watson et al., GCN 43103; Kuin and Eyles-Ferris, GCN 43105; Pérez-Fournon et al., GCN 43123; Volnova et al., GCN 43124; de Ugarte Postigo et al., GCN 43131). Photometry and observational details are the following:

Date        UT start  t-T0       Exp.    Filter   Obj.   Err.  UL         Site/Telescope
                     (mid,days)  (n*s)                         (3sigma)
2025-12-14  10:44:26  0.09073    57*60   R        n/d    n/d   19.4       UAFO/RC500

The photometry is based on several nearby stars from the USNO-B1 catalogue (R2 magnitudes) and is not corrected for the Galactic extinction.