TITLE:   GCN CIRCULAR
NUMBER:  43141
SUBJECT: GRB 251214B: Mondy optical upper limit
DATE:    25/12/16 13:49:15 GMT
FROM:    Alina Volnova at IKI RAS <alinusss@gmail.com>

A. A. Volnova (IKI), E. Klunko (ISTP), A. S. Pozanenko (IKI), N. S. Pankov (HSE, 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 AZT-33IK 1.5m telescope of the Sayan Solar Observatory (Mondy) taking several 120-second expositions in R-band starting on Dec.15 UT 11:36:28. 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; Pankov et al., GCN 43132; Lin et al., GCN 43134). Preliminary photometry and observational details are the following:

Date        UT start  t-T0       Exp.    Filter  Obj.  Err.  UL       Site/Telescope
                     (mid,days)  (n*s)                      (3sigma)
2025-12-15  11:36:28  1.12792    30*120  R       n/d   n/d   22.6     Mondy/AZT-33IK


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