TITLE: GCN CIRCULAR NUMBER: 42110 SUBJECT: GRB 251002A: Mondy/AZT-33IK optical observations DATE: 25/10/05 07:05:17 GMT FROM: Nicolai Pankov at HSE, IKI RAS colinsergesen@gmail.com

N. Pankov (HSE, IKI), A. Pozanenko (IKI), E. Klunko (ISTP) report on behalf of IKI-GRB-FuN:

We performed optical observations of the field of GRB 251002A detected by SVOM (Saccardi et. al, GCN 42060) in the R-filter with the AZT-33IK 1.5m telescope of the Sayan Solar Observatory (Mondy). The observations began on 2025-10-03 17:00 UT, i.e. ~0.88 days since trigger and consisted of 30x120 s exposures. The optical source found by SVOM (Palmerio et. al, GCN 42061) at z = 2.178 (Saccardi et. al, GCN 42076) and also observed by (Turpin et. al, GCN 42062; Jelinek et. al, GCN 42063; Juliá-Maroto et. al, GCN 42064; Moskvitin et. al, GCN 42065; Perez-Garcia et. al, GCN 42066; Saccardi et. al, GCN 42076; Mandarakas et. al, GCN 42077; Cao et. al, GCN 42078; Schneider et. al, GCN 42080; Pankov et. al, GCN 42081; Leonini et. al, GCN 42082; Odeh et. al, GCN 42087; Wortley et. al, GCN 42091; Shilling, GCN 42099; Calapai & Giorgio, GCN 42101) is detected in the co-add image of 30x120 s. Preliminary photometry and observation details are presented below:

Date UT start t-T0 Exp. Filter OT Err. UL (mid,days) (nxs) (3sigma) 2025-10-03 17:00:32 0.88586 30x120 R 20.96 0.12 22.0

The photometry was calibrated using reference stars from (Moskvitin et. al, GCN 42065) and not corrected for the Galactic extinction.

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