TITLE:   GCN CIRCULAR
NUMBER:  42081
SUBJECT: GRB 251002A: AbAO optical observations
DATE:    25/10/03 08:39:52 GMT
FROM:    Nicolai Pankov at HSE, IKI RAS <colinsergesen@gmail.com>

N. Pankov (HSE, IKI), A. Pozanenko (IKI), R. Ya. Inasaridze (AbAO) 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 AS-32 0.7m telescope of the Abastumani Observatory (AbAO). The observations began on 2025-10-02 21:46 UT, i.e. ~0.09 days since trigger and consisted of 87x60 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) is clearly visible in the co-add image of 87x60 s. Preliminary photometry and observation details are presented below:

Date       UT start  t-T0       Exp.  Filter OT    Err. UL
                     (mid,days) (s)                     (3sigma)
2025-10-02 21:46:03  0.09351    87*60 R      19.48 0.16 21.7

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