TITLE:   GCN CIRCULAR
NUMBER:  41870
SUBJECT: GRB 250916A: further SAO RAS optical observations
DATE:    25/09/18 15:39:58 GMT
FROM:    Alexander Moskvitin at SAO RAS <mosk@sao.ru>

A. Moskvitin (SAO RAS), A. Pozanenko (IKI), N. Pankov (HSE, IKI)
report on behalf of GRB follow-up collaboration and IKI-GRB-FuN.

We observed the field of the GRB 250916A (Fermi GBM team, GCN 41839; 
Arya et al., GCN 41843; Cheung et al., GCN 41855) with the BTA, 
6-m telescope of SAO RAS equipped with SCORPIO-1 focal reducer.
We obtained 3 x 60 sec. images in Rc band  under mediocre weather 
conditions on September 18, 00:07:09--00:15:29 UT 
(t_mid - T0 = 1.4458 days = 34.6994 hours).

The OT (Belkin et al., GCN 41847; Mohan et al., GCN 41858; 
Burkhonov et al., GCN 41860) at the redshift z = 2.015 
(de Ugarte Postigo et al., GCN 41863) is clearly detected 
in the stacked frame with a brightness of R = 19.72 +/- 0.05.

The preliminary photometry is based on PanSTARRS data on nearby
objects (magnitudes calculated using the Lupton 2005 transformations)
and does not take into account Galactic extinction.