TITLE:   GCN CIRCULAR
NUMBER:  34567
SUBJECT: GRB 230826A: Mondy optical observations
DATE:    23/08/27 01:28:38 GMT
FROM:    Alexei Pozanenko at IKI, Moscow <apozanen@iki.rssi.ru>

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

We observed the field of GRB 230826A detected by Fermi GBM (Fermi GBM Team, GCN 34564) and Swift (Eyles-Ferris et al, 34565) with AZT-33IK telescope of Sayan observatory (Mondy).  Observations started on 2023-08-26 220:06:00  (UT) (i.e. ~33 min since trigger). We obtained  
series of images in R-filter. We do not detect evident candidate within XRT error  circle (Swift-XRT Position: +05h 32m 14.20s +66d 07' 30.0" 5.3 arcsec, radius) in a stacked image.  Preliminary photometry is following:

Date       UT start   t-T0    Filter Exp.    OT   Err.  UL(3sigma)
                       (mid, days)    (s)

2023-08-26 20:06:00   0.038345  R     44*60  n/d  n/d   22.0

We note the presence of the object USNO-B1.0 1561-0095652 at 8.8 arces from the Swift-XRT Position. Measured brightness of the object is R = 18.1 +/- 0.01 what is brighter than USNO-B1.0 R2=18.22 magnitude.

All photometry is based on nearby USNO-B1.0 stars, R2 magnitudes