TITLE:   GCN CIRCULAR
NUMBER:  35299
SUBJECT: GRB 231205B: optical upper limit in TSHAOand AbAO
DATE:    23/12/07 04:13:53 GMT
FROM:    Alexei Pozanenko at IKI, Moscow <apozanen@iki.rssi.ru>

N. Pankov (HSE, IKI), I. Reva (FAI), R. Inasaridze (AbAO), A. Pozanenko (IKI), S. Belkin (IKI, HSE) report on behalf of GRB-IKI-FuN:

We observed the field of GRB 231205B (Evans et al, GCN 35269; Liu & Xiong, GCN 35279) with Zeiss-1000 telescope of Tien-Shan Observatory (TSHAO), and AS-32 telescope of Abastumani Observatory (AbAO). No new optical sources have been found at the enhanced XRT position (Osborne et al, GCN 35275) in our observations, which is consistent with results reported early (Odeh et al, GCN 35270; Strausbaugh & Cucchiara, GCN 35278; Jiang et al, GCN 35280; Jiang et al, GCN 35281; Gendre et al, GCN 35282; Sasada et al, GCN 35284; Adami et al, GCN 35286; Komesh et al, GCN 35287; Brivio et al, GCN 35289;  Malenakova et al, GCN 35292). Preliminary photometry is following:

Date       UT start  t-T0     Exp.   Filter  OT Err.    UL  Telescope
                   (mid, days)  (s)                    (3sigma) 
2023-12-05 16:43:59  0.0208333 30x120  R   n/d    n/d  22.0  Zeiss-10000
2023-12-05 17:16:09  0.0315857 59x60   R   n/d    n/d  19.6  AS-32