TITLE: GCN CIRCULAR NUMBER: 30972 SUBJECT: GRB 211023B: TSHAO optical observation DATE: 21/10/24 13:54:08 GMT FROM: Alexei Pozanenko at IKI, Moscow <apozanen@iki.rssi.ru> A. Pozanenko (IKI), I. Reva (FAP), M.Krugov (FAP), S. Belkin (IKI), V. Kim (FAP), N. Pankov (HSE) report on behalf of GRB-IKI-FuN: We observed the field of possible short GRB 211023B detected by Swift (Dichiara et al., GCN 30960) with Zeiss-1000 telescope of Tien Shan Astronomical Observatory stating on Oct. 23 (UT) 21:17:06. We obtained series with 120 sec expositions in R-filter. Within enhanced Swift-XRT position (Beardmore et al., GCN 30966) we do not detected any source (see upper limits below). In particular we do not detect possible optical afterglow (Dichiara et al., GCN 30960). Preliminary photometry of stacked images is following Date UT start t-T0 Filter Exp. OT Err. UL(3 sigma) (mid, days) (s) 2021-10-23 21:17:06 0.01127 R 5*120 n/d n/d 18.9 2021-10-23 21:17:06 0.02238 R 21*120 n/d n/d 19.5 The photometry is based on nearby USNO-B1.0 stars. In addition we found a source in Legacy Survey (https://www.legacysurvey.org) which is coincident with UVOT detection (Dichiara et al., GCN 30960). This is a point-like object at ~0.67 arces distance from UVOT position and has a LS DR9 photometry g=24.32, r=24.36, z=23.31