TITLE:   GCN CIRCULAR
NUMBER:  34423
SUBJECT: GRB 230812B: CrAO ZTSh optical observations
DATE:    23/08/14 19:08:13 GMT
FROM:    Alexei Pozanenko at IKI, Moscow <apozanen@iki.rssi.ru>

S. Belkin (IKI), V. Rumyantsev (CrAO), N. Pankov (HSE, IKI),  A. Pozanenko (IKI) report on behalf of GRB IKI FuN:

We observed the field of GRB 230812B (Fermi GBM Team, GCN 34386; Scotton et al., GCN 34392; Page et al. GCN 34394; Kuin et al., GCN 34399; Casentini et al., GCN 34402; Frederiks et al., GCN 34403) with ZTSH 2.6m telescope of CrAO observatory in R-filter. We  detected the  afterglow (e.g. Lesage et al., GCN 34387; Scotton et al., GCN 34392; Page, GCN 34394; Zheng & Filippenko, GCN 34395; Lipunov et al., GCN 34396; Salgundi et al., GCN 34397; Ackley et al., GCN 34398; Xiong et al., GCN 34401; Casentini et al., GCN 34402; Mao et al., GCN 34404; Odeh et al., GCN 34405; Moskvitin et al., GCN 34406; Leonini et al., GCN 34408; de Ugarte Postigo et al., GCNs 24409, 34410; Belkin et al., GCN 34412, 34421) in a stacked image. Preliminary photometry of the object is following

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

2023-08-13 19:24:53   1.03829  R     39*120 20.25 0.05  23.3  

The photometry is based on nearby SDSS stars used in (Moskvitin et al, GCN 34406):
RA DEC R (Lupton transformations)
16:36:35.9365104 +47:52:54.574320 14.893 0.008
16:36:32.6835360 +47:53:44.537784 16.531 0.009
16:36:25.6055880 +47:53:20.456304 16.827 0.009
16:36:25.1691816 +47:52:20.931816 16.068 0.008
16:36:44.6580984 +47:50:56.806944 15.785 0.008
16:36:40.1374488 +47:54:02.128752 15.698 0.008