TITLE:   GCN CIRCULAR
NUMBER:  34412
SUBJECT: GRB 230812B: AbAO optical observations
DATE:    23/08/14 08:02:51 GMT
FROM:    Alexei Pozanenko at IKI, Moscow <apozanen@iki.rssi.ru>

S. Belkin (IKI),  R. Ya. Inasaridze (AbAO),  A. Pozanenko (IKI), N. 
Pankov (HSE, 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) with AS-32 telescope of Abastumani observatory (AbAO) in R-filter starting on Aug. 13 (UT) 17:32:00. We  detected the  afterglow (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; Frederiks et al., GCN 34403; 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) in the 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 17:32:00   0.97336  R     54*60  20.35 0.24    20.9

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

The underlying extended source galaxy mentioned by GOTO (Ackley et al., GCN 34398) is visible in Legacy Survey DR10 Catalog with r~22.66 and classified as round exponential galaxy.