TITLE:   GCN CIRCULAR
NUMBER:  34396
SUBJECT: Fermi GRB 230812B: MASTER optical counterpart
DATE:    23/08/13 05:28:50 GMT
FROM:    Vladimir Lipunov at Moscow State U/Krylov Obs <lipunov@xray.sai.msu.ru>


V.Lipunov (Lomonosov MSU),
D.Svinkin (Ioffe Institute),
A.Kuznetsov, A.Sosnovskiy, N.Tiurina, E.Gorbovskoy, Ya.Kechin, P.Balanutsa, K.Zhirkov,
O.Gress,  A.Chasovnikov, G.Antipov, D.Vlasenko, V.Senik, V.Topolev, Yu.Tselik, Siyu Wu, D.Cheryasov, V.Shumkov, T.Pogrosheva (Lomonosov Moscow State University,SAI,Physics Department),
C.Francile, F. Podesta, C.Lopez, R. Podesta (Observatorio Astronomico Felix Aguilar OAFA),
D.Buckley (SAAO),
R. Rebolo, M. Serra (The Instituto de Astrofisica de Canarias),
L.Carrasco, J.R.Valdes, V.Chavushyan, V.M.Patino
Alvarez,J.Martinez,A.Corella,L.H.Rodriguez (INAOE, Guillermo Haro Astrophysics Observatory),
N.M.Budnev, O.Gress (ISU,API),
A.Gabovich, V.Yurkov (BSPU),
A. Tlatov, D. Dormidontov (Kislovodsk Solar Station of the Pulkovo Observatory),

MASTER started Fermi GRB 230812B (Fermi GBM team GCN 34386, Ttrigger=18:58:12,
Lesage et al. GCN 34387, Evans et al. GCN 34388, Scotton  et al. GCN 34387, Roberts et al. GCN 34391)
at MASTER-SAAO (Lipunov et al GCN 34389, see covermap, near horizont; GCN 34390) by MASTER-II and MASTER very wide field cameras (Lipunov et al. 2010)

Fermi GBM error-box was covered by MASTER-SAAO, MASTER-Tavrida (since 2023-08-12 21:56:45 UT), MASTER-OAFA.

There is optical counterpart at
R.A.,Dec.2000= 16 36 31.48 +47 51 35.14
with m=18.2 at several set of images.

that is in ~18" of Swift-XRT preliminary counterpart (Swift GCN 34393)

We observed it till sunrise in MASTER-Tavrida , reduction will be continued.