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GCN Circular 33728

Subject
GRB 230506B: MASTER optical observations
Date
2023-05-06T15:27:59Z (a year ago)
From
Vladimir Lipunov at Moscow State U/Krylov Obs <lipunov@xray.sai.msu.ru>

V.Lipunov, P.Balanutsa, A.Kuznetsov, N.Tiurina, O.Gress, E.Gorbovskoy, G.Antipov,K.Zhirkov, D.Vlasenko,
Ya.Kechin, A.Chasovnikov,V.Senik, V.Topolev, Yu.Tselik, Siyu Wu, V.Vladimirov, D.Cheryasov (Lomonosov Moscow State University, SAI,Physics Department),
C.Francile, F. Podesta, C.Lopez, R. Podesta (Observatorio Astronomico Felix Aguilar OAFA),
D.A.H.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.Ershova (ISU,API),
A. Tlatov, D. Dormidontov (Kislovodsk Solar Station of the Pulkovo Observatory),
A. Gabovich, V.Yurkov (Blagoveschensk Educational State University),
K.Vetrov, V.Shumkov, T.Pogrosheva, E.Minkina, O.Ershova (Lomonosov MSU)

MASTER-Amur robotic telescope  (Global MASTER-Net http://observ.pereplet.ru, Lipunov et al., 2010, Advances in Astronomy, vol. 2010, 30L)  located in Russia (Blagoveshchensk State Pedagogical University) was pointed to the SWIFT GRB230506.53 (trigger No 1167266,21h 47m 54.90s , +44d 30m 39.9s, R=0.1) errorbox  6276 sec after trigger time at 2023-05-06 14:29:54 UT, so as alert didn't come from GCN socket system.

The observations began at zenith distance = 72 deg. The sun  altitude  is -22.3 deg.The galactic latitude b = -7 deg., longitude l = 92 deg.


Real time updated cover map and OT discovered available here:
https://master.sai.msu.ru/site/master2/observ.php?id=2214809

We obtained following upper limits.

Tmid-T0  |          Site       |Filt.| Expt. | Limit| Comment
_________|_____________________|_____|_______|______|________

    6367 |         MASTER-Amur |   C |   180 | 16.8 |
    6567 |         MASTER-Amur |   C |   180 | 17.2 |
    6767 |         MASTER-Amur |   C |   180 | 17.3 |
    7037 |         MASTER-Amur |   C |   720 | 18.0 |  Coadd
    6966 |         MASTER-Amur |   C |   180 | 17.3 |
    7166 |         MASTER-Amur |   C |   180 | 17.4 |
    7366 |         MASTER-Amur |   C |   180 | 17.4 |
Filter C is a clear (unfiltred) band.

Observations and analysis will be  continued.
The message may be cited.