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GCN Circular 32570

GRB 220921A: MASTER OT inside Fermi-LAT error-box
2022-09-21T22:44:10Z (2 years ago)
Vladimir Lipunov at Moscow State U/Krylov Obs <>
V.Lipunov (Lomonosov MSU), D.A.H.Buckley (SAAO),
N.Tiurina, A.Kuznetsov, O.Gress, E.Gorbovskoy, G.Antipov,
P.Balanutsa, K.Zhirkov, A.Chasovnikov, D.Vlasenko, V.Senik, D.Kuvshinov,
V.Topolev,Ya.Kechin, Yu.Tselik (Lomonosov Moscow State University, SAI, Physics Department),
C.Francile, R. Podesta, C.Lopez, F. Podesta (Observatorio Astronomico Felix Aguilar OAFA),
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 (ISU,API),
A. Tlatov, D. Dormidontov (Kislovodsk Solar Station of the Pulkovo Observatory),
A. Gabovich, V.Yurkov (Blagoveschensk Educational State University)

MASTER OT J042553.42-402420.7 discovery as possibly counterpart of GRB 220921A

MASTER-SAAO auto-detection system ( Lipunov et al., "MASTER Global Robotic Net", Advances in Astronomy, 2010, 30L )
  discovered OT source at (RA, Dec) = 04h 25m 53.42s -40d 24m 20.7s on 
2022-09-21.82255 UT during Fermi trigger 685451164 inspection(T0=2022-09-21 11:05:59.07) 
(Lipunov et al. GCN 32569, Fermi-LAT GCN 32568, also detected by GECAM-B)  .

The OT unfiltered magnitude is 17.8m (automatic), mlim=19.8.

The OT is seen in 24 images. There is no minor planet at this place.

We have 600 reference images without any OT since 2014, for ex., on 
2018-11-12.98741 UT with  unfiltered mlim=20.3m.

Spectral observations are required.

There is possible host galaxy in VIZIER database (DES, rmag=24.3)

The message may be cited.
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