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GCN Circular 27555

GRB 200412B: MASTER Optical Couterpart in Gagarin day!
2020-04-12T15:28:52Z (4 years ago)
Vladimir Lipunov at Moscow State U/Krylov Obs <>
V. Lipunov (Lomonosov MSU) and  V. Yurkov, A. Gabovich, Yu. Sergienko( 
Educational State University)

E. Gorbovskoy, V.Kornilov, N.Tyurina,
V.Vladimirov, D. Vlasenko, I.Gorbunov, D.Zimnukhov, V.Senik, T.Pogrosheva,
D.Kuvshinov(Lomonosov Moscow State University, SAI, Physics Department),
A. Tlatov, D. Dormidontov (Kislovodsk Solar Station of the Pulkovo Observatory),
R. Podesta, C.Lopez, F. Podesta, C.Francile(Observatorio Astronomico Felix Aguilar OAFA),
H.Levato(Instituto de Ciencias Astronomicas, de la Tierra y del Espacio ICATE),
R. Rebolo, M. Serra(The Instituto de Astrofisica de Canarias),
D. Buckley(South African Astronomical Observatory),
O.A. Gres, N.M. Budnev, O.Ershova (Irkutsk State University, API),
V. Yurkov, A. Gabovich, Yu. Sergienko(Blagoveschensk Educational State

MASTER OT J183315.33+623157.0 (AT2020har) discovery new OT inside Fermi GRB 200412B
(trigger 608375325).

MASTER-Amur auto-detection system ( located near Russia Kosmodrom 
Vostochniy) discovered OT source at (RA, Dec) = 18h 33m 15.33s +62d 31m 
57.0s on 
2020-04-12.48156 UT in Fermi error box (GCN 27547, 27548) Lipunov et al., 
GCN  27549).

The OT unfiltered magnitude is 16.6m

The OT is seen in 2 images. There is no minor planet at this place.

We have reference image on 2016-08-12.64123 UT with unfiltered mlim= 

Spectral observations are required.

The discovery and reference images are available at:

[GCN OPS NOTE(13apr20):  Per author's request, In the first sentence change
"J111012.51+274912.8" to "J183315.33+623157.0 (AT2020har)" and change
"200325B" to "200412B" and "606840801" to "608375325".
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