MASTER OT J111012.51+274912.8 - optical counterpart of GRB 200412B in Gagarin Day

ATel #13627; V. Lipunov, E. Gorbovskoy, V. Kornilov, N. Tyurina, P. Balanutsa, A. Kuznetsov, F. Balakin, V. Vladimirov, D. Vlasenko, I. Gorbunov, D. Zimnukhov, V. Senik, T. Pogrosheva, D. Kuvshinov, D. Cheryasov (Lomonosov Moscow State University), V. Yurkov, A. Gabovich, Yu. Sergienko (Blagoveschensk Educational State University), 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), A. Tlatov, D. Dormidontov (Kislovodsk Solar Station of the Pulkovo Observatory)
on 12 Apr 2020; 16:10 UT
Credential Certification: Nataly Tyurina (tiurina@sai.msu.ru)

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MASTER OT J111012.51+274912.8 discovery - optical counterpart inside Fermi GRB 200325B

MASTER-Amur(twin 40cm robotic telescope of MASTER Global Robotic Net (Lomonosov MSU), that is located near Cosmodrom Vostochniy) started alert observations of Fermi GRB 200412B / trigger 606840801 (Fermi GCN #27547, BALROG GCN #27548) at 2020-04-12 11:32:08 UT just after sunset (Lipunov et al. GCN #27549, GCN #27555 https://master.sai.msu.ru/site/master2/event.php?id=1335007 )

During inspect
MASTER-Amur auto-detection system ( Lipunov et al., "MASTER Global Robotic Net", Advances in Astronomy, 2010, 30L )

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 (mlim=18.0).
The OT is seen in several images (there is no minor planet at this place). OT is fading, and (for example) has unfiltered m_OT~17.5 at 2020-04-12 14:05:34UT.

We have reference image on 2016-08-12.64123 UT with unfiltered mlim= 19.3m.

Spectral observations and deep photometry are required.

The discovery and reference images are available at:
http://master.sai.msu.ru/static/OT/183315.33623157.0.png
This work was supported by RFBR BRICS grant 17-52-80133.

MASTER Global Robotic Net