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GCN Circular 29339

GRB 210120A: MASTER OT (possibly) discovery
2021-01-20T20:41:29Z (3 years ago)
Vladimir Lipunov at Moscow State U/Krylov Obs <>
V. Lipunov, V.Kornilov, E.Gorbovskoy,N.Tiurina,P.Balanutsa,F.Balakin, V.Vladimirov, A.Kuznetsov,K.Zhirkov,D. Vlasenko, I.Gorbunov, D.Zimnukhov, 
V.Senik, A.Chasovnikov,A.Pozdnyakov,V.Topolev, D.Cheryasov(Lomonosov Moscow State University, SAI, Physics Department),
R. Podesta, C.Lopez, F. Podesta, C.Francile (Observatorio Astronomico FelixAguilar OAFA),
R. Rebolo, M. Serra(The Instituto de Astrofisica de Canarias),
D. Buckley (South African Astronomical Observatory),
O.A. Gres, N.M. Budnev (Irkutsk State University, API),
A. Tlatov, D. Dormidontov (Kislovodsk Solar Station of the Pulkovo Observatory),
A. Gabovich, V.Yurkov, Yu. Sergienko (Blagoveschensk Educational StateUniversity)

MASTER-OAFA robotic telescope (MASTER-Net:  Lipunov et al.,2010,Advances in Astronomy,2010,30L)
automatically was pointed (Lipunov et al. GCN 29336)
to Fermi GRB210120A (Ttrigger=07:10:44UT, Fermi GCN 29334, BALROG localization Biltzinger et al. GCN 29335,
Barthelmy )
80s after notice time (143s after trigger time) at 2021-01-20 07:13:07UT

At first images MASTER auto-detection system found fast changing optical transient
  MASTER OT J105242.66+152355.0 / AT2021axc
at (RA, Dec) = 10h 52m 42.66s +15d 23m 55.0s at 2021-01-20 07:20:30UT
with unfiltered m_OT=18.6 at the beginning stage.

The OT is seen at several images. There is no any sources at this place in 
MASTER database since 2004.

The nearest source in VIZIER is SDSS galaxy in 4.9" with rmag(as most 
closest to MASTER unfiltered)=22.217 (22.088 in PanSTARRS)

The reduction will be continued.
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