TITLE:   GCN CIRCULAR
NUMBER:  28718
SUBJECT: GRB 201020B: MASTER bright optical afterglow detection
DATE:    20/10/21 12:19:33 GMT
FROM:    Vladimir Lipunov at Moscow State U/Krylov Obs  <lipunov@xray.sai.msu.ru>

V. Lipunov, V.Kornilov, E.Gorbovskoy, N.Tiurina, P.Balanutsa, A.Kuznetsov, K.Zhirkov, F.Balakin,
V.Vladimirov, D. Vlasenko, I.Gorbunov, D.Zimnukhov, V.Senik, A.Chasovnikov, 
A.Pozdnyakov, 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 State University)

MASTER-Tavrida wide field robotic-telescope (Lipunov et al. GCN 28704) and 
very wide field cameras observed in alert mode Fermi GRB201020B
(GBM GCN 28703, LAT GCN 28716
https://gcn.gsfc.nasa.gov/other/201020B.gcn3 )

MASTER auto-detection system (Lipunov et al. 2010, Advances in Astronomy, vol. 2010, 30L)
discovered  MASTER OT J050152.74+770406.3
with afterglow light curve at
(RA, Dec2000) = 05h 01m 52.74s +77d 04m 06.3s

with m_OT=13.7 at 2020-10-20.73413 UT.

The OT is seen in 35 images with afterglow behaviour.

We have reference image on 2020-01-02.78682 UT with unfiltered mlim=19.5m.