TITLE:   GCN CIRCULAR
NUMBER:  30166
SUBJECT: Swift GRB 210610A: MASTER optical counterpart observation
DATE:    21/06/10 18:47:50 GMT
FROM:    Vladimir Lipunov at Moscow State U/Krylov Obs  <lipunov@xray.sai.msu.ru>

V. Lipunov, K.Zhirkov, V.Kornilov, E.Gorbovskoy, I.Gorbunov,P.Balanutsa,V.Vladimirov,A.Kuznetsov,
D. Vlasenko, N.Tiurina, D.Zimnukhov, V.Senik, V.Topolev, A.Chasovnikov, D.Cheryasov (Lomonosov MSU,SAI,PhysicsDepartment),
D. Buckley (South African Astronomical Observatory),
O.A. Gres, N.M. Budnev (Irkutsk State University, API),
R. Podesta, C.Lopez, F. Podesta, C.Francile (Observatorio Astronomico FelixAguilar OAFA),
R. Rebolo, M. Serra(The Instituto de Astrofisica de Canarias),
A. Tlatov, D. Dormidontov (Kislovodsk Solar Station of the Pulkovo Observatory),
A. Gabovich, V.Yurkov (Blagoveschensk Educational StateUniversity)

MASTER Global robotic net (MASTER-Net:http://observ.pereplet.ru Lipunov et al.,2010,Advances in Astronomy,2010,30L)
started Swift GRB 210610A (Page et al. GCN 30160) error box observation 
at 2021-06-10 16:23:35UT at MASTER-SAAO.

There is MASTER OT J133707.60+142755.0 with m_OT~20.1m (unfiltered), that was 
discovered by Swift-UVOT (Page et al. 30160) and confirmed by
Hosokawa et al. GCN 30161, Xu et al. GCN 30162, Kumar et al. GCN 30163, 
and with redshift z=3.54 detected by Zhu et al. GCN 30164.

Observation and reduction will be continued.