TITLE: GCN CIRCULAR NUMBER: 30119 SUBJECT: MAXI GRB210602.50: Global MASTER-Net observations report DATE: 21/06/03 10:17:09 GMT FROM: Vladimir Lipunov at Moscow State U/Krylov Obs 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, SAI, Physics Department), R. Podesta, C.Lopez, F. Podesta, C.Francile (Observatorio Astronomico Felix Aguilar OAFA), 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), V. Yurkov, A. Gabovich, Yu. Sergienko (Blagoveschensk Educational State University) MASTER-OAFA robotic telescope (Global MASTER-Net: http://observ.pereplet.ru, Lipunov et al., 2010, Advances in Astronomy, vol. 2010, 30L) located in Argentina (OAFA observatory of San Juan National University) started inspect of the MAXI GRB210602.50 (trigger No 367443743,02h 58m 31.20s , -02d 40m 19.2s, R=1) errorbox 76251 sec after notice time and 77693 sec after trigger time at 2021-06-03 09:39:01 UT, with upper limit up to 17.0 mag. The observations began at zenith distance = 77 deg. The sun altitude is -22.4 deg. The galactic latitude b = -50 deg., longitude l = 180 deg. Real time updated cover map and OT discovered available here: https://master.sai.msu.ru/site/master2/observ.php?id=1626919 We obtain a following upper limits. Tmid-T0 | Date Time | Site | Coord (J2000) |Filt.| Expt. | Limit| Comment _________|_____________________|_____________________|____________________________________|_____|_______|_______|________ 77784 | 2021-06-03 09:39:01 | MASTER-OAFA | (02h 56m 34.35s , -03d 25m 33.9s) | C | 180 | 17.0 | 77923 | 2021-06-03 09:42:21 | MASTER-OAFA | (02h 56m 37.84s , -03d 22m 41.9s) | C | 60 | 16.7 | 78003 | 2021-06-03 09:43:40 | MASTER-OAFA | (03h 04m 35.58s , -03d 20m 47.3s) | C | 60 | 16.5 | Filter C is a clear (unfiltred) band. The observation and reduction will continue. The message may be cited.