TITLE: GCN CIRCULAR NUMBER: 30095 SUBJECT: MAXI GRB210528.95: Global MASTER-Net observations report DATE: 21/05/29 00:51:13 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-IAC robotic telescope (Global MASTER-Net: http://observ.pereplet.ru, Lipunov et al., 2010, Advances in Astronomy, vol. 2010, 30L) located in Spain (IAC Teide Observatory) started inspect of the MAXI GRB210528.95 (trigger No 362758075,15h 58m 09.36s , +05d 58m 58.8s, R=1) errorbox 10 sec after notice time and 4707 sec after trigger time at 2021-05-29 00:10:22 UT, with upper limit up to 18.8 mag. The observations began at zenith distance = 23 deg. The sun altitude is -39.0 deg. The galactic latitude b = 40 deg., longitude l = 16 deg. Real time updated cover map and OT discovered available here: https://master.sai.msu.ru/site/master2/observ.php?id=1623577 We obtain a following upper limits. Tmid-T0 | Date Time | Site | Coord (J2000) |Filt.| Expt. | Limit| Comment _________|_____________________|_____________________|____________________________________|_____|_______|_______|________ 4798 | 2021-05-29 00:10:22 | MASTER-IAC | (15h 57m 01.56s , +06d 02m 14.3s) | P| | 180 | 18.5 | 4798 | 2021-05-29 00:10:22 | MASTER-IAC | (15h 56m 10.28s , +06d 08m 43.9s) | P- | 180 | 18.3 | 4998 | 2021-05-29 00:13:42 | MASTER-IAC | (15h 57m 09.19s , +06d 02m 16.4s) | P| | 180 | 18.7 | 4998 | 2021-05-29 00:13:42 | MASTER-IAC | (15h 56m 17.67s , +06d 08m 46.0s) | P- | 180 | 18.3 | 5198 | 2021-05-29 00:17:02 | MASTER-IAC | (15h 57m 06.12s , +06d 03m 54.3s) | P| | 180 | 18.7 | 5198 | 2021-05-29 00:17:02 | MASTER-IAC | (15h 56m 14.54s , +06d 10m 23.3s) | P- | 180 | 18.4 | 5398 | 2021-05-29 00:20:22 | MASTER-IAC | (15h 57m 06.18s , +06d 02m 37.0s) | P| | 180 | 18.8 | 5398 | 2021-05-29 00:20:22 | MASTER-IAC | (15h 56m 14.59s , +06d 09m 05.6s) | P- | 180 | 18.4 | The observation and reduction will continue. The message may be cited.