TITLE: GCN CIRCULAR NUMBER: 30055 SUBJECT: Fermi GRB 210519A: Global MASTER-Net observations report DATE: 21/05/19 23:35:36 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-Kislovodsk robotic telescope (Global MASTER-Net: http://observ.pereplet.ru, Lipunov et al., 2010, Advances in Astronomy, vol. 2010, 30L) located in Russia (Lomonosov MSU, Kislovodsk Solar Station of Pulkovo observatory) started inspect of the Fermi GRB 210519A ( Fermi GBM team, GCN 30050) errorbox 40250 sec after notice time and 40298 sec after trigger time at 2021-05-19 17:50:32 UT, with upper limit up to 16.7 mag. Observations started at twilight. The observations began at zenith distance = 78 deg. The sun altitude is -12.6 deg. MASTER-SAAO robotic telescope located in South Africa (South African Astronomical Observatory) started inspect of the Fermi GRB 210519A errorbox 58554 sec after notice time and 58602 sec after trigger time at 2021-05-19 22:55:36 UT, with upper limit up to 18.5 mag. The observations began at zenith distance = 43 deg. The sun altitude is -77.1 deg. The galactic latitude b = 22 deg., longitude l = 299 deg. Real time updated cover map and OT discovered available here: https://master.sai.msu.ru/site/master2/observ.php?id=1616830 We obtain a following upper limits. Tmid-T0 | Date Time | Site | Coord (J2000) |Filt.| Expt. | Limit| Comment _________|_____________________|_____________________|____________________________________|_____|_______|_______|________ 40328 | 2021-05-19 17:50:32 | MASTER-Kislovodsk | (12h 22m 19.71s , -34d 52m 18.4s) | C | 60 | 14.0 | 41150 | 2021-05-19 18:04:13 | MASTER-Kislovodsk | (12h 40m 51.34s , -34d 52m 59.1s) | C | 60 | 16.4 | 41150 | 2021-05-19 18:04:13 | MASTER-Kislovodsk | (12h 36m 11.32s , -34d 30m 24.5s) | C | 60 | 16.7 | 41230 | 2021-05-19 18:05:33 | MASTER-Kislovodsk | (12h 22m 17.46s , -34d 51m 54.8s) | C | 60 | 16.3 | 43450 | 2021-05-19 18:42:34 | MASTER-Kislovodsk | (12h 40m 49.26s , -34d 51m 23.6s) | C | 60 | 15.9 | 43450 | 2021-05-19 18:42:34 | MASTER-Kislovodsk | (12h 36m 08.06s , -34d 29m 00.1s) | C | 60 | 16.3 | 43530 | 2021-05-19 18:43:54 | MASTER-Kislovodsk | (12h 22m 26.48s , -34d 52m 33.3s) | C | 60 | 15.8 | 58633 | 2021-05-19 22:55:36 | MASTER-SAAO | (12h 35m 09.15s , -40d 27m 20.7s) | C | 60 | 18.2 | 58713 | 2021-05-19 22:56:56 | MASTER-SAAO | (12h 45m 32.72s , -40d 28m 26.9s) | C | 60 | 18.5 | 58794 | 2021-05-19 22:58:18 | MASTER-SAAO | (12h 37m 03.01s , -42d 22m 05.2s) | C | 60 | 18.2 | 59083 | 2021-05-19 23:03:06 | MASTER-SAAO | (12h 47m 51.42s , -42d 23m 06.8s) | C | 60 | 18.4 | 59890 | 2021-05-19 23:16:33 | MASTER-SAAO | (12h 35m 08.28s , -40d 27m 54.7s) | C | 60 | 18.4 | 59970 | 2021-05-19 23:17:53 | MASTER-SAAO | (12h 45m 36.10s , -40d 27m 13.1s) | C | 60 | 18.3 | Filter C is a clear (unfiltred) band. The observation and reduction will continue. The message may be cited.