TITLE: GCN CIRCULAR NUMBER: 29801 SUBJECT: Fermi GRB 210411B: Global MASTER-Net observations report DATE: 21/04/11 21:45:12 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-SAAO robotic telescope (Global MASTER-Net: http://observ.pereplet.ru, Lipunov et al., 2010, Advances in Astronomy, vol. 2010, 30L) located in South Africa (South African Astronomical Observatory) started inspect of the Fermi GRB 210411B ( Fermi GBM team, GCN 29792) errorbox 23474 sec after notice time and 23504 sec after trigger time at 2021-04-11 20:04:29 UT, with upper limit up to 19.5 mag. The observations began at zenith distance = 48 deg. The sun altitude is -47.0 deg. The galactic latitude b = -23 deg., longitude l = 287 deg. Real time updated cover map and OT discovered available here: https://master.sai.msu.ru/site/master2/observ.php?id=1589472 We obtain a following upper limits. Tmid-T0 | Date Time | Site | Coord (J2000) |Filt.| Expt. | Limit| Comment _________|_____________________|_____________________|____________________________________|_____|_______|_______|________ 23535 | 2021-04-11 20:04:29 | MASTER-SAAO | (08h 39m 30.90s , -77d 56m 23.8s) | C | 60 | 19.1 | 23614 | 2021-04-11 20:05:48 | MASTER-SAAO | (09h 17m 38.95s , -77d 58m 02.2s) | C | 60 | 19.1 | 23694 | 2021-04-11 20:07:08 | MASTER-SAAO | (06h 05m 46.43s , -77d 55m 48.7s) | C | 60 | 19.2 | 23774 | 2021-04-11 20:08:28 | MASTER-SAAO | (06h 44m 09.25s , -77d 56m 38.9s) | C | 60 | 19.5 | 23853 | 2021-04-11 20:09:48 | MASTER-SAAO | (06h 49m 34.90s , -69d 55m 53.0s) | C | 60 | 19.3 | 23933 | 2021-04-11 20:11:07 | MASTER-SAAO | (07h 13m 02.86s , -69d 56m 51.4s) | C | 60 | 19.1 | 24013 | 2021-04-11 20:12:27 | MASTER-SAAO | (08h 22m 55.69s , -69d 57m 59.8s) | C | 60 | 19.3 | 24331 | 2021-04-11 20:17:45 | MASTER-SAAO | (08h 49m 46.39s , -79d 56m 17.7s) | C | 60 | 19.3 | 25214 | 2021-04-11 20:32:28 | MASTER-SAAO | (06h 31m 44.71s , -79d 54m 54.6s) | C | 60 | 19.5 | 25772 | 2021-04-11 20:41:47 | MASTER-SAAO | (09h 17m 41.73s , -77d 57m 08.2s) | C | 60 | 18.5 | 25852 | 2021-04-11 20:43:06 | MASTER-SAAO | (06h 44m 10.04s , -77d 54m 52.8s) | C | 60 | 18.7 | 25932 | 2021-04-11 20:44:26 | MASTER-SAAO | (07h 12m 53.13s , -69d 55m 51.2s) | C | 60 | 17.8 | 26331 | 2021-04-11 20:51:05 | MASTER-SAAO | (06h 31m 40.60s , -79d 54m 22.4s) | C | 60 | 16.8 | 28128 | 2021-04-11 21:20:02 | MASTER-SAAO | (06h 40m 14.19s , -74d 54m 56.2s) | C | 180 | 18.5 | 28328 | 2021-04-11 21:23:22 | MASTER-SAAO | (06h 40m 12.18s , -74d 53m 09.6s) | C | 180 | 17.6 | 28528 | 2021-04-11 21:26:42 | MASTER-SAAO | (07h 20m 04.43s , -74d 54m 54.3s) | C | 180 | 17.7 | 28727 | 2021-04-11 21:30:01 | MASTER-SAAO | (07h 20m 07.24s , -74d 52m 59.5s) | C | 180 | 18.2 | 28927 | 2021-04-11 21:33:21 | MASTER-SAAO | (08h 07m 54.55s , -74d 54m 18.5s) | C | 180 | 17.7 | 29127 | 2021-04-11 21:36:41 | MASTER-SAAO | (08h 07m 54.94s , -74d 53m 12.7s) | C | 180 | 17.6 | Filter C is a clear (unfiltred) band. The observation and reduction will continue. The message may be cited.