TITLE: GCN CIRCULAR NUMBER: 30764 SUBJECT: Fermi GRB 210904A: Global MASTER-Net observations report DATE: 21/09/05 00:15:17 GMT FROM: Vladimir Lipunov at Moscow State U/Krylov Obs <lipunov@xray.sai.msu.ru> 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 210904A ( Fermi GBM team, GCN 30763) errorbox 8467 sec after notice time and 8548 sec after trigger time at 2021-09-04 23:10:08 UT, with upper limit up to 18.4 mag. The observations began at zenith distance = 81 deg. The sun altitude is -63.8 deg. The galactic latitude b = -6 deg., longitude l = 260 deg. Real time updated cover map and OT discovered available here: https://master.sai.msu.ru/site/master2/observ.php?id=1709787 We obtain a following upper limits. Tmid-T0 | Date Time | Site | Coord (J2000) |Filt.| Expt. | Limit| Comment _________|_____________________|_____________________|____________________________________|_____|_______|_______|________ 8579 | 2021-09-04 23:10:08 | MASTER-SAAO | (07h 13m 56.09s , -50d 06m 24.2s) | C | 60 | 17.5 | 8818 | 2021-09-04 23:14:07 | MASTER-SAAO | (07h 19m 10.91s , -51d 59m 24.1s) | C | 60 | 17.7 | 9296 | 2021-09-04 23:22:05 | MASTER-SAAO | (07h 08m 22.61s , -48d 12m 57.4s) | C | 60 | 17.8 | 9376 | 2021-09-04 23:23:25 | MASTER-SAAO | (07h 38m 53.16s , -53d 54m 13.5s) | C | 60 | 17.9 | 9536 | 2021-09-04 23:26:05 | MASTER-SAAO | (07h 13m 58.12s , -50d 07m 33.3s) | C | 60 | 17.8 | 9775 | 2021-09-04 23:30:04 | MASTER-SAAO | (07h 19m 06.81s , -51d 59m 26.1s) | C | 60 | 17.8 | 9854 | 2021-09-04 23:31:23 | MASTER-SAAO | (07h 32m 12.17s , -51d 59m 49.4s) | C | 60 | 17.7 | 10014 | 2021-09-04 23:34:03 | MASTER-SAAO | (07h 04m 54.17s , -46d 20m 01.5s) | C | 60 | 18.0 | 10253 | 2021-09-04 23:38:02 | MASTER-SAAO | (07h 08m 27.37s , -48d 12m 23.6s) | C | 60 | 18.1 | 10333 | 2021-09-04 23:39:22 | MASTER-SAAO | (07h 20m 20.55s , -48d 12m 41.9s) | C | 60 | 17.8 | 10412 | 2021-09-04 23:40:41 | MASTER-SAAO | (07h 38m 52.71s , -53d 52m 36.0s) | C | 60 | 18.0 | 10492 | 2021-09-04 23:42:01 | MASTER-SAAO | (07h 52m 31.79s , -53d 52m 56.7s) | C | 60 | 18.0 | 10651 | 2021-09-04 23:44:40 | MASTER-SAAO | (07h 13m 59.74s , -50d 08m 01.5s) | C | 60 | 18.1 | 10890 | 2021-09-04 23:48:40 | MASTER-SAAO | (07h 19m 12.08s , -52d 00m 03.6s) | C | 60 | 18.2 | 10970 | 2021-09-04 23:49:59 | MASTER-SAAO | (07h 32m 06.04s , -52d 00m 12.5s) | C | 60 | 18.0 | 11130 | 2021-09-04 23:52:39 | MASTER-SAAO | (07h 04m 54.64s , -46d 19m 44.5s) | C | 60 | 18.3 | 11369 | 2021-09-04 23:56:38 | MASTER-SAAO | (07h 08m 23.65s , -48d 12m 55.9s) | C | 60 | 18.4 | 11449 | 2021-09-04 23:57:58 | MASTER-SAAO | (07h 20m 23.73s , -48d 13m 57.4s) | C | 60 | 18.1 | 11528 | 2021-09-04 23:59:17 | MASTER-SAAO | (07h 38m 57.95s , -53d 53m 04.8s) | C | 60 | 18.3 | 11608 | 2021-09-05 00:00:37 | MASTER-SAAO | (07h 52m 26.26s , -53d 53m 22.3s) | C | 60 | 18.0 | 11691 | 2021-09-05 00:02:00 | MASTER-SAAO | (07h 25m 12.86s , -50d 06m 49.5s) | C | 60 | 18.2 | 11771 | 2021-09-05 00:03:20 | MASTER-SAAO | (07h 37m 35.60s , -50d 07m 15.3s) | C | 60 | 18.0 | 11850 | 2021-09-05 00:04:39 | MASTER-SAAO | (07h 43m 49.99s , -51d 59m 23.6s) | C | 60 | 17.9 | 11930 | 2021-09-05 00:05:59 | MASTER-SAAO | (07h 56m 49.28s , -52d 00m 07.8s) | C | 60 | 17.9 | 12010 | 2021-09-05 00:07:19 | MASTER-SAAO | (07h 31m 08.10s , -48d 12m 41.2s) | C | 60 | 18.1 | 12089 | 2021-09-05 00:08:39 | MASTER-SAAO | (07h 43m 08.49s , -48d 11m 09.0s) | C | 60 | 17.8 | 12169 | 2021-09-05 00:09:58 | MASTER-SAAO | (07h 48m 48.15s , -50d 06m 50.2s) | C | 60 | 17.8 | Filter C is a clear (unfiltred) band. The observation and reduction will continue. The message may be cited.