TITLE: GCN CIRCULAR NUMBER: 30661 SUBJECT: Swift GRB 210818A: Global MASTER-Net observations report DATE: 21/08/19 01:06:55 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) was pointed to the Swift GRB 210818A ( A. P. Beardmore et al., GCN 30652) errorbox 22995 sec after notice time and 23077 sec after trigger time at 2021-08-18 07:27:44 UT, with upper limit up to 18.9 mag. The observations began at zenith distance = 62 deg. The sun altitude is -47.3 deg. The galactic latitude b = -25 deg., longitude l = 301 deg. Real time updated cover map and OT discovered available here: https://master.sai.msu.ru/site/master2/observ.php?id=1693376 We obtain a following upper limits. Tmid-T0 | Site |Filt.| Expt. | Limit| Comment _________|_____________________|_____|_______|______|________ 23167 | MASTER-OAFA | C | 180 | 13.8 | 23347 | MASTER-OAFA | C | 540 | 14.9 | Coadd 23379 | MASTER-OAFA | C | 180 | 14.9 | 23559 | MASTER-OAFA | C | 540 | 15.3 | Coadd 23592 | MASTER-OAFA | C | 180 | 14.6 | 23812 | MASTER-OAFA | C | 180 | 14.3 | 24026 | MASTER-OAFA | C | 180 | 14.8 | 24242 | MASTER-OAFA | C | 180 | 15.8 | 24456 | MASTER-OAFA | C | 180 | 15.0 | 24636 | MASTER-OAFA | C | 540 | 17.0 | Coadd 24668 | MASTER-OAFA | C | 180 | 14.9 | 24883 | MASTER-OAFA | C | 180 | 16.4 | 25099 | MASTER-OAFA | C | 180 | 17.3 | 25279 | MASTER-OAFA | C | 540 | 18.0 | Coadd 25329 | MASTER-OAFA | C | 180 | 17.4 | 25546 | MASTER-OAFA | C | 180 | 17.4 | 25762 | MASTER-OAFA | C | 180 | 16.9 | 25942 | MASTER-OAFA | C | 540 | 18.0 | Coadd 25975 | MASTER-OAFA | C | 180 | 18.0 | 26190 | MASTER-OAFA | C | 180 | 17.3 | 26405 | MASTER-OAFA | C | 180 | 17.3 | 26585 | MASTER-OAFA | C | 540 | 17.6 | Coadd 26621 | MASTER-OAFA | C | 180 | 17.7 | 26833 | MASTER-OAFA | C | 180 | 17.5 | 27049 | MASTER-OAFA | C | 180 | 17.7 | 27229 | MASTER-OAFA | C | 540 | 18.3 | Coadd 27264 | MASTER-OAFA | C | 180 | 17.5 | 27479 | MASTER-OAFA | C | 180 | 17.7 | 27691 | MASTER-OAFA | C | 180 | 17.5 | 27871 | MASTER-OAFA | C | 540 | 18.5 | Coadd 27906 | MASTER-OAFA | C | 180 | 17.6 | 28123 | MASTER-OAFA | C | 180 | 18.2 | 28337 | MASTER-OAFA | C | 180 | 17.7 | 28517 | MASTER-OAFA | C | 540 | 18.1 | Coadd 28551 | MASTER-OAFA | C | 180 | 17.3 | 28765 | MASTER-OAFA | C | 180 | 18.0 | 28983 | MASTER-OAFA | C | 180 | 18.0 | 29199 | MASTER-OAFA | C | 180 | 17.9 | 29415 | MASTER-OAFA | C | 180 | 17.7 | 29595 | MASTER-OAFA | C | 540 | 18.0 | Coadd 29630 | MASTER-OAFA | C | 180 | 17.5 | 29810 | MASTER-OAFA | C | 540 | 18.6 | Coadd 29842 | MASTER-OAFA | C | 180 | 18.2 | 30058 | MASTER-OAFA | C | 180 | 18.4 | 30272 | MASTER-OAFA | C | 180 | 18.2 | 30488 | MASTER-OAFA | C | 180 | 17.8 | 30701 | MASTER-OAFA | C | 180 | 18.0 | 30881 | MASTER-OAFA | C | 540 | 18.9 | Coadd 30917 | MASTER-OAFA | C | 180 | 18.1 | 31130 | MASTER-OAFA | C | 180 | 18.3 | 31329 | MASTER-OAFA | C | 180 | 18.3 | 31729 | MASTER-OAFA | C | 180 | 18.4 | 31909 | MASTER-OAFA | C | 540 | 18.5 | Coadd 31928 | MASTER-OAFA | C | 180 | 18.4 | 32127 | MASTER-OAFA | C | 180 | 18.0 | 32327 | MASTER-OAFA | C | 180 | 17.4 | 32507 | MASTER-OAFA | C | 540 | 18.0 | Coadd 32527 | MASTER-OAFA | C | 180 | 17.3 | 32726 | MASTER-OAFA | C | 180 | 17.1 | 32926 | MASTER-OAFA | C | 180 | 17.3 | 33106 | MASTER-OAFA | C | 540 | 17.9 | Coadd 33125 | MASTER-OAFA | C | 180 | 17.5 | 33325 | MASTER-OAFA | C | 180 | 17.1 | 33524 | MASTER-OAFA | C | 180 | 16.7 | Filter C is a clear (unfiltred) band. The observation and reduction will continue. The message may be cited.