TITLE: GCN CIRCULAR NUMBER: 30847 SUBJECT: Swift GRB 210919A: Global MASTER-Net observations report DATE: 21/09/19 01:48:24 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) was pointed to the Swift GRB 210919A ( A. Tohuvavohu et al., GCN 30846) errorbox 47 sec after trigger time at 2021-09-19 00:29:20 UT, with upper limit up to 18.6 mag. The observations began at zenith distance = 61 deg. The sun altitude is -49.0 deg. MASTER-Kislovodsk robotic telescope located in Russia (Lomonosov MSU, Kislovodsk Solar Station of Pulkovo observatory) was pointed to the Swift GRB 210919A errorbox 363 sec after notice time and 790 sec after trigger time at 2021-09-19 00:41:44 UT, with upper limit up to 14.3 mag. The observations began at zenith distance = 50 deg. The sun altitude is -24.1 deg. The galactic latitude b = -19 deg., longitude l = 201 deg. Real time updated cover map and OT discovered available here: https://master.sai.msu.ru/site/master2/observ.php?id=1725958 We obtain a following upper limits. Tmid-T0 | Site |Filt.| Expt. | Limit| Comment _________|_____________________|_____|_______|______|________ 52 | MASTER-SAAO | P\ | 10 | 16.1 | 67 | MASTER-SAAO | P\ | 40 | 17.0 | Coadd 397 | MASTER-SAAO | P\ | 700 | 18.4 | Coadd 77 | MASTER-SAAO | P\ | 10 | 16.4 | 103 | MASTER-SAAO | P\ | 20 | 16.6 | 141 | MASTER-SAAO | P\ | 30 | 16.0 | 176 | MASTER-SAAO | P\ | 100 | 16.6 | Coadd 183 | MASTER-SAAO | P\ | 30 | 14.7 | 230 | MASTER-SAAO | P\ | 40 | 16.4 | 288 | MASTER-SAAO | P\ | 50 | 15.9 | 358 | MASTER-SAAO | P\ | 190 | 16.6 | Coadd 355 | MASTER-SAAO | P\ | 60 | 15.1 | 437 | MASTER-SAAO | P\ | 80 | 16.4 | 541 | MASTER-SAAO | P\ | 100 | 17.8 | 676 | MASTER-SAAO | P\ | 370 | 18.6 | Coadd 662 | MASTER-SAAO | P\ | 120 | 17.8 | 810 | MASTER-SAAO | P\ | 150 | 18.1 | 871 | MASTER-Kislovodsk | P| | 160 | 14.2 | 987 | MASTER-SAAO | P\ | 180 | 17.5 | 1167 | MASTER-SAAO | P\ | 540 | 17.9 | Coadd 1048 | MASTER-Kislovodsk | P- | 180 | 12.4 | 1048 | MASTER-Kislovodsk | P| | 180 | 14.1 | 1188 | MASTER-SAAO | P\ | 180 | 17.4 | 1249 | MASTER-Kislovodsk | P- | 180 | 12.9 | 1249 | MASTER-Kislovodsk | P| | 180 | 14.2 | 1387 | MASTER-SAAO | P\ | 180 | 17.4 | 1449 | MASTER-Kislovodsk | P- | 180 | 13.4 | 1449 | MASTER-Kislovodsk | P| | 180 | 14.3 | 1587 | MASTER-SAAO | P\ | 180 | 17.4 | 1650 | MASTER-Kislovodsk | P- | 180 | 13.6 | The observation and reduction will continue. The message may be cited.