TITLE: GCN CIRCULAR NUMBER: 29751 SUBJECT: Swift GRB210403.35: Global MASTER-Net observations report DATE: 21/04/03 13:20:29 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 GRB210403.35 (trigger No 1040345,00h 11m 04.08s , -32d 59m 56.4s, R=0.05) errorbox 1478 sec after notice time and 1500 sec after trigger time at 2021-04-03 08:52:14 UT, with upper limit up to 18.8 mag. The observations began at zenith distance = 85 deg. The sun altitude is -25.4 deg. The galactic latitude b = -80 deg., longitude l = 356 deg. Real time updated cover map and OT discovered available here: https://master.sai.msu.ru/site/master2/observ.php?id=1582518 We obtain a following upper limits. Tmid-T0 | Site |Filt.| Expt. | Limit| Comment _________|_____________________|_____|_______|______|________ 1591 | MASTER-OAFA | C | 180 | 16.2 | 2025 | MASTER-OAFA | C | 180 | 17.0 | 2205 | MASTER-OAFA | C | 540 | 18.0 | Coadd 3222 | MASTER-OAFA | C | 180 | 17.8 | 3422 | MASTER-OAFA | C | 180 | 17.9 | 3621 | MASTER-OAFA | C | 180 | 18.0 | 3801 | MASTER-OAFA | C | 540 | 18.8 | Coadd 3820 | MASTER-OAFA | C | 180 | 18.0 | 4020 | MASTER-OAFA | C | 180 | 18.1 | 4219 | MASTER-OAFA | C | 180 | 18.1 | 4419 | MASTER-OAFA | C | 180 | 18.0 | Filter C is a clear (unfiltred) band. The observation and reduction will continue. The message may be cited.