TITLE: GCN CIRCULAR NUMBER: 29667 SUBJECT: Fermi trigger No 637729731: Global MASTER-Net observations report DATE: 21/03/18 21:45:09 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 GRB210318.13 (trigger No 637729731,17h 16m 14.40s , -30d 17m 24.0s, R=9.71) errorbox 18422 sec after notice time and 65890 sec after trigger time at 2021-03-18 21:26:56 UT, with upper limit up to 14.9 mag. The observations began at zenith distance = 83 deg. The sun altitude is -52.2 deg. The galactic latitude b = 4 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=1571245 We obtain a following upper limits. Tmid-T0 | Date Time | Site | Coord (J2000) |Filt.| Expt. | Limit| Comment _________|_____________________|_____________________|____________________________________|_____|_______|_______|________ 65920 | 2021-03-18 21:26:56 | MASTER-SAAO | (17h 36m 50.52s , -35d 54m 24.3s) | C | 60 | 14.1 | 66000 | 2021-03-18 21:28:16 | MASTER-SAAO | (17h 36m 56.20s , -35d 54m 15.6s) | C | 60 | 14.5 | 66080 | 2021-03-18 21:29:36 | MASTER-SAAO | (17h 36m 53.97s , -35d 52m 26.2s) | C | 60 | 14.9 | Filter C is a clear (unfiltred) band. The observation and reduction will continue. The message may be cited.