TITLE: GCN CIRCULAR NUMBER: 28728 SUBJECT: MAXI GRB201021.68: Global MASTER-Net observations report DATE: 20/10/21 20:17:21 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 MAXI GRB201021.68 (trigger No 143544224,00h 14m 16.08s , -63d 29m 31.2s, R=1) errorbox 9280 sec after notice time and 13381 sec after trigger time at 2020-10-21 20:02:07 UT, with upper limit up to 20.2 mag. The observations began at zenith distance = 33 deg. The sun altitude is -35.3 deg. The galactic latitude b = -53 deg., longitude l = 309 deg. Real time updated cover map and OT discovered available here: https://master.sai.msu.ru/site/master2/observ.php?id=1466520 We obtain a following upper limits. Tmid-T0 | Date Time | Site | Coord (J2000) |Filt.| Expt. | Limit| Comment _________|_____________________|_____________________|____________________________________|_____|_______|_______|________ 13471 | 2020-10-21 20:02:07 | MASTER-SAAO | (00h 15m 17.20s , -63d 33m 50.4s) | C | 180 | 19.9 | 13471 | 2020-10-21 20:02:07 | MASTER-SAAO | (00h 13m 23.07s , -63d 34m 18.3s) | C | 180 | 19.8 | 13671 | 2020-10-21 20:05:27 | MASTER-SAAO | (00h 15m 23.28s , -63d 34m 57.6s) | C | 180 | 20.1 | 13671 | 2020-10-21 20:05:27 | MASTER-SAAO | (00h 13m 29.09s , -63d 35m 25.1s) | C | 180 | 19.9 | 13871 | 2020-10-21 20:08:46 | MASTER-SAAO | (00h 15m 17.91s , -63d 36m 02.6s) | C | 180 | 20.2 | 13871 | 2020-10-21 20:08:46 | MASTER-SAAO | (00h 13m 23.46s , -63d 36m 29.5s) | C | 180 | 20.0 | Filter C is a clear (unfiltred) band. The observation and reduction will continue. The message may be cited.