TITLE: GCN CIRCULAR NUMBER: 29582 SUBJECT: Integral GRB210227.20: Global MASTER-Net observations report DATE: 21/02/27 05:19:08 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 Integral GRB210227.20 (trigger No 140092,06h 23m 30.88s , +07d 53m 32.5s, R=0.052) errorbox 139 sec after notice time and 146 sec after trigger time at 2021-02-27 04:47:09 UT, with upper limit up to 17.5 mag. The observations began at zenith distance = 73 deg. The sun altitude is -50.6 deg. The galactic latitude b = -2 deg., longitude l = 203 deg. Real time updated cover map and OT discovered available here: https://master.sai.msu.ru/site/master2/observ.php?id=1556899 We obtain a following upper limits. Tmid-T0 | Site |Filt.| Expt. | Limit| Comment _________|_____________________|_____|_______|______|________ 162 | MASTER-OAFA | C | 30 | 16.5 | 207 | MASTER-OAFA | C | 120 | 17.2 | Coadd 216 | MASTER-OAFA | C | 40 | 16.6 | 281 | MASTER-OAFA | C | 50 | 16.8 | 356 | MASTER-OAFA | C | 60 | 16.8 | 446 | MASTER-OAFA | C | 240 | 17.5 | Coadd 445 | MASTER-OAFA | C | 80 | 16.9 | 555 | MASTER-OAFA | C | 100 | 17.0 | 684 | MASTER-OAFA | C | 120 | 17.0 | 839 | MASTER-OAFA | C | 150 | 17.0 | 1023 | MASTER-OAFA | C | 180 | 17.1 | 1223 | MASTER-OAFA | C | 180 | 17.0 | 1423 | MASTER-OAFA | C | 180 | 17.0 | 1623 | MASTER-OAFA | C | 180 | 16.9 | Filter C is a clear (unfiltred) band. The observation and reduction will continue. The message may be cited.