TITLE: GCN CIRCULAR NUMBER: 30029 SUBJECT: IceCube Alert 210516.61: Global MASTER-Net observations report DATE: 21/05/16 17:39:15 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) was pointed to the IceCube Alert 210516.61 (trigger No 56063172,06h 07m 02.40s , +09d 31m 12.0s, R=0.78) errorbox 9449 sec after notice time and 9500 sec after trigger time at 2021-05-16 17:16:40 UT, with upper limit up to 16.0 mag. The observations began at zenith distance = 72 deg. The sun altitude is -18.6 deg. The galactic latitude b = -5 deg., longitude l = 200 deg. Real time updated cover map and OT discovered available here: https://master.sai.msu.ru/site/master2/observ.php?id=1614326 We obtain a following upper limits. Tmid-T0 | Date Time | Site | Coord (J2000) |Filt.| Expt. | Limit| Comment _________|_____________________|_____________________|____________________________________|_____|_______|_______|________ 9591 | 2021-05-16 17:16:40 | MASTER-SAAO | (06h 07m 17.31s , +09d 33m 08.0s) | C | 180 | 16.0 | 9790 | 2021-05-16 17:20:00 | MASTER-SAAO | (06h 07m 24.28s , +09d 35m 15.5s) | C | 180 | 14.3 | 9990 | 2021-05-16 17:23:20 | MASTER-SAAO | (06h 07m 20.24s , +09d 34m 25.3s) | C | 180 | 15.4 | 10190 | 2021-05-16 17:26:40 | MASTER-SAAO | (06h 07m 22.59s , +09d 35m 32.8s) | C | 180 | 15.4 | Filter C is a clear (unfiltred) band. The observation and reduction will continue. The message may be cited.