TITLE: GCN CIRCULAR NUMBER: 30054 SUBJECT: IceCube Alert 210519.86: Global MASTER-Net observations report DATE: 21/05/19 21:39:16 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-IAC robotic telescope (Global MASTER-Net: http://observ.pereplet.ru, Lipunov et al., 2010, Advances in Astronomy, vol. 2010, 30L) located in Spain (IAC Teide Observatory) started inspect of the IceCube Alert 210519.86 (trigger No 36915486,11h 10m 45.60s , -25d 52m 19.2s, R=2.15) errorbox 14 sec after notice time and 67 sec after trigger time at 2021-05-19 20:41:10 UT, with upper limit up to 16.9 mag. Observations started at twilight. The observations began at zenith distance = 54 deg. The sun altitude is -11.4 deg. The galactic latitude b = 32 deg., longitude l = 277 deg. Real time updated cover map and OT discovered available here: https://master.sai.msu.ru/site/master2/observ.php?id=1616980 We obtain a following upper limits. Tmid-T0 | Date Time | Site | Coord (J2000) |Filt.| Expt. | Limit| Comment _________|_____________________|_____________________|____________________________________|_____|_______|_______|________ 72 | 2021-05-19 20:41:10 | MASTER-IAC | (11h 08m 55.90s , -25d 38m 10.6s) | P- | 10 | 15.1 | 107 | 2021-05-19 20:41:39 | MASTER-IAC | (11h 09m 02.01s , -25d 39m 13.2s) | P- | 20 | 15.5 | 152 | 2021-05-19 20:42:20 | MASTER-IAC | (11h 08m 56.29s , -25d 40m 15.3s) | P- | 30 | 15.9 | 207 | 2021-05-19 20:43:10 | MASTER-IAC | (11h 09m 01.66s , -25d 39m 50.0s) | P- | 40 | 16.1 | 272 | 2021-05-19 20:44:09 | MASTER-IAC | (11h 08m 59.49s , -25d 38m 47.2s) | P- | 50 | 16.2 | 347 | 2021-05-19 20:45:19 | MASTER-IAC | (11h 08m 59.47s , -25d 39m 57.2s) | P- | 60 | 16.4 | 437 | 2021-05-19 20:46:40 | MASTER-IAC | (11h 09m 01.95s , -25d 38m 32.7s) | P- | 80 | 16.6 | 547 | 2021-05-19 20:48:20 | MASTER-IAC | (11h 08m 56.19s , -25d 39m 26.4s) | P- | 100 | 16.8 | 677 | 2021-05-19 20:50:20 | MASTER-IAC | (11h 08m 56.18s , -25d 38m 29.3s) | P- | 120 | 16.9 | The observation and reduction will continue. The message may be cited.