TITLE: GCN CIRCULAR NUMBER: 30072 SUBJECT: Fermi GRB 210524A: Global MASTER-Net observations report DATE: 21/05/24 05:32:00 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 Fermi GRB 210524A ( Fermi GBM team, GCN 30071) errorbox 559 sec after notice time and 597 sec after trigger time at 2021-05-24 05:09:56 UT, with upper limit up to 17.0 mag. Observations started at twilight. The observations began at zenith distance = 81 deg. The sun altitude is -12.3 deg. The galactic latitude b = -56 deg., longitude l = 348 deg. Real time updated cover map and OT discovered available here: https://master.sai.msu.ru/site/master2/observ.php?id=1620119 We obtain a following upper limits. Tmid-T0 | Date Time | Site | Coord (J2000) |Filt.| Expt. | Limit| Comment _________|_____________________|_____________________|____________________________________|_____|_______|_______|________ 657 | 2021-05-24 05:09:56 | MASTER-IAC | (22h 28m 27.06s , -47d 09m 06.7s) | P| | 120 | 16.8 | 657 | 2021-05-24 05:09:56 | MASTER-IAC | (22h 27m 16.27s , -47d 03m 27.4s) | P- | 120 | 16.4 | 812 | 2021-05-24 05:12:16 | MASTER-IAC | (22h 28m 21.78s , -47d 10m 15.3s) | P| | 150 | 17.0 | 812 | 2021-05-24 05:12:16 | MASTER-IAC | (22h 27m 11.27s , -47d 04m 34.4s) | P- | 150 | 16.6 | 997 | 2021-05-24 05:15:06 | MASTER-IAC | (22h 28m 27.57s , -47d 09m 54.6s) | P| | 180 | 16.9 | 997 | 2021-05-24 05:15:06 | MASTER-IAC | (22h 27m 17.33s , -47d 04m 12.7s) | P- | 180 | 16.5 | 1197 | 2021-05-24 05:18:26 | MASTER-IAC | (22h 28m 24.64s , -47d 08m 43.0s) | P| | 180 | 16.7 | 1197 | 2021-05-24 05:18:26 | MASTER-IAC | (22h 27m 14.65s , -47d 03m 01.0s) | P- | 180 | 16.2 | 1397 | 2021-05-24 05:21:45 | MASTER-IAC | (22h 28m 24.73s , -47d 10m 02.6s) | P| | 180 | 16.4 | 1397 | 2021-05-24 05:21:45 | MASTER-IAC | (22h 27m 14.82s , -47d 04m 19.1s) | P- | 180 | 15.9 | The observation and reduction will continue. The message may be cited.