TITLE: GCN CIRCULAR NUMBER: 30107 SUBJECT: Fermi trigger No 644155206: Global MASTER-Net observations report DATE: 21/05/31 22:46:49 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 GRB210531.50 (trigger No 644155206,09h 03m 09.60s , +03d 31m 12.0s, R=1) errorbox 31477 sec after notice time and 31529 sec after trigger time at 2021-05-31 20:45:30 UT, with upper limit up to 18.9 mag. Observations started at twilight. The observations began at zenith distance = 53 deg. The sun altitude is -10.7 deg. The galactic latitude b = 31 deg., longitude l = 226 deg. Real time updated cover map and OT discovered available here: https://master.sai.msu.ru/site/master2/observ.php?id=1625124 We obtain a following upper limits. Tmid-T0 | Date Time | Site | Coord (J2000) |Filt.| Expt. | Limit| Comment _________|_____________________|_____________________|____________________________________|_____|_______|_______|________ 31619 | 2021-05-31 20:45:30 | MASTER-IAC | (09h 01m 58.63s , +03d 35m 59.8s) | C | 180 | 16.3 | 31889 | 2021-05-31 20:45:30 | MASTER-IAC | (09h 01m 58.61s , +03d 35m 59.6s) | C | 720 | 17.8 | Coadd 31619 | 2021-05-31 20:45:30 | MASTER-IAC | (09h 01m 09.51s , +03d 42m 42.6s) | C | 180 | 16.3 | 31889 | 2021-05-31 20:45:30 | MASTER-IAC | (09h 01m 09.51s , +03d 42m 42.7s) | C | 720 | 17.5 | Coadd 31819 | 2021-05-31 20:48:51 | MASTER-IAC | (09h 02m 03.56s , +03d 34m 51.8s) | C | 180 | 17.1 | 31999 | 2021-05-31 20:48:51 | MASTER-IAC | (09h 02m 03.55s , +03d 34m 51.8s) | C | 540 | 18.0 | Coadd 31819 | 2021-05-31 20:48:51 | MASTER-IAC | (09h 01m 14.60s , +03d 41m 35.0s) | C | 180 | 16.7 | 31999 | 2021-05-31 20:48:51 | MASTER-IAC | (09h 01m 14.60s , +03d 41m 35.0s) | C | 540 | 17.6 | Coadd 32019 | 2021-05-31 20:52:10 | MASTER-IAC | (09h 01m 58.25s , +03d 33m 47.5s) | C | 180 | 17.5 | 32019 | 2021-05-31 20:52:10 | MASTER-IAC | (09h 01m 09.13s , +03d 40m 29.8s) | C | 180 | 17.0 | 32219 | 2021-05-31 20:55:31 | MASTER-IAC | (09h 02m 03.70s , +03d 33m 45.0s) | C | 180 | 17.8 | 32219 | 2021-05-31 20:55:31 | MASTER-IAC | (09h 01m 14.66s , +03d 40m 26.7s) | C | 180 | 17.4 | 32419 | 2021-05-31 20:58:50 | MASTER-IAC | (09h 10m 31.15s , +05d 33m 53.4s) | C | 180 | 18.0 | 32419 | 2021-05-31 20:58:51 | MASTER-IAC | (09h 02m 25.96s , +05d 39m 31.3s) | C | 180 | 17.8 | 32619 | 2021-05-31 21:02:10 | MASTER-IAC | (09h 10m 31.20s , +05d 32m 18.4s) | C | 180 | 18.4 | 32619 | 2021-05-31 21:02:10 | MASTER-IAC | (09h 02m 25.88s , +05d 37m 56.6s) | C | 180 | 18.1 | 32819 | 2021-05-31 21:05:30 | MASTER-IAC | (09h 10m 34.22s , +05d 33m 37.5s) | C | 180 | 18.6 | 32819 | 2021-05-31 21:05:30 | MASTER-IAC | (09h 02m 28.72s , +05d 39m 15.9s) | C | 180 | 18.1 | 33019 | 2021-05-31 21:08:50 | MASTER-IAC | (09h 14m 27.85s , +03d 32m 58.2s) | C | 180 | 18.7 | 33019 | 2021-05-31 21:08:50 | MASTER-IAC | (09h 06m 23.72s , +03d 38m 36.5s) | C | 180 | 18.3 | 33219 | 2021-05-31 21:12:10 | MASTER-IAC | (09h 14m 28.75s , +03d 33m 56.8s) | C | 180 | 18.7 | 33219 | 2021-05-31 21:12:10 | MASTER-IAC | (09h 06m 24.31s , +03d 39m 35.8s) | C | 180 | 18.4 | 33419 | 2021-05-31 21:15:30 | MASTER-IAC | (09h 14m 35.97s , +03d 32m 55.5s) | C | 180 | 18.9 | 33419 | 2021-05-31 21:15:30 | MASTER-IAC | (09h 06m 31.18s , +03d 38m 34.9s) | C | 180 | 18.5 | 36021 | 2021-05-31 21:58:53 | MASTER-IAC | (09h 06m 36.51s , +03d 33m 01.6s) | C | 180 | 18.5 | 36021 | 2021-05-31 21:58:53 | MASTER-IAC | (08h 58m 30.18s , +03d 38m 38.2s) | C | 180 | 17.9 | 36221 | 2021-05-31 22:02:12 | MASTER-IAC | (09h 06m 30.00s , +03d 32m 24.2s) | C | 180 | 18.3 | 36221 | 2021-05-31 22:02:12 | MASTER-IAC | (08h 58m 23.57s , +03d 38m 00.4s) | C | 180 | 17.8 | 36421 | 2021-05-31 22:05:32 | MASTER-IAC | (09h 06m 29.26s , +03d 33m 22.4s) | C | 180 | 18.4 | 36421 | 2021-05-31 22:05:32 | MASTER-IAC | (08h 58m 22.70s , +03d 38m 58.4s) | C | 180 | 17.6 | 36621 | 2021-05-31 22:08:52 | MASTER-IAC | (09h 06m 35.13s , +03d 32m 20.8s) | C | 180 | 18.3 | 36621 | 2021-05-31 22:08:52 | MASTER-IAC | (08h 58m 28.54s , +03d 37m 55.9s) | C | 180 | 17.6 | 36822 | 2021-05-31 22:12:13 | MASTER-IAC | (09h 06m 30.15s , +03d 31m 18.9s) | C | 180 | 18.2 | 36822 | 2021-05-31 22:12:13 | MASTER-IAC | (08h 58m 23.44s , +03d 36m 53.2s) | C | 180 | 17.4 | 37022 | 2021-05-31 22:15:33 | MASTER-IAC | (09h 06m 35.84s , +03d 31m 35.1s) | C | 180 | 18.2 | 37022 | 2021-05-31 22:15:33 | MASTER-IAC | (08h 58m 28.97s , +03d 37m 08.8s) | C | 180 | 16.8 | Filter C is a clear (unfiltred) band. The observation and reduction will continue. The message may be cited.