TITLE: GCN CIRCULAR NUMBER: 29742 SUBJECT: Fermi trigger No 639093861: Global MASTER-Net observations report DATE: 21/04/02 22:15:15 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-Tavrida robotic telescope (Global MASTER-Net: http://observ.pereplet.ru, Lipunov et al., 2010, Advances in Astronomy, vol. 2010, 30L) located in Russia (Lomonosov MSU, SAI Crimea astronomical station) started inspect of the Fermi GRB210402.92 (trigger No 639093861,13h 06m 43.20s , +45d 02m 24.0s, R=10.41) errorbox 120 sec after notice time and 138 sec after trigger time at 2021-04-02 22:06:35 UT, with upper limit up to 18.8 mag. The observations began at zenith distance = 3 deg. The sun altitude is -40.6 deg. MASTER-IAC robotic telescope located in Spain (IAC Teide Observatory) started inspect of the Fermi GRB210402.92 errorbox 185 sec after notice time and 203 sec after trigger time at 2021-04-02 22:07:40 UT, with upper limit up to 19.1 mag. The observations began at zenith distance = 42 deg. The sun altitude is -35.7 deg. MASTER-SAAO robotic telescope located in South Africa (South African Astronomical Observatory) started inspect of the Fermi GRB210402.92 errorbox 344 sec after notice time and 361 sec after trigger time at 2021-04-02 22:10:18 UT, with upper limit up to 16.0 mag. The observations began at zenith distance = 78 deg. The sun altitude is -62.1 deg. The galactic latitude b = 72 deg., longitude l = 113 deg. Real time updated cover map and OT discovered available here: https://master.sai.msu.ru/site/master2/observ.php?id=1582244 We obtain a following upper limits. Tmid-T0 | Date Time | Site | Coord (J2000) |Filt.| Expt. | Limit| Comment _________|_____________________|_____________________|____________________________________|_____|_______|_______|________ 169 | 2021-04-02 22:06:35 | MASTER-Tavrida | (12h 53m 56.10s , +46d 16m 08.2s) | C | 60 | 18.8 | 233 | 2021-04-02 22:07:40 | MASTER-IAC | (13h 02m 48.24s , +44d 08m 22.0s) | C | 60 | 19.1 | 233 | 2021-04-02 22:07:40 | MASTER-IAC | (12h 51m 27.91s , +44d 13m 49.5s) | C | 60 | 18.9 | 249 | 2021-04-02 22:07:55 | MASTER-Tavrida | (13h 11m 59.89s , +44d 16m 23.4s) | C | 60 | 18.8 | 386 | 2021-04-02 22:10:18 | MASTER-IAC | (13h 12m 20.00s , +44d 37m 33.9s) | P| | 50 | 18.1 | 387 | 2021-04-02 22:10:18 | MASTER-SAAO | (13h 14m 02.65s , +44d 32m 46.0s) | P\ | 50 | 16.0 | 467 | 2021-04-02 22:11:28 | MASTER-SAAO | (13h 14m 04.20s , +44d 31m 15.3s) | P\ | 70 | 15.7 | Filter C is a clear (unfiltred) band. The observation and reduction will continue. The message may be cited.