TITLE: GCN CIRCULAR NUMBER: 29264 SUBJECT: Fermi GRB 210105A: Global MASTER-Net observations report DATE: 21/01/05 20:30:09 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 210105A ( Fermi GBM team, GCN 29261) errorbox 11240 sec after notice time and 11295 sec after trigger time at 2021-01-05 19:11:21 UT, with upper limit up to 18.5 mag. Observations started at twilight. The observations began at zenith distance = 77 deg. The sun altitude is -11.0 deg. The galactic latitude b = -40 deg., longitude l = 239 deg. Real time updated cover map and OT discovered available here: https://master.sai.msu.ru/site/master2/observ.php?id=1519938 We obtain a following upper limits. Tmid-T0 | Date Time | Site | Coord (J2000) |Filt.| Expt. | Limit| Comment _________|_____________________|_____________________|____________________________________|_____|_______|_______|________ 11326 | 2021-01-05 19:11:21 | MASTER-IAC | (04h 40m 37.16s , -30d 00m 42.3s) | C | 60 | 14.9 | 11326 | 2021-01-05 19:11:21 | MASTER-IAC | (04h 31m 18.61s , -29d 56m 05.8s) | C | 60 | 15.6 | 11405 | 2021-01-05 19:12:41 | MASTER-IAC | (04h 30m 25.22s , -26d 01m 59.9s) | C | 60 | 16.6 | 12227 | 2021-01-05 19:26:23 | MASTER-IAC | (04h 40m 44.73s , -30d 02m 48.9s) | C | 60 | 17.0 | 12227 | 2021-01-05 19:26:23 | MASTER-IAC | (04h 31m 25.39s , -29d 58m 12.6s) | C | 60 | 17.1 | 12307 | 2021-01-05 19:27:43 | MASTER-IAC | (04h 30m 21.85s , -26d 01m 27.7s) | C | 60 | 18.2 | 13048 | 2021-01-05 19:40:04 | MASTER-IAC | (04h 35m 50.16s , -40d 03m 02.2s) | C | 60 | 16.9 | 13048 | 2021-01-05 19:40:04 | MASTER-IAC | (04h 25m 17.91s , -39d 58m 24.3s) | C | 60 | 17.1 | 15230 | 2021-01-05 20:16:26 | MASTER-IAC | (04h 40m 38.58s , -30d 00m 38.9s) | C | 60 | 18.3 | 15230 | 2021-01-05 20:16:26 | MASTER-IAC | (04h 31m 17.88s , -29d 56m 09.0s) | C | 60 | 17.8 | 15310 | 2021-01-05 20:17:45 | MASTER-IAC | (04h 30m 26.00s , -26d 02m 02.7s) | C | 60 | 18.5 | Filter C is a clear (unfiltred) band. The observation and reduction will continue. The message may be cited.