TITLE:   GCN CIRCULAR
NUMBER:  30075
SUBJECT: Fermi  trigger No 643548039: Global MASTER-Net observations report 
DATE:    21/05/24 18:47:52 GMT
FROM:    Vladimir Lipunov at Moscow State U/Krylov Obs  <lipunov@xray.sai.msu.ru>

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 GRB210524.47 (trigger No 643548039,09h 53m 50.40s , +07d 47m 24.0s, R=4.76) errorbox  25626 sec after notice time and 25720 sec after trigger time at 2021-05-24 18:29:15 UT, with upper limit up to  17.5 mag. Observations started at twilight.  The observations began at zenith distance = 54 deg. The sun  altitude  is -11.9 deg. 

The galactic latitude b = 44 deg., longitude l = 230 deg.


Real time updated cover map and OT discovered available here: 
https://master.sai.msu.ru/site/master2/observ.php?id=1620292

We obtain a following upper limits.  

Tmid-T0  |      Date Time      |          Site       |             Coord (J2000)          |Filt.| Expt. | Limit| Comment
_________|_____________________|_____________________|____________________________________|_____|_______|_______|________

   25751 | 2021-05-24 18:29:15 |      MASTER-Tavrida | (09h 57m 34.97s , +06d 54m 04.1s) |   C |    60 | 16.9 |        
   25751 | 2021-05-24 18:29:15 |      MASTER-Tavrida | (09h 57m 54.42s , +06d 55m 56.4s) |   C |    60 | 16.4 |        
   25830 | 2021-05-24 18:30:34 |      MASTER-Tavrida | (10h 00m 24.90s , +08d 47m 08.9s) |   C |    60 | 17.0 |        
   25830 | 2021-05-24 18:30:34 |      MASTER-Tavrida | (10h 00m 44.12s , +08d 48m 59.5s) |   C |    60 | 16.9 |        
   26096 | 2021-05-24 18:35:00 |      MASTER-Tavrida | (09h 52m 01.50s , +10d 41m 18.0s) |   C |    60 | 17.2 |        
   26096 | 2021-05-24 18:35:00 |      MASTER-Tavrida | (09h 45m 55.55s , +10d 43m 26.2s) |   C |    60 | 16.7 |        
   26176 | 2021-05-24 18:36:20 |      MASTER-Tavrida | (09h 59m 20.94s , +04d 58m 32.0s) |   C |    60 | 17.5 |        
   26176 | 2021-05-24 18:36:20 |      MASTER-Tavrida | (09h 53m 19.61s , +05d 00m 41.1s) |   C |    60 | 17.1 |        
   26415 | 2021-05-24 18:40:19 |      MASTER-Tavrida | (10h 07m 31.68s , +10d 41m 56.8s) |   C |    60 | 17.4 |        
   26415 | 2021-05-24 18:40:19 |      MASTER-Tavrida | (10h 01m 24.84s , +10d 44m 03.9s) |   C |    60 | 17.0 |        
   26494 | 2021-05-24 18:41:38 |      MASTER-Tavrida | (09h 36m 41.20s , +10d 39m 13.7s) |   C |    60 | 17.3 |        
   26494 | 2021-05-24 18:41:38 |      MASTER-Tavrida | (09h 30m 34.16s , +10d 41m 18.3s) |   C |    60 | 16.7 |        
Filter C is a clear (unfiltred) band. 


The observation and reduction will continue. 
The message may be cited.