GCN Circular 35977

V. Lipunov, V.Kornilov, E. Gorbovskoy, K. Zhirkov, N.Tyurina, P.Balanutsa, A.Kuznetsov, V.Senik,  D. Vlasenko,
G.Antipov, D.Zimnukhov, E.Minkina, A.Chasovnikov, V.Topolev, D.Kuvshinov, D. Cheryasov, Ya.Kechin, Yu.Tselik, A. Sosnovskij
(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. Gress, N.M. Budnev, O.Ershova
(Irkutsk State University, API),

L.Carrasco, J.R.Valdes, V.Chavushyan, V.M.Patino Alvarez, J.Martinez,
A.R.Corella, L.H.Rodriguez
(INAOE, Guillermo Haro Astrophysics Observatory),

A. Tlatov, D. Dormidontov
(Kislovodsk Solar Station of the Pulkovo Observatory),

V. Yurkov, A. Gabovich
(Blagoveschensk Educational State University)

MASTER-Tunka robotic telescope  (Global MASTER-Net: http://observ.pereplet.ru, Lipunov et al., 2010, Advances in Astronomy, vol. 2010, 30L)  located in Russia (Applied Physics Institute, Irkutsk State University) started inspect of the Fermi GRB240325.87 (trigger No 733092476,23h 52m 16.08s , +12d 55m 58.8s, R=26.23) errorbox  2625 sec after notice time and 2658 sec after trigger time at 2024-03-25 21:32:10 UT, with upper limit up to  15.0 mag. Observations started at twilight.  The observations began at zenith distance = 64 deg. The sun  altitude  is -13.7 deg. 

The galactic latitude b = -47 deg., longitude l = 102 deg.


Real time updated cover map and OT discovered available here: 
https://master.sai.msu.ru/site/master2/observ.php?id=2406760

We obtain a following upper limits.  

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

    2689 | 2024-03-25 21:32:10 |        MASTER-Tunka | (22h 40m 57.63s , +34d 24m 37.9s) |   C |    60 | 14.7 |        
    2782 | 2024-03-25 21:33:43 |        MASTER-Tunka | (22h 53m 51.34s , +30d 36m 29.5s) |   C |    60 | 13.9 |        
    2876 | 2024-03-25 21:35:17 |        MASTER-Tunka | (22h 28m 39.00s , +32d 33m 13.4s) |   C |    60 | 15.0 |        
    2972 | 2024-03-25 21:36:53 |        MASTER-Tunka | (22h 55m 29.91s , +36d 18m 16.9s) |   C |    60 | 14.8 |        
    3647 | 2024-03-25 21:48:09 |        MASTER-Tunka | (22h 41m 06.08s , +34d 25m 20.8s) |   C |    60 | 14.6 |        
    3903 | 2024-03-25 21:52:24 |        MASTER-Tunka | (22h 28m 41.31s , +32d 32m 29.2s) |   C |    60 | 13.1 |        
Filter C is a clear (unfiltred) band. 


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