TITLE:   GCN CIRCULAR
NUMBER:  38693
SUBJECT: Swift GRB 241228A: Global MASTER-Net observations report
DATE:    24/12/28 19:16:36 GMT
FROM:    Vladimir Lipunov at Moscow State U/Krylov Obs <lipunov@xray.sai.msu.ru>

V.Lipunov, E.Gorbovskoy, N.Tiurina,  P.Balanutsa, , D.Vlasenko, I.Panchenko,
A.Kuznetsov,  G.Antipov,  A.Sankovich, A.Sosnovskij, Yu.Tselik, M.Gulyaev, Ya.Kechin,
V.Senik, A.Chasovnikov, K.Labsina, I. Gorbunov (Lomonosov MSU),
O.Gress, N.Budnev (ISU),
C.Francile,  F. Podesta, R.Podesta, E. Gonzalez  (Observatorio Astronomico Felix Aguilar (OAFA),
A. Tlatov, D. Dormidontov (Kislovodsk Solar Station of the Pulkovo Observatory),
A. Gabovich, V.Yurkov (Blagoveschensk Educational StateUniversity)
D.Buckley (SAAO),
R.Rebolo (The Instituto de Astrofisica de Canarias),
L.Carrasco, J.R.Valdes, V.Chavushyan, V.M.Patino Alvarez, J.Martinez,
A.R.Corella, L.H.Rodriguez (INAOE, Guillermo Haro Astrophysics Observatory) 

MASTER-SAAO robotic telescope  (Global MASTER-Net: http://observ.pereplet.ru, Lipunov et al., 2010, Advances in Astronomy, vol. 2010, 30L)  located in South Africa (South African Astronomical Observatory) was pointed to the Swift GRB 241228A ( V. D'Elia et al., GCN 38681) errorbox  53242 sec after notice time and 53275 sec after trigger time at 2024-12-28 18:45:10 UT, with upper limit up to  16.7 mag. Observations started at twilight.  The observations began at zenith distance = 72 deg. The sun  altitude  is -11.2 deg. 

The galactic latitude b = -37 deg., longitude l = 90 deg.


Real time updated cover map and OT discovered available here: 
https://master.sai.msu.ru/site/master2/observ.php?id=2724378

We obtain a following upper limits.  

Tmid-T0  |          Site       |Filt.| Expt. | Limit| Comment
_________|_____________________|_____|_______|______|________

   53366 |         MASTER-SAAO |   C |   180 | 12.2 |        
   53565 |         MASTER-SAAO |   C |   180 | 16.4 |        
   53764 |         MASTER-SAAO |   C |   180 | 16.5 |        
   53964 |         MASTER-SAAO |   C |   180 | 16.6 |        
   54163 |         MASTER-SAAO |   C |   180 | 16.7 |        
   54364 |         MASTER-SAAO |   C |   180 | 16.5 |        
   54563 |         MASTER-SAAO |   C |   180 | 16.6 |        
   54763 |         MASTER-SAAO |   C |   180 | 16.5 |        
Filter C is a clear (unfiltred) band. 


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