GCN Circular 35875

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-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) started inspect of the Fermi GRB240305.16 (trigger No 731303574,00h 41m 28.80s , -21d 58m 48.0s, R=3.05) errorbox  51405 sec after notice time and 51438 sec after trigger time at 2024-03-05 18:10:08 UT, with upper limit up to  18.3 mag. Observations started at twilight.  The observations began at zenith distance = 75 deg. The sun  altitude  is -13.6 deg. 

The galactic latitude b = -84 deg., longitude l = 105 deg.


Real time updated cover map and OT discovered available here: 
https://master.sai.msu.ru/site/master2/observ.php?id=2392576

We obtain a following upper limits.  

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

   51469 | 2024-03-05 18:10:08 |         MASTER-SAAO | (00h 44m 52.10s , -22d 07m 09.6s) |   C |    60 | 17.7 |        
   51529 | 2024-03-05 18:10:08 |         MASTER-SAAO | (00h 44m 52.08s , -22d 07m 09.4s) |   C |   180 | 18.3 |  Coadd 
   51548 | 2024-03-05 18:11:27 |         MASTER-SAAO | (00h 44m 52.84s , -22d 07m 05.6s) |   C |    60 | 17.6 |        
   51628 | 2024-03-05 18:12:46 |         MASTER-SAAO | (00h 44m 53.68s , -22d 07m 01.3s) |   C |    60 | 17.6 |        
   51707 | 2024-03-05 18:14:06 |         MASTER-SAAO | (00h 44m 54.61s , -22d 06m 57.7s) |   C |    60 | 17.7 |        
Filter C is a clear (unfiltred) band. 


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