GCN Circular 35561

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) was pointed to the LAT GRB240118.08 (trigger No 727235294,01h 14m 18.00s , +29d 47m 20.4s, R=0.05) errorbox  10304 sec after notice time and 31631 sec after trigger time at 2024-01-18 10:35:21 UT, with upper limit up to  18.5 mag. Observations started at twilight.  The observations began at zenith distance = 21 deg. The sun  altitude  is -9.7 deg. 

The galactic latitude b = -32 deg., longitude l = 130 deg.


Real time updated cover map and OT discovered available here: 
https://master.sai.msu.ru/site/master2/observ.php?id=2359238

We obtain a following upper limits.  

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

   31635 | 2024-01-18 10:35:21 |        MASTER-Tunka | (01h 13m 06.36s , +29d 39m 31.5s) |   C |     5 | 17.8 |        
   31652 | 2024-01-18 10:35:38 |        MASTER-Tunka | (01h 13m 12.82s , +29d 38m 32.5s) |   C |     5 | 17.8 |        
   31673 | 2024-01-18 10:35:58 |        MASTER-Tunka | (01h 13m 08.08s , +29d 37m 33.4s) |   C |     5 | 17.8 |        
   31714 | 2024-01-18 10:36:40 |        MASTER-Tunka | (01h 13m 10.17s , +29d 37m 47.6s) |   C |     5 | 17.8 |        
   31735 | 2024-01-18 10:37:01 |        MASTER-Tunka | (01h 13m 12.22s , +29d 39m 24.1s) |   C |     5 | 17.9 |        
   31777 | 2024-01-18 10:37:43 |        MASTER-Tunka | (01h 13m 07.26s , +29d 39m 47.9s) |   C |     5 | 17.9 |        
   31817 | 2024-01-18 10:38:23 |        MASTER-Tunka | (01h 13m 08.69s , +29d 37m 54.6s) |   C |     5 | 13.8 |        
   31831 | 2024-01-18 10:38:37 |        MASTER-Tunka | (01h 13m 12.69s , +29d 38m 21.9s) |   C |     5 | 17.8 |        
   31905 | 2024-01-18 10:39:51 |        MASTER-Tunka | (01h 13m 07.30s , +29d 39m 58.4s) |   C |     5 | 18.0 |        
   31986 | 2024-01-18 10:41:10 |        MASTER-Tunka | (01h 13m 10.45s , +29d 38m 10.4s) |   C |    10 | 18.5 |        
Filter C is a clear (unfiltred) band. 


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