TITLE:   GCN CIRCULAR
NUMBER:  35614
SUBJECT: Fermi GRB 240123B: Global MASTER-Net observations report
DATE:    24/01/23 23:15:32 GMT
FROM:    Vladimir Lipunov at Moscow State U/Krylov Obs <lipunov@xray.sai.msu.ru>

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 GRB 240123B ( Fermi GBM team, GCN 35608) errorbox  17492 sec after notice time and 17523 sec after trigger time at 2024-01-23 22:40:06 UT, with upper limit up to  17.1 mag. The observations began at zenith distance = 79 deg. The sun  altitude  is -21.0 deg. 

The galactic latitude b = -17 deg., longitude l = 64 deg.


Real time updated cover map and OT discovered available here: 
https://master.sai.msu.ru/site/master2/observ.php?id=2363736

We obtain a following upper limits.  

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

   17534 | 2024-01-23 22:40:06 |        MASTER-Tunka | (20h 45m 43.98s , +25d 49m 07.9s) |   C |    20 | 16.9 |        
   17626 | 2024-01-23 22:41:41 |        MASTER-Tunka | (20h 25m 46.01s , +22d 02m 50.8s) |   C |    15 | 16.9 |        
   17669 | 2024-01-23 22:42:23 |        MASTER-Tunka | (20h 26m 42.78s , +23d 55m 03.1s) |   C |    15 | 17.1 |        
Filter C is a clear (unfiltred) band. 


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