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GCN Circular 40368

Subject
IceCube Alert 250506.59: Global MASTER-Net observations report
Date
2025-05-06T17:26:50Z (7 days ago)
From
Vladimir Lipunov at Moscow State U/Krylov Obs <lipunov@xray.sai.msu.ru>
Via
V.Lipunov, E.Gorbovskoy, A.Kuznetsov, K.Zhirkov, I.Panchenko, N.Tiurina, P.Balanutsa, V.Topolev, D.Vlasenko, 
G.Antipov,  A.Sankovich, Yu.Tselik, 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.Sosnovskij (CrAO),
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 IceCube Alert 250506.59 (trigger No 73492707,07h 45m 48.00s , +35d 19m 26.4s, R=0.51) errorbox  9145 sec after notice time and 9189 sec after trigger time at 2025-05-06 16:47:21 UT, with upper limit up to  18.3 mag. Observations started at twilight.  The observations began at zenith distance = 70 deg. The sun  altitude  is -11.2 deg. 

The galactic latitude b = 26 deg., longitude l = 185 deg.


Real time updated cover map and OT discovered available here: 
https://master.sai.msu.ru/site/master2/observ.php?id=2862958

We obtain a following upper limits.  

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

    9220 | 2025-05-06 16:47:21 |         MASTER-SAAO | (07h 45m 13.02s , +35d 13m 49.3s) |   C |    60 | 17.2 |        
    9299 | 2025-05-06 16:48:41 |         MASTER-SAAO | (07h 40m 43.94s , +35d 18m 38.4s) |   C |    60 | 17.3 |        
    9378 | 2025-05-06 16:50:00 |         MASTER-SAAO | (07h 50m 27.69s , +35d 17m 49.3s) |   C |    60 | 17.4 |        
    9458 | 2025-05-06 16:51:19 |         MASTER-SAAO | (07h 45m 10.27s , +35d 14m 19.7s) |   C |    60 | 17.6 |        
   10259 | 2025-05-06 17:04:41 |         MASTER-SAAO | (07h 40m 37.95s , +35d 19m 20.4s) |   C |    60 | 18.2 |        
   10338 | 2025-05-06 17:06:00 |         MASTER-SAAO | (07h 50m 33.38s , +35d 18m 23.3s) |   C |    60 | 18.1 |        
   10418 | 2025-05-06 17:07:19 |         MASTER-SAAO | (07h 45m 09.40s , +35d 12m 53.7s) |   C |    60 | 18.3 |        
   10577 | 2025-05-06 17:09:58 |         MASTER-SAAO | (07h 45m 12.90s , +35d 14m 31.9s) |   C |    60 | 18.3 |        
   10894 | 2025-05-06 17:15:16 |         MASTER-SAAO | (07h 40m 44.89s , +35d 18m 43.8s) |   C |    60 | 18.2 |        
   10973 | 2025-05-06 17:16:35 |         MASTER-SAAO | (07h 50m 27.54s , +35d 17m 46.4s) |   C |    60 | 18.0 |        
   11053 | 2025-05-06 17:17:54 |         MASTER-SAAO | (07h 45m 16.27s , +35d 13m 44.9s) |   C |    60 | 18.1 |        
   11212 | 2025-05-06 17:20:33 |         MASTER-SAAO | (07h 45m 12.65s , +35d 13m 41.6s) |   C |    60 | 18.0 |        
Filter C is a clear (unfiltred) band. 


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