GCN Circular 41821

Subject
EP250911a: Global MASTER-Net observations report
Event
EP250911a
Date
2025-09-13T00:18:39Z (9 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-Tavrida robotic telescope  (Global MASTER-Net: http://observ.pereplet.ru, Lipunov et al., 2010, Advances in Astronomy, vol. 2010, 30L)  located in Russia (Lomonosov MSU, SAI Crimea astronomical station) was pointed to the EP250911a ( EP Team et al., GCN 41788Loading...
 
 ) errorbox  27051 sec after notice time and 30571 sec after trigger time at 2025-09-11 17:27:59 UT, with upper limit up to  13.6 mag. Observations started at twilight.  The observations began at zenith distance = 57 deg. The sun  altitude  is -15.9 deg. 

MASTER-Kislovodsk robotic telescope  located in Russia (Lomonosov MSU, Kislovodsk Solar Station of Pulkovo observatory) was pointed to the EP250911a errorbox  1 days 51178 sec after notice time and 1 days 54698 sec after trigger time at 2025-09-13 00:10:06 UT, with upper limit up to  17.5 mag. The observations began at zenith distance = 34 deg. The sun  altitude  is -27.5 deg. 

The galactic latitude b = -32 deg., longitude l = 108 deg.


Real time updated cover map and OT discovered available here: 
https://master.sai.msu.ru/site/master2/observ.php?id=2989778

We obtain a following upper limits.  

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

   13450 | 2025-09-11 12:42:07 |             MASTER- | (23h 49m 56.46s , +28d 43m 10.6s) |   C |    60 | 16.4 |  Coadd 
   30602 | 2025-09-11 17:27:59 |      MASTER-Tavrida | (23h 49m 27.05s , +29d 17m 08.7s) |   C |    60 | 13.6 |        
  141129 | 2025-09-13 00:10:06 |   MASTER-Kislovodsk | (23h 49m 03.03s , +29d 23m 20.1s) |   C |    60 | 17.1 |        
  141292 | 2025-09-13 00:12:50 |   MASTER-Kislovodsk | (23h 49m 01.01s , +29d 23m 04.4s) |   C |    60 | 17.5 |        
Filter C is a clear (unfiltred) band. 


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