TITLE:   GCN CIRCULAR
NUMBER:  31929
SUBJECT: IceCube Alert 220421.22: Global MASTER-Net observations report 
DATE:    22/04/21 05:39:20 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, D. Vlasenko, 
G.Antipov, D.Zimnukhov, V.Senik, E.Minkina, A.Chasovnikov, V.Topolev, D.Kuvshinov,  D.Cheryasov, Ya.Kechin
(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. Gres, N.M. Budnev
(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),

A. Gabovich, V.Yurkov 
(Blagoveschensk Educational State University)


MASTER-OAGH robotic telescope  (Global MASTER-Net: http://observ.pereplet.ru, Lipunov et al., 2010, Advances in Astronomy, vol. 2010, 30L)  located in Mexico (OAGH National Institute for Astrophysics, Optics and Electronics) was pointed to the IceCube Alert 220421.22 (trigger No 43687362,07h 37m 27.60s , +06d 02m 13.2s, R=0.74) errorbox  314 sec after notice time and 361 sec after trigger time at 2022-04-21 05:26:19 UT, with upper limit up to  17.8 mag. The observations began at zenith distance = 67 deg. The sun  altitude  is -39.6 deg. 

The galactic latitude b = 14 deg., longitude l = 213 deg.


Real time updated cover map and OT discovered available here: 
https://master.sai.msu.ru/site/master2/observ.php?id=1949987

We obtain a following upper limits.  

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

     396 | 2022-04-21 05:26:19 |         MASTER-OAGH | (07h 37m 41.98s , +06d 02m 00.1s) |   C |    70 | 17.0 |        
     396 | 2022-04-21 05:26:19 |         MASTER-OAGH | (07h 37m 05.71s , +06d 30m 58.4s) |  P- |    70 | 16.8 |        
     653 | 2022-04-21 05:30:10 |         MASTER-OAGH | (07h 37m 05.77s , +06d 29m 03.1s) |  P- |   120 | 17.1 |        
     653 | 2022-04-21 05:30:10 |         MASTER-OAGH | (07h 37m 42.24s , +06d 00m 03.1s) |   C |   120 | 17.8 |        
Filter C is a clear (unfiltred) band. 


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