GCN Circular 34048

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-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) started inspect of the LIGO/Virgo S230620au errorbox  18081 sec after notice time and 18166 sec after trigger time at 2023-06-20 17:00:36 UT, with upper limit up to  19.7 mag. Observations started at twilight.  The observations began at zenith distance = 59 deg. The sun  altitude  is -16.3 deg. 

The galactic latitude b =  2 deg., longitude l = 273 deg.


Real time updated cover map and OT discovered available here: 
https://master.sai.msu.ru/site/master2/ligo_1.php?id=12200

We obtain a following upper limits.  

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

   18256 | 2023-06-20 17:00:36 |         MASTER-SAAO | (08h 34m 25.24s , -03d 56m 38.3s) |   C |   180 | 18.6 |        
   18256 | 2023-06-20 17:00:36 |         MASTER-SAAO | (08h 35m 08.87s , -03d 56m 45.2s) |   B |   180 | 18.7 |        
   18456 | 2023-06-20 17:03:56 |         MASTER-SAAO | (08h 34m 29.52s , -03d 57m 26.0s) |   C |   180 | 18.8 |        
   18636 | 2023-06-20 17:03:56 |         MASTER-SAAO | (08h 34m 29.53s , -03d 57m 26.0s) |   C |   540 | 19.2 |  Coadd 
   18456 | 2023-06-20 17:03:56 |         MASTER-SAAO | (08h 35m 12.59s , -03d 57m 40.0s) |   C |   180 | 18.9 |        
   18636 | 2023-06-20 17:03:56 |         MASTER-SAAO | (08h 35m 12.59s , -03d 57m 40.0s) |   C |   540 | 19.2 |  Coadd 
   19301 | 2023-06-20 17:18:00 |         MASTER-SAAO | (08h 34m 26.64s , -03d 57m 00.2s) |   C |   180 | 18.8 |        
   19301 | 2023-06-20 17:18:00 |         MASTER-SAAO | (08h 35m 09.59s , -03d 57m 05.1s) |   B |   180 | 18.9 |        
   19500 | 2023-06-20 17:21:20 |         MASTER-SAAO | (08h 34m 26.95s , -03d 55m 54.2s) |   C |   180 | 18.6 |        
   19500 | 2023-06-20 17:21:20 |         MASTER-SAAO | (08h 35m 09.64s , -03d 56m 05.9s) |   C |   180 | 18.8 |        
   20981 | 2023-06-20 17:46:01 |         MASTER-SAAO | (07h 43m 52.14s , -19d 33m 05.3s) |   C |   180 | 17.2 |        
   20981 | 2023-06-20 17:46:01 |         MASTER-SAAO | (07h 43m 07.44s , -19d 32m 48.1s) |   C |   180 | 16.0 |        
   21406 | 2023-06-20 17:53:05 |         MASTER-SAAO | (07h 51m 35.92s , -19d 33m 24.0s) |   C |   180 | 16.4 |        
   21406 | 2023-06-20 17:53:05 |         MASTER-SAAO | (07h 52m 20.59s , -19d 33m 43.2s) |   C |   180 | 17.1 |        
   23259 | 2023-06-20 18:23:59 |         MASTER-SAAO | (07h 44m 22.51s , -19d 31m 52.7s) |   C |   180 | 16.5 |        
   23731 | 2023-06-20 18:31:51 |         MASTER-SAAO | (07h 52m 50.48s , -19d 32m 37.4s) |   C |   180 | 16.4 |        
   42394 | 2023-06-20 23:42:54 |         MASTER-SAAO | (20h 43m 50.18s , -67d 22m 01.0s) |   C |   180 | 19.1 |        
   42394 | 2023-06-20 23:42:54 |         MASTER-SAAO | (20h 46m 24.78s , -67d 23m 12.5s) |   C |   180 | 19.2 |        
   42605 | 2023-06-20 23:46:25 |         MASTER-SAAO | (21h 04m 38.75s , -67d 21m 51.9s) |   C |   180 | 19.0 |        
   42605 | 2023-06-20 23:46:25 |         MASTER-SAAO | (21h 07m 13.12s , -67d 23m 01.8s) |   C |   180 | 19.2 |        
   43239 | 2023-06-20 23:56:58 |         MASTER-SAAO | (20h 43m 56.31s , -67d 22m 17.0s) |   C |   180 | 18.6 |        
   43239 | 2023-06-20 23:56:58 |         MASTER-SAAO | (20h 46m 27.93s , -67d 23m 45.4s) |   C |   180 | 18.7 |        
   43450 | 2023-06-21 00:00:30 |         MASTER-SAAO | (21h 04m 40.96s , -67d 21m 46.0s) |   C |   180 | 18.3 |        
   43450 | 2023-06-21 00:00:30 |         MASTER-SAAO | (21h 07m 12.43s , -67d 23m 13.0s) |   C |   180 | 18.3 |        
   48734 | 2023-06-21 01:28:34 |         MASTER-SAAO | (20h 26m 06.37s , -65d 23m 58.7s) |   C |   180 | 19.0 |        
   48734 | 2023-06-21 01:28:34 |         MASTER-SAAO | (20h 28m 12.80s , -65d 25m 54.9s) |   C |   180 | 19.0 |        
   48946 | 2023-06-21 01:32:05 |         MASTER-SAAO | (20h 45m 18.31s , -65d 26m 20.4s) |   C |   180 | 19.6 |        
   48946 | 2023-06-21 01:32:05 |         MASTER-SAAO | (20h 47m 24.83s , -65d 28m 16.2s) |   C |   180 | 19.7 |        
   49574 | 2023-06-21 01:42:33 |         MASTER-SAAO | (20h 23m 48.34s , -65d 24m 32.3s) |   C |   180 | 19.2 |        
   49574 | 2023-06-21 01:42:33 |         MASTER-SAAO | (20h 25m 44.35s , -65d 26m 06.5s) |   C |   180 | 19.3 |        
   49785 | 2023-06-21 01:46:04 |         MASTER-SAAO | (20h 44m 43.46s , -65d 28m 01.1s) |   C |   180 | 19.2 |        
   49785 | 2023-06-21 01:46:04 |         MASTER-SAAO | (20h 42m 47.24s , -65d 26m 27.2s) |   C |   180 | 19.2 |        
   56291 | 2023-06-21 03:34:31 |             MASTER- | (08h 35m 24.83s , -04d 35m 28.9s) |   C |   180 | 14.2 |        
   56635 | 2023-06-21 03:40:14 |             MASTER- | (08h 35m 25.15s , -04d 34m 54.1s) |   V |   180 | 13.5 |        
Filter C is a clear (unfiltred) band. 


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