TITLE: GCN CIRCULAR NUMBER: 34005 SUBJECT: LIGO/Virgo S230618r: Global MASTER-Net observations report DATE: 23/06/18 09:30:00 GMT FROM: Vladimir Lipunov at Moscow State U/Krylov Obs 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-OAFA robotic telescope (Global MASTER-Net: http://observ.pereplet.ru, Lipunov et al., 2010, Advances in Astronomy, vol. 2010, 30L) located in Argentina (OAFA observatory of San Juan National University) started inspect of the LIGO/Virgo S230618r errorbox 91 sec after notice time and 149 sec after trigger time at 2023-06-18 09:09:56 UT, with upper limit up to 17.5 mag. The observations began at zenith distance = 81 deg. The sun altitude is -29.5 deg. The galactic latitude b = -28 deg., longitude l = 258 deg. Real time updated cover map and OT discovered available here: https://master.sai.msu.ru/site/master2/ligo_1.php?id=12104 We obtain a following upper limits. Tmid-T0 | Date Time | Site | Coord (J2000) |Filt.| Expt. | Limit| Comment _________|_____________________|_____________________|____________________________________|_____|_______|_______|________ 159 | 2023-06-18 09:09:56 | MASTER-OAFA | (06h 03m 46.35s , -50d 36m 58.8s) | C | 20 | 16.7 | 220 | 2023-06-18 09:10:47 | MASTER-OAFA | (06h 03m 41.23s , -50d 37m 39.3s) | C | 40 | 17.0 | 503 | 2023-06-18 09:15:04 | MASTER-OAFA | (06h 03m 40.85s , -50d 38m 32.5s) | C | 90 | 17.5 | Filter C is a clear (unfiltred) band. The observation and reduction will continue. The message may be cited.