TITLE: GCN CIRCULAR NUMBER: 23258 SUBJECT: GRB 180923A: MASTER inspection MAXI/GSC error box DATE: 18/09/23 08:38:06 GMT FROM: Vladimir Lipunov at Moscow State U/Krylov Obs V. Lipunov, E. Gorbovskoy, D. Vlasenko, N.Tiurina, V.Kornilov, A.Kuznetsov, V.Chazov, I. Gorbunov, D.Zimnukhov, D.Kuvshinov, P.Balanutsa, V.Vladimirov, Lomonosov Moscow State University,SAI A. Tlatov, V.Senik, D. Dormidontov Kislovodsk Solar Station of the Pulkovo Observatory D. Buckley, South African Astronomical Observatory (SAAO) R. Rebolo, M. Serra, N. Lodieu, G. Israelian, L. Suarez-Andres The Instituto de Astrofisica de Canarias (IAC) R. Podesta, F. Podesta, C. Lopez, C.Francile Observatorio Astronomico Felix Aguilar (OAFA) H.Levato, Instituto de Ciencias Astronomicas, de la Tierra y del Espacio (ICATE) O. Gres, N.M.Budnev , Yu.Ishmuhametova Irkutsk State University (ISU) A. Gabovich, V. Yurkov, Yu. Sergienko Blagoveschensk Educational State University (BSPU) MASTER-OAFA robotic telescope (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) was starting survey on the MAXI GRB180923.17 error-box (ra=02 33 12 dec=+06 18 02 r=1) 2777 sec after notice time and 7954 sec after trigger time at 2018-09-23 06:21:04 UT. The 5-sigma upper limit on our first (60s exposure) set is about 17.9 mag No OT detected. The galacitc latitude b = 0 deg. The observations made on zenit distance = 39 deg.The moon (97 % bright part) is 42 deg. above the horizon. The distance between moon and object is 59 The sun altitude is -48.6 deg. The object can be observed till sunrise at 2018-09-23 10:25:33 . The cover map is availavle at http://observ.pereplet.ru/images/GRB180923A_cover_map.png Only for MASTER-team: The OT candidate available here https://200.123.254.238:49004//master2/trans.php?wh=transients.coord2000@%27%3C%2838.3d%2C6.30056d%29%2C2d%3E%27%3A%3Ascircle+and+transients.datetime%3E%3D%272018-09-23+04%3A08%3A30%27&class=9&t2=MAXI+GRB180923.17+optical+counterpart+candidate The full information about this GRB180923.17 available here https://200.123.254.238:49004//master2/grb.php?not=2018-09-23+05%3A34%3A46.484065&sat=MAXI&gcrd=%2838.3d%2C6.30056d%29&eb=1&trig=2018-09-23+04%3A08%3A30&n=GRB180923.17 The message may be cited.