TITLE: GCN CIRCULAR NUMBER: 18333 SUBJECT: LIGO/Virgo G184098: observations by MASTER DATE: 15/09/20 01:18:59 GMT FROM: Vladimir Lipunov at Moscow State U/Krylov Obs V. Lipunov, E. Gorbovskoy, N.Tyurina, V.Kornilov, P.Balanutsa, A.Kuznetsov, D.Kuvshinov, Lomonosov Moscow State University, Sternberg Astronomical Institute D.Buckley, S. Potter, A.Kniazev, M.Kotze South African Astronomical Observatory N.M.Budnev, O.Gres, K.Ivanov, S.A.Yazev, A.V.Poleshuk Irkutsk State University A. Tlatov, V.Sennik, A.V. Parhomenko, D. Dormidontov Kislovodsk Solar Station of the Pulkovo Observatory V.Yurkov, Yu.Sergienko, A.Gabovich Blagoveschensk Educational State University, Blagoveschensk Hugo Levato and Carlos Saffe Instituto de Ciencias Astronomicas, de la Tierra y del Espacio (ICATE) Claudio Mallamaci, Carlos Lopez and Federico Podest Observatorio Astronomico Felix Aguilar (OAFA) MASTER II twin robotic telescope (MASTER-Net: http://observ.pereplet.ru, FOV= 2x4 square degrees) located in SAAO was starting survey on the aLIGO trigger G184098 error-box 220517 sec after trigger time at 2015-09-16 20:18:11 UT. The 5-sigma upper limit on our sets is about 18.4 mag - 19.9 mag . We observed 212 square degrees by 3 images for each field during ~2 hours. There are LMC near the center error box and Milky Way at the east edge of the error box. Because large number of stars the redaction is delay and continueted. The cover map is available at http://master.sai.msu.ru/static/G184098.png . We started from the left edge of the error box as its rise. The gap between green sets is due to meteo restrictions. This circular is an official product of the MASTER team. [GCN OPS NOTE(19sep15): This Circular was originally published on 19:01 17-Sep-2015 UT.]