TITLE: GCN CIRCULAR NUMBER: 26467 SUBJECT: LIGO/Virgo S191213g: MASTER OT detection in BNS error-box DATE: 19/12/17 09:03:27 GMT FROM: Vladimir Lipunov at Moscow State U/Krylov Obs V. Lipunov, E. Gorbovskoy, V.Kornilov, N.Tyurina, P.Balanutsa, A.Kuznetsov,F.Balakin, V.Vladimirov, D. Vlasenko, I.Gorbunov, D.Zimnukhov, V.Senik, T.Pogrosheva, D.Kuvshinov(Lomonosov Moscow State University, SAI, Physics Department), R. Podesta, C.Lopez, F. Podesta, C.Francile(Observatorio Astronomico Felix Aguilar OAFA), H.Levato(Instituto de Ciencias Astronomicas, de la Tierra y del Espacio ICATE), R. Rebolo, M. Serra(The Instituto de Astrofisica de Canarias), D. Buckley(South African Astronomical Observatory), O.A. Gres, N.M. Budnev, O.Ershova (Irkutsk State University, API), A. Tlatov, D. Dormidontov (Kislovodsk Solar Station of the Pulkovo Observatory), V. Yurkov, A. Gabovich, Yu. Sergienko(Blagoveschensk Educational State University) MASTER Global Robotic Net found OT during S191213g (LVC GCN 26402) inspection (Lipunov et al. GCN 26400) MASTER OT J064855.37-055545.7 discovery MASTER-OAFA auto-detection system ( Lipunov et al., "MASTER Global Robotic Net",Advances in Astronomy, 2010, 30L ) discovered OT source at (RA, Dec) = 06h 48m 55.37s -05d 55m 45.7s on 2019-12-16.07539 UT. The OT unfiltered magnitude is 16.0m (mlim=18.7m). The OT is seen in 4 images. There is no minor planet at this place. We have reference image without OT on 2017-10-26.30777 UT with unfiltered magnitude 18.6m. Spectral observations are required. The discovery and reference images are available at: http://master.sai.msu.ru/static/OT/064855.37-055545.7.png The observation and reduction will continue. The message may be cited.