TITLE: GCN CIRCULAR NUMBER: 25649 SUBJECT: LIGO/Virgo S190901ap: MASTER OT J171434.95+280725.6/AT2019pjv detection DATE: 19/09/04 08:42:33 GMT FROM: Vladimir Lipunov at Moscow State U/Krylov Obs V. Lipunov, T.Pogrosheva, E. Gorbovskoy, F.Balakin, V.Kornilov, N.Tyurina, P.Balanutsa,A.Kuznetsov, V.Vladimirov, D. Vlasenko, I.Gorbunov, D.Zimnukhov, V.Senik, T.Pogrosheva, D.Kuvshinov, A.Chasovnikov,V.Topolev, A.Posdnyakov(Lomonosov Moscow State University, SAI, Physics Department), R. Rebolo, M. Serra (The Instituto de Astrofisica de Canarias), V. Yurkov, A. Gabovich, Yu. Sergienko (Blagoveschensk Educational State University) A. Tlatov, D. Dormidontov (Kislovodsk Solar Station of the Pulkovo Observatory), 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), D. Buckley (South African Astronomical Observatory), O.A. Gres, N.M. Budnev, O.Ershova (Irkutsk State University, API), MASTER Global Robotic Net ( http://observ.pereplet.ru, Lipunov et al., 2010, Advances in Astronomy, vol. 2010, 30L) started LIGO/Virgo S190901ap error-box (LVC GCN 25606) alert and inspect observations at 2019-09-02 01:42:16 UT (Lipunov et al GCN 25609). During inspection we found OT, that can be assotiated with known PGC059913 (distance ~ 100Mpc, Btot=15.7), see image. OT offset are 44W 10.8N arcsec. MASTER OT J171434.95+280725.6 discovery - possibly LVC S190901ap optical counterpart. MASTER-IAC auto-detection system discovered OT source at (RA, Dec) = 17h 14m 34.95s +28d 07m 25.6s on 2019-09-03.97890 UT. The OT unfiltered magnitude is 18.9m (limit 19.7m). The OT is seen in 2 inspect images. There is no minor planet at this place. We have reference image without OT on 2015-09-15.93950 UT with unfiltered magnitude limit 20.4m. Spectral observations are required. The discovery and reference images are available at: http://master.sai.msu.ru/static/OT/171434.95280725.6.png This OT is in TNS as AT2019pjv