TITLE: GCN CIRCULAR NUMBER: 13162 SUBJECT: long/intense GRB 120328B: MASTER follow up observations DATE: 12/03/28 16:26:33 GMT FROM: Vladimir Lipunov at Moscow State U/Krylov Obs E. Gorbovskoy, V. Lipunov, V.Kornilov, D.Kuvshinov, A.Belinski, N.Tyurina, N.Shatskiy, P.Balanutsa, D.Zimnukhov, A.Kuznetsov, V.V.Chazov, A.Kuznetsov, A.Sankovich Moscow Lomonosov State University, Sternberg Astronomical Institute, K.Ivanov, S.Yazev, N.M.Budnev, O.Gres, O.Chuvalaev, V.A.Poleshchuk Irkutsk State University V.Yurkov, Yu.Sergienko, D.Varda, E.Sinyakov Blagoveschensk Educational State University, Blagoveschensk A. Tlatov, A.V. Parhomenko, D. Dormidontov, V.Sennik Kislovodsk Solar Station of the Pulkovo Observatory V.Krushinski, I.Zalozhnich, A. Popov, A. Bourdanov, A. Punanova Ural Federal University 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 robotic telescope (MASTER-Net: http://observ.pereplet.ru) located in Tunka was started to survey IPN error box of the long/intense GRB 120328B (Hurley et al., GCN Circ 13157) 6 hours after GRB time at 2012-03-28 13:26:23 UT. The eroor box was arised. The weather was changed. The better images limit was about 18 unfiltered magnitudes. There is no OT inside IPN error box with 18 mag limit. MASTER-Tunka auto-detection system discovered faint OT source (4.1 sigma) at (RA, Dec) = 15h 06m 01.01s +28d 41m 59.8s on 2012-03-28.59161 UT (~7h45 min after GRB time) outside error IPN box (see map http://observ.pereplet.ru/images/GRB120328B_IPN_map_MASTER$ GRB120328B_IPN_map_MASTER.png ). The OT unfiltered magnitude is 17.9m (limit 18.0m). The OT is marginally seen at several images 2 images. There is no minor planet at this place. There is no known source at this place. We have reference image without OT on 2011-06-04.67172 UT with unfiltered magnitude limit 20.1m. Follow up observations will be continuated. The discovery and reference images are available at: http://master.sai.msu.ru/static/OT/150601.01284159.8.png The message may be cited.