TITLE: GCN CIRCULAR NUMBER: 11426 SUBJECT: GRB 101123A: MASTER prompt optical observations DATE: 10/11/27 15:55:17 GMT FROM: Vladimir Lipunov at Moscow State U/Krylov Obs E. Gorbovskoy, V. Lipunov, V.Kornilov, A.Belinski, N.Shatskiy, N.Tyurina, D.Kuvshinov, P.Balanutsa, V.V.Chazov, P.V.Kortunov, A.Kuznetsov, D.Zimnukhov, M. Kornilov Sternberg Astronomical Institute, Moscow State University V.Krushinski, I.Zalozhnich, T.Kopytova, A. Popov Ural State University, Kourovka K.Ivanov, O.Chuvalaev, V.Poleschuk, E.Konstantinov, O.Gres,S.Yazev, N.M.Budnev, Irkutsk State University A. Tlatov, A.V. Parhomenko, D. Dormidontov, V.Sennik Kislovodsk Solar Station of the Pulkovo Observatory V.Yurkov, Yu.Sergienko, D.Varda, I.Kudelina Blagoveschensk Educational State University, Blagoveschensk MASTER II robotic telescope (MASTER-Net: http://observ.pereplet.ru, 2x400 mm, 2x4 square degrees) located at Kislovodsk and 6 very wide field cameras (420 square degrees)was pointed to the long bright GRB101123A (Fermi/GBM trigger 312245496 / 101123952: Guiriec, GCN 11423; localized by IPN: Hurley et al., GCN 11424) 23 sec after notice time and 39 sec after trigger under Moon light with some haze. After some repointing and imaging due to continuously updating GRB socket position robotic telescope was made several frames at IPN error box (Hurley et al., GCN 11424). The first 2 telescope images (20 sec exp. time) covered 90% IPN error box was maded 111 sec after GRB. The 3-sigma upper limit has been about 15.0 (telescopes) and 10.0 (wide field cameras). There is no OT brighter 10 mag on Very Wide Field Cameras. Robot find two merginally OT candidates on telescope images: OT Date Time Ra Dec Mag(R) 1. 2010-11-23 22:53:25 08h 45m 06.61s , +05d 14m 47s.1 14.3 2. 2010-11-23 22:55:28 08h 45m 52.58s , +05d 48m 00s.4 13.2 However both transients are visible only on single image. The images, OT candidates and map of the error boxes position are available at http://observ.pereplet.ru/images/GRB101123A/grb.html . The message may be cited. mailto: lipunov@sai.msu.ru