TITLE: GCN CIRCULAR NUMBER: 16629 SUBJECT: GRB 140723A: MASTER optical observation DATE: 14/07/24 13:49:03 GMT FROM: Vladimir Lipunov at Moscow State U/Krylov Obs E. Gorbovskoy, D.Denisenko, V. Lipunov, M.Pruzhinskaya, V.Kornilov, D.Kuvshinov, A.Belinski, N.Tyurina, N.Shatskiy, P.Balanutsa, D.Zimnukhov, A.Kuznetsov, V.V.Chazov, A.Sankovich Lomonosov Moscow State University, Sternberg Astronomical Institute, Moscow State University 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.Krushinsky, I.Zalozhnih, A. Popov Ural Federal University, Yekaterinburg, Kourovka 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 pointed to the GRB 140723A (Fermi trigger 427772193) 48377 s (~13.4 h) after trigger time at 2014-07-23 15:02:47 UT directly after sunset. Observations were made at high zenith distance (z ~ 76d) with the error box setting to the horizon. Therefore we have only two (180s exposure) successful images. On our images we have not found optical transient within Fermi-LAT error-box (Bissaldi et al. GCN 16623, Burns et. al GCN 16626) and IPN (Hurley et al. GCN 16625, Golenetskii et. al GCN 16628) brighter than 18.3 mag. Thus we can not confirm the LCO-Sutherland OT (Guidorzi et al. GCN 16627) despite ~2 hours earlier time of observations and our upper limit being 1 magnitude deeper than the estimated object magnitude. The 6x6 acrminutes MASTER-Tunka image around probable OT position (Guidorzi et al. GCN 16627) is available here: http://master.sai.msu.ru/static/GRB/GRB140723_LAT.png Our white (clear) band is well described by a parity 0.8R+0.2B (USNO B1). The message may be cited.