TITLE: GCN CIRCULAR NUMBER: 21291 SUBJECT: GRB 170705A: MASTER-OAFA early OT observations DATE: 17/07/05 09:26:46 GMT FROM: Vladimir Lipunov at Moscow State U/Krylov Obs V. Lipunov, E. Gorbovskoy, V.Kornilov, N.Tyurina, D.Kuvshinov, A.V.Krylov, I.Gorbunov, P.Balanutsa, A.Kuznetsov, V.V.Chazov, D. Vlasenko Lomonosov Moscow State University, Sternberg Astronomical Institut of MSU R.Podesta, C.Lopez, F. Podesta Observatorio Astronomico Felix Aguilar (OAFA), National University of San Juan, Argentina H. Levato, C. Saffe Instituto de Ciencias Astronomicas,de la Tierra y del Espacio (ICATE), San Juan, Argentina K.Ivanov, S.Yazev, N.M.Budnev, O.Gres, O.Chuvalaev, V.A.Poleshchuk, O. Ershova Irkutsk State University V.Yurkov, Yu.Sergienko Blagoveschensk Educational State University, Blagoveschensk A. Tlatov, V.Senik, A.V. Parhomenko, D. Dormidontov Kislovodsk Solar Station of the Pulkovo Observatory D.Buckley, S. Potter, A.Kniazev, M.Kotze South African Astronomical Observatory R. Rebolo, M. Serra, N. Lodieu, G. Israelian, L. Suarez-Andres The Instituto de Astrofisica de Canarias MASTER II robotic telescope (MASTER-Net: http://observ.pereplet.ru) located in OAFA was pointed to the GRB170705A (Starling et al.,GCN #21289) 24 sec after notice time and 38 sec after trigger time at 2017-07-05 02:46:27 UT at high zenit distance. On our first (10s exposure) unfiltered exposition we haven`t found optical transient within SWIFT error-box (ra=191.704 dec=18.2928 r=0.05) brighter than 15.0. We marginally found OT at Swift UVOT position (Starling et al.,GCN #21289) on coaded image ID=79921 with m ~ 17.0. ID DATE UT Exp Type Limit Note 79817 2017-07-05 02:46:27 10 Alert (SWIFT) 15.0 no 79921 2017-07-05 02:46:27 190 SumAlert (SWIFT) 16.9 79817+79825+79820+79818 79818 2017-07-05 02:47:20 20 Alert (SWIFT) 15.8 yes 79819 2017-07-05 02:48:24 30 Alert (SWIFT) 15.9 no 79820 2017-07-05 02:49:38 50 Alert (SWIFT) 16.2 yes 79822 2017-07-05 02:51:13 60 Alert (SWIFT) 16.3 no 79824 2017-07-05 02:52:57 90 Alert (SWIFT) 16.5 no 79825 2017-07-05 02:55:11 110 Alert (SWIFT) 16.4 yes 79826 2017-07-05 02:57:46 140 Alert (SWIFT) 16.4 no 79827 2017-07-05 03:00:48 180 Alert (SWIFT) 16.7 no 79829 2017-07-05 03:04:32 180 Alert (SWIFT) 16.3 no 79830 2017-07-05 03:08:12 180 Alert (SWIFT) 16.0 no The unfiltered magnitude is about ~17 m . The big differences with UVOT magnitude may be connected with high GRB redshift because our CCD is more red. The observations made on zenit distance = 79 degrees, galaxy latitude b = 81 degree. The moon (86 % bright part) is 66 degrees above the horizon. The distance between moon and object is 56 The sun altitude is -63.1 degree. The object can be observed till 2017-07-05 03:46:20 . The message may be cited.