TITLE: GCN CIRCULAR NUMBER: 21199 SUBJECT: Swift Trigger 755873: MASTER Net optical observations DATE: 17/06/05 10:40:54 GMT FROM: Vladimir Lipunov at Moscow State U/Krylov Obs O. Ershova Irkutsk State University V. Lipunov, V.Kornilov, N.Tyurina, E.Gorbovskoy, 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. Rebolo, M. Serra, N. Lodieu, G. Israelian, L. Suarez-Andres The Instituto de Astrofisica de Canarias O.Gres, N.M.Budnev Irkutsk State University D.Buckley South African Astronomical Observatory A. Tlatov, V.Senik, A.V. Parhomenko, D. Dormidontov Kislovodsk Solar Station of the Pulkovo Observatory A.Gabovich, V.Yurkov, Yu.Sergienko Blagoveschensk Educational State University, Blagoveschensk 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 MASTER Kislovodsk was observed Swift Trigger 755873 since 62 sec to 2957 sec after trigger time in SWIFT error box (K.L. Page et al., GCN # 21193). MASTER -IAC and MASTER-Kislovodsk had credible conditions for observations. MASTER-Kislovodsk was pointed to the Swift Trigger 755873 12 sec after notice time and 62 sec after trigger time at 2017-06-04 21:31:54 UT. On our first (10s exposure) set we haven`t found optical transient within SWIFT error-box. The 5-sigma upper limit has been about 16.9mag . This limit in agreement with Jelinek et al. (GCN #21194) The observations made on zenit distance = 38 degrees, galaxy latitude b = 53 degree. The moon (81 % bright part) is 20 degrees above the horizon. The distance between moon and object is 69. The sun altitude is -23.5 degree. The object can be observed till sunrise at 2017-06-05 01:28:56 . MASTER-IAC robotic telescope located in IAC was pointed to the Swift Trigger 755873 1001 sec after notice time and 1051 sec after trigger time at 2017-06-04 22:05:58 UT. The 5-sigma upper limit has been about 20.2 mag The observations made on zenit distance = 36 degrees, galaxy latitude b = 53 degree. The moon (82 % bright part) is 56 degrees above the horizon. The distance between moon and object is 69 The sun altitude is -23.6 degree. The object can be observed till sunrise at 2017-06-05 06:07:42. All our observations are in agreement with Ondrejov Robotic Telescope Limit (Jelinek et al. GCN #21194 ). This message cab be cited.