TITLE: GCN CIRCULAR NUMBER: 23091 SUBJECT: GRB 180806.94: MASTER possible OT detection in Fermi GMB trigger 555287944 error box DATE: 18/08/07 10:01:59 GMT FROM: Vladimir Lipunov at Moscow State U/Krylov Obs V. Lipunov, N.Tiurina, E. Gorbovskoy, V.Kornilov, A.Kuznetsov, V.Chazov, I. Gorbunov, D.Zimnukhov, D.Kuvshinov, P.Balanutsa, V.Vladimirov, D. Vlasenko Lomonosov Moscow State University,SAI R. Rebolo, M. Serra, N. Lodieu, G. Israelian, L. Suarez-Andres The Instituto de Astrofisica de Canarias (IAC) D. Buckley, South African Astronomical Observatory (SAAO) A. Tlatov, V.Senik, D. Dormidontov Kislovodsk Solar Station of the Pulkovo Observatory R. Podesta, F. Podesta, C. Lopez, C.Francile Observatorio Astronomico Felix Aguilar (OAFA) H.Levato, Instituto de Ciencias Astronomicas, de la Tierra y del Espacio (ICATE) O. Gres, N.M.Budnev , Yu.Ishmuhametova Irkutsk State University (ISU) A. Gabovich, V. Yurkov, Yu. Sergienko Blagoveschensk Educational State University (BSPU) MASTER-IAC robotic telescope (MASTER-Net: http://observ.pereplet.ru, Lipunov et al., 2010, Advances in Astronomy, vol. 2010, 30L) located in Spain (IAC Teide Observatory) was pointed to the GRB180806.94 (GBM trigger 555287944) 77 sec after notice time and 122 sec after trigger time at 2018-08-06 22:41:02 UT. The observations made on zenit distance = 78 deg., galactic latitude b = -36 deg. The moon (27 % bright part) below the horizon (The altitude of the Moon is -36 deg ). The sun altitude is -32.4 deg. The object can be observed till sunrise at 2018-08-07 06:29:57 UT. We found OT inside 3 sigma Fermi GBM error box. The Cover Map is available at http://master.sai.msu.ru/static/OT/MASTERmapFermi555287944.jpg MASTER OT J004613.05+242014.1 discovery MASTER-IAC auto-detection system discovered OT source at (RA, Dec) = 00h 46m 13.05s +24d 20m 14.1s 109.3 min after trigger on 2018-08-07 00:28:20.467 UT . The OT unfiltered magnitude is 17.0m (limit 17.9m). The OT is seen in 4 images. There is no minor planet at this place. We have reference image without OT on 2016-10-05.08846 UT with unfiltered magnitude limit 20.2m. There is no USNO-B1 sources, it means 22mag limit in history and more then 5m amplitude of current outburst. There is Sloan star in 2.9" Spectral observations are required. The discovery and reference images are available at: http://master.sai.msu.ru/static/OT/004613.05242014.1.png This message can be cited. [GCN OPS NOTE(07aug18): Per admin, the double use of "GRB" in the Subject-line was removed; from "GRB GRB180806.94" to "GRB 180806.94".]