TITLE: GCN CIRCULAR NUMBER: 28249 SUBJECT: HAWC alert 200815.26: MASTER optical observations DATE: 20/08/15 19:10:03 GMT FROM: Vladimir Lipunov at Moscow State U/Krylov Obs V. Lipunov, E. Gorbovskoy, V.Kornilov, N.Tyurina, K.Zhirkov,P.Balanutsa,A.Kuznetsov,F.Balakin, V. Vladimirov, A.Chasovnikov, D. Vlasenko, I.Gorbunov, D.Zimnukhov, V. Topolev, V.Senik, T.Pogrosheva, D.Kuvshinov(Lomonosov Moscow State University, SAI, Physics Department), R. Podesta, C.Lopez, F. Podesta, C.Francile(Observatorio Astronomico Felix Aguilar OAFA), H.Levato(Instituto de Ciencias Astronomicas, de la Tierra y del Espacio ICATE), R. Rebolo, M. Serra(The Instituto de Astrofisica de Canarias), D. Buckley(South African Astronomical Observatory), O.A. Gres, N.M. Budnev (Irkutsk State University, API), A. Gabovich, Yu. Sergienko, V.Yurkov (Blagoveschensk Educational State University), A. Tlatov, D. Dormidontov (Kislovodsk Solar Station of the Pulkovo Observatory) MASTER Global Robotic Net ( Lipunov et al., "MASTER Global Robotic Net",Advances in Astronomy, 2010, 30L ) started HAWC alert 200815.26 (Ttrigger=2020-08-15 06:20:17UT, Tnotice=2020-08-15 06:21:34UT) observations 92s after notice time at 2020-08-15 06:23:06UT at altitude 42 deg (sun altitude -60deg) with unfiltered upper limit 20.0m. Observations and analysis will be continued. The cover map is (and far information will be) available at https://master.sai.msu.ru/site/master2/event.php?id=1420231