TITLE: GCN CIRCULAR NUMBER: 15608 SUBJECT: GRB 131224A: MASTER-Net early optical observations DATE: 13/12/25 08:14:39 GMT FROM: Vladimir Lipunov at Moscow State U/Krylov Obs E. Gorbovskoy, V. Lipunov, V.Kornilov, D.Kuvshinov, A.Belinski, N.Tyurina, N.Shatskiy, P.Balanutsa, D.Zimnukhov, A.Kuznetsov, V.V.Chazov, D.Denisenko, A.Sankovich Sternberg Astronomical Institute, Moscow State University A. Tlatov, A.V. Parhomenko, D. Dormidontov, V.Sennik Kislovodsk Solar Station of the Pulkovo Observatory V.Yurkov, Yu.Sergienko, D.Varda, E.Sinyakov Blagoveschensk Educational State University, Blagoveschensk K.Ivanov, S.Yazev, N.M.Budnev, O.Gres, O.Chuvalaev, V.A.Poleshchuk Irkutsk State University V.Krushinski, I.Zalozhnih, A. Popov Ural Federal University, 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 Kislovodsk was pointed to the GRB131224A 33 sec after notice time and 39 sec after trigger time at 2013-12-24 16:55:24 UT in two polarizations. Observations were made on high (z=75 deg) zenith distance and on the extremely stars rich field (with galactic latitude b=3 deg). On our first (10s exposure) set we haven`t found optical transient within INTEGRAL error-box (S.Mereghetti et. al. GCN 15607). The 5-sigma upper limit has been about 15.5 mag The message may be cited.