TITLE: GCN CIRCULAR NUMBER: 23558 SUBJECT: GRB 181222B: Global MASTER Net observations of short bright Fermi GRB DATE: 18/12/25 11:34:42 GMT FROM: Vladimir Lipunov at Moscow State U/Krylov Obs V. Lipunov, E. Gorbovskoy, V.Kornilov, N.Tyurina, P.Balanutsa, A.Kuznetsov, D. Vlasenko, D.Kobtsev Lomonosov Moscow State University, SAI R. Rebolo, M. Serra, N. Lodieu, G. Israelian, L. Suarez-Andres The Instituto de Astrofisica de Canarias D. Buckley, South African Astronomical Observatory A. Tlatov, V.Senik, D. Dormidontov Kislovodsk Solar Station of the Pulkovo Observatory O. Gres, N.M. Budnev, S. Yazev, O. Chuvalaev, Irkutsk State University V. Yurkov, A. Gabovich, Yu. Sergienko, Blagoveschensk Educational State University, Blagoveschensk R. Podesta, C.Lopez, F. Podesta Observatorio Astronomico Felix Aguilar (OAFA) H. Levato Instituto de Ciencias Astronomicas, de la Tierra y del Espacio (ICATE) The Global MASTER network continues to inspect error box of the short bright gamma-ray burst GRB 181222B (Veres, GCN #23551; Lipunov et al., GCN #23552) MASTER-IAC robotic telescope (Global MASTER-Net: http://observ.pereplet.ru, Lipunov et al., 2010, Advances in Astronomy, vol. 2010, 30L) located in Spain (IAC Teide Observatory) started inspect survey of Fermi GRB18122B IPN error-box (Svinkin et al., GCN #23556) 36801 sec after notice time and 36801 sec after trigger time at 2018-12-24 19:07:42 UT. There are 479 galaxies in IPN localization. MASTER auto-detection system found optical transient: MASTER OT J204928.79+245744.0 detection. MASTER-IAC auto-detection system discovered OT source at (RA, Dec)=20h 49m 28.79s +24d 57m 44.0s on 2018-12-24.81773 UT. The OT unfiltered magnitude is 16.9m (limit 18.6m). The OT is seen in 2 images. There is no minor planet at this place. We have reference image without OT on 2018-08-02.04970 UT with 18.7m unfiltered magnitude limit . There is red start in PanSTARR (rmag=21.7) and SDSS.9 (r=21.9) Spectral observations are required. Observations started at twilight.The sun altitude was -11.5 deg. The observations made on zenit distance = 29 deg. The moon (94 % bright part) below the horizon The altitude of the Moon is -14 deg. The object can be observed till 2018-12-25 00:54:38. The galactic latitude b = -60 deg., longitude l = 98 deg. MASTER-Amur robotic telescope located in Russia (Blagoveshchensk State Pedagogical University) was pointed to the FERMI GRB181222B 46503 sec after trigger time at 2018-12-23 09:06:40 UT, with upper limit up to 17.8 mag. Observations started at twilight. The observations began at zenit distance = 44 deg. The sun altitude is -14.2 deg. MASTER-Tunka robotic telescope located in Russia (Applied Physics Institute, Irkutsk State University) was pointed to the FERMI GRB181222B 52255 sec after trigger time at 2018-12-23 10:42:32 UT, with upper limit up to 18.6 mag. Observations started at twilight. The observations began at zenit distance = 44 deg. The sun altitude is -14.5 deg. The cover map is available at https://master.sai.msu.ru/site/master2/observ.php?id=890715 The message may be cited.