TITLE: GCN CIRCULAR NUMBER: 18818 SUBJECT: GRB 160104B: MAXI/GSC detection DATE: 16/01/04 12:54:30 GMT FROM: H. Negoro at Nihon U. Y. Kawakubo (AGU), M. Nakajima, H. Negoro (Nihon U.), M. Serino (RIKEN), S. Ueno, H. Tomida, S. Nakahira, M. Ishikawa, Y. E. Nakagawa (JAXA), T. Mihara, M. Sugizaki, M. Shidatsu, J. Sugimoto, T. Takagi, M. Matsuoka (RIKEN), N. Kawai, M. Arimoto, T. Yoshii, Y. Tachibana, Y. Ono, T. Fujiwara (Tokyo Tech), A. Yoshida, T. Sakamoto, H. Ohtsuki (AGU), H. Tsunemi, R. Imatani (Osaka U.), K. Tanaka, T. Masumitsu (Nihon U.), Y. Ueda, T. Kawamuro, T. Hori, A. Tanimoto (Kyoto U.), Y. Tsuboi, S. Kanetou, Y. Nakamura, R. Sasaki (Chuo U.), M. Yamauchi, D. Itoh, K. Furuya (Miyazaki U.), K. Yamaoka (Nagoya U.), M. Morii (ISM) report on behalf of the MAXI team: The MAXI/GSC nova alert system triggered a bright uncatalogued X-ray transient source at 10:13:03 UT on on 2016 January 4. Assuming that the source flux was constant over the transit, we obtain the source position at (R.A., Dec) = (108.879 deg, 54.865 deg) = (07 15 30, +54 51 54) (J2000) with a statistical 90% C.L. elliptical error region with long and short radii of 0.32 deg and 0.29 deg, respectively. The roll angle of long axis from the north direction is 72.0 deg counterclockwise. There is an additional systematic uncertainty of 0.1 deg (90% containment radius). The X-ray flux averaged over the scan was 123 +- 24 mCrab (4-10keV, 1 sigma error). Without assumptions on the source constancy,we obtain a rectangular error box for the transient source with the following corners: (R.A., Dec) = (109.823 deg, 54.028 deg) = (07 19 17, +54 01 40) (J2000) (R.A., Dec) = (108.777 deg, 53.855 deg) = (07 15 06, +53 51 17) (J2000) (R.A., Dec) = (107.662 deg, 55.997 deg) = (07 10 38, +55 59 47) (J2000) (R.A., Dec) = (108.739 deg, 56.218 deg) = (07 14 57, +56 13 04) (J2000) There was no significant excess flux in the previous transit at UT 08:40 UT on 2016 January 4 with an upper limit of 20 mCrab for each. For more information: http://maxi.riken.jp/alert/novae/7391314067/7391314067.htm