TITLE: GCN CIRCULAR NUMBER: 14130 SUBJECT: GRB 130102B: MAXI/GSC detection DATE: 13/01/03 05:48:37 GMT FROM: Motoko Suzuki at RIKEN M. Higa (Chuo U.), H. Negoro (Nihon U.), M. Serino (RIKEN), S. Ueno, H. Tomida, S. Nakahira, M. Kimura, M. Ishikawa (JAXA), T. Mihara, M. Sugizaki, K. Morihana, T. Yamamoto, J. Sugimoto, T. Takagi, M. Matsuoka (RIKEN), N. Kawai, M. Morii, R. Usui, K. Ishikawa (Tokyo Tech), A. Yoshida, T. Sakamoto, Y. Nakano (AGU), H. Tsunemi, M. Sasaki (Osaka U.), M. Nakajima, M. Asada (Nihon U.), Y. Ueda, K. Hiroi, M. Shidatsu, R. Sato, T. Kawamuro (Kyoto U.), Y. Tsuboi (Chuo U.), M. Yamauchi, Y. Nishimura, T. Hanayama, K. Yoshidome, Y. Ogawa (Miyazaki U.), K. Yamaoka (ISAS) report on behalf of the MAXI team At 2013-01-02T04:41:42 UT, the MAXI/GSC nova alert system triggered on a bright uncatalogued X-ray transient source. The transient emission started at 04:41:42 and lasted at least 45 seconds within the 74 second long triangular transit response of MAXI/GSC. We identify this event as GRB 130102B. Assuming that the source flux was constant over the transit, we obtain the source position at (R.A., Dec) = (309.58 deg, -72.38 deg ) = (20 38 20, -72 22 36)(J2000) with a 90% C.L. statistical error of 0.2 deg and an additional systematic uncertainty of 0.2 deg (90% containment radius). The 4-10 keV flux was 320 +- 40 mCrab. There was no significant excess flux in the previous transit at 03:09UT and in the next transit at 06:15 UT with an upper limit of 20 mCrab for each.