GCN Circular 17719

GRB 150418A: MAXI/GSC detection
M. Serino (RIKEN), H. Negoro (Nihon U.), S. Nakahira (JAXA),
S. Ueno, H. Tomida, M. Kimura, M. Ishikawa, Y. E. Nakagawa (JAXA),
T. Mihara, M. Sugizaki, M. Shidatsu, J. Sugimoto, T. Takagi, M. Matsuoka (RIKEN),
N. Kawai, T. Yoshii, Y. Tachibana (Tokyo Tech),
A. Yoshida, T. Sakamoto, Y. Kawakubo, H. Ohtsuki (AGU),
H. Tsunemi, R. Imatani (Osaka U.),
M. Nakajima, T. Namba, M. Fujita, F. Honda, K. Tanaka, T. Masumitsu (Nihon U.),
Y. Ueda, T. Kawamuro, T. Hori (Kyoto U.),
Y. Tsuboi, S. Kanetou (Chuo U.),
M. Yamauchi, D. Itoh (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 00:52:08 UT.
Without assumptions on the source constancy, we obtain a rectangular error
box for the transient source with the following corners:
(159.791 deg, -4.326 deg) = (10 39 09, -04 19 34) (J2000)
(159.898 deg, -4.194 deg) = (10 39 35, -04 11 39) (J2000)
(161.225 deg, -5.494 deg) = (10 44 53, -05 29 39) (J2000)
(161.114 deg, -5.624 deg) = (10 44 27, -05 37 25) (J2000)
There is an additional systematic uncertainty of 0.1 deg (90% containment radius).
The X-ray flux averaged over the scan was 597 +- 45 mCrab
(4-10keV, 1 sigma error).
There was no significant excess flux in the previous transit at UT 23:19 on
April 17 with an upper limit of 20 mCrab.