K. Fukushima, M. Nakajima, H. Negoro (Nihon U.), M. Serino (RIKEN),
S. Ueno, H. Tomida, S. Nakahira, M. Kimura, M. Ishikawa (JAXA),
T. Mihara, M. Sugizaki, M. Morii, T. Yamamoto, J. Sugimoto, T. Takagi, M. Matsuoka (RIKEN),
N. Kawai, R. Usui, K. Ishikawa, T. Yoshii (Tokyo Tech),
A. Yoshida, T. Sakamoto, Y. Nakano (AGU),
H. Tsunemi, M. Sasaki (Osaka U.),
T. Onodera, K. Suzuki (Nihon U.),
Y. Ueda, M. Shidatsu, T. Kawamuro (Kyoto U.),
Y. Tsuboi, M. Higa (Chuo U.),
M. Yamauchi, K. Yoshidome, Y. Ogawa, H. Yamada (Miyazaki U.),
K. Yamaoka (Nagoya U.) report on behalf of the MAXI team
At 2013-04-07T23:37:01 UT, the MAXI/GSC nova alert system triggered on
a bright uncatalogued X-ray transient source.
The transient emission started at and lasted at least 25 seconds
within the 41 second long triangular transit response of
MAXI/GSC. We identify this event as GRB 130407A.
Assuming that the source flux was constant over the transit,
we obtain the source position at
(R.A., Dec) = (248.10 deg, 10.51 deg) = (16 32 23, +10 30 39) (J2000)
with a 90% C.L. statistical error of 0.2 deg and an additional systematic
uncertainty of 0.1 deg (90% containment radius). The 4-10 keV flux was
170 +- 30 mCrab.
There was no significant excess flux in the previous transit at 22:04UT
and in the next transit at 4/8 01:10 UT with an upper limit of 20 mCrab for each.