GCN Circular 15248

K. Suzuki, H. Sakakibara, H. Negoro (Nihon U.),
S. Nakahira, H. Tomida, S. Ueno, M. Kimura, M. Ishikawa, Y. E. Nakagawa (JAXA),
T. Mihara, M. Sugizaki, M. Morii, M. Serino, 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.),
M. Nakajima, K. Fukushima, T. Onodera (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:

The MAXI/GSC Nova alert system triggered a bright uncatalogued X-ray transient source at
UT 2013-09-25T05:13:41.
Assuming that the source flux was constant over the transit,
we obtain the source position at
(41.38 deg, -25.91 deg) = (02 45 32, -25 54 54)(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 position is consistent with that of GRB 130925A (Lien et al. GCN #15246),
and apart from GRB 130925A by 0.30 deg.
This detection is, however, about 1 hour after the Swift detection.
The 2-20 keV flux was 290 (-51/+53) mCrab. An absorbed power-law fit to the burst spectrum
gives a photon index 1.62 +/- 0.27.

There was no significant excess flux in the previous transit at 03:41 UT
and in the next transit at 06:47 UT with an upper limit of 20 mCrab for each.

[GCN OPS NOTE(25sep13): Per author's request, the Lien citation of 12526
was changed to 15246.]