GCN Circular 10739

M. Morii (Tokyo Tech), M. Nakajima (Nihon U.), S. Nakahira (AGU),
N. Kawai, K. Sugimori (Tokyo Tech), M. Matsuoka, K. Kawasaki, S. Ueno,
H. Tomida, M. Kohama, M. Ishikawa (JAXA), T. Mihara, Y.E. Nakagawa,
M. Sugizaki, M. Suzuki, T. Yamamoto, T. Sootome (RIKEN), A. Yoshida,
K. Yamaoka (AGU), H. Tsunemi, M. Kimura (Osaka U.), H. Negoro, H. Ozawa,
F. Suwa (Nihon U.), Y. Ueda, N. Isobe, S. Eguchi, K. Hiroi (Kyoto U.),
A. Daikyuji (Miyazaki U.), A. Uzawa, T. Matsumura, K. Yamazaki (Chuo U.)
report on behalf of the MAXI team

MAXI/GSC detected a bright X-ray transient at a scan transit from
2010-05-10T19:27:09 to 19:27:37 UT. The transient emission lasted at least
for 28 seconds within the 50 second long triangular transit response of
MAXI/GSC.
This event is temporary coincident with the Fermi-GBM Trigger #295212428 at
2010-05-10T19:27:06.97, thus we identify this event as GRB 100510A.

The best-fit position of the source is
(R.A., Dec) = (+355.8 deg, -35.6 deg) = (23 43 10, -35 37 25)(J2000),
with a rectangular statistical error box (90%C.L.) of the following corners:

 (R.A., Dec) = (+355.69 deg, -35.79 deg) = (23 42 45, -35 47  8)(J2000)
 (R.A., Dec) = (+355.58 deg, -35.55 deg) = (23 42 19, -35 32 49)(J2000)
 (R.A., Dec) = (+355.90 deg, -35.46 deg) = (23 43 35, -35 27 38)(J2000)
 (R.A., Dec) = (+356.00 deg, -35.70 deg) = (23 44  1, -35 41 56)(J2000).

There is additional systematic uncertainty of 0.2 deg (90% containment radius).

Without assumptions on the source constancy, we obtain a rectangular error
box for the transient source with the following corners:

 (R.A., Dec) = (+355.18 deg, -35.92 deg) = (23 40 43, -35 55 12)(J2000)
 (R.A., Dec) = (+355.08 deg, -35.68 deg) = (23 40 18, -35 40 49)(J2000)
 (R.A., Dec) = (+356.70 deg, -35.24 deg) = (23 46 47, -35 14 11)(J2000)
 (R.A., Dec) = (+356.81 deg, -35.47 deg) = (23 47 14, -35 28 27)(J2000).

The peak X-ray flux was at least 650 +- 70 mCrab (4-10 keV, 1 sigma error).

The position above is consistent with the Fermi-GBM flight position
on 2010-05-10T19:27:33 UT (record #58, RA=345.10, Dec=-20.03, error=18.37),
but outside of the ground position on 2010-05-10T19:27:40 UT (record #57,
RA=31.87, Dec=-31.55, error=19.12).

The all-sky image and the light curve will be shown at the MAXI web site
http://maxi.riken.jp/ at the "News" section.