S. Nakahira (RIKEN), H. Negoro (Nihon U.), M. Matsuoka ,
T. Mihara, M. Sugizaki, M. Serino, T. Yamamoto, T. Sootome (RIKEN),
S. Ueno, H. Tomida, M. Kohama, M. Ishikawa (JAXA),
N. Kawai, M. Morii, K. Sugimori, R. Usui, T. Toizumi (Tokyo Tech),
A. Yoshida, K. Yamaoka (AGU),
H. Tsunemi, M. Kimura, H. Kitayama (Osaka U.),
M. Nakajima, F. Suwa (Nihon U.),
Y. Ueda, K. Hiroi, M. Shidatsu (Kyoto U.),
Y. Tsuboi, T. Matsumura, K. Yamazaki (Chuo U.)
report on behalf of the MAXI team:
At the scan transit centered at UT 2011-04-26T15:08:36,
MAXI/GSC detected a short X-ray transient lasting about 18 seconds
within the 46 seconds triangular transit response of MAXI/GSC.
Judging from its location and spectral hardness ratio, this transient is
probably a gamma-ray burst.
Since the emission was detected only for a fraction of the triangular
transit response, the uncertainty of its position along the scan direction
is large. Without assuming the source constancy, we obtain a rectangular
error box (90%C.L.) with the following corners:
(R.A., Dec) = (+219.64 deg,-9.51 deg) = (14 38 34, -09 30 36)(J2000)
(R.A., Dec) = (+222.36 deg,-12.97 deg) = (14 49 26, -12 58 12)(J2000)
(R.A., Dec) = (+222.57 deg,-12.77 deg) = (14 50 17, -12 46 12)(J2000)
(R.A., Dec) = (+219.84 deg,-9.31 deg) = (14 39 21, -09 18 36)(J2000)
There is additional systematic uncertainty of 0.2 deg (90% containment radius).
The preliminary flux (2-20 keV) of the source was at least 200 mCrab.
There was no significant detection at the transit location in the
previous and following orbits (92 min before or after the detection)
with an upper limit of 20 mCrab. There is no known bright X-ray source
at the detected position.
Follow-up observations are encouraged.