GCN Circular 12489

T. Toizumi, M. Morii,(Tokyo Tech), M. Shidatsu (Kyoto U.), M. Serino(RIKEN),
S. Ueno, H. Tomida, M. Kohama, M. Ishikawa (JAXA),
T. Mihara, M. Sugizaki, S. Nakahira, T. Yamamoto, T. Sootome, M. Matsuoka (RIKEN), 
N. Kawai, K. Sugimori, R. Usui (Tokyo Tech),
A. Yoshida, K. Yamaoka (AGU),
H. Tsunemi, M. Kimura, H. Kitayama (Osaka U.), 
H. Negoro, M. Nakajima, F. Suwa (Nihon U.), 
Y. Ueda, K. Hiroi (Kyoto U.),
Y. Tsuboi, T. Matsumura, K. Yamazaki (Chuo U.)
report on behalf of the MAXI team:

MAXI/GSC triggered at UT 2011-10-24T07:21:27 on a bright uncatalogued X-ray 
transient source.  Judging from its location and spectral hardness ratio, 
this transient is probably a gamma-ray burst. 
Assuming that the source flux was constant over the transit, 
we obtain the source position at

(R.A., Dec) = (+222.18 deg, +25.84 deg) = (14 48 42, +25 50 40)(J2000)  

with a rectangular error box (90%C.L.) with the following corners: 

(R.A., Dec) = (+222.22 deg, +25.74 deg) = (14 48 54, +25 44 11)(J2000) 
(R.A., Dec) = (+222.32 deg, +25.86 deg) = (14 49 16, +25 51 37)(J2000) 
(R.A., Dec) = (+222.13 deg, +25.95 deg) = (14 48 31, +25 57 15)(J2000) 
(R.A., Dec) = (+222.04 deg, +25.83 deg) = (14 48  9, +25 49 49)(J2000) 

There is additional systematic uncertainty of 0.2 deg (90% containment radius).
The preliminary flux of the transient source was 700 mCrab (4-10 keV).
There was no significant detection at the transit location in the
previous orbit (92 min before 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.