[vsnet-grb-info 12544] GRB 121027A: MAXI/GSC detection 40 minutes after the Swift Trigger

[GCN Circulars]

TITLE:   GCN CIRCULAR
NUMBER:  13908
SUBJECT: GRB 121027A: MAXI/GSC detection 40 minutes after the Swift Trigger
DATE:    12/10/27 09:51:02 GMT
FROM:    Motoko Suzuki at RIKEN  <motoko at crab.riken.jp>

M. Serino (RIKEN), S. Nakahira (JAXA), N. Negoro, M. Asada (Nihon U.), 
K. Yamaoka (ISAS), S. Ueno, H. Tomida, M. Ishikawa (JAXA),
T. Mihara, M. Sugizaki, T. Yamamoto, J. Sugimoto, M. Matsuoka (RIKEN), 
N. Kawai,  M. Morii,  R. Usui, K. Ishikawa, T. Yoshii  (Tokyo Tech),
A. Yoshida (AGU), H. Tsunemi, M. Kimura (Osaka U.), 
M. Nakajima (Nihon U.), 
Y. Ueda, K. Hiroi, M. Shidatsu, R. Sato (Kyoto U.),
Y. Tsuboi, M. Higa (Chuo U.)
M. Yamauchi, Y. Nishimura, T. Hanayama, K. Yoshidome (Miyazaki U.)
report on behalf of the MAXI team:

At 2012-10-27T08:12:53UT, the MAXI/GSC nova alert system triggered on a
bright uncatalogued X-ray transient source.
The transient emission lasted at least 38 seconds within the 41 second
long triangular transit response of MAXI/GSC. 

Assuming that the source flux was constant over the transit,
we obtain the source position at

 (R.A., Dec) = (63.75 deg, -58.68 deg) = (04:15:00, -58:40:59)(J2000)

with a 90% C.L. statistical error of 0.43 deg and an additional systematic
uncertainty of 0.1 deg (90% containment radius). 
The 4-10 keV flux was ~150 mCrab.

The position is consistent with GRB 121027A (GCN 13906, 13907), 
so we identify the source is GRB 121027A observed 40 minutes after 
the Swift Trigger.

There was no significant excess flux in the previous transit at 06:40 UT
(92 min before the trigger time) with an upper limit of 20 mCrab.