[vsnet-grb-info 8427] GRB 090926B: MAXI GSC detection

[GCN Circulars]

TITLE:   GCN CIRCULAR
NUMBER:  9943
SUBJECT: GRB 090926B: MAXI GSC detection
DATE:    09/09/27 07:27:48 GMT
FROM:    Nobuyuki Kawai at Tokyo Tech  <nkawai at hp.phys.titech.ac.jp>

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

The Gas Slit Camera (GSC) of MAXI, the all-sky X-ray monitor on the ISS,
detected a bright X-ray source at the position consistent with GRB 090926B
(Grupe et al, GCN Circ. 9935) in the energy range of 2-30 keV.
The nominal location of the source as measured by GSC is 

(R.A., Dec.) = (46.3 deg, -39.1 deg) = (03:05:12, -39:06:00)(J2000) 

with an estimated systematic uncertainty of about 1 degree.

The start time of the source detection (above 3 sigma level) was
21:55:31 UT on 26 September 2009, and seen until 21:55:55 UT.
The start time was 17 sec earlier than the Swift-BAT trigger time,
approximately consistent with the rise epoch (T-20) reported in the BAT 
refined analysis (Baumgartner et al., GCN Circ. 9939).

The X-ray flux at the peak was about 0.3 Crab (uncorrected).
There are significant time structures within the transit light curve, 
which would be simply triangular for a steady source.

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

MAXI is currently in the commissioning phase that runs for three months.
The systematic uncertainty in localization will be significantly improved
with the progress of the alignment calibration.