[vsnet-grb-info 11871] GRB 120424A: MAXI/GSC detection of a burst

[GCN Circulars]

TITLE:   GCN CIRCULAR
NUMBER:  13261
SUBJECT: GRB 120424A: MAXI/GSC detection of a burst
DATE:    12/04/25 12:00:14 GMT
FROM:    Motoko Suzuki at RIKEN  <motoko at crab.riken.jp>

M. Serino, T. Yamamoto, T. Mihara, M. Sugizaki, M. Matsuoka (RIKEN), 
S. Ueno, H. Tomida, S. Nakahira, M. Ishikawa (JAXA),
N. Kawai, M. Morii, R. Usui, K. Ishikawa (Tokyo Tech),
A. Yoshida (AGU),
H. Tsunemi, M. Kimura (Osaka U.), 
H. Negoro, M. Nakajima, M. Asada, H. Sakakibara, N. Serita (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.), 
K. Yamaoka (Waseda U.)
report on behalf of the MAXI team:

At the scan transit centered at UT 2012-04-24 16:47:14,
MAXI/GSC detected a short X-ray transient lasting about 34 seconds 
within the 40 seconds triangular transit response of MAXI/GSC.
Judging from its high galactic latitude (-80deg) 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) = (+23.985deg,-29.879deg) = (01 35 56.40, -29 52 44.0)(J2000)

which has a statistical uncertainty of 16 arcmin at the 90% confidence limit 
and an additional systematic uncertainty of 6 arcmin (90% containment radius).

The preliminary flux (4-10 keV) of the source was 170 +- 30 mCrab.

There was no significant detection at the transit location in the
next orbit (92 min after the detection) with an upper limit of 20 mCrab.
Unfortunately the source position went out of view of the MAXI/GSC sky 
coverage at 2012/04/23 22:20, the upper limit at that time was 20 mCrab.
There is no known bright X-ray source at the detected position. 

Follow-up observations are encouraged.