[vsnet-grb-info 21158] GRB 180923A: MAXI/GSC detection

[GCN Circulars]

TITLE:   GCN CIRCULAR
NUMBER:  23257
SUBJECT: GRB 180923A: MAXI/GSC detection
DATE:    18/09/23 06:57:35 GMT
FROM:    Motoko Suzuki at RIKEN  <motoko at crab.riken.jp>

W. Maruyama, H. Negoro (Nihon U.), M. Serino (AGU),
M. Nakajima, A. Sakamaki (Nihon U.),
T. Mihara, S. Nakahira, F. Yatabe, Y. Takao, M. Matsuoka (RIKEN),
T. Sakamoto, S. Sugita, Y. Kawakubo, T. Hashimoto, A. Yoshida (AGU),
N. Kawai, M. Sugizaki, Y. Tachibana, K. Morita (Tokyo Tech),
S. Ueno, H. Tomida, M. Ishikawa, Y. Sugawara, N. Isobe, R. Shimomukai (JAXA),
Y. Ueda, A. Tanimoto, T. Morita, S. Yamada (Kyoto U.),
Y. Tsuboi, W. Iwakiri, R. Sasaki, H. Kawai, T. Sato (Chuo U.),
H. Tsunemi, T. Yoneyama, K. Asakura, S. Ide (Osaka U.),
M. Yamauchi, K. Hidaka, S. Iwahori (Miyazaki U.),
T. Kawamuro (NAOJ),
K. Yamaoka (Nagoya U.),
M. Shidatsu (Ehime U.) 
report on behalf of the MAXI team:

The MAXI/GSC nova alert system triggered a bright uncatalogued X-ray transient source 
at 2018-09-23T04:08:25 UT .
We obtain the source position at
(R.A., Dec) = (38.304 deg, 6.301 deg) = (02 33 12, +06 18 03) (J2000)
with a rectangular error box with the following corners:
(R.A., Dec) = (37.429, 7.302) deg = (02 29 42, +07 18 07) (J2000)
(R.A., Dec) = (37.165, 6.998) deg = (02 28 39, +06 59 52) (J2000)
(R.A., Dec) = (39.010, 5.456) deg = (02 36 02, +05 27 21) (J2000)
(R.A., Dec) = (39.274, 5.760) deg = (02 37 05, +05 45 35) (J2000) .
There is an additional systematic uncertainty of 0.1 deg (90% containment radius).
The X-ray flux averaged over the scan was 162 +- 26 mCrab
(4.0-10.0keV, 1 sigma error).
There was no significant excess flux in the previous transit at UT 02:35
and in the next transit at 05:41 UT with an upper limit of 20 mCrab for each.