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GCN Circular 23186

Subject
GRB 180829A/MAXI J0406-019: MAXI/GSC detection
Date
2018-08-29T08:06:22Z (6 years ago)
From
Motoko Suzuki at RIKEN <motoko@crab.riken.jp>
S. Yamada (Kyoto U.), H. Negoro (Nihon U.), M. Serino (AGU), 
M. Nakajima, A. Sakamaki, W. Maruyama (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 (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 2018-08-29T00:05:31UT .
Assuming that the source flux was constant over the transit,
we obtain the source position at
(R.A., Dec) = (61.729 deg, -1.976 deg) = (04 06 54, -01 58 33) (J2000)
with a statistical 90% C.L. elliptical error region
with long and short radii of 0.36 deg and 0.29 deg, respectively.
The roll angle of long axis from the north direction is 53.0 deg counterclockwise.
Without assumptions on the source constancy,we obtain a rectangular error
box for the transient source with the following corners:
(60.951, -3.048) deg = (04 03 48, -03 02 54) (J2000)
(60.690, -2.747) deg = (04 02 45, -02 44 49) (J2000)
(62.767, -0.848) deg = (04 11 04, -00 50 53) (J2000)
(63.028, -1.149) deg = (04 12 06, -01 08 57) (J2000)
There is an additional systematic uncertainty of 0.1 deg (90% containment radius).
The X-ray flux averaged over the scan was 71 +- 17 mCrab
(4.0-10.0keV, 1 sigma error).
There was no significant excess flux in the previous transit at UT 8/28 22:32
and in the next transit at 03:10 UT with an upper limit of 20 mCrab for each.
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