TITLE:   GCN CIRCULAR
NUMBER:  28240
SUBJECT: GRB 200809B: MAXI/GSC detection
DATE:    20/08/10 03:27:53 GMT
FROM:    Satoshi Sugita at Aoyama Gakuin U.  <sugita@phys.aoyama.ac.jp>

S. Sugita (AGU), H. Negoro, M. Nakajima, M. Aoki,
K. Kobayashi, R. Takagi, K, Asakura, K, Seino (Nihon U.),
T. Mihara, C. Guo, Y. Zhou, T. Tamagawa, M. Matsuoka (RIKEN),
T. Sakamoto, M. Serino, H. Nishida, A. Yoshida (AGU),
Y. Tsuboi, W. Iwakiri, R. Sasaki, H. Kawai, Y. Okamoto, S. Kitakoga (Chuo U.),
M. Shidatsu (Ehime U.), N. Kawai, R. Adachi, M. Niwano (Tokyo Tech),
S. Nakahira, Y. Sugawara, S. Ueno, H. Tomida, M. Ishikawa, M.
Tominaga, T. Nagatsuka (JAXA),
Y. Ueda, S. Yamada, S. Ogawa, K. Setoguchi, T. Yoshitake (Kyoto U.),
H. Tsunemi (Osaka U.), M. Yamauchi, K. Kurogi, K. Miike (Miyazaki U.),
Y. Kawakubo (LSU), T. Kawamuro (NAOJ), K. Yamaoka (Nagoya U.), M.
Sugizaki (NAOC)
report on behalf of the MAXI team:

The MAXI/GSC nova alert system triggered a bright uncatalogued X-ray
transient source at 15:41:27 UT on 2020 Aug 9.
Assuming that the source flux was constant over the transit,
we obtain the source position at
(R.A., Dec) = (15.369 deg, -73.867 deg) = (01 01 28, -73 52 01) (J2000)
with a 90% C.L. statistical error of 0.38 deg and an additional
systematic uncertainty of 0.1 deg (90% containment radius).
The position was consistent with GRB200809B (Fermi GBM: GCN 28236,
Swift BAT: 28237).
The X-ray flux averaged over the scan was 94 +- 17 mCrab
(4.0-10.0keV, 1 sigma error).
There was no significant excess flux in the next transit at 8/9
17:14 UT with an upper limit of 20 mCrab.