[vsnet-grb-info 23403] GRB 190828A: MAXI/GSC detection

[GCN Circulars]

TITLE:   GCN CIRCULAR
NUMBER:  25502
SUBJECT: GRB 190828A: MAXI/GSC detection
DATE:    19/08/28 08:44:15 GMT
FROM:    Satoshi Sugita at Aoyama Gakuin U.  <sugita at phys.aoyama.ac.jp>

S. Sugita,  H. Nishida, M. Serino (AGU), H. Negoro (Nihon U.), K.
Asakura (Osaka U.),
M. Nakajima, W. Maruyama, M. Aoki, K. Kobayashi (Nihon U.),
T. Mihara, T. Tamagawa, M. Matsuoka (RIKEN),
T. Sakamoto, A. Yoshida (AGU),
W. Iwakiri, Y. Tsuboi,  R. Sasaki, H. Kawai, T. Sato (Chuo U.),
M. Shidatsu (Ehime U.),
N. Kawai, M. Sugizaki, M. Oeda, K. Shiraishi (Tokyo Tech),
S. Nakahira, Y. Sugawara, S. Ueno, H. Tomida, M. Ishikawa, N.Isobe, R.
Shimomukai, M. Tominaga (JAXA),
Y. Ueda, A. Tanimoto, S. Yamada, S. Ogawa, K. Setoguchi, T. Yoshitake
(Kyoto U.),
H. Tsunemi, T. Yoneyama, S. Ide (Osaka U.),
M. Yamauchi, S. Iwahori, Y. Kurihara, K. Kurogi, K. Miike (Miyazaki U.),
T. Kawamuro (NAOJ),
K. Yamaoka (Nagoya U.),
Y. Kawakubo (LSU)
report on behalf of the MAXI team:

The MAXI/GSC nova alert system triggered a bright uncatalogued X-ray
transient source at 07:58:01 UT on 2019 August 28.
Assuming that the source flux was constant over the transit,
we obtain the source position at
(R.A., Dec) = (58.011 deg, 46.448 deg) = (03 52 02, +46 26 52)  (J2000)
with a 90% C.L. statistical error of 0.25 deg and an additional
systematic uncertainty of 0.1 deg (90% containment radius).

Without assumptions on the source constancy, we obtain a rectangular error
box for the transient source with the following corners:
(56.303, 46.041) deg = (03 45 12, +46 02 27) (J2000)
(56.644, 45.605) deg = (03 46 34, +45 36 17) (J2000)
(60.044, 46.816) deg = (04 00 10, +46 48 57) (J2000)
(59.724, 47.262) deg = (03 58 53, +47 15 43) (J2000)

The X-ray flux averaged over the scan was 193 +- 27 mCrab
(4.0-10.0keV, 1 sigma error).