[vsnet-grb-info 21834] GRB 190305A: MAXI/GSC detection

[GCN Circulars]

TITLE:   GCN CIRCULAR
NUMBER:  23933
SUBJECT: GRB 190305A: MAXI/GSC detection
DATE:    19/03/06 05:10:26 GMT
FROM:    Satoshi Nakahira at RIKEN  <nakahira at crab.riken.jp>

S. Nakahira (RIKEN), S. Sugita (AGU), W. Iwakiri(Chuo U.), 
T. Mihara, F. Yatabe, Y. Takao, M. Matsuoka (RIKEN),
H. Negoro, M. Nakajima, A. Sakamaki, W. Maruyama, M. Aoki, K. Kobayashi (Nihon U.), 
T. Sakamoto, M. Serino, 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, T. Midooka (JAXA), 
Y. Ueda, A. Tanimoto, T. Morita, S. Yamada, S. Ogawa (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.),
Y. Kawakubo (LSU) 
report on behalf of the MAXI team:
Using the MAXI/GSC count rate monitor data collected at one second intervals,
we have detected GRB 190305A reported by AGILE (Ursi et al., GCN23930) and CALET 
CGBM (Trigger ID 1235826131) with a duration of 1-2 sec.
Because this event is considered to be coming from outside of field of view, 
no localization was given.

Then, about two minutes after the first event, MAXI/GSC nova alert system triggered 
an uncatalogued X-ray transient source at 2019/03/05 13:07:43 UT.
Assuming that the source flux was constant over the transit,
we obtain the source position at
(R.A., Dec) = (11.326 deg, -50.122 deg) = (00 45 18, -50 07 19) (J2000) 
with a statistical 90% C.L. elliptical error region 
with long and short radii of 0.39 deg and 0.34 deg, respectively. 
The roll angle of long axis from the north direction is 68.0 deg counterclockwise. 
There is an additional systematic uncertainty of 0.1 deg (90% containment radius).
The X-ray flux averaged over the scan was 101 +- 22 mCrab
(4.0-10.0keV, 1 sigma error).
There was no significant excess flux in the previous transit at UT 11:35 
and in the next transit at 14:40 UT with an upper limit of 20 mCrab for each.

The second event is possibly an extended mission of GRB 190305A.
However, we cannot distinguish whether these two events are the same origin for now.
Further analysis is still in progress.