[vsnet-grb-info 19756] GRB 170830A: MAXI/GSC detection

[GCN Circulars]

TITLE:   GCN CIRCULAR
NUMBER:  21761
SUBJECT: GRB 170830A: MAXI/GSC detection
DATE:    17/08/30 05:53:04 GMT
FROM:    H. Negoro at Nihon U.  <negoro at phys.cst.nihon-u.ac.jp>

T. Yoneyama (Osaka U.), S. Nakahira  (RIKEN), S. Sugita (Tokyo Tech),
T. Mihara, M. Sugizaki, M. Serino,
W. Iwakiri, M. Shidatsu, M. Matsuoka (RIKEN), 
H. Negoro, M. Nakajima, T. Kawase, A. Sakamaki (Nihon U.),
S. Ueno, H. Tomida, M. Ishikawa, Y. Sugawara, N. Isobe, R. Shimomukai (JAXA),
N. Kawai, T. Yoshii, Y. Tachibana, S. Harita, Y. Muraki, K. Morita (Tokyo Tech), 
A. Yoshida, T. Sakamoto, Y. Kawakubo, Y. Kitaoka, T. Hashimoto (AGU), 
H. Tsunemi, (Osaka U.), 
Y. Ueda, T. Hori, A. Tanimoto, S. Oda (Kyoto U.), 
Y. Tsuboi, Y. Nakamura, R. Sasaki, H. Kawai  (Chuo U.), 
M. Yamauchi, C. Hanyu, K, Hidaka (Miyazaki U.), 
T. Kawamuro (NAOJ), 
K. Yamaoka (Nagoya U.) 


GRB 170830A: MAXI/GSC detection

 The MAXI/GSC nova alert system triggered a bright uncatalogued X-ray transient source at UT 03:15:29 UT on 2017 August 30. 
Assuming that the source flux was constant over the transit,
we obtain the source position at
(R.A., Dec) = (267.244 deg, -2.000 deg) = (17 48 58, -02 00 00) (J2000) 
with a statistical 90% C.L. elliptical error region 
with long and short radii of 0.09 deg and 0.05 deg, respectively. 
The roll angle of long axis from the north direction is 41.0 deg counterclockwise. 
We estimated a rectangular error box for the transient source with the following corners:
(266.590, -1.392) deg = (17 46 21, -01 23 31) (J2000) 
(266.518, -1.475) deg = (17 46 04, -01 28 30) (J2000) 
(267.633, -2.210) deg = (17 50 31, -02 12 36) (J2000) 
(267.637, -2.281) deg = (17 50 32, -02 16 50) (J2000).
There is an additional systematic uncertainty of 0.1 deg (90% containment radius).

The X-ray flux averaged over the scan was 1330 +- 75 mCrab
(4.0-10.0keV, 1 sigma error).
There was no significant excess flux in the previous transit at UT 01:42
and in the next transit at UT 04:48 with an upper limit of 20 mCrab for each.