GCN Circular 22118

GRB 171112A: MAXI/GSC detection

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

The MAXI/GSC nova alert system triggered a bright uncatalogued X-ray transient source 
at 20:50:01 UT on 2017 November 12. 
Assuming that the source flux was constant over the transit,
we obtain the source position at
(R.A., Dec) = (20.467 deg, -59.678 deg) = (01 21 52, -59 40 40) (J2000) 
with a statistical 90% C.L. elliptical error region 
with long and short radii of 0.17 deg and 0.12 deg, respectively. 
The roll angle of long axis from the north direction is 107.0 deg counterclockwise. 
There is an additional systematic uncertainty of 0.1 deg (90% containment radius).

We estimated a rectangular error box for the transient source with the following corners
which were independently calculated with respect to each camera.
camera 2:
(20.320, -61.117) deg = (01 21 16, -61 07 01) (J2000)
(19.513, -61.013) deg = (01 18 03, -61 00 47) (J2000)
(21.134, -58.662) deg = (01 24 32, -58 39 42) (J2000)
(21.890, -58.756) deg = (01 27 33, -58 45 23) (J2000)
camera 7:
(19.831, -60.456) deg = (01 19 19, -60 27 20) (J2000)
(19.396, -60.398) deg = (01 17 35, -60 23 51) (J2000)
(20.488, -58.842) deg = (01 21 57, -58 50 31) (J2000)
(20.905, -58.897) deg = (01 23 37, -58 53 48) (J2000)
There is an additional systematic uncertainty of 0.1 deg (90% containment radius).

The X-ray flux averaged over the scan was 437 +- 44 mCrab
(4.0-10.0keV, 1 sigma error).
There was no significant excess flux in the previous transit at UT 19:14
and in the next transit at UT 22:19:10 with an upper limit of 20 mCrab for each.