GCN Circular 22347

H. Kawai (Chuo U.), H. Negoro (Nihon U.), M. Serino (AGU), 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, S. Sugita, 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, 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, Y. Nakamura, R. Sasaki, T. Sato (Chuo U.),
M. Yamauchi, C. Hanyu, K, Hidaka (Miyazaki U.),
T. Kawamuro (NAOJ),
K. Yamaoka (Nagoya U.)

report on behalf of the MAXI team:
The MAXI/GSC nova alert system triggered a bright uncatalogued X-ray transient 
source at 00:37:30 UT on 16 January 2018.
Assuming that the source flux was constant over the transit,
we obtain the source position at
(R.A., Dec) = (215.655 deg, 18.959 deg) = (14 22 37, +18 57 32) (J2000)
with a statistical 90% C.L. elliptical error region
with long and short radii of 0.13 deg and 0.11 deg, respectively.
The roll angle of long axis from the north direction is 158.0 deg counterclockwise.
There is an additional systematic uncertainty of 0.1 deg (90% containment radius).
The X-ray flux averaged over the scan was 609 +- 65 mCrab
(4.0-10.0keV, 1 sigma error).
Without assumptions on the source constancy,we obtain a rectangular error
box for the transient source with the following corners:
(R.A., Dec) = (214.873, 19.864) deg = (14 19 29, +19 51 48) (J2000)
(R.A., Dec) = (214.781, 19.788) deg = (14 19 07, +19 47 16) (J2000)
(R.A., Dec) = (216.314, 18.226) deg = (14 25 15, +18 13 31) (J2000)
(R.A., Dec) = (216.405, 18.300) deg = (14 25 37, +18 18 01) (J2000)
There was no significant excess flux in the previous transit at UT 23:04
with an upper limit of 20 mCrab.