GCN Circular 18793

D. Itoh (Miyazaki U.), H. Negoro (Nihon U.), 
H. Tomida,  S. Nakahira, M. Ishikawa, Y. E. Nakagawa (JAXA), 
T. Mihara, M. Sugizaki, M. Serino, M. Shidatsu, J. Sugimoto, T. Takagi, M. Matsuoka (RIKEN), 
N. Kawai, M. Arimoto, T. Yoshii, Y. Tachibana, Y. Ono, T. Fujiwara (Tokyo Tech), 
A. Yoshida, T. Sakamoto, Y. Kawakubo, H. Ohtsuki (AGU), 
H. Tsunemi, R.Imatani (Osaka U.), 
M. Nakajima, K. Tanaka, T. Masumitsu (Nihon U.), 
Y. Ueda, T. Kawamuro, T. Hori, A. Tanimoto (Kyoto U.), 
Y. Tsuboi, S. Kanetou, Y. Nakamura, R. Sasaki (Chuo U.), 
M. Yamauchi, K. Furuya (Miyazaki U.), 
K. Yamaoka (Nagoya U.), M. Morii (ISM)
report on behalf of the MAXI team:

The MAXI/GSC nova alert system triggered a bright uncatalogued X-ray transient 
source at 00:43:52 UT on 2016 January 1.
Assuming that the source flux was constant over the transit,
we obtain the source position at
(R.A., Dec) = (219.733 deg, -13.823 deg) = (14 38 55, -13 49 22) (J2000) 
with a statistical 90% C.L. elliptical error region 
with long and short radii of 0.10 deg and 0.09 deg, respectively. 
The roll angle of long axis from the north direction is 150.0 deg counterclockwise. 
There is an additional systematic uncertainty of 0.1 deg (90% containment radius).
The X-ray flux averaged over the scan was 1543 +- 100 mCrab (4-10keV, 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) = (219.635 deg, -14.100 deg) = (14 38 32, -14 05 59) (J2000)
(R.A., Dec) = (219.486 deg, -13.957 deg) = (14 37 56, -13 57 24) (J2000)
(R.A., Dec) = (220.532 deg, -12.732 deg) = (14 42 07, -12 43 54) (J2000)
(R.A., Dec) = (220.677 deg, -12.878 deg) = (14 42 42, -12 52 39) (J2000)
There was no significant excess flux in the previous transit at 23:11 UT on 2015 December 31
with an upper limit of 20 mCrab for each.