GCN Circular 23327

Y. Kawakubo (AGU), M. Nakajima, H. Negoro (Nihon U.), M. Serino (AGU), 
S. Nakahira (RIKEN), A. Sakamaki, W. Maruyama, M. Aoki, K. Kobayashi (Nihon U.),  
T. Mihara, F. Yatabe, Y. Takao, M. Matsuoka (RIKEN), T. Sakamoto, S. Sugita, 
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.) 
report on behalf of the MAXI team:

The MAXI/GSC nova alert system triggered on a bright uncatalogued X-ray 
transient source at 2018-10-11T03:36:12 UT.
Assuming that the source flux was constant over the transit, we obtain 
the source position at

(R.A., Dec) = (93.500 deg, 20.837 deg) = (06 14 00, +20 50 13) (J2000) 

with a statistical 90% C.L. elliptical error region with long and short 
radii of 0.26 deg and 0.18 deg, respectively. The roll angle of the long axis 
from the north direction is 101.0 deg counterclockwise. There is an additional 
systematic uncertainty of 0.1 deg (90% containment radius).
The X-ray flux averaged over the scan was 167 +- 28 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) = (94.338, 21.465) deg = (06 17 21, +21 27 53) (J2000)
(R.A., Dec) = (93.931, 21.742) deg = (06 15 43, +21 44 31) (J2000)
(R.A., Dec) = (92.419, 19.784) deg = (06 09 40, +19 47 02) (J2000)
(R.A., Dec) = (92.824, 19.511) deg = (06 11 17, +19 30 39) (J2000)

There was no significant excess flux in the next transit at 03:55 UT with 
an upper limit of 20 mCrab.

We note that this burst was detected just after the ISS maneuver, and 
the data arrived at JAXA/TKSC about about 8 hr late. 
This and the confirmation of the event result in the late notice of this burst.