TITLE:   GCN CIRCULAR
NUMBER:  31319
SUBJECT: GRB 211227A: MAXI/GSC detection
DATE:    21/12/28 01:13:44 GMT
FROM:    Motoko Serino at Aoyama Gakuin U.  <serino@phys.aoyama.ac.jp>

M. Tominaga (JAXA), Y. Kawakubo (LSU), M. Serino (AGU), 
H. Negoro, M. Nakajima, K. Kobayashi, K. Asakura, K. Seino (Nihon U.), 
T. Mihara, T. Tamagawa, J. Li, M. Matsuoka (RIKEN), 
T. Sakamoto,  S. Sugita, K. Komachi, H. Hiramatsu, A. Yoshida (AGU), 
Y. Tsuboi, W. Iwakiri,  H. Kawai, Y. Okamoto, S. Kitakoga (Chuo U.), 
M. Shidatsu, M. Iwasaki (Ehime U.), 
N. Kawai, M. Niwano, R. Hosokawa, Y. Imai, N. Ito, Y. Takamatsu (Tokyo Tech), 
S. Nakahira,  S. Ueno, H. Tomida, M. Ishikawa, T. Nagatsuka, T. Kurihara(JAXA), 
Y. Ueda, S. Yamada, S. Ogawa, K. Setoguchi, T. Yoshitake, Y. Goto, R. Uematsu, K. Inaba (Kyoto U.), 
H. Tsunemi (Osaka U.), M. Yamauchi, Y. Nonaka, T. Sato, R. Hatsuda, R. Fukuoka (Miyazaki U.), 
T. Kawamuro (UDP/NAOJ), K. Yamaoka (Nagoya U.), M. Sugizaki (NAOC) 

report on behalf of the MAXI team:
The MAXI/GSC nova alert system triggered a bright uncatalogued X-ray transient 
source at 23:32:06 UT on 2021 December 27.
Assuming that the source flux was constant over the transit,
we obtain the source position at
(R.A., Dec) = (132.253 deg, -2.658 deg) = (08 49 00, -02 39 28) (J2000) 
with a statistical 90% C.L. elliptical error region 
with long and short radii of 0.12 deg and 0.09 deg, respectively. 
The roll angle of long axis from the north direction is 66.0 deg counterclockwise. 
There is an additional systematic uncertainty of 0.1 deg (90% containment radius).
The X-ray flux averaged over the scan was 630 +- 48 mCrab
(4.0-10.0keV, 1 sigma error).

We conclude that this event is coincidence with the GRB event reported by Swift
(R.A., Dec) = (132.14898,-2.73556) (J2000)  (GCN #31316).