TITLE:   GCN CIRCULAR
NUMBER:  35223
SUBJECT: GRB 231129C: MAXI/GSC detection
DATE:    23/11/29 22:19:44 GMT
FROM:    kurihara@ac.jaxa.jp

Y. Kawakubo (LSU),
H. Negoro, M. Nakajima, K. Kobayashi, M. Tanaka, Y. Soejima, Y. Kudo (Nihon U.),
T. Mihara, T. Kawamuro, S. Yamada, T. Tamagawa, N. Kawai, M. Matsuoka (RIKEN),
T. Sakamoto, M. Serino, S. Sugita, H. Hiramatsu, H. Nishikawa, A. Yoshida (AGU),
Y. Tsuboi, S. Urabe, S. Nawa, N. Nemoto, E.Goto (Chuo U.),
M. Shidatsu (Ehime U.),
I. Takahashi, M. Niwano, S. Sato, N. Higuchi, Y. Yatsu (Tokyo Tech),
S. Nakahira, S. Ueno, H. Tomida, M. Ishikawa, S. Ogawa, T. Kurihara (JAXA),
Y. Ueda, K. Setoguchi, T. Yoshitake, Y. Nakatani, Y. Okada (Kyoto U.),
M. Yamauchi, Y. Hagiwara, Y. Umeki, Y. Otsuki (Miyazaki U.),
K. Yamaoka (Nagoya U.),
M. Sugizaki (NAOC),
W. Iwakiri (Chiba U.)
report on behalf of the MAXI team:
 
The MAXI/GSC nova alert system triggered a bright uncatalogued X-ray transient
source at 2023/11/29 19:10:18 UT.
Assuming that the source flux was constant over the transit,
we obtain the source position at
(R.A., Dec) = (11.910 deg, -81.636 deg) = (00 47 38, -81 38 09) (J2000)
with a statistical 90% C.L. elliptical error region
with long and short radii of 0.09 deg and 0.07 deg, respectively.
The roll angle of long axis from the north direction is 90.0 deg counterclockwise.
There is an additional systematic uncertainty of 0.1 deg (90% containment radius).
The X-ray flux averaged over the scan was 1355 +- 82 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) = (12.351, -81.744) deg = (00 49 24, -81 44 38) (J2000)
(R.A., Dec) = (11.353, -81.663) deg = (00 45 24, -81 39 46) (J2000)
(R.A., Dec) = (12.374, -81.394) deg = (00 49 29, -81 23 38) (J2000)
(R.A., Dec) = (13.350, -81.472) deg = (00 53 23, -81 28 19) (J2000)
There was no significant excess flux in the previous transit at 17:37 UT
 with an upper limit of 20 mCrab for each.