TITLE:   GCN CIRCULAR
NUMBER:  38555
SUBJECT: GRB 241213B: MAXI/GSC detection
DATE:    24/12/13 13:30:39 GMT
FROM:    Hitoshi Negoro at Nihon University/MAXI team <negoro.hitoshi@nihon-u.ac.jp>

H. Negoro (Nihon U.), M. Serino, Y. Kawakubo (AGU), W. Iwakiri (Chiba U.),
M. Nakajima, Y. Kudo, H. Shibui, K. Takagi, H. Takahashi, K. Tatano, H. Nishio (Nihon U.), 
T. Mihara, T. Kawamuro, S. Yamada, S. Wang, T. Tamagawa, N. Kawai, M. Matsuoka (RIKEN), 
T. Sakamoto, S. Sugita, H. Hiramatsu, H. Nishikawa, Y. Kondo, S. Sasao, A. Yoshida (AGU), 
Y. Tsuboi, H. Sugai, N. Nagashima (Chuo U.), M. Shidatsu, Y. Niida (Ehime U.),
I. Takahashi, M. Niwano, N. Higuchi, Y. Yatsu (Tokyo Tech), S. Nakahira, S. Ueno, H. Tomida,
 M. Ishikawa, S. Ogawa, M. Kurihara (JAXA), Y. Ueda, Y. Okada, K. Fujiwara (Kyoto U.),  
M. Yamauchi, Y. Otsuki, T. Hasegawa, M. Nishio (Miyazaki U.), K. Yamaoka (Nagoya U.), 
and M. Sugizaki (Kanazawa U.)

The MAXI/GSC nova alert system triggered on a bright uncatalogued X-ray transient source 
at 12:56:30 UT on 2024 December 13. Assuming that the source flux was constant over the transit,
we obtain the source position at
(R.A., Dec) = (331.450 deg, 4.282 deg) = (22 05 48, +04 16 55) (J2000) 
with a statistical 90% C.L. elliptical error region 
with long and short radii of 0.16 deg and 0.15 deg, respectively. 
The roll angle of the long axis from the north direction is 141.0 deg counterclockwise. 
There is an additional systematic uncertainty of 0.1 deg (90% containment radius).
The X-ray flux averaged over the scan was 465 +- 58 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) = (331.162, 4.788) deg = (22 04 38, +04 47 16) (J2000)
(R.A., Dec) = (330.936, 4.585) deg = (22 03 44, +04 35 05) (J2000)
(R.A., Dec) = (331.900, 3.518) deg = (22 07 35, +03 31 04) (J2000)
(R.A., Dec) = (332.126, 3.721) deg = (22 08 30, +03 43 15) (J2000)
There was no significant excess flux in the previous transit at 11:23 UT 
with an upper limit of 20 mCrab.