TITLE:   GCN CIRCULAR
NUMBER:  34068
SUBJECT: GRB 230623A: MAXI/GSC detection
DATE:    23/06/23 09:39:20 GMT
FROM:    Motoko Serino at Aoyama Gakuin U. <serino@phys.aoyama.ac.jp>

Y. Hagiwara (Miyazaki U.), H. Negoro, M. Nakajima (Nihon U.), M. Serino (AGU),
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, S. Sugita, H. Hiramatsu, H. Nishikawa, A. Yoshida (AGU),
Y. Tsuboi, S. Urabe, S. Nawa, N. Nemoto (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 (Kyoto U.),
M. Yamauchi, Y. Umeki, Y. Otsuki (Miyazaki U.),
K. Yamaoka (Nagoya U.),
Y. Kawakubo (LSU),
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 07:23:37 UT on 23 June 2023.
Assuming that the source flux was constant over the transit,
we obtain the source position at
(R.A., Dec) = (349.981 deg, -17.842 deg) = (23 19 55, -17 50 31) (J2000)
with a statistical 90% C.L. elliptical error region
with long and short radii of 0.23 deg and 0.2 deg, respectively.
The roll angle of long axis from the north direction is 40.0 deg counterclockwise.
There is an additional systematic uncertainty of 0.1 deg (90% containment radius).
The X-ray flux averaged over the scan was 185 +- 29 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) = (349.422, -18.340) deg = (23 17 41, -18 20 23) (J2000)
(R.A., Dec) = (349.773, -18.563) deg = (23 19 05, -18 33 46) (J2000)
(R.A., Dec) = (350.604, -17.375) deg = (23 22 24, -17 22 30) (J2000)
(R.A., Dec) = (350.255, -17.153) deg = (23 21 01, -17 09 10) (J2000)
There was no significant excess flux in the previous transit at 05:50 UT
and in the next transit at 08:56 UT with an upper limit of 20 mCrab for each.