GCN Circular 35495

T. Kurihara (JAXA), 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, Y. Niida (Ehime U.),
I. Takahashi, M. Niwano, S. Sato, N. Higuchi, Y. Yatsu (Tokyo Tech),
S. Nakahira, S. Ueno, H. Tomida, M. Ishikawa, S. Ogawa (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.), Y. Kawakubo (LSU), M. Sugizaki (NAOC), and W. Iwakiri (Chiba U.)

The MAXI/GSC nova alert system triggered on a bright uncatalogued X-ray transient source
at 19:15:47 UT on January 7, 2023.
Assuming that the source flux was constant over the transit,
we obtain the source position at
(R.A., Dec) = (298.014 deg, -68.228 deg) = (19 52 03, -68 13 39) (J2000)
with a 90% C.L. statistical error of 0.41 deg and an additional systematic uncertainty of 0.1 deg
(90% containment radius). The X-ray flux averaged over the scan was 114 +- 24 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) = (296.278, -67.736) deg = (19 45 06, -67 44 09) (J2000)
(R.A., Dec) = (296.022, -68.496) deg = (19 44 05, -68 29 45) (J2000)
(R.A., Dec) = (303.762, -68.679) deg = (20 15 02, -68 40 44) (J2000)
(R.A., Dec) = (303.766, -67.913) deg = (20 15 03, -67 54 46) (J2000)
There was no significant excess flux in the previous transit at 17:42 UT
and in the next transit at 20:48 UT with an upper limit of 20 mCrab for each.