GCN Circular 27355

R. Adachi (Tokyo Tech),  R. Takagi, H. Negoro (Nihon U.), S. Nakahira (JAXA),
M. Nakajima, W. Maruyama, M. Aoki, K. Kobayashi (Nihon U.), 
T. Mihara, C. Guo, Y. Zhou, T. Tamagawa, M. Matsuoka (RIKEN), 
T. Sakamoto, M. Serino, S. Sugita, H. Nishida, A. Yoshida (AGU), 
Y. Tsuboi, W. Iwakiri, R. Sasaki, H. Kawai, T. Sato (Chuo U.), 
M. Shidatsu (Ehime U.), N. Kawai, M. Oeda, K. Shiraishi (Tokyo Tech), 
S. Nakahira, Y. Sugawara, S. Ueno, H. Tomida, M. Ishikawa, R. Shimomukai, M. Tominaga (JAXA), 
Y. Ueda, A. Tanimoto, S. Yamada, S. Ogawa, K. Setoguchi, T. Yoshitake (Kyoto U.), 
H. Tsunemi, T. Yoneyama, K. Asakura, S. Ide (Osaka U.), 
M. Yamauchi, S. Iwahori, Y. Kurihara, K. Kurogi, K. Miike (Miyazaki U.), 
T. Kawamuro (NAOJ), K. Yamaoka (Nagoya U.), Y. Kawakubo (LSU), M. Sugizaki (NAOC) 
report on behalf of the MAXI team:

The MAXI/GSC nova alert system triggered on a bright uncatalogued X-ray transient source 
at 09:23:08 UT on March 10, 2020. Assuming that the source flux was constant over the transit,
we obtain the source position at
(R.A., Dec) = (227.499 deg, 48.325 deg) = (15 09 59, +48 19 31) (J2000)
with a 90% C.L. statistical error of 0.44 deg and an additional systematic uncertainty of 
0.1 deg (90% containment radius).
Without assuming the source constancy, we obtain a rectangular 
error box (90%C.L.) with the following corners: 
(225.938, 49.050) deg = (15 03 45, +49 02 59) (J2000) 
(225.620, 48.200) deg = (15 02 28, +48 12 00) (J2000) 
(229.907, 47.407) deg = (15 19 37, +47 24 25) (J2000) 
(230.291, 48.244) deg = (15 21 09, +48 14 38) (J2000)
There is an additional systematic uncertainty of 0.2 deg (90% containment radius).

The X-ray flux averaged over the scan was 71 +- 17 mCrab (4.0-10.0keV, 1 sigma error).
There was no significant excess flux in the previous transit at 07:50 UT,
and in the next transit at 10:56 UT with an upper limit of 20 mCrab for each.