TITLE:   GCN CIRCULAR
NUMBER:  33367
SUBJECT: GRB 230220A: Correction to GCN 33352
DATE:    23/02/22 11:20:31 GMT
FROM:    Hitoshi Negoro at Nihon U  <negoro.hitoshi@nihon-u.ac.jp>

S. Nawa (Chuo U.), H. Negoro, M. Nakajima, K. Kobayashi, M. Tanaka, Y. Soejima (Nihon U.), 
T. Mihara, T. Kawamuro, S. Yamada, T. Tamagawa, M. Matsuoka (RIKEN), 
T. Sakamoto, M. Serino, S. Sugita, H. Hiramatsu, H. Nishikawa, A. Yoshida (AGU), 
Y. Tsuboi, J. Kohara, S. Urabe, N. Nemoto (Chuo U.), M. Shidatsu, M. Iwasaki (Ehime U.),
N. Kawai, M. Niwano, R. Hosokawa, Y. Imai, N. Ito, Y. Takamatsu (Tokyo Tech), 
S. Nakahira,  S. Ueno, H. Tomida, M. Ishikawa,  T. Kurihara (JAXA), 
Y. Ueda, S. Ogawa, K. Setoguchi, T. Yoshitake, K. Inaba, Y. Nakatani (Kyoto U.), 
M. Yamauchi, T. Sato, R. Hatsuda, R. Fukuoka, Y. Hagiwara, Y. Umeki (Miyazaki U.), 
K. Yamaoka (Nagoya U.), Y. Kawakubo (LSU), M. Sugizaki (NAOC), and W. Iwakiri (Chiba U.)
report on behalf of the MAXI team:

Because the error box information for GRB 230220A reported in GCN #33352 was incorrect,
we correct it as follows.

The MAXI/GSC nova alert system triggered a bright uncatalogued X-ray transient source 
at 08:55:58 UT on 20  Feb 2023. Assuming that the source flux was constant over the transit,
we obtain the source position at
(R.A., Dec) = (346.565 deg, 18.607 deg) = (23 06 15, +18 36 25) (J2000)
with a statistical 90% C.L. elliptical error region
with long and short radii of 0.22 deg and 0.19 deg, respectively.
The roll angle of long axis from the north direction is 153.0 deg counterclockwise.
Without assumptions on the source constancy, we obtain a rectangular error box 
for the transient source with the following corners.
(345.720, 19.547) deg = (23 02 52, +19 32 49) (J2000)
(345.464, 19.290) deg = (23 01 51, +19 17 23) (J2000)
(347.309, 17.634) deg = (23 09 14, +17 38 02) (J2000)
(347.566, 17.889) deg = (23 10 15, +17 53 20) (J2000)
There is an additional systematic uncertainty of 0.1 deg (90% containment radius).
The X-ray flux averaged over the scan was 182 +- 28 mCrab
(4.0-10.0keV, 1 sigma error).
There was no significant excess flux in the previous transit at 07:22 UT with an upper limit of 20 mCrab.