TITLE:   GCN CIRCULAR
NUMBER:  34304
SUBJECT: LIGO/Virgo/KAGRA S230731an: Coverage and upper limits from MAXI/GSC observations
DATE:    23/07/31 23:47:05 GMT
FROM:    Satoshi Sugita at Aoyama Gakuin U. <sugita@phys.aoyama.ac.jp>

M. Nakajima, H. Negoro,  (Nihon U.),
T. Mihara, N. Kawai (RIKEN),
S. Sugita, M. Serino, H. Hiramatsu, H. Nishikawa, Y. Kondo (AGU),
Y. Kawakubo (LSU)
report on behalf of the MAXI team:

We examined MAXI/GSC all-sky X-ray images (2-20 keV)
after compact binary merger candidate S230731an at 2023-07-31 21:53:07
UTC (GCN 34303).

At the trigger time of S230731an, the high-voltage of MAXI/GSC was off,
and it was turned on at T0+628 sec (+10.5 min).
The first one-orbit (92 min) scan observation with GSC after the event
covered 95%
of the 90% credible region of the bayestar skymap from 22:03:35 to
23:07:43 UTC (T0+628 to T0+4476 sec).

No significant new source was found in the region in the one-orbit
scan observation.
A typical 1-sigma averaged upper limit obtained in one scan observation
is 20 mCrab at 2-20 keV.