TITLE:   GCN CIRCULAR
NUMBER:  34871
SUBJECT: LIGO/Virgo/KAGRA S231021az: Coverage and upper limits from MAXI/GSC observations
DATE:    23/10/22 05:11:59 GMT
FROM:    Motoko Serino at Aoyama Gakuin U. <serino@phys.aoyama.ac.jp>

H. Hiramatsu, S. Sugita, M. Serino, H. Nishikawa, Y. Kondo (AGU),
N. Kawai (RIKEN), H. Negoro, M. Nakajima (Nihon U.),
T. Mihara (RIKEN),
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 S231021az at 2023-10-21 23:37:57 UTC .

At the trigger time of S231021az, the high-voltage of MAXI/GSC was on.
The instantaneous field of view of GSC at the GW trigger time covered 1% of the 90% credible region
of the bayestar sky map, in which we found no significant new X-ray source.
The first one-orbit (92 min) scan observation with GSC after the event covered 86%
of the 90% credible region of the bayestar skymap from 23:37:57 to 01:09:53 UTC (T0+0 to T0+5516 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.

If you require information about X-ray flux by MAXI/GSC at specific coordinates,
please contact the submitter of this circular by email.