TITLE: GCN CIRCULAR NUMBER: 38748 SUBJECT: LIGO/Virgo/KAGRA S241231du: Coverage and upper limit from MAXI/GSC observations DATE: 25/01/01 02:29:35 GMT FROM: Motoko Serino at Aoyama Gakuin U. serino@phys.aoyama.ac.jp

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

We examined MAXI/GSC all-sky X-ray images (2-20 keV) after compact binary merger candidate S241231du at 2024-12-31 13:16:46.194 UTC.

At the trigger time of S241231du, the high-voltage of MAXI/GSC was on. The instantaneous field of view of GSC at the GW trigger time covered 4% 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 90% of the 90% credible region of the bayestar skymap from 13:16:46 to 14:48:44 UTC (T0+0 to T0+5518 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.

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