TITLE: GCN CIRCULAR NUMBER: 37520 SUBJECT: LIGO/Virgo/KAGRA S240915b: Coverage and upper limits from MAXI/GSC observations DATE: 24/09/16 06:13:06 GMT FROM: Motoko Serino at Aoyama Gakuin U. serino@phys.aoyama.ac.jp

H. Nishikawa, S. Sugita, M. Serino, Y. Kawakubo, H. Hiramatsu, 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 S240915b at 2024-09-15 00:13:57.715 UTC (GCN 37512, 37513).

At the trigger time of S240915b, the high-voltage of MAXI/GSC was off, and it was turned on at T0+707 sec (+11.8 min). The first one-orbit (92 min) scan observation with GSC after the event covered 100% of the 90% credible region of the Bilby skymap from 01:17:12 to 01:19:17 UTC (T0+3795 to T0+3920 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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