TITLE: GCN CIRCULAR NUMBER: 24153 SUBJECT: LIGO/Virgo S190421ar: MAXI/GSC Observations DATE: 19/04/23 05:58:11 GMT FROM: Motoko Serino at RIKEN/MAXI M. Serino, S. Sugita (AGU), H. Negoro (Nihon U.), M. Sugizaki, N. Kawai (Tokyo Tech), M. Nakajima, W. Maruyama, M. Aoki, K. Kobayashi (Nihon U.), S. Nakahira, T. Mihara, T. Tamagawa, M. Matsuoka (RIKEN), T. Sakamoto, H. Nishida, A. Yoshida (AGU), Y. Tsuboi, W. Iwakiri, R. Sasaki, H. Kawai, T. Sato (Chuo U.), M. Shidatsu (Ehime U.), Y. Tachibana, K. Morita, M. Oeda, K. Shiraishi (Tokyo Tech), S. Ueno, H. Tomida, M. Ishikawa, Y. Sugawara, N. Isobe, R. Shimomukai, M. Tominaga (JAXA), Y. Ueda, A. Tanimoto, T. Morita, S. Yamada, S. Ogawa (Kyoto U.), H. Tsunemi, T. Yoneyama, K. Asakura, S. Ide (Osaka U.), M. Yamauchi, S. Iwahori, Y. Kurihara (Miyazaki U.), T. Kawamuro (NAOJ), K. Yamaoka (Nagoya U.), Y. Kawakubo (LSU) report on behalf of the MAXI team: We examined the MAXI/GSC all-sky X-ray images (2-20 keV) obtained in the orbit after the LVC trigger S190421ar at 2019-04-21 21:38:56 UTC (GCN 24141). At the trigger time of S190421ar, the high-voltage of MAXI/GSC was on, and it was turned off at T0+78 sec. The one-orbit (92 min) scan of GSC covered 63% of the 90% error region of the bayestar skymap from 21:38:56 to 23:10:54 UTC (T0 to T0+5518 sec). No significant new source was found in the error region at the one-orbit scan. The 1-sigma averaged upper limit obtained from the scan was 18 mCrab at 4-10 keV. If you require information of X-ray flux by MAXI/GSC at specific coordinates, please contact the submitter of this circular by email. -- Motoko SERINO