MAXI/GSC fifth detection of X-ray reflaring activity of the black hole X-ray binary 4U 1543-47

ATel #15715; H. Negoro, M. Nakajima (Nihon U.), S. Urabe (Chuo U.), K. Kobayashi, M. Tanaka, Y. Soejima (Nihon U.), T. Mihara, T. Kawamuro, S. Yamada, T. Tamagawa, M. Matsuoka (RIKEN), T. Sakamoto, M. Serino, S. Sugita, H. Hiramatsu, H. Nishikawa, A. Yoshida (AGU), Y. Tsuboi, W. Iwakiri, J. Kohara, S. Nawa, N. Nemoto (Chuo U.), M. Shidatsu, M. Iwasaki (Ehime U.), N. Kawai, M. Niwano, R. Hosokawa, Y. Imai, N. Ito, Y. Takamatsu (Tokyo Tech), S. Nakahira, S. Ueno, H. Tomida, M. Ishikawa, T. Kurihara (JAXA), Y. Ueda, S. Ogawa, K. Setoguchi, T. Yoshitake, K. Inaba (Kyoto U.), M. Yamauchi, T. Sato, R. Hatsuda, R. Fukuoka, Y. Hagiwara, Y. Umeki (Miyazaki U.), K. Yamaoka (Nagoya U.),Y. Kawakubo (LSU), and M. Sugizaki (NAOC)
on 25 Oct 2022; 05:47 UT
Credential Certification: Hitoshi Negoro (negoro@phys.cst.nihon-u.ac.jp)

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The MAXI/GSC nova alert system triggered on X-ray enhancement from the black hole X-ray binary 4U 1543-47 at 21:49 UT on October 21, 2022. The X-ray flux averaged over nine scan transits from 07:53 to 00:54 on October 22 (MJD 59873) was 36 +- 5 mCrab (4.0-10.0keV, 1 sigma error). The X-ray flux continues to increase, and the 2-4 keV and 4-10 keV count fluxes reached 0.105 +/- 0.009 photons/cm2/s (about 50 mCrab) and 0.072 +/- 0.007 photons/cm2/s (about 58 mCrab), respectively, on October 24.
This is the fifth detection by the MAXI/GSC after the main outburst. The main outburst started from June 11, 2021 (MJD 59376) (ATel #14701, #14708, #14715, #14719, #14721, #14725, #14749, #14795, #14878, #14888, #15157), and the source flux decreased to below the one-day detection limit of about 15 mCrab around December 16, 2021 (MJD 59564). After that, mini-outbursts lasting 20-30 days were detected four times around February 20, 2022 (MJD 59630, also see ATel #15253, #15255, #15261), March 22 (MJD 59660), May 1 (MJD 59700), and June 10 (MJD 59740). The peak fluxes of those mini-outbursts are 20-80 mCrab, and the source was likely in the hard state except for the third one. (The state of the third mini-outburst was not clear because of bad observation condition.) This time, the source flux still increases and the spectrum tends to soften suggesting a hard-to-soft state transition.

Followup observations are encouraged.

MAXI data for 4U 1543-47