MAXI/GSC detection of a new outburst from the black hole binary 4U 1543-47

ATel #14701; H. Negoro, M. Nakajima (Nihon U.), M. Niwano (Tokyo Tech), K. Kobayashi, K. Asakura, K. Seino (Nihon U.), T. Mihara, T. Tamagawa, M. Matsuoka (RIKEN), T. Sakamoto, M. Serino, S. Sugita, K. Komachi, A. Yoshida (AGU), Y. Tsuboi, W. Iwakiri, H. Kawai, Y. Okamoto, S. Kitakoga (Chuo U.), M. Shidatsu (Ehime U.), N. Kawai, R. Hosokawa (Tokyo Tech), S. Nakahira, Y. Sugawara, S. Ueno, H. Tomida, M. Ishikawa, M. Tominaga, T. Nagatsuka (JAXA), Y. Ueda, S. Yamada, S. Ogawa, K. Setoguchi, T. Yoshitake, Y. Goto, R. Uematsu (Kyoto U.), H. Tsunemi (Osaka U.), M. Yamauchi, Y. Nonaka, T. Sato, R. Hatsuda, R. Fukuoka (Miyazaki U.), T. Kawamuro (UDP/NAOJ), K. Yamaoka (Nagoya U.), Y. Kawakubo (LSU), M. Sugizaki (NAOC) report on behalf of the MAXI team:
on 12 Jun 2021; 00:59 UT
Distributed as an Instant Email Notice Transients
Credential Certification: Hitoshi Negoro (negoro@phys.cst.nihon-u.ac.jp)

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The MAXI/GSC nova alert system triggered on a bright X-ray enhancement from the source positionally consistent with the black hole binary 4U 1543-47 at 12:00 on June 11, 2021. This is the first detection with the MAXI/GSC since 2009, and the last outburst was in 2004 (Park et al. 2004, ApJ, 610, 378, Kalemci et al. 2005, ApJ, 622, 508). The outburst is also confirmed with the Swift/BAT light curve at https://swift.gsfc.nasa.gov/results/transients/weak/4U1543-47/.

A hard-to-soft state transition started soon after the detection similar to the outburst in 2004. Currently the source is in a soft state, and the 2-4 keV flux reaches about 3 Crab at 22:51 on June 11. The energy spectrum obtained from the four scan transits from 18:12 to 22:51 is well represented with an absorbed disk blackbody model with an equivalent hydrogen column density fixed at N_H of 4e21, an inner disk temperature of 0.95 +/- 0.02 keV, and a disk normalization of 4084 +/- 465. The deduced inner disk radius from the disk normalization is about 50 km (= 3.6 rg) for the distance 7.5 kpc and the disk inclination angle 21 deg (see Park et al. 2005). These parameters are similar to those obtained by Park et al. 2005.

The followup observations are encouraged.

Trigger Information about 4U 1543-47