XRISM follow-up observation of the black hole X-ray binary MAXI J1543-564
ATel #17643; M. Parra, M. Shidatsu (Ehime U.), B. Coughenour (Utah Valley U.), J. A. Tomsick (UCB/SSL), K. Mori (Columbia U.), T. Enoto, S. Majumder (Kyoto U.), K. Fukushima, Y. Kanemaru, S. Ogawa, Y. Uchida, T. Yoneyama (JAXA/ISAS), C. Baluta (NASA/GSFC), Y. Terada (Saitama U.), E. Costantini (SRON), M. Guainazzi (ESA/ESTEC), R. Kelley (NASA/GSFC), K. Matsushita (TUS), R. Petre, B. Williams (NASA/GSFC), H. Yamaguchi, S. Watanabe (JAXA/ISAS), M. Tashiro (Saitama U.)
on 2 Feb 2026; 02:08 UT
Credential Certification: Kotaro Fukushima (kxfukushima@gmail.com)
Subjects: X-ray, Black Hole, Transient
The follow-up XRISM observation has been performed for the black hole binary MAXI J1543-564. The X-ray transient event from this object was reported and identified by MAXI in December 2025 (ATels #17552, #17559, and #17560). This source was followed by NuSTAR on December 26-28, 2025 (ATel #17569), and was confirmed to have hosted a new outburst since the last one in 2011. Based on these reports, an unanticipated ToO observation of this transient was made from 21:13 UT on January 28, 2026, to 02:50 on January 30, using 74 ks of exposure time in the Director's Discretionary Time allocation for XRISM Cycle 2. Here, we report the quick-look results of this ToO observation. All statistical uncertainties in this report are provided at a 90% confidence level unless stated otherwise.
The 2–10 keV Xtend image extracted from the quick-look event data shows a prominent source at the aim point of the instrument. The position of this source is determined to be (R.A., Dec.) = (235.823, -56.4147), which corresponds to (15:43:17.5, -56:24:53.0), with a systematic error of approximately 40 arcseconds. As the coordinates are fully consistent with the NuSTAR report (ATel #17569), we identify this source as the transient MAXI J1543-564.
We fit the 1.8–12 keV Resolve spectrum with TBabs × (diskbb + powerlaw) and find the absorption column density of NH = (1.86 +/- 0.08) × 1022 cm-2 and the disc temperature of kTin = 0.901 +/- 0.004 keV. Assuming d = 10 kpc for the distance and cosi = 0.5 for the inclination, the inner radius is estimated as Rin = 17 +1.0/-0.3 km. The power-law index is fixed at 2.2. We obtain the unabsorbed flux in 2–10 keV as Fdisc = (8.22 +/- 0.02) × 10-10 erg s-1cm-2 (34.25 +/- 0.08 mCrab) and Fpl = (1.72 +/- 0.12) × 10-11 erg s-1cm-2 (0.72 +/- 0.05 mCrab). Given that the flux contribution from the disc component has become dominant at about 98% (it was 65% in December, ATel #17569), the source would be near the end of its hard-to-soft transition.
Follow-up observations are encouraged.
