XRISM/Xtend Transient Search (XTS) detected two X-ray flares from CD-46 4813
ATel #17946; M. Kikuchi (Ehime U.), M. Nobukawa (NUE), T. Hakamata, Y. Kanemaru, A. Miyamoto, Y. Omiya, Y. Uchida, T. Yoneyama (JAXA), M. Audard (U. de Geneve), E. Behar (Technion), K. Fukushima (TUS), H. Iinuma (Tohoku U.), S. Inoue (Kyoto U.), Y. Ishihara (Chuo U.), S. Ishiwata (Chuo U.), C. Kang (Ehime U.), T. Kiyomoto (Saitama U.), T. Kohmura (TUS), H. Kuramoto (UOsaka), Y. Maeda (JAXA), H. Matsumoto (UOsaka), A. Miyamoto (UOsaka), M. Mizumoto (UTEF), Y. Motogami (Saitama U.), H. Murakami (TGU), T. Narita (RIKEN), H. Noda (Tohoku U.), S. Ogawa (TUS), Y. Sakamoto (Tohoku U.), M. Shidatsu (Ehime U.), H. Takahashi (Hiroshima U.), T. Takagi (Ehime U.), S. Takatsuka (UOsaka), F. Takisawa (Ehime U.), Y. Terada (Saitama U., JAXA), Y. Terashima (Ehime U.), Y. Tsuboi (Chuo U.), H. Uchida (Kyoto U.), T. Usuki (Ehime U.), A. Yoshimoto (NWU), M. Yoshimoto (Ehime U.)
on 7 Aug 2026; 14:35 UT
Credential Certification: Masayoshi Nobukawa (nobukawa@cc.nara-edu.ac.jp)
Subjects: X-ray, Star, Transient
XRISM/Xtend Transient Search (XTS) detected two X-ray flares from an X-ray source XRISM J0859-4709 on 2026-08-05 TT. The source position is determined to be (R.A., Dec.) = (134.852, -47.157), with a systematic error of ∼40 arcsec. The plausible counterpart is CD-46 4813, located ∼5 arcsec apart from the position of XRISM J0859-4709. CD-46 4813 is a G-type star with a distance of ∼203 pc.
The first flare started on 2026-08-05 at ∼ 10:45 TT, reached its peak at ∼ 11:19, and exponentially decayed in 5 × 103 sec. In contrast, the second one started at ∼ 14:22 TT, reached its peak at ∼ 15:29, and exponentially decayed in 5 × 103 sec.
The averaged spectrum of the entire observation is reproduced with an APEC model with a temperature of kT = 0.80 keV without significant interstellar absorption. The averaged flux is calculated as 2 × 10-13 erg s-1cm-2 (0.4 – 2.0 keV). For the first flare, the peak flux is calculated as 1 × 10-12 erg s-1 cm-2 (0.4 – 2.0 keV), which corresponds to luminosity of 5 × 1030 erg s-1, assuming the distance of 203 pc. In contrast, the second peak flux and corresponding luminosity are 5 × 10-13 erg s-1 cm-2 and 2 × 1030 erg s-1, respectively.
A systematic error of roughly 20% should be considered for all the fluxes calculated above.
We estimated the systematic error for the source position from the separations between the detected sources with the corresponding counterparts in the same field of view.
