XRISM/Xtend Transient Search (XTS) detected an X-ray flare from CD-61 901
ATel #17994; H. Kuramoto (UOsaka), T. Narita (RIKEN), S. Ogawa (TUS), 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.), M. Kikuchi (Ehime U.), T. Kiyomoto (Saitama U.), T. Kohmura (TUS), Y. Maeda (JAXA), H. Matsumoto (UOsaka), A. Miyamoto (UOsaka), M. Mizumoto (UTEF), Y. Motogami (Saitama U.), H. Murakami (TGU), M. Nobukawa (NUE), H. Noda (Tohoku U.), 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.), A. Heinrich (U. Chicago)
on 20 Aug 2026; 13:32 UT
Credential Certification: Shoji Ogawa (ogawa.shohji@jaxa.jp)
Subjects: X-ray, Star, Transient
XRISM/Xtend Transient Search (XTS) detected an X-ray flare from an X-ray source XRISM J0433-6129 on 2026-08-18 TT. The source position is determined to be (R.A., Dec.) = (68.486, -61.493), with a systematic error of ∼40 arcsec. The plausible counterpart is CD-61 901, located ∼18 arcsec apart from the position of XRISM J0433-6129. CD-61 901 is a rotating variable star with a distance of ∼93 pc.
The flare started on 2026-08-18 at ∼ 17:09 TT, reached its peak at ∼ 18:16 TT, and exponentially decayed in 8.2 × 103 sec. Prior to this flare, two brightness variations by a factor of ∼2–3 were observed, starting around 2026-08-17 at ~08:00 TT.
The averaged spectrum of the entire observation is reproduced with an APEC model with a temperature of kT = 1.13+0.11-0.08 keV without significant interstellar absorption. The averaged flux is calculated as 2.7+0.3-0.2 × 10-12 erg s-1 cm-2 (0.5 – 10.0 keV).
The peak flux is calculated as 5.0 × 10-12 erg s-1 cm-2 (0.5 – 10.0 keV), which corresponds to a luminosity of 5.2 × 1030 erg s-1, assuming the distance of 93 pc. All the errors quoted above are given at the 90% confidence level.
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 source and its corresponding counterpart in the same field of view.
