XRISM/Xtend Transient Search (XTS) detected an X-ray brightening of XRISM J1847+8008
ATel #17768; Y. Ishihara (Chuo U.), K. Fukushima (TUS), Y. Kanemaru, Y. Omiya, Y. Uchida, T. Yoneyama (JAXA), M. Audard (U. de Geneve), E. Behar (Technion), T. Hakamata (UOsaka), S. Inoue (Kyoto U.), C. Kang (Ehime U.), T. Kiyomoto (Saitama U.), T. Kohmura (TUS), H. Kuramoto (UOsaka), J. Kurashima (U. of Miyazaki), Y. Maeda (JAXA), H. Matsumoto (UOsaka), A. Miyamoto (UOsaka), M. Mizumoto (UTEF), K. Mori (U. of Miyazaki), Y. Motogami (Saitama U.), T. Narita (RIKEN), M. Nobukawa (NUE), 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.), A. Yoshimoto (NWU), M. Yoshimoto (Ehime U.), E. Kammoun (Caltech)
on 27 Apr 2026; 12:26 UT
Credential Certification: Kotaro Fukushima (kxfukushima@gmail.com)
Subjects: X-ray, Transient
XRISM/Xtend Transient Search (XTS) detected an X-ray transient from the X-ray source XRISM J1847+8008 on 2026-04-26 TT. The source position was determined to be (R.A., Dec.) = (281.654, 80.133), with a systematic error of ∼ 40 arcsec. A plausible X-ray counterpart is 1RXS J184638.8+800757, which is located ∼ 20 arcsec from the XTS position. 7 Gaia sources are within 40 arcsec of the XTS position, including the white dwarf GALEX J184630.2+800753.
The flare started at 2026-04-26 at ∼ 01:25 TT. The flare reached its peak on 2026-04-26 at ∼ 01:42. The flare exponentially decayed in 1.6 × 104 sec.
The peak flux is calculated as 7 × 10-12 erg s-1 cm-2 (0.4 – 10.0 keV). A systematic error of roughly 20% should be added to the statistical error. The corresponding luminosity is 3 × D183pc2 × 1031 erg s-1, assuming XRISM J1847+8008 is associated with the white dwarf GALEX J184630.2+800753 at 183 pc.
We derived the above systematic error for the flux by comparing our derived values for the sources detected with XTS in several observations with those for the corresponding X-ray counterparts. 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.
