XRISM/Xtend Transient Search (XTS) detected an X-ray flare from 1eRASS J065514.6-584848
ATel #17401; T. Narita (Kyoto U.), K. Fukushima (JAXA), T. Kohmura (TUS), Y. Kanemaru, S. Ogawa, Y. Uchida, T. Yoneyama (JAXA), M. Audard (U. de Geneve), E. Behar (Technion), T. Hakamata (UOsaka), S. Inoue (Kyoto U.), Y. Ishihara (Chuo U.), C. Kang (Ehime U.), T. Kiyomoto (Saitama U.), H. Kuramoto (UOsaka), J. Kurashima (U. of Miyazaki), Y. Maeda (JAXA), H. Matsumoto (UOsaka), T. Matsushima (U. of Miyazaki), A. Miyamoto (UOsaka), M. Mizumoto (UTEF), K. Mori (U. of Miyazaki), Y. Motogami (Saitama U.), N. Nagashima (Chuo U.), M. Nobukawa (NUE), H. Noda (Tohoku U.), Y. Sakamoto (Tohoku U.), M. Shidatsu (Ehime U.), H. Sugai (Chuo U.), H. Takahashi (Hiroshima U.), T. Takagi (Ehime U.), S. Takatuska (UOsaka), R. Takemoto (U. of Miyazaki), Y. Terada (Saitama U.), Y. Terashima (Ehime U.), Y. Tsuboi (Chuo U.), H. Uchida (Kyoto U.), M. Yoshimoto (Ehime U.)
on 19 Sep 2025; 15:14 UT
Credential Certification: Kotaro Fukushima (kxfukushima@gmail.com)
Subjects: X-ray, Transient
XRISM/Xtend Transient Search (XTS) detected an X-ray flare from an X-ray source XRISM J0655-5848 on 2025-09-09 TT. The source position is determined to be (R.A., Dec.) = (103.805, -58.807), with a systematic error of ∼ 40 arcsec. XRISM J0655-5848 is located approximately 27 arcsec from an X-ray source 1eRASS J065514.6-584848, which may correspond to the optical object Gaia DR3 5480685965450413184. Simultaneously, several other sources in the Gaia DR3 catalogue align with this source within the margin of uncertainty. All statistical uncertainties in this report are provided as a 90% confidence level unless stated otherwise.
The flare started at 2025-09-09 at ∼10:22 TT. The flare reached its peak on 2025-09-09 at ∼10:55. The flare exponentially decayed in ∼3×103 sec. Although the origin of this event remains unknown, the flux is estimated using an emission model of collisionally-ionized gas, assuming conditions similar to stellar flares. The peak flux is calculated as 3.4 × 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 4.1 D2100 pc × 1030 erg s-1.
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.
