XRISM/Xtend Transient Search (XTS) detected an X-ray flare from XRISM J0057+6021
ATel #16962; N. Nagashima (Chuo U.), Y. Kanemaru, T. Yoshida, K. Fukushima, K. Hayashi, S. Ogawa (JAXA), M. Audard (U. de Geneve), E. Behar (Technion), S. Inoue (Kyoto U.), Y. Ishihara (Chuo U.), T. Kohmura (TUS), Y. Maeda (JAXA), M. Mizumoto (UTEF), M. Nobukawa (NUE), K. Pottschmidt (UMBC, NASA GSFC, CRESST), M. Shidatsu (Ehime U.), H. Sugai (Chuo U.), Y. Terada (Saitama U.), Y. Terashima (Ehime U.), Y. Tsuboi (Chuo U.), H. Uchida (Kyoto U.), T. Yanagi (Chuo U.), T. Yoneyama (Chuo U.), M. Yoshimoto (Osaka U.)
on 31 Dec 2024; 12:15 UT
Credential Certification: Yoshiaki Kanemaru (kanemaru.yoshiaki@jaxa.jp)
Subjects: X-ray, Star, Transient, Variables
XRISM/Xtend Transient Search (XTS) detected an X-ray flare from an X-ray source XRISM J0057+6021 on 2024-12-29 TT. The source position is determined to be (R.A., Dec.) = (14.195, 60.356), with a systematic error of ∼ 40 arcsec. A plausible counterpart is a multiple star HD 5408 (B7Vn+B9VHgMn+A1V). HD 5408 is located ∼ 20 arcsec apart from the position of XRISM J0057+6021. All statistical uncertainties in this report will be provided as a 90% confidence level unless stated otherwise.
The flare started on 2024-12-29 at ∼ 11h TT. The flare exponentially decayed in 5 × 103 sec. In order to estimate the source flux, we fit the spectrum in the flare phase with an absorbed APEC model with a temperature of kT = 0.5 keV and hydrogen column density NH = 6 × 1021 cm-2. Then, the model peak flux is calculated as 1 × 10-12 erg s-1cm-2 (0.4 – 10.0 keV). A systematic error of roughly 20% should be added to the statistical error. Corresponding luminosity is 3 × D165pc2 × 1030 erg s-1 by assuming the distance to XRISM J0057+6021 of D165pc. 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.
