MAXI/GSC detection of an X-ray flares from UX Ari on 2026-10-17 UT
ATel #18111; Y. Ishihara, H. Ogaki (Chuo U.), S. Yatsuzuka (Ehime U.), T. Mihara(RIKEN), W. Iwakiri (Chiba U.), H. Negoro, M. Nakajima, K. Saito, T. Yokoyama, M. Wada (Nihon U.), A. Aoyama, M. Ota, T. Tamagawa, N. Kawai, M. Matsuoka (RIKEN), T. Sakamoto, M. Serino, S. Sugita, Y. Kawakubo, H. Hiramatsu, T. Kato, A. Yoshida (AGU), Y. Tsuboi (Chuo U.), M. Shidatsu, C. Kang, M. Uenishi, T. Usuki, H. Aoe (Ehime U.), I. Takahashi, Y. Yatsu (Science Tokyo), S. Nakahira, S. Ueno, H. Tomida, M. Kurihara (JAXA), Y. Ueda, K. Fujiwara, S. Kobayashi (Kyoto U.), M. Yamauchi, M. Nishio, C. Hiraizumi (Miyazaki U.), K. Yamaoka (Nagoya U.), M. Sugizaki (Kanazawa U.), T. Kawamuro (Osaka U.), S. Yamada (Tohoku U), S. Ogawa (TUS)
on 19 Oct 2026; 09:55 UT
Credential Certification: Tatehiro Mihara (mihara@crab.riken.jp)
Subjects: X-ray, Binary, Star, Transient, Variables
At 07:20 on 2026-10-17 UT, the MAXI/GSC nova alert system triggered on a source at a position consistent with that of the RS CVn star UX Ari.
The light curve showed two peaks. The first brightening started at 05:04 on 2026-10-17 UT, peaked at 07:00 UT, and decayed with an e-folding time of 0.25 days. The flux then increased again starting at 14:05 UT, reached the second peak at 16:30 UT, and decayed with an e-folding time of 0.25 days.
The peak fluxes of the first and second brightenings were 4.7 × 10-9 erg s-1 cm-2 and 3.5 × 10-9 erg s-1 cm-2 (2-10 keV), respectively. The corresponding luminosities were 1.4 × 1033 erg s-1 and 1.1 × 1033 erg s-1 for an assumed distance of 51 pc. The total energies radiated during the first and second brightenings were estimated to be 3.2 × 10 37 erg and 2.4 × 10 37 erg, respectively.
