MAXI/GSC detection of an X-ray flare from HR1099 (V711 Tau) on January 9th 2025
ATel #16971; N. Nagashima, Y. Tsuboi (Chuo U.), H. Negoro, M. Nakajima, Y. Kudo, H. Shibui, K. Takagi, H. Takahashi, K. Tatano, H. Nishio (Nihon U.), T. Mihara, T. Kawamuro, S. Yamada, S. Wang, T. Tamagawa, N. Kawai, M. Matsuoka (RIKEN), T. Sakamoto, M. Serino, S. Sugita, Y. Kawakubo, H. Hiramatsu, H. Nishikawa, Y. Kondo, S. Sasao, A. Yoshida (AGU), H. Sugai (Chuo U.), M. Shidatsu, Y. Niida (Ehime U.), I. Takahashi, M. Niwano, N. Higuchi, Y. Yatsu (Tokyo Tech), S. Nakahira, S. Ueno, H. Tomida, M. Ishikawa, S. Ogawa, M. Kurihara (JAXA), Y. Ueda, Y. Okada, K. Fujiwara (Kyoto U.), M. Yamauchi, Y. Otsuki, T. Hasegawa, M. Nishio (Miyazaki U.), K. Yamaoka (Nagoya U.), M. Sugizaki (Kanazawa U.), W. Iwakiri (Chiba U.) report on behalf of the MAXI team:
on 10 Jan 2025; 11:09 UT
Credential Certification: Yohko Tsuboi (tsuboi@phys.chuo-u.ac.jp)
Subjects: X-ray, Binary, Star, Transient, Variables
At 13:56 UT on January 9th 2025, the MAXI/GSC nova alert system triggered on a bright source at a position consistent with that of an RS CVn star HR 1099 (V711 Tau).
The position was determined from the data at the triggered scan, as (R.A., Dec) = (54.308, 1.340 deg) = (03 37 13, +01 20 24) (J2000) with a systematic uncertainty of 0.1 deg (90% containment radius). This position is consistent with that of HR1099. No other source is listed in the ROSAT Bright Source Catalog in this error region. This is the first X-ray flare from HR 1099 since March 29th 2024, while in the active phases, this binary star flares about once every three months.
The peak spectrum is reproduced with a thermal plasma (apec) model. The flux is 144 (+11/-63) mCrab (2-10 keV; 68% confidence level) at the triggered scan, corresponding to a luminosity of 1.51e+32 ergs/s for an assumed distance of 29 pc. The e-folding time is derived to be 1.8 (+0.9/-0.6) h with 68% C.L.
