MAXI/GSC detection of an X-ray flare from sigma Gem on 2025-03-12 UT
ATel #17078; H. Sugai, 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), 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 12 Mar 2025; 10:57 UT
Credential Certification: Yohko Tsuboi (tsuboi@phys.chuo-u.ac.jp)
Subjects: X-ray, Binary, Star, Transient, Variables
At 05:18 on 2025-03-12 UT, the MAXI/GSC nova alert system triggered on a bright source at a position consistent with that of an RS CVn star sigma Gem.
The position is determined from the data at the triggered scan, as (R.A., Dec) = (115.83, 28.88 deg) = (07 40 48, +28 37 48) (J2000) with a statistical 90% C.L. elliptical error region with long and short radii of 0.17 deg and 0.17 deg, respectively. The roll angle of long axis from the north direction is 107.0 deg counterclockwise. There is an additional systematic uncertainty of 0.1 deg (90% containment radius). This position is consistent with that of an RS CVn star sigma Gem. No other source is listed in the ROSAT Bright Source Catalog in this error region.
The flux was 168 +/- 28 mCrab (4.0-10.0keV, 1 sigma error) at the triggered scan, corresponding to a luminosity of 6 × 1032 erg s-1 s -1 for an assumed distance of 37 pc.
