MAXI/GSC detection of an X-ray flare from YY Gem on 2025-06-04 UT
ATel #17217; N. Nagashima, Y. Ishihara, H. Sugai, Y. Tsuboi (Chuo U.), H. Negoro, H. Nishio, M. Nakajima, K. Takagi, H. Takahashi, K. Tatano (Nihon U.), T. Mihara, T. Tamagawa, N. Kawai, M. Matsuoka (RIKEN), T. Sakamoto, M. Serino, S. Sugita, Y. Kawakubo, H. Hiramatsu, Y. Kondo, A. Yoshida (AGU), M. Shidatsu, Y. Niida, C. Kang, T. Nakamoto (Ehime U.), I. Takahashi, Y. Yatsu (Science Tokyo), S. Nakahira, S. Ueno, H. Tomida, M. Ishikawa, S. Ogawa, M. Kurihara (JAXA), Y. Ueda, K. Fujiwara (Kyoto U.), M. Yamauchi, M. Nishio, C. Hiraizumi (Miyazaki U.), K. Yamaoka (Nagoya U.), M. Sugizaki (Kanazawa U.), W. Iwakiri (Chiba U.), T. Kawamuro (Osaka U.), S. Yamada (Tohoku U), report on behalf of the MAXI team:
on 4 Jun 2025; 12:07 UT
Credential Certification: Yohko Tsuboi (tsuboi@phys.chuo-u.ac.jp)
Subjects: X-ray, Binary, Star, Transient, Variables
At 08:54 on 2025-06-04 UT, the MAXI/GSC nova alert system triggered on an X-ray enhancement from a position consistent with the dMe star YY Gem.
The enhanced emission was detected during a scan transit at 08:51 UT on the same day.
The source position is determined as
(R.A., Dec) = (113.658 deg, 31.773 deg) = (07 34 37, +31 46 22) (J2000),
with a 90% confidence elliptical error region with long and short radii of 0.22 deg and 0.2 deg, respectively. The long axis is rotated 53.0 deg counterclockwise from the north.
A systematic uncertainty of 0.1 deg (90% containment radius) also applies.
During this scan, the observed X-ray flux reached 3 × 10-9 erg s-1 cm-2 (2-20 keV), corresponding to a luminosity of 8 × 1031 erg s-1 at an assumed distance of 15 pc. No significant emission was seen before this transit.
