MAXI/GSC detection of a bright X-ray flare from an RS CVn star VY Ari
ATel #7839; S. Kanetou, Y. Tsuboi (Chuo U.), T. Masumitsu (Nihon U.), S. Ueno, H. Tomida, S. Nakahira, M. Kimura, M. Ishikawa, Y. E. Nakagawa (JAXA), T. Mihara, M. Sugizaki, M. Serino, M. Shidatsu, J. Sugimoto, T. Takagi, M. Matsuoka (RIKEN), N. Kawai, M. Arimoto, T. Yoshii, Y. Tachibana, Y. Ono, T. Fujiwara (Tokyo Tech), A. Yoshida, T. Sakamoto, Y. Kawakubo, H. Ohtsuki (AGU), H. Tsunemi, R. Imatani (Osaka U.), H. Negoro, M. Nakajima, K. Tanaka (Nihon U.), Y. Ueda, T. Kawamuro, T. Hori (Kyoto U.), M. Yamauchi, D. Itoh (Miyazaki U.), K. Yamaoka (Nagoya U.), M. Morii (ISM)
on 25 Jul 2015; 10:35 UT
Distributed as an Instant Email Notice Transients
Credential Certification: Yohko Tsuboi (tsuboi@phys.chuo-u.ac.jp)
Subjects: X-ray, Binary, Star, Transient, Variables
Referred to by ATel #: 9044
At 22:12:45 UT on July 24 2015, the MAXI/GSC nova alert system triggered on a bright source at a position consistent with that of an RS CVn star VY Ari. The flux increase started at 22:15:00 UT on July 2015 and peaked at the next scan transit at 23:45:15 UT on July 24 with a value of 62+-21mCrab (90% error) in the 4-10 keV band, corresponding to a luminosity of 3 ×1032 ergs s-1 for an assumed distance of 44 pc. At the scan following the peak, the source started to fade. In the past, the MAXI/GSC detected three flares and the highest flux was recorded as 40 mCrab in December 2014.
The position was determined from the data at the flare peak, as (R.A., Dec) = (42.355 deg, 31.449 deg) = (02 49 25, +31 26 56) (J2000) with a statistical 90% C.L. elliptical error region with long and short radii of 0.55 deg and 0.51 deg respectively. The roll angle of long axis from the north direction is 114.0 deg. There is an additional systematic uncertainty of 0.1 deg (90% containment radius). This position is consistent with that of an RS CVn star VY Ari. No other source is listed in the ROSAT Bright Source Catalog in this error region.
