MAXI/GSC detection of a soft-to-hard state transition of the BHC Swift J1910.2-0546 / MAXI J1910-057
ATel #4273; S. Nakahira (JAXA), Y. Ueda (Kyoto U.), T. Takagi, T. Mihara, M. Sugizaki, M. Serino, T. Yamamoto, J. Sugimoto, M. Matsuoka (RIKEN), S. Ueno, H. Tomida, M. Ishikawa (JAXA), N. Kawai, M. Morii, R. Usui, K. Ishikawa, T. Yoshii (Tokyo Tech), H. Negoro, M. Nakajima, M. Asada, H. Sakakibara, N. Serita (Nihon U.), A. Yoshida (AGU), H. Tsunemi, M. Kimura (Osaka U.), K. Hiroi, M. Shidatsu, R. Sato (Kyoto U.), Y. Tsuboi, M. Higa (Chuo U.) M. Yamauchi, Y. Nishimura, T. Hanayama, K. Yoshidome (Miyazaki U.), K. Yamaoka (Waseda U.) report on behalf of the MAXI team
on 25 Jul 2012; 01:15 UT
Credential Certification: Satoshi NAKAHIRA (nakahira@crab.riken.jp)
Subjects: X-ray, Binary, Black Hole, Transient
We report on an ongoing soft-to-hard transition of the newly
discovered X-ray transient Swift J1910.2-0546/MAXI J1910-057 (Krimm at
al. #4139, Usui et al.#4140). Immediately after the discovery of the
source, it entered into the soft state or intermediate/very high state
(Kimura et al.#4198).
The 2-10 keV X-ray flux peaked at ∼1 Crab on MJD56088, and then
decayed down to 190 mCrab on MJD56120-56125. Meanwhile the innermost
disk temperature obtained from the MAXI/GSC spectra by employing a
multi-color disk plus a power-law model changed from ∼0.6 keV to
∼0.45 keV. At 2012-07-24T04:29 (MJD56132.1868), the MAXI/GSC nova
alert system triggered on a gradual spectral change of Swift
J1910.2-0546 / MAXI J1910-057. The recent light curve of MAXI/GSC shows
an increase of the 4-10 keV X-ray flux against the 2-4 keV flux. The
2-4 keV flux slightly decreased from 310 ± 16 mCrab
(MJD56127.0-56130.0) to 270 ± 13 mCrab (MJD 56131.0-56132.5),
while the 4-10 keV X-ray flux increased from 33 ± 8 mCrab
(MJD56127.0-56130.0) to 77 ± 8 mCrab (MJD56131.0-56132.0), and then
to 112 ± 12 mCrab (MJD56132.0-56132.5). We suggest that the
source is entering into the hard state.
Further observations are encouraged.
The latest source flux can be checked at the following page: http://maxi.riken.jp/top/index.php?cid=1&jname=J1910-057