MAXI/GSC detection of an undergoing soft-to-hard state transition of MAXI J1535-571
ATel #11682; H. Negoro (Nihon U.), Y. Sugawara (JAXA), M. Nakajima, A. Sakamaki, W. Maruyama (Nihon U.), T. Mihara, S. Nakahira, F. Yatabe, Y. Takao, M. Matsuoka (RIKEN), N. Kawai, M. Sugizaki, Y. Tachibana, K. Morita (Tokyo Tech), T. Sakamoto, M. Serino, S. Sugita, Y. Kawakubo, T. Hashimoto, A. Yoshida (AGU), S. Ueno, H. Tomida, M. Ishikawa, N. Isobe, R. Shimomukai (JAXA), Y. Ueda, A. Tanimoto, T. Morita, S. Yamada (Kyoto U.), Y. Tsuboi, W. Iwakiri, R. Sasaki, H. Kawai, T. Sato (Chuo U.), H. Tsunemi, T. Yoneyama (Osaka U.), M. Yamauchi, K. Hidaka, S. Iwahori (Miyazaki U.), T. Kawamuro (NAOJ), K. Yamaoka (Nagoya U.), M. Shidatsu (Ehime U.)
on 5 Jun 2018; 07:57 UT
Credential Certification: Hitoshi Negoro (negoro@phys.cst.nihon-u.ac.jp)
Subjects: X-ray, Black Hole
We report an undergoing soft-to-hard state transition of the black hole candidate MAXI J1535-571 in outburst (ATel #10699).
After the unexpectedly rapid decrease in the X-ray flux remaining in the soft state from 2018 April 16 (ATel #11568), the source underwent a hard state transition around April 30 (ATel #11611). Interestingly, X-ray re-brightening by a factor of about 400 was recognized on May 16, and the source has been in the soft state again since May 18 (ATel #11652).
MAXI/GSC also monitored the source in the soft state from May 19, and recent GSC observations showed that a soft-to-hard state transition started to occur around May 26 (MJD 58264). The average 2-4 keV and 4-10 keV X-ray fluxes on June 2-4 were (4.2+/-0.6)e-2 photons/s/cm2 (~25 mCrab) and (2.7+/-0.5)e-2 photons/s/cm2 (~23 mCrab), respectively. The hardness ratio in the 4-10 keV to 2-4 keV band was ~ 0.64. This ratio is a similar one obtained on October 17-26 (MJD 58043-58052),
suggesting that the source is still in an intermediate state. We also note that the current X-ray flux is about 1% of the flux on October 17-26 which is about one-third of the peak flux in this outburst (Nakahira et al. 2018, PASJ, submitted).
MAXI data of MAXI J1535-571
