Long-term X-ray variability and state transition of GX 339–4 |
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| Authors: | AKH Kong † PA Charles E Kuulkers S Kitamoto |
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| Institution: | 1Department of Astrophysics, University of Oxford, Keble Road, Oxford OX1 3RH;2Department of Physics and Astronomy, University of Southampton, Southampton SO17 1BJ;3Space Research Organization Netherlands, Sorbonnelaan 2, 3584 CA Utrecht, the Netherlands;4Astronomical Institute, Utrecht University, PO Box 80000, 3507 TA Utrecht, the Netherlands;5Department of Physics, College of Science, Rikkyo University, 3-34-1, Nishi-Ikebukuro, Toshima-ku, Tokyo 171-8501, Japan |
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| Abstract: | With extensive monitoring data spanning over 30 years from Vela 5B , Ariel 5 , Ginga , Compton Gamma Ray Observatory , Rossi X-ray Timing Explorer and BeppoSAX , we find evidence for long-term X-ray variability on time-scales  from the black hole low-mass X-ray binary system  . Such variability resembles the outburst cycle of Z Cam-type dwarf novae, in which the standard disc instability model plays a crucial role. If such a model is applicable to  , then the observed variability might be due to the irradiation of an unstable accretion disc. We show that within the framework of the X-ray irradiation model, when the accretion rate exceeds a critical value,  enters a 'flat-topped' high/soft state, such as seen in 1998, which we suggest corresponds to the 'standstill' state of Z Cam systems. |
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| Keywords: | accretion accretion discs black hole physics binaries: close stars: individual: " target="_blank"> X-rays: stars |
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