Long - term X - ray variability and state transition of GX 339 – 4
نویسنده
چکیده
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 timescales ∼ 190–240 d from the black hole low-mass X-ray binary system GX339–4. 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 GX339–4, 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, GX 339–4 enters a ‘flat-topped’ high/soft state, such as seen in 1998, which we suggest corresponds to the ‘standstill’ state of Z Cam systems.
منابع مشابه
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