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Long-term X-ray variability and state transition of GX 339-4

A. K. H. Kong·P. A. Charles·E. Kuulkers·S. Kitamoto
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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 timescales ~190-240 d from the black hole low-mass X-ray binary system GX 339-4. 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 GX 339-4, 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.

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A. K. H. Kong, P. A. Charles, E. Kuulkers, S. Kitamoto. 2001-10-01. Long-term X-ray variability and state transition of GX 339-4. https://doi.org/10.1046/j.1365-8711.2002.05022.x

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