Study of the long-term evolution of the accretion dynamics of GX 339-4

We study the dynamical behaviour of the galactic black hole source GX 339-4 during 2002-2011 outbursts using RXTE, Swift-XRT, XMM-Newton (PN) archival data. We present the spectral evolution of the source using four outburst data and discuss their similarities and differences between outbursts. We infer that the second peak in the 2002/03 and 2004/05 outbursts could be due to a second instant of triggered instability in the accretion disc due to irradiation from the central X-ray source after peak I. This propagates on a viscous time-scale and takes ∼80-90 d after peak I to produce peak II. This unifies all four outbursts with a long rising time of ∼90 d. The dynamical evolution of the accretion parameters has been studied by modelling the individual observed spectrum with a two-component accretion-disc model where a Keplerian accretion disc produces the soft photons and the hard part of the spectrum originates from a hot sub-Keplerian central corona. A generic mathematical model has been proposed to understand the evolution of accretion parameters for sources like GX 339-4 that have longer rising times. In addition, the possible differences in physical scenarios for outbursts with shorter rising times are also discussed.