Correlation time scales of the X-ray flux in low mass X-ray binaries

Recent studies of several soft X-ray transients (SXTs) show that the X-ray flux at which the low/hard(LH)-to-high/soft(HS) state transition occurs in the rising phase of an outburst is nearly linearly correlated with the peak flux of the following (HS) state. By analyzing the data of the ASM on board the RXTE, we show that the flux correlation holds even after an outburst or flare reaches its flux peak. In GX 339-4, Aql X-1 and the quasi transient 4U 1705-44, the flux of the LH-to-HS state transition and the flux of the following HS state are positively correlated up to a time scale of 250 days, 40 days and 50 days following the corresponding LH-to-HS state transition, respectively. We discuss the implications of our study in the framework of a two-flow accretion geometry.