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We have used INTEGRAL & RXTE data to investigate the timing properties of thesource in correlation with its spectral states as defined by differentpositions in the colour-colour diagram. The source shows two distinct branchesin the colour-colour diagram that resemble those of the Z sources. The hardbranch (similar to the horizontal branch of Z sources) is characterised by alow-amplitude change of the hard colour compared to the change in the softcolour. In the soft branch (analogue to the normal branch) the amplitude ofvariability of the hard colour is about three times larger than that of thesoft colour. As the count rate decreases the source moves up gradually throughthe soft to the hard branch. The aperiodic variability (excluding the pulsenoise) consists of band-limited noise (represented by three broad Lorentziancomponents) and two QPOs at 0.05 Hz and 0.22 Hz. The strength of the lowerfrequency QPO increases as the source approaches the hard branch (similar toHBOs in Z sources). The higher frequency QPO reaches maximum significance whenthe source is in the middle of the branch (like NBOs). We have performed thefirst measurements of phase lags in the band limited noise below 8 Hz in anaccreting X-ray pulsar and found that soft lags dominate at high frequencies.Above the pulse frequency (0.23 Hz), the amplitude of the lag increases as theX-ray flux increases. The Z topology appears to be a signature of the neutronstar binaries as it is present in all types of neutron-star binaries (Z, atolland, as we show here, in accreting pulsars as well). However, the motion alongthis track, the time scales through the different branches of the diagram andthe aperiodic variability associated with portions of the Z track differ foreach subclass of neutron-star binary.Comment: 8 pages, 6 figures, accepted by A&

Correlated X-ray spectral and timing variability of the Be/X-ray binary V0332+53/BQ Camelopardalis during a type II outburst