  The black hole candidates exhibit fast variability of their X-ray emission on
a wide range of timescales. The short, coherent variations, with frequencies
above 1 Hz, are referred to as quasi-periodic oscillations, and are generally
explained by resonant effects in the black hole accretion flow. The purely
stochastic variability that occurs due to turbulent conditions in the plasma,
is quantified by the power density spectra and appears practically in all types
of sources and their spectral states. The specific kind of quasi-periodic
flares is expected, when the global structure of the accretion flow, governed
by the nonlinear hydrodynamics, induces fluctuations around a fixed point
solution. These conditions, which occur at high accretion rates, lead to the
variability in the sense of deterministic chaos. We study the nonlinear
behaviour of X-ray sources using the recurrence analysis method. We estimate
quantitatively the indications for deterministic chaos, such as the Renyi's
entropy, for the observed time series, and we compare them with the surrogate
data. Using the data collected by RXTE satellite, we reveal the oscillations
pattern and the observable properties of six black hole systems. We confirm
that both the well known microquasar GRS 1915+105, as well as its recently
discovered analogue, IGR J17091-3624, exhibit variability characteristic to
deterministic chaotic system. We conclude therefore that the underlying nature
of the process must be intrinsically connected in these sources with the
accretion flow instability, that leads to the limit cycle oscillations around a
fixed point. Furthermore, we studied four other black hole candidates with high
accretion rates. For GX 339-4, GRO J1655-40 and XTE J1550-564 we obtained
significant results for some observations, whereas for XTE J1650-500 no such
data set was found.
