  We found the black hole candidate MAXI J1659-152 showed distinct power
spectra, i.e., a power-law noise (PLN) vs. band-limited noise (BLN) plus
quasi-periodic oscillations (QPOs), below and above about 2 keV respectively,
in the observations with the Swift and the RXTE during the 2010 outburst,
indicating a high energy cut-off of the PLN and a low energy cut-off of the BLN
and the QPOs around 2 keV. The emergence of the PLN and the fading of the BLN
and the QPOs initially took place from below 2 keV when the source entered the
hard intermediate state and finally settled in the soft state three weeks
later. The evolution was accompanied by the emergence of the disk spectral
component and decreases in the amplitudes of variability in the soft X-ray and
the hard X-ray bands. Our results indicate that the PLN is associated with the
optically thick disk in both hard and intermediate states, and power spectral
state is independent of the X-ray energy spectral state in a broadband view. We
suggest that in the hard and the intermediate state, the BLN and the QPOs
emerge from the innermost hot flow subjected to Comptonization, while the PLN
originates from the optically thick disk further out. The energy cut-offs of
the PLN and the BLN or QPOs then follow the temperature of the seed photons
from the inner edge of the optically thick disk, while the high frequency
cut-off of the PLN follows the orbital frequency at the inner edge of the
optically thick disk as well.
