Swift/XRT 0.5-10keV obs. of MAXI J1659-152

The broadband noise components and the quasi-periodic oscillations (QPO) observed in the power spectra show a strong and varied energy dependence. Combining Swift XRT data with data from the Rossi X-ray Timing Explorer, we report, for the first time, an rms spectrum (fractional rms amplitude as a function of energy) of these components in the 0.5-30keV energy range.

We find that the strength of the low-frequency component (<0.1Hz) decreases with energy, contrary to the higher frequency components (>0.1Hz) whose strengths increase with energy. In the context of the propagating fluctuations model for X-ray variability, we suggest that the low-frequency component originates in the accretion disk (which dominates emission below ~2keV) and the higher frequency components are formed in the hot flow (which dominates emission above ~2keV).