The PDS is used extensively in this work. The continuum power in the PDS is of interest for both its shape and its integrated amplitude (e.g., 0.1–10 Hz), which is usually expressed in units of rms fluctuations scaled to the mean count rate. PDSs of BHBs also exhibit transient, discrete features known as quasi-periodic oscillations (QPOs) that may range in frequency from 0.01 to 450 Hz. QPOs are generally modeled with Lorentzian profiles, and they are distinguished from broad power peaks using a coherence parameter, (Nowak 2000; van der Klis 2005). PDSs are frequently computed for a number of energy intervals. This is an important step in linking oscillations to an individual component in the X-ray spectrum.