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We propose that high frequency quasi-periodic oscillations (HFQPOs) can beproduced from randomly-formed X-ray bursts (flashes) by plasma interior to theergosphere of a rapidly-rotating black hole. We show by direct computation oftheir orbits that the photons comprising the observed X-ray light curves, ifdue to a multitude of such flashes, are affected significantly by the blackhole's dragging of inertial frames; the photons of each such burst arrive to anobserver at infinity in multiple (double or triple), distinct "bunches"separated by a roughly constant time lag of t/M~14, regardless of the bursts'azimuthal position. We argue that every other such "bunch" represents photonsthat follow trajectories with an additional orbit around the black hole at thephoton circular orbit radius (a photon "echo"). The presence of this constantlag in the response function of the system leads to a QPO feature in its powerdensity spectra, even though the corresponding light curve consists of atotally stochastic signal. This effect is by and large due to the black holespin and is shown to gradually diminish as the spin parameter a decreases orthe radial position of the burst moves outside the static limit surface(ergosphere). Our calculations indicate that for a black hole with Kerrparameter of a/M=0.99 and mass of M=10*Msun the QPO is expected at a frequencyof ~ 1.3-1.4 kHz. We discuss the plausibility and observational implications ofour model/results as well as its limitations.

Light Echoes in Kerr Geometry: A Source of High Frequency QPOs from Random X-ray Bursts