A New Model for the Hard Time Lags in Black Hole X-Ray Binaries
  The time-dependent Comptonized output of a cool soft X-ray source drifting inward through an inhomogeneous hot inner disk or corona is numerically simulated. We propose that this scenario can explain from first principles the observed trends in the hard time lags and power spectra of the rapid aperiodic variability of the X-ray emission of Galactic black-hole candidates. 
M. Boettcher and E. P. Liang (Rice University)