Interpreting the High Frequency QPO Power Spectra of Accreting Black
Holes
Jeremy D. Schnittman
Recent RXTE observations have shown evidence for quasi-periodic
oscillations (QPOs) at frequencies with a 2:3 ratio in a number of
accreting black hole systems. In the context of a relativistic hot spot
model, we investigate different physical mechanisms to explain these high
frequency QPOs. The locations and amplitudes of the QPO peaks are
determined by general relativistic ray-tracing calculations. The inclusion
of multiple hot spots with finite lifetimes and distributed over a range
of geodesic orbits allows us to explain the widths of the various
peaks. A simple model for electron scattering in the corona helps
account for the damping of higher frequency harmonic modes.
Finally, the complete model is used to fit the observed power
spectra of both type A and type B QPOs seen in XTE J1550-564, giving
confidence limits on each of the model parameters.