Inertial-Acoustic Oscillations in Black Hole Accretion Disks
Luminosity variations are common features of black holes in binary systems.
It is likely that these variations are due to the physics of the accretion
process. In this thesis, we study the possibility that inertial-acoustic
optically thick black hole accretion disks can produce luminosity variations
on dynamical timescales. One and two-dimensional radiation hydrodynamic
simulations have been used to study these oscillations. We find that
global oscillations are possible at the maximum epicyclic frequency in the
disk and local oscillations are possible at the local epicyclic frequencies.
The global oscillations can produce rms luminosity variations of
and their existence depends in detail on physical conditions in the system.
For a small range (which is viscosity dependent)
of accretion rates, strong global oscillations exist.
These global oscillations produce strong peaks in luminosity power spectra
with a full width at half maximum (in Hz) of approximately one-twelfth
of the peak frequency. The local oscillations produce rms
luminosity variations of \lapprox 1 and continuum spectral slopes
between 0.80 and 1.95 with the flattest slopes corresponding to the
We find that both local and global oscillations are favored for low accretion
rates and large viscosities. We have observed
qualitatively similar behavior for
disks described by an alpha law or a constant for the kinematic viscosity
(\nu) and we predict that oscillations may be
present for a restricted range of parameters for any viscosity law in which
the shear viscosity (\mu=\rho\nu) increases upon compression.
We also find that the results are
relatively mass independent when accretion rate (relative to the Eddington
accretion rate) and viscosity are held fixed.
We conclude that these oscillations may be detectable by the recently
launched X-ray Timing Explorer.