Astronomy and Astrophysics – Astrophysics
Scientific paper
1994-10-06
Astronomy and Astrophysics
Astrophysics
19 pages, uuencoded postscript, CITA Preprint 94-?
Scientific paper
The high state of black hole candidates is characterized by a quasi- thermal emission component at $kT \sim 1$ keV. In addition, this state tends to have very low variability which indicates that it is relatively stable, at least on {\it short} time scales. Most models of the high state imply that the bulk of the emission comes from an optically thick accretion disc; therefore, this state may be an excellent laboratory for testing our ideas about the physics of accretion discs. In this work we consider the implications of assuming that accretion disc viscosity arises from some form of turbulence. Specifically, we consider the simple case of three dimensional hydrodynamic turbulence. It is found that the coupling of such turbulence to acoustic modes in the disc can alter the disc emission. We calculate the amplitude and frequencies of this modulation, and we express our results in terms of the X-ray power spectral density. We compare our calculations with observations of the black hole candidate GS 1124-683, and show that for certain parameters we can reproduce some of the high frequency power. We then briefly explore mechanisms for producing the low frequency power, and note the difficulty that a single variability mechanism has in reproducing the full range of observed variability. In addition, we outline ways in which future spacecraft missions -- such as USA and XTE -- can further constrain our model, especially at frequencies above $\sim 10^2$ Hz.
Nowak Michael A.
Wagoner Robert V.
No associations
LandOfFree
Accretion Disc Turbulence and the X-Ray Power Spectra of Black Hole High States does not yet have a rating. At this time, there are no reviews or comments for this scientific paper.
If you have personal experience with Accretion Disc Turbulence and the X-Ray Power Spectra of Black Hole High States, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Accretion Disc Turbulence and the X-Ray Power Spectra of Black Hole High States will most certainly appreciate the feedback.
Profile ID: LFWR-SCP-O-244223