| 1. |
|
|
| 2. |
- Horak, J., et al.
(författare)
-
Alpha-Viscosity Effects in Slender Tori
- 2012
-
Ingår i: Publications of the Astronomical Society of Japan. - 0004-6264. ; 64:4
-
Tidskriftsartikel (refereegranskat)abstract
- We explore effects of the Shakura-Sunyaev alpha-viscosity on the dynamics and oscillations of slender tori. We start with a slow secular evolution of the torus. We show that the angular-momentum profile approaches the Keplerian one on a timescale longer than a dynamical one by a factor on the order of 1/alpha. We then focus our attention on the oscillations of the torus. We discuss the effects of various angular-momentum distributions. Using a perturbation theory, we have found a rather general result that the high-order acoustic modes are damped by the viscosity, while the high-order inertial modes are enhanced. We calculate viscous growth rates for the lowest-order modes, and show that already the lowest-order inertial mode is unstable for less-steep angular-momentum profiles, or very close to the central gravitating object.
|
|
| 3. |
- Horák, Jíri, et al.
(författare)
-
Of NBOs and kHz QPOs: a Low-Frequency Modulation in Resonant Oscillations of Relativistic Accretion Disks
- 2004
-
Ingår i: Publications of the Astronomical Society of Japan. - 0004-6264. ; 56:5, s. 819-822
-
Tidskriftsartikel (refereegranskat)abstract
- The origin of quasi-periodic modulations of flux in the kilohertz range (kHz QPOs), observed in low-mass X-ray binaries, is usually assumed to be physically distinct from that of the "normal branch oscillations" (NBOs) in the Z-sources. We show that a low-frequency modulation of the kHz QPOs is a natural consequence of the non-linear relativistic resonance suggested previously to explain the properties of the high-frequency twin peaks. The theoretical results discussed here are reminiscent of the 6 Hz variations of frequency and amplitude of the kHz QPOs reported by Yu, van der Klis, and Jonker (2001).
|
|
