Oscillations of the Inner Regions of Viscous Accretion Disks

Abstract

Although quasi-periodic oscillations (QPOs) have been discovered in different X-ray sources, their origin is still a matter of debate. Analytical studies of hydrodynamic accretion disks have shown three types of trapped global modes with properties that appear to agree with the observations. However, these studies take only linear effects into account and do not address the issues of mode excitation and decay. Moreover, observations suggest that resonances between modes play a crucial role. A systematic, numerical study of this problem is therefore needed. In this paper, we use a pseudo-spectral algorithm to perform a parameter study of the inner regions of hydrodynamic disks. By assuming alpha-viscosity, we show that steady state solutions rarely exist. The inner edges of the disks oscillate and excite axisymmetric waves. In addition, the flows inside the inner edges are sometimes unstable to non-axisymmetric perturbations. One-armed, or even two-armed, spirals are developed, which provides a plausible explanation for the high-frequency QPOs observed from accreting black holes. When the Reynolds numbers are above certain critical values, the inner disks go through some transient turbulent states characterized by strong trailing spirals; while large-scale leading spirals developed in the outer disks. We compared our numerical results with standard thin disk oscillation models. Although the non-axisymmetric features have their analytical counterparts, more careful study is needed to explain the axisymmetric oscillations.

12 pages including 7 figures, submitted to ApJ, comments welcome, movies are available at http://www.cfa.harvard.edu/~ckchan/astrophysics/inner

References in corpus (10)

• X-ray Properties of Black-Hole Binaries
• Three-Dimensional Simulations of Magnetized Thin Accretion Disks around Black Holes: Stress in the Plunging Region
• Kerr Black Holes are Not Unique to General Relativity
• Resonant Excitation of Disk Oscillations in Deformed Disks II: A Model of High Frequency QPOs
• On the time variability of geometrically-thin black hole accretion disks I : the search for modes in simulated disks
• The fundamental difference between shear alpha viscosity and turbulent magnetorotational stresses
• On the Time Variability of Geometrically-Thin Black Hole Accretion Disks II: Viscosity-Induced Global Oscillation Modes in Simulated Disks
• Resonant Excitation of Disk Oscillations in Deformed Disks III: Revision of Mathematical Treatment
• Memory Effect and Fast Spinodal Decomposition
• Super-Keplerian Frequencies in Accretion Disks. Implications for Mass and Spin Measurements of Compact Objects from X-ray Variability Studies

Cited by in corpus (11)

• Testing the No-Hair Theorem with Observations in the Electromagnetic Spectrum. III. Quasi-Periodic Variability
• Near infrared flares of Sagittarius A*: Importance of near infrared polarimetry
• Diskoseismology and QPOs Confront Black Hole Spin
• When models fail: an introduction to posterior predictive checks and model misspecification in gravitational-wave astronomy
• $(2+1)$-dimensional charged black holes with scalar hair in Einstein-Power-Maxwell Theory
• HFQPOs and discoseismic mode excitation in eccentric, relativistic discs. II. Magnetohydrodynamic simulations
• HFQPOs and discoseismic mode excitation in eccentric, relativistic discs. I. Hydrodynamic simulations
• Viscous Driving of Global Oscillations in Accretion Discs Around Black Holes
• Simulations of Overstable Inertial-acoustic Modes in Black-Hole Accretion Discs
• The stress-pressure lag in MRI turbulence and its implications for thermal instability in accretion discs
• Evidences of an innermost stable bound orbit predicted by general relativity from the amplitude of the twin-peak quasi-periodic oscillations