Models of Quasi-Periodic Variability in Neutron Stars and Black Holes

Abstract

Black holes and weakly-magnetic accreting neutron stars show strong quasi-periodic variability over timescales that span a very wide range. This property offer us a unique opportunity to improve our understanding of basic physical processes in strong gravitational fields as it reveals, for the first time, phenomena that occur on the most fundamental timescales near accreting compact objects. In this article, I review our current understanding of the variability properties of accretion flows onto neutron stars and black holes. I discuss a number of challenges faced by theoretical models, in order to identify open questions in accretion physics that need to be addressed. Finally, I discuss the relation to and implications for variability models of the detection of nearly coherent oscillations during type I X-ray bursts in several neutron-star sources.

10 pages, 10 figures; Advances for Space Research; invited review talk at the 33rd COSPAR Scientific Assembly, Warsaw, Poland

References in corpus (2)

• Millisecond Oscillations and Photospheric Radius Expansion in Thermonuclear X-Ray Bursts
• The first outburst of SAX J1808.4-3658 revisited

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• The Frequency Stability of Millisecond Oscillations in Thermonuclear X-Ray Bursts
• Correlated modulation between the redshifted Fe K alpha line and the continuum emission in NGC 3783
• Spectral Methods for Time-Dependent Studies of Accretion Flows. I. Two-dimensional, Viscous, Hydrodynamic Disks
• The impact of neutron star spin on X-ray spectra
• SPH simulations of Shakura-Sunyaev instability at intermediate accretion rates
• Modelling the energy dependencies of X-ray quasi-periodic oscillations in accreting compact objects
• Microlensing in phase space II: Correlations analysis
• Lags of the KiloHertz Quasi-Periodic Oscillations in the transient source XTE J1701$-$462