A review of quasi-periodic oscillations from black hole X-ray binaries: Observation and theory

Abstract

Black hole and neutron star X-ray binary systems routinely show quasiperiodic oscillations (QPOs) in their X-ray flux. Despite being strong, easily measurable signals, their physical origin has long remained elusive. However, recent observational and theoretical work has greatly improved our understanding. Here, we briefly review the basic phenomenology of the different varieties of QPO in both black hole and neutron star systems before focusing mainly on low frequency QPOs in black hole systems, for which much of the recent progress has been made. We describe the detailed statistical properties of these QPOs and review the physical models proposed in the literature, with particular attention to those based on Lense-Thirring precession. This is a relativistic effect whereby a spinning massive object twists up the surrounding spacetime, inducing nodal precession in inclined orbits. We review the theory describing how an accretion flow reacts to the Lense-Thirring effect, including analytic theory and recent numerical simulations. We then describe recent observational tests that provide very strong evidence that at least a certain type of low frequency QPOs are a geometric effect, and good evidence that they are the result of precession. We discuss the possibility of the spin axis of the compact object being misaligned with the binary rotation axis for a large fraction of X-ray binaries, as is required for QPOs to be driven specifically by Lense-Thirring precession, as well as some outstanding gaps in our understanding and future opportunities provided by X-ray polarimeters and/or high throughput X-ray detectors.

Disk, Corona, Jet Connection in the Intermediate State of MAXI J1820+070 Revealed by NICER Spectral-timing Analysis

“…This result was interpreted as a contraction in the X-ray corona. This hypothesis has been later confirmed by reflection spectroscopy in the context of a dual-lamppost, where the height of the upper lamppost decreased while the lower one stayed constant (Buisson et al 2019), and by the increase of the peak frequency of the quasi-periodic oscillations (QPOs; Ingram & Motta 2019). During the hard-to-soft transition, an extremely powerful superluminal ejection was observed in the radio band (Bright et al 2020) very close in time with a small flare in the 7-12 keV band and a transition from type-C to type-B QPO (Homan et al 2020).…”

NICER uncovers the transient nature of the type-B quasi-periodic oscillation in the black hole candidate MAXI J1348−630

“…A distinctive timing characteristic of BHBs is the evolution of the low-frequency QPOs with spectral states (see Ingram & Motta 2019 for a recent review of different types of QPOs). As a source evolves from the bright end of the HS to the HIMS, type-C QPOs (up to 20 per cent rms in the 2-60 keV, the full energy band of the Proportional Counter Array aboard the Rossi X-ray Timing Explorer, hereafter RXTE/PCA) always appear in the power density spectra (PDS), superimposed on a strong band-limited noise component.…”

The black hole transient MAXI J1348–630: evolution of the compact and transient jets during its 2019/2020 outburst

“…During an outburst, the system cycles through different accretion states that are characterized by distinct spectral and timing signatures (e.g. Remillard & McClintock 2006;Belloni 2010;Belloni & Motta 2016;Ingram & Motta 2019). As the outburst begins, these systems are typically observed in a rising hard X-ray state with high rms variability, during which the X-ray spectrum is dominated by a non-thermal power law that is thought to be the result of inverse-Compton scattering by a corona of hot electrons close to the compact object (e.g.…”