Fast variability from X-ray binaries

TL;DR

This paper reviews the complex fast variability observed in X-ray emissions from accreting black holes and neutron stars, highlighting its importance for understanding astrophysical processes and fundamental physics.

Contribution

It provides a comprehensive review of observational properties and discusses future prospects and observational needs for studying fast variability in X-ray binaries.

Findings

Characterization of high-frequency QPOs and burst oscillations

Implications for accretion flow properties and relativistic effects

Identification of observational challenges and future instrument needs

Abstract

The X-ray emission from accreting black-holes and neutron stars features strong variability on sub-second time scales, with very complex and broad phenomenology. From high-frequency quasi-periodic oscillations to rapidly changing X-ray burst oscillations to millisecond pulsations, these are weak signals immersed in strong noise and their study is pushing instrument capabilities to their limit. The scientific significance of fast time variability studies are both astronomical (properties of accretion flows, nature and evolution of sources) and physical (effects of General Relativity, equation of state of degenerate matter). I first review the main observational properties, then discuss the future prospects and observational needs.