Studying accreting black holes and neutron stars with time series: beyond the power spectrum

TL;DR

This paper reviews recent advances in analyzing time series data from accreting black holes and neutron stars, focusing on methods beyond traditional power spectrum analysis to understand complex physical processes.

Contribution

It discusses new approaches utilizing non-linear, non-Gaussian, and higher-order spectral analyses enabled by improved data quality and quantity.

Findings

Enhanced understanding of turbulent accretion flows

Detection of non-linear and non-Gaussian features in X-ray variability

Insights into matter behavior on neutron star surfaces

Abstract

The fluctuating brightness of cosmic X-ray sources, particularly accreting black holes and neutron star systems, has enabled enormous progress in understanding the physics of turbulent accretion flows, the behaviour of matter on the surfaces of neutron stars and improving the evidence for black holes. Most of this progress has been made by analysing and modelling time series data in terms of their power and cross spectra, as will be discussed in other articles in this volume. Recently, attempts have been made to make use of other aspects of the data, by testing for non-linearity, non-Gaussianity, time asymmetry and by examination of higher order Fourier spectra. These projects, which have been made possible by the vast increase in data quality and quantity over the past decade, are the subject of this article.