Identification of black hole power spectral components across all canonical states

TL;DR

This study provides a comprehensive identification of variability components in black hole power spectra across all canonical states, revealing similarities with neutron stars and implications for the origin of X-ray variability.

Contribution

It offers a unified identification of spectral components in black hole states, based on frequency shifts and correlations, enhancing understanding of variability origins.

Findings

Variability components are consistent across black hole states and similar to neutron stars.

High-frequency variability in black holes is about six times lower than in neutron stars.

X-ray variability likely originates in the disk or corona, not the outer jet.

Abstract

From a uniform analysis of a large (8.5 Ms) Rossi X-ray Timing Explorer data set of Low Mass X-ray Binaries, we present a complete identification of all the variability components in the power spectra of black holes in their canonical states. It is based on gradual frequency shifts of the components observed between states, and uses a previous identification in the black hole low hard state as a starting point. It is supported by correlations between the frequencies in agreement with those previously found to hold for black hole and neutron stars. Similar variability components are observed in neutron stars and black holes (only the component observed at the highest frequencies is different) which therefore cannot depend on source-specific characteristics such as the magnetic field or surface of the neutron star or spin of the black hole. As the same variability components are also observed across the jet-line the X-ray variability cannot originate from the outer-jet but is most likely produced in either the disk or the corona. We use the identification to directly compare the difference in strength of the black hole and neutron star variability and find these can be attributed to differences in frequency and strength of high frequency features, and do not require the absence of any components. Black holes attain their highest frequencies (in the hard-intermediate and very-high states) at a level a factor ~6 below the highest frequencies attained by the corresponding neutron star components, which can be related to the mass difference between the compact objects in these systems.