The First Hard X-Ray Power Spectral Density Functions of AGN

TL;DR

This study presents the first analysis of AGN power spectral density functions in the hard X-ray band, revealing unbroken power laws with no breaks or correlations, suggesting similarities to high-state Galactic Black Holes.

Contribution

It provides the first hard X-ray PSD functions for a sample of AGN, showing they follow unbroken power laws without breaks or correlations with AGN properties.

Findings

Most AGN PSDs fit well with an unbroken power law of slope ~-1.

No evidence of a break in the PSDs was found.

No significant energy dependence or correlation with luminosity or black hole mass.

Abstract

We present results of our Power Spectral Density (PSD) analysis of 30 AGN using the 58 month light curves from Swift's Burst Alert Telescope (BAT) in the 14-150 keV band. PSDs were fit using a Monte Carlo based algorithm to take into account windowing effects and measurement error. All but one source were found to be fit very well using an unbroken power law with a slope of ~-1, consistent at low frequencies with previous studies in the 2-10 keV band, with no evidence of a break in the PSD. For 5 of the highest S/N sources we tested the energy dependence of the PSD and found no significant difference in the PSD at different energies. Unlike previous studies of X-ray variability in AGN, we do not find any significant correlations between the hard X-ray variability and different properties of the AGN including luminosity and black hole mass. The lack of break frequencies and correlations seem to indicate that AGN are similar to the high state of Galactic Black Holes.