The rhythm of Fairall 9 -- I: Observing the spectral variability with XMM-Newton and NuSTAR

TL;DR

This study analyzes multi-epoch X-ray spectra of Fairall 9, revealing consistent spectral variability patterns and identifying the soft excess as a combination of ionized reflection and Comptonization processes.

Contribution

It provides new insights into the spectral variability and soft excess origin in Fairall 9 using simultaneous XMM-Newton and NuSTAR observations.

Findings

Spectral ratio residuals remain constant over time despite flux changes.

Soft excess is a superposition of blurred ionized reflection and Comptonization.

Source geometry and emission processes are stable across observations.

Abstract

We present a multi-epoch X-ray spectral analysis of the Seyfert 1 galaxy Fairall 9. Our analysis shows that Fairall 9 displays unique spectral variability in that its ratio residuals to a simple absorbed power law in the 0.5-10 keV band remain constant with time in spite of large variations in flux. This behavior implies an unchanging source geometry and the same emission processes continuously at work at the timescale probed. With the constraints from NuSTAR on the broad-band spectral shape, it is clear that the soft excess in this source is a superposition of two different processes, one being blurred ionized reflection in the innermost parts of the accretion disk, and the other a continuum component such as spatially distinct Comptonizing region. Alternatively, a more complex primary Comptonization component together with blurred ionized reflection could be responsible.