Characterising continuum variability in the radio-loud narrow-line Seyfert 1 galaxy IRAS 17020+4544

TL;DR

This study analyzes X-ray variability and spectral features of the radio-loud narrow-line Seyfert 1 galaxy IRAS 17020+4544, revealing unique spectral states, reverberation signatures, and a broad Fe K emission line, indicating complex accretion and jet processes.

Contribution

It provides the first detailed temporal and spectral analysis of IRAS 17020+4544, highlighting its distinct variability patterns and spectral components compared to radio-quiet counterparts.

Findings

Spectral hardening correlates with increased flux.

Detection of a broad Fe K emission line.

Identification of a soft spectral state in the latest observation.

Abstract

We present results of temporal and spectral analyses on four XMM-Newton EPIC pn observations of IRAS 17020+4544, a narrow-line Seyfert 1 galaxy with evidence of a radio jet. Analysis of the light curves reveals that this radio-loud source does not behave like the bulk population of its radio-quiet counterparts. A trend of spectral hardening with increased flux is found. Variability is found to increase with energy, though it decreases as the spectrum hardens. The first 40 ks of the most recent observation behave uniquely among the epochs, exhibiting a softer spectral state than at any other time. Possible non-stationarity at low energies is found, with no such effect present at higher energies, suggesting at least two distinct spectral components. A reverberation signature is confirmed, with the lag-frequency, lag-energy, and covariance spectra changing significantly during the soft-state epoch. The temporal analysis suggests a variable power-law in the presence of a reflection component, thus motivating such a fit for the 0.3-10 keV EPIC pn spectra from all epochs. We find an acceptable spectral fit using the timing-motivated parameters and report the detection of a broad Fe K emission line, requiring an additional model component beyond the reflection spectrum. We discuss links between this source and other narrow-line Seyfert 1 sources that show evidence of jet activity, finding similarities among this currently very limited sample of interesting objects.