The effect of UV/Soft X-ray excess emission on the warm absorber properties of Active Galactic Nuclei -- A case study of IRAS 13349+2438

TL;DR

This study examines how different models of the soft X-ray excess in AGN influence the properties of warm absorbers, using IRAS 13349+2438 as a case, and finds current data insufficient to distinguish between models.

Contribution

It introduces a case study analyzing the impact of soft-excess models on warm absorber properties in AGN, highlighting the challenge in identifying the soft-excess origin with existing data.

Findings

Different soft-excess models predict varying fluxes in unobserved energy ranges.

Current X-ray data quality cannot distinguish between soft-excess models based on WA features.

Determining the soft-excess origin from WA features remains challenging.

Abstract

The UV to X-ray continuum of active galactic nuclei (AGN) is important for maintaining the ionisation and thermal balance of the warm absorbers (WAs). However, the spectra in the sensitive energy range $\sim \,13.6 -300 \ev$ are unobservable due to Galactic extinction. Moreover, many AGN show soft X-ray excess emission of varying strength in the $0.1-2\kev$ band whose origin is still highly debated. This soft-excess connects to the UV bump in the unobserved region of $13.6 -300 \ev$. Here we investigate the effect of the assumed physical model for the soft-excess on the flux of the unobserved part of the spectrum and its effect on the WA properties. We perform a case study using the \xmm{} observations of the bright Seyfert 1 galaxy IRAS 13349+2438 with WA features. The two different physical models for the soft excess: blurred Compton reflection from an ionised disk, and, optically thick thermal Comptonisation of the disk photons, predict different fluxes in the unobserved energy range. However the current X-ray data quality does not allow us to distinguish between them using derived WA parameters. This, in turn, implies that it is difficult to determine the origin of the soft-excess emission using the warm absorber features.