What can we learn from EPIC X-ray spectra of Seyfert 1 galaxies?

TL;DR

This study analyzes XMM-Newton EPIC spectra of six Seyfert 1 galaxies to understand their X-ray emission features, soft excess variability, and the role of absorption, revealing common spectral components and the importance of broad Fe K line modeling.

Contribution

First comprehensive analysis of broad-band X-ray spectra of multiple Seyfert 1 galaxies highlighting the impact of absorption and the presence of a common underlying continuum.

Findings

Soft excess present in all galaxies with luminosity-dependent spectral forms.

Line-of-sight absorption influences observed spectral differences.

Narrow Fe K emission line at 6.4 keV is consistently detected.

Abstract

The EPIC detectors on XMM-Newton provide the most sensitive broad band (0.3-12 keV) X-ray spectra to date. Observations of 6 Seyfert 1 galaxies, covering a wide luminosity range, are examined with the aim of identifying the primary X-ray continuum and constraining superimposed emission and absorption features. A soft excess emission component is seen in every case, but with a spectral form which differs markedly with luminosity across our sample. Current interpretations of the soft excess range from intrinsic thermal emission from the accretion disc to reprocessing of harder radiation absorbed in the disc skin. Visual examination of the broad-band EPIC spectra suggest that the luminosity trend in the observed spectral profiles may be governed primarily by differences in the line-of-sight absorption. In that case the underlying continuum could have a common form across the sample. Examination of spectral features in the Fe K band confirm the common presence of a narrow emission line at 6.4 keV. Modelling of the EPIC spectra above 7 keV is shown to be critical to quantifying (or confirming) a broad Fe K line in at least some cases.