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arXiv · 0804.4467

The warm absorber in NGC 5548: The lean years

R. G. Detmers·J. S. Kaastra·E. Costantini·I. M. McHardy·F. Verbunt
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Abstract

We study the variability of the warm absorber and the gas responsible for the emission lines in the Seyfert 1 galaxy NGC 5548, in order to constrain the location and physical properties of these components. Using X-ray spectra taken with the \textit{Chandra}$-$LETGS in 2002 and 2005, we study variability in the ionic column densities and line intensities. We find a lower \ion{O}{vii} forbidden emission line flux in 2005, while the Fe K$\alpha$ line flux stays constant. The warm absorber is less ionized in 2005, allowing us to constrain its location to within 7 pc of the central source. Using both the observed variability and the limit on the FWHM of the \ion{O}{vii} f line, we have constrained the location of the narrow line region to a distance of 1 pc from the central source. The apparent lack of variability of the Fe K$ \alpha$ line flux does not allow for a unique explanation.

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R. G. Detmers, J. S. Kaastra, E. Costantini, I. M. McHardy, F. Verbunt. 2008-04-28. The warm absorber in NGC 5548: The lean years. https://doi.org/10.1051/0004-6361:200809862

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