2000/02/17 by J. S. Kaastra, Kaastra, J. S., R. Mewe +7 · 1 citation
Physics and Astronomy · #Advanced X-ray Imaging Techniques #Astrophysics (astro-ph) #Atomic and Molecular Physics #FOS: Physical sciences #X-ray Spectroscopy and Fluorescence Analysis #astro-ph
paper · pdf · doi:10.48550/arxiv.astro-ph/0002345
4 pages, 3 figures, accepted for publication in Astronomy & Astrophysics, Letters
arxiv created 2000/02/17 · openalex publication_date 2000/02/17 · arxiv updated 2009/12/01 · openalex created_date 2025/10/10 · openalex updated_date 2026/07/28
We present for the first time a high-resolution X-ray spectrum of a Seyfert galaxy. The Chandra-LETGS spectrum of NGC 5548 shows strong, narrow absorption lines from highly ionised species (the H-like and He-like ions of C, N, O, Ne, Na, Mg, Si, as well as Fe XIV--XXI). The lines are blueshifted by a few hundred km/s. The corresponding continuum absorption edges are weak or absent. The absorbing medium can be modelled by an outflowing, thin and warm shell in photoionization equilibrium. The absorption lines are similar to lower ionization absorption lines observed in the UV, although these UV lines originate from a different location or phase of the absorbing medium. Redshifted with respect to the absorption lines, emission from the O VIII Lyman alpha line as well as the O VII triplet is visible. The flux of these lines is consistent with emission from the absorbing medium. The O VII triplet intensity ratios demonstrate that photoionization dominates and yield an upper limit to the electron density.