1997/11/06 by Amri Wandel, Thomas Böller, Thomas Boller +2
Physics and Astronomy · #Astronomy and Astrophysical Research #Astrophysical Phenomena and Observations #Astrophysics (astro-ph) #FOS: Physical sciences #Galaxies: Formation, Evolution, Phenomena #astro-ph
paper · pdf · doi:10.48550/arxiv.astro-ph/9711047
7 page latex, 8 figs (ps). Also available at http://shum.cc.huji.ac.il/~amri/papers, accepted by A&A
arxiv created 1997/11/06 · openalex publication_date 1997/11/06 · arxiv updated 2009/12/01 · openalex created_date 2025/10/10 · openalex updated_date 2026/07/28
Recent ROSAT studies of narrow-line Seyfert 1 galaxies revealed these objects (with FWHM Hβ ≤ 2000 km s-1) generally show steeper soft X-ray spectra than broad line Seyfert 1's and that there are no AGN with broad lines and steep X-ray spectra. We derive a simple theoretical model which explains the observed correlation between the line width and the spectral index for Seyfert 1 galaxies by assuming the line width is due to gravitational velocity dispersion and showing that steeper soft X-ray spectra yield larger BLR radii. We test the model over a hetrogeneous (normal and narrow-line) sample of some 50 AGN finding a good agreement with the data. We give empirical relations for the dependence of the line width and Eddington ratio on the X-ray luminosity and apply variability analyses for direct estimation of the mass part in the line width.