An Active Galactic Nucleus Sample with High X-Ray-to-Optical Flux Ratio from RASS. II. Optical Emission Line Properties of Seyfert 1-Type Active Galactic Nuclei

This work studies the optical emission line properties of a sample of 155 low-redshift bright X-ray-selected ROSAT Seyfert 1-type active galactic nuclei for which adequate signal-to-noise ratio spectroscopic observations are available. We measured emission-line properties by performing multicomponent fits to the emission-line profiles, covering the effect of blended iron emission. We also obtained continuum parameters, including 250 eV X-ray luminosities derived from the ROSAT database. In addition, the measured properties are gathered for a correlation analysis, which confirms the well-known relations between the strengths of Fe II, [O III] emission and the X-ray slope. We also detect striking correlations between Hβ redshift (or blueshift) and flux ratios of Fe II to Hβ broad component and [O III] to Hβ narrow component. These trends are most likely driven by the Eddington ratio.