The spectra of narrow-line Seyfert 1 galaxies

Measurements are presented of a group of active galactic nuclei with all the properties of Seyfert 1 or 1.5 galaxies, but with unusually narrow H I lines. They include Mrk 42, 359, and 1239 as well as Mrk 493, 766, 783, and 1126. One other somewhat similar object, Mrk 1388, is also included in the discussion. For these objects, narrow-line widths and intensities of the emission lines are discussed. Overall, these narrow-line Seyfert 1 galaxies show a wide variety of deviations from the properties of typical Seyfert 1 objects. They clearly demonstrate that the Seyfert phenomenon is not a simple one-parameter effect.