Ultraviolet spectra of a large sample of quasars - II. Variability ofLy-alpha and C IV emission lines.

Abstract

The analysis of spectra of 34 quasars observed more than once with IUE is presented. The Lyα + N V and C IV emission lines in the spectra of some quasars in this sample change in intensity over a short time-scale. This time-scale is comparable to the time-scale for change observed in the intensity of emission lines in the spectra of low-luminosity active galactic nuclei. The data suggest that in high-luminosity active galactic nuclei the broad emission line region (if spherical) is considerably smaller than that required to model the spectra of these active galaxies. Also, the size of the broad emission line region does not appear to scale with luminosity of the nucleus as required by the present generation of models of this region.