Models of optical/UV continuum in AGN: constraints from the NGC 5548 monitoring campaign

Abstract

We analyse the data from the International Ultraviolet Explorer (IUE) observational campaign on the Seyfert galaxy NGC 5548 in the context of 10 phenomenological models. On the basis of the optical/UV data, as well as of constraints from the X-ray observations, we can favour one model of the nucleus: an accretion disc with an inner radius cut-off surrounded by a hot corona. The second acceptable model for optical/UV data is a distribution of optically thin clouds. However, X-ray constraints which were crucial in the analysis of disc-type models could not be applied; further development of this model is necessary.