A link between X-ray variability and ultraviolet emission in Seyfert 1 type AGN.

Abstract

We analyse the behaviour of X-ray spectral variations in Seyfert 1 type active galactic nuclei observed many times in the 2-10 keV energy band. The selected sources are compatible with a separation into two groups distinguished by different kinds of X-ray variability and by different ratios of ultraviolet to X-ray fluxes. In the first group of objects the X-ray spectral variations are related to the ratio of the medium X-ray flux to the ultraviolet or soft X-ray flux while in the second group the spectra steepen when the sources brighten. The two different kinds of X-ray variability are related to the strength of the blue bump and may be linked to the relative importance of different cooling processes in the X-ray sources of these objects.