Ultraviolet variability of the Seyfert 1 galaxy Fairall 9

The large amplitude of the variations of the Seyfert I Galaxy Fairall-9 between 1978 and 1991 make this Active Galaxy especially suitable for a combined study in terms of reverberation analysis and photoioniza- tion modeling over the velocity eld of the broad lines of its ultraviolet spectrum. We have combined our ultravio- let data with those available at other wavelengths to de- rive the intrinsic ionizing continuum and to compare the predictions of the photoionization models with the obser- vations. The UV continuum varies with a factor of 33 4 on a characteristic time scale of 182 days. The intrinsic spectral index UV-optical is = 0:07 0:02 and the optical variations do not lag behind the UV variations at the mean sampling interval of 96 days. In the near IR, the J band flux presents a direct extension of the UV-optical continuum (J UV = 0:07 0:05). Only at low flux levels is the 2 10 keV flux proportional to the UV contin- uum, at higher UV flux levels proportionality between the X-rays and the UV brightness breaks down. The con- tinuum spectral energy distribution (SED) of the nu- cleus supports the previously reported FIR-NIR excess associated with 0.02 M dust at a distance of some 400 100 light-days, as well as a soft X-ray excess, possi- bly associated with the reprocessing on an accretion disk of the hard X-rays emitted from a region above the disk. The presence of strong Fe Kline in the GINGA spec- tra of this galaxy does lend support to this model. Line prole variability has been used to isolate four gaussian line components, which are sucient to describe all lines at all levels of brightness in a consistent way: one nar- row (i.e. unresolved at the IUE resolution), and three broad components: a central (velocity same as the nar-