New constraints on the continuum emission mechanism of active galactic nuclei: Intensive monitoring of NGC 7469 in the x-ray and ultraviolet

We have undertaken near-continuous monitoring of the Seyfert 1 galaxy NGC 7 469 in the X-ray with RXTE over a similar to 30 day baseline. The source sh ows strong variability with a root mean square (rms) amplitude of similar t o 16% and peak-to-peak variations of a factor of order 2. Simultaneous data over this period were obtained in the ultraviolet (UV) using IUE; making t his the most intensive X-ray WUV/X-ray variability campaign performed for a ny active galaxy. Comparison of the continuum light curves reveals very sim ilar amplitudes of variability but different variability characteristics, w ith the X-rays showing much more rapid variations. The data are not strongl y correlated at zero lag. The largest absolute value of the correlation coe fficient occurs for an anticorrelation between the two bands, with the X-ra y variations leading the UV by similar to 4 days. The largest positive corr elation is for the ultraviolet to lead the X-rays by similar to 4 days. Nei ther option appears to be compatible with any simple interband transfer fun ction. The peak positive correlation at similar to 4 days occurs because th e more prominent peaks in the UV light curve appear to lead those in the X- rays by this amount. However, the minima of the light curves are near simul taneous. These observations provide new constraints on theoretical models o f the central regions of active galactic nuclei. Models in which the observ ed UV emission is produced solely by reradiation of absorber X-rays are rul ed out by our data, as are those in which the X-rays are produced solely by Compton upscattering of the observed UV component by a constant distributi on of particles. New or more complex models must be sought to explain the d ata. We require at least-two variability mechanisms, which have no simple r elationship. We briefly explore means by which these observations could be reconciled with theoretical models.