New Constraints on the Continuum-emission Mechanism of Agn: Intensive Monitoring of Ngc 7469 in the X-ray and Ultraviolet

We have undertaken near-continuous monitoring of the Seyfert 1 galaxy NGC 7469 in the X-ray with RXTE over a ∼ 30 d baseline. The source shows strong variability with a root-mean-square (rms) amplitude of ∼ 16 per cent, 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 this the most intensive X-ray UV/X-ray variability campaign performed for any active galaxy. Comparison of the continuum light curves reveals very similar amplitudes of variability, but different variability characteristics, with the X–rays showing much more rapid variations. The data are not strongly correlated at zero lag. The largest absolute value of the correlation coefficient occurs for an anticorrelation between the two bands, with the X-ray variations leading the UV by ∼ 4 d. The largest positive correlation is for the ultraviolet to lead the X-rays by ∼ 4 d. Neither option appears to be compatible with any simple interband transfer function. The peak positive correlation at ∼ 4d occurs because the 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-simultaneous. These observations provide new constraints on theoretical models of the central Laboratory for High Energy Astrophysics, Code 660, NASA/Goddard Space Flight Center, Greenbelt, MD 20771 NAS/NRC Research Associate ISO Observatory, European Space Agency. Apartado 50727, 28080 Madrid, Spain X-ray Astronomy Group, Department of Physics and Astronomy, University of Leicester, University Road, Leicester, LE1 7RH, United Kingdom Universities Space Research Association Department of Astronomy, University of California, Los Angeles,CA 90024 Department of Astronomy, The Ohio State University, 174 West 18th Avenue, Columbus, OH 43210