Using a month-long X-ray lightcurve from RXTE /PCA and 1.5 month long UV continuum lightcurves from IUE spectra in 1220 - 1970 Å , we performed a detailed time-lag study of the Seyfert 1 galaxy NGC 7469 .
Our cross-correlation analysis confirms previous results showing that the X-rays are delayed relative to the UV continuum at 1315 Å by 3.49 \pm 0.22 days which is possibly caused by either propagating fluctuation or variable comptonisation .
However , if variations slower than 5 days are removed from the X-ray lightcurve , the UV variations then lag behind the X-rays variations by 0.37 \pm 0.14 days , consistent with reprocessing of the X-rays by a surrounding accretion disc .
A very similar reverberation delay is observed between Swift /XRT X-ray and Swift /UVOT UVW2 , U lightcurves .
Continuum lightcurves extracted from the Swift /GRISM spectra show delays with respect to X-rays consistent with reverberation .
Separating the UV continuum variations faster and slower than 5 days , the slow variations at 1825 Å lag those at 1315 Å by 0.29 \pm 0.06 days , while the fast variations are coincident ( 0.04 \pm 0.12 day ) .
The UV/optical continuum reverberation lag from IUE , Swift and other optical telescopes at different wavelengths are consistent with the relationship : \tau \propto \lambda ^ { 4 / 3 } , predicted for the standard accretion disc theory while the best-fit X-ray delay from RXTE and Swift /XRT shows a negative X-ray offset of \sim 0.38 days from the standard disc delay prediction .