Blazar nuclei in radio-loud narrow-line Seyfert 1?

It has been suggested that some radio-loud narrow-line Seyfert 1 contain relativistic jets, on the basis of their flat-spectrum radio nuclei and studies on variability. We present preliminary results of an ongoing investigation of the X-ray and multiwavelength properties of 5 radio-loud NLS1 based on archival data from Swift and XMM-Newton. Some sources present interesting characteristics, very uncharacteristic for a radio-quiet narrow-line Seyfert 1, such as very hard X-ray spectra, and correlated optical and ultraviolet variability. However, none of the studied sources show conclusive evidence for relativistic jets. gamma-ray observations with Fermi are strongly recommended to definitely decide on the presence or not of relativistic jets.
Comment: 9 pages, 4 figures. Talk presented at the 37th COSPAR Assembly (Montreal, Canada, July 13-20, 2008), Session E17. Accepted for publication on Advances in Space Research