Investigating powerful jets in radio-loud narrow-line Seyfert 1s

Abstract

We report results on multiband observations from radio to γ -rays of the two radio-loudnarrow-line Seyfert 1 (NLSy1) galaxies PKS 2004-447 and J1548+3511. Both sources showa core-jet structure on parsec scale, while they are unresolved at the arcsecond scale. The highcore dominance and the high variability brightness temperature make these NLSy1 galaxiesgood γ -ray source candidates. Fermi-Large Area Telescope detected γ -ray emission only fromPKS 2004-447, with a γ -ray luminosity comparable to that observed in blazars. No γ -rayemission is observed for J1548+3511. Both sources are variable in X-rays. J1548+3511 showsa hardening of the spectrum during high activity states, while PKS 2004-447 has no spectralvariability. A spectral steepening likely related to the soft excess is hinted below 2 keV forJ1548+3511, while the X-ray spectra of PKS 2004-447 collected by XMM-Newton in 2012are described by a single power law without significant soft excess. No additional absorptionabove the Galactic column density or the presence of an Fe line is detected in the X-ray spectraof both sources.