BeppoSAX observations of Narrow-Line Seyfert 1 galaxies - II. Ionized ironfeatures in Arakelian 564

The BeppoSAX observations of the bright Narrow-Line Seyfert I galaxy Ark 56 4 are presented along with a high quality optical spectrum taken at the 1.5 m telescope at La Silla. The 0.1-10 keV X-ray spectrum is characterized by a strong soft; component which is best described by blackbody-like emissio n with a temperature of similar to 160 eV. At higher energies a steep (Gamm a similar or equal to 2.4) power-law tail is present. There is evidence of an ionized reflector in the form of an iron line and edge. We do not find s ignificant evidence of soft X-ray features if the spectrum is modelled with a two component continuum. The optical and X-ray spectral properties suppo rt the hypothesis of a high accretion rate onto a low mass black hole.