BeppoSAX observations of 2-Jy lobe-dominated broad-line sources -- I. The discovery of a hard X-ray component

Abstract

We present new BeppoSAX LEGS, MECS and PDS observations of five lobe-dominated, broad-line active galactic nuclei selected from the 2-Jy sample of southern radio sources. These include three radio quasars and two broad-line radio galaxies. ROSAT PSPC data, available for all the objects, are also used to constrain the spectral shape better in the soft X-ray band. The collected data cover the energy range 0.1-10 keV, reaching similar to 50 keV for one source (Pictor A), The main result from the spectral fits is that all sources have a hard X-ray spectrum with energy index alpha(x) similar to 0.75 in the 2-10 keV range. This is at variance with the situation at lower energies where these sources exhibit steeper spectra. Spectral breaks Delta alpha(x) similar to 0.5 at 1-2 keV characterize in fact the overall X-ray spectra of our objects. The flat, high-energy slope is very similar to that displayed by flat-spectrum/core-dominated quasars, which suggests that the same emission mechanism (most likely inverse Compton) produces the hard X-ray spectra in both classes. Finally, a tweak) thermal component is also present at low energies in the two broad-line radio galaxies included in our study.