STScI Preprint #1317

BeppoSax Observations of 2-Jy Lobe-Dominated Broad-Line Sources. I. The Discovery of a Hard X-Ray Component

We present new BeppoSax LECS, 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 better constrain the spectral shape in the soft X-ray band. The collected data cover the energy range 0.1-10 keV, reaching ~50keV 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 _x~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 _x~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 bu 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 (weak) thermal component is also present at low energies in the two broad-line radio galaxies included in our study.

Status:

Appeared in: Monthly Notices of the R.A.S., 304:829-838, 1999

Affiliations:

¹)Space Telescope Science Institute, 3700 San Martin Drive, Baltimore MD. 21218, USA
²)Affiliated to the Astrophysics Division, Space Science Department, European Space Agency
³)Dipartimento di Fisica, II Università di Roma "Tor Vergata", Via della Ricerca Scientifica 1, I-00133 Roma Italy
⁴)Istituto di Radioastronomia, Via Gobetti 101, I-40129 Bologna, Italy
⁵)Max-Planck-Institut für Extraterrestrische Physik, Giessenbackstrasse, D-85740 Garching bei München, Germany
⁶)Osservatorio Astrofisico di Arcetri, Largo E. Fermi 5, I-50125 Firenze, Italy