Open AccessBeppoSAX observations of 2‐Jy lobe‐dominated broad‐line sources ‐‐ I. The discovery of a hard X‐ray component
Author(s) -
Padovani Paolo,
Morganti Raffaella,
Siebert Joachim,
Vagnetti Fausto,
Cimatti Andrea
Publication year - 1999
Publication title -
monthly notices of the royal astronomical society
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.058
H-Index - 383
eISSN - 1365-2966
pISSN - 0035-8711
DOI - 10.1046/j.1365-8711.1999.02371.x
Subject(s) - physics , astrophysics , rosat , quasar , spectral line , galaxy , line (geometry) , astronomy , radio galaxy , spectral index , emission spectrum , geometry , mathematics
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 constrain the spectral shape better in the soft X‐ray band. The collected data cover the energy range 0.1 ‐ 10 keV, reaching ∼ 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 α 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 Δα 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 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 (weak) thermal component is also present at low energies in the two broad‐line radio galaxies included in our study.