150 keV emission from PKS 2149-306 with BeppoSAX

A BeppoSAX observation of the z = 2.34 quasar PKS 2149 - 306 produced a strong signal in the high-energy PDS instrument up to a maximum observed energy of nearly 50 keV, 150 keV in the quasar frame. The BeppoSAX spectrum spans almost three decades (0.3-150 keV, quasar frame) and shows an extremely hard (alpha = 0.4 +/- 0.05) X-ray spectrum above 3 keV (comparable to XJB the X-ray background slope), and either a softer (alpha = 1.0(-0.3)(+0.6)) low-energy component or an ionized absorber at zero redshift. No evidence is seen of an Fe-K emission line (EW < 167 eV at 6.5 keV quasar frame), a Compton hump (R < 0.3). A bremsstrahlung fit gives kT(rest) = 46(-16)(+32) keV, similar to the X-ray background value, and a high-energy cut off power law requires E-cut > 120 keV (quasar frame). The SED of PKS 2149-306 shows two peaks at similar to 10(12+/-0.5) Hz and similar to 10(21+/-1.0) Hz (similar to0.3 mm and similar to4 MeV), strongly resembling a low-energy cut off BL Lac object (LBL). The ratio of the two peaks shows an extreme Compton dominance (C-D = 1.4 +/- 0.4), as in flat-spectrum radio quasars (FSRQs). The presence of an additional " optical/ UV big bump" component may provide photons that cool the jet, suppressing the radio emission.