2000ApJ...543..545E

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 (α=0.4±0.05) X-ray spectrum above 3 keV (comparable to XJB the X-ray background slope), and either a softer (α=1.0^+0.6_–0.3) 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⁺³²_–16 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 ∼10^12±0.5 Hz and ∼10^21±1.0 Hz (∼0.3 mm and ∼4 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.