1999ApJ...525L...9Y

We report the results from an ASCA observation of the high-luminosity, radio-loud quasar PKS 2149-306 (redshift 2.345), covering the ∼1.7-30 keV band in the quasar frame. We find the source to have a luminosity ∼6x10⁴⁷ ergs.s^–1 in the 2-10 keV band (quasar frame). We detect an emission line centered at ∼17 keV in the quasar frame. Line emission at this energy has not been observed in any other active galaxy or quasar to date. We present evidence rejecting the possibility that this line is the result of instrumental artifacts or a serendipitous source. The most likely explanation is blueshifted Fe-K emission (the equivalent width is EW∼300±200 eV, quasar frame). Bulk velocities of the order of 0.75c are implied by the data. We show that Fe-K line photons originating in an accretion disk and Compton scattering off a leptonic jet aligned along the disk axis can account for the emission line. Curiously, if the emission-line feature recently discovered in another quasar (PKS 0637-752, z=0.654) at 1.6 keV in the quasar frame is due to blueshifted O VII emission, the Doppler blueshifting factor in both quasars is similar (∼2.7-2.8).