We report the results from an ASCA observation of the high-luminosity , radio-loud quasar PKS 0637 - 752 ( redshift 0.654 ) , covering the 0.8–15 keV band in the quasar-frame .
We find the source to have a luminosity \sim 10 ^ { 46 } { erg s ^ { -1 } } in the 2–10 keV band , a factor of \sim 3 lower than during a previous Ginga observation .
The continuum appears to be well modeled by a simple power-law with \Gamma = 1.64 \pm 0.07 , with no evidence for absorption by material intrinsic to the quasar , or Fe-K emission ( with an equivalent width \lesssim 80 eV at 90 % confidence ) .
However we do find evidence for a narrow emission line at an energy 1.60 \pm 0.07 keV and equivalent width 59 ^ { +38 } _ { -34 } eV ( both in the quasar frame ) .
Line emission at these energies has not been observed in any other active galaxy or quasar to date .
We reject the possibility that this line is the result of instrumental artifacts , and briefly explore possible identifications .