QUASAR X-RAY-SPECTRA REVISITED

A sample of 45 quasars observed by the IPC on the Einstein satellite i s used to reexamine the relationship of the soft (0.2-3.5 keV) X-ray e nergy index with radio properties and the optical Fe ii emission. We f ind that (1) the tendency for radio-loud quasars to have systematicall y flatter X-ray energy indices than radio-quiet quasars is confirmed w ith the soft X-ray excess having negligible effect; (2) there is a ten dency for the flatness of the X-ray slope to correlate with radio core dominance for radio-loud quasars, suggesting that a component of the X-ray emission is relativistically beamed; (3) for the radio-quiet qua sars, the soft X-ray energy indices with a mean of approximately 1.0 a re consistent with the indices found at higher energies (2-10 keV), al though steeper than those observed for Seyfert 1 galaxies (also 2-10 k eV) where the reflection model gives a good fit to the data; (4) the c orrelation of Fe II emission line strength with X-ray energy index is confirmed for radio-quiet quasars using a subset of 18 objects. The ra dio-loud quasars show no evidence for a correlation. This relation sug gests a connection between the ionizing continuum and line emission fr om the broad emission-line region (BELR) of radio-quiet quasars, but i n the opposite sense to that predicted by current photoionization mode ls; (5) the correlations of X-ray slope with radio core dominance and Fe II equivalent width within the radio-loud and radio-quiet subclasse s, respectively, imply that the observed wide range of X-ray energy in dices is real rather than due to the large measuring uncertainties for individual objects.