BeppoSAX broad-band observations of low-redshift quasars: spectral curvature and iron K-alpha lines

We present results from BeppoSAX observations of 10 low redshift quasars. T he quasars are part of the Laor et al. (1997) sample of 23 optically select ed PG quasars with redshift < 0.4 and low Galactic absorption along the lin e of sight. Significant spectral curvature is detected for the 6 quasars wi th the highest signal to noise ratio in their low energy spectra. The avera ge curvature can be parameterized as a flattening of the underlying power l aw by Delta alpha similar to 0.5 above similar to 1 keV. We find that quasa rs with a steeper soft X-ray (0.1-2 keV) spectrum tend to be steeper also a t higher (2-10 keV) energies. The distribution of the best fit 2-10 keV slo pes is similar to that found for other radio-quiet AGN and characterized by a large dispersion around the mean: alpha(E) similar or equal to 1.0 +/- 0 .3. Iron K-alpha lines are detected in 4 quasars. In the narrow-line quasar PG 1115+407, the rest frame line energy (6.69+/-0.11 keV) and equivalent w idth (580+/-280 eV) are consistent with these found in a few low redshift n arrow-line Seyfert 1 galaxies (NLSy1). This, together with the similarity o f the 0.1-10 keV X-ray continuum, suggests that this quasar is the higher r edshift and luminosity analog of a NLSy 1. In the broad line quasar PG 0947 +396, the rest-frame line energy suggests fluorescence from cold iron. The line equivalent width (> 400 eV) is however about 2-3 times higher than tha t usually found in Seyfert 1 galaxies. The high energy power-law slopes and the iron line emission properties seem to be unrelated to the X-ray lumino sity.