X-RAY STUDY OF THE DISTANT QSO PKS-0237-233 WITH ASCA AND ROSAT

The X-ray spectrum of the distant QSO PKS 0237-233 (z = 2.223) has bee n studied with ASCA and ROSAT. The spectrum in the energy range 0.1 ke V to 8 keV in the observer's frame is well fitted by a power-law model with a photon index of 1.54 +/- 0.06 absorbed by the galactic interst ellar matter. The lack of excess absorption confirms that such absorpt ion is not a universal property of the high-redshift GHz-peaked spectr um (GPS) sources. From a comparison of the Lyman alpha and the metal a bsorption lines in the optical and UV bands, small amount of X-ray abs orption constrains the ionization state of the metal line system at z = 1.65 as [HI/H] > 2.5 x 10(-4) and [CIV/C] > 0.11 if the metal line s ystems have a metal abundance of 0.1 Z..