PKS-2351-154 - A HIGH-REDSHIFT QUASAR WITH VARIABLE X-RAY-ABSORPTION

The ROSAT PSPC spectrum of the high-redshift quasar PKS 2351-154 (z = 2.671) shows absorption which is significantly larger than the Galacti c value in the direction of the source. This absorption is variable on time scales of less than or equal to 1.5 years corresponding to 0.41 years in the quasar's rest frame. In addition, we find indications tha t absorbing material is located at high redshifts. Optical observation s revealed a CN system with z(abs) approximate to z(em). We conclude t hat this CIV system is related to the variable X-ray absorption. The v ariations can be explained in terms of changes in the ionization state of the absorbing material. In that case, the CIV system could be vari able, too, and it could be close to the active galactic nucleus itself .