X-ray observations of distant Abell clusters

We present results from a ROSAT HRI study of II distant (z similar to 0.2-0 .3) Abell clusters. We have performed a morphological analysis to search fo r and quantify substructure in the clusters. About 70 per cent of the sampl e shows significant evidence of substructure in the form of centroid shift or obvious X-ray clumps. We examine the clusters for the presence of coolin g flows, and determine the physical propel tics of the ICM by deprojecting the HRI data. Nine of the clusters have central cooling times less than the age of the system, in agreement with fractions determined from nearby, X-r ay-bright samples. Additional PSPC results are presented for four clusters in the sample, and ASCA results for six clusters. The temperatures and meta llicities for these distant clusters appear to be consistent with nearby cl usters of similar richness.