Study of 7 Massive Galaxy Clusters for the use as Gravitational Lensing Telescop

The most massive galaxy clusters are extremely valuable study objects for a widerange of astrophysical and cosmological studies. In our completed allskyXray cluster survey we found 7 rare massive galaxy clusters with masses above6.4e14 solar masses at z0.250.5 (the sweet spot for gravitational lensingstudies), which have not been observed in Xray pointed observations so far. Wepropose these objects for observations with XMMNewton and the three mostinteresting systems for HST observations, with a main goal to characterise theiruse as gravitational lensing telescopes. In addition these observations completean important sample of massive clusters to be used for a range of cosmologicalstudies. truncated!, Please see actual data for full text [truncated!, Please see actual data for full text]