XMM-Newton Snapshots of Unusual Gravitational Lenses

We propose XMMNewton observations of three very unusual strong gravitationallenses discovered in the SDSS. All three lenses appear to be high massconcentration groups/galaxies with extreme properties. Hall.s Lens is anopticallyunimpressive group for which the derived mass inside the 78 kpcEinstein radius is an astounding >1e14 solar masses. The Cosmic Horseshoe Lensand the Cassowary 20 Lens are giant elliptical galaxies with extremely largestellar velocity dispersions and absolute optical magnitudes, both of which arecandidates for the most massive galaxy in the Universe. We propose modestexposures of these intriguing systems to obtain luminosities and temperatures toidentify which are worthy of longer followup observations. truncated!, Please see actual data for full text [truncated!, Please see actual data for full text]