086396

The dark matter self-interaction cross-section depends on velocity and their model claims to explain observations from dwarfs to massive clusters. We need to test these models at galaxy group scales comma where no usable data exist. Analysis from even a single system will be valuable. We propose a 40 ksec observation of a massive galaxy group HSC J1441-0053 to put the first constraints in this mass range. This is no ordinary openParlensingclosePar galaxy-group -it has lensed images of different sources at varying angular radii which allows us to get more accurate constraints on the inner density profile than any other openParnon-closePar lensing galaxy groups at similar masses and redshift. The accurate centroid determination and independent mass estimation with XMM are vital to derive accurate mass model.