The aim of our work Elyiv et al. (2013) was to identify gravitational lens candidates among 5500 optical counterparts of the X-ray point-like sources in the medium-deep∼ 11 deg2 XMM -LSS survey. We have visually inspected the optical counterparts of each QSOs/AGN using CFHTLS T006 images. We have selected compact pairs and groups of sources which could be multiply imaged QSO/AGN. We have measured the colours and characterized the morphological types of the selected sources using the multiple point spread function fitting technique.
We found three good gravitational lens candidates: J021511.4− 034306, J022234.3− 031616 and J022607.0− 040301 (fig. 13) which consist of pairs of point-like sources having similar colours. On the basis of a colour–colour diagram and X-ray properties we could verify that all these sources are good QSO/AGN candidates rather than stars. Additional secondary gravitational lens candidates are also reported.