ИСТИНА

We present a method to search for off-nuclear X-ray sources in the XMM-Newton source catalog by cross-matching it with large spectroscopic galaxy catalogs (e.g. SDSS) using special non-central match condition. Known distances to expected host galaxies then allow to select X-ray sources from their outskirts within specific luminosity range, 10^{41} < L_{X} < 10^{44} erg s^{-1}. We attempt to discard various possible contaminating foreground and background object classes such as AGN, BL Lacs, Galactic stars and compact objects by analyzing broadband radio-to-X-ray spectral energy distribution properties of selected sources available from other public wide area surveys. As an early result of our method we present several candidates to hyperluminous X-ray sources with high X-ray-to-optical flux ratios that can hardly be explained by invoking any conventional object type.