Statistical Identification of XMM-Newton Sources Using XID Database
  The XMM identification programme (XID) is accumulating Optical/IR images and spectra to identify thousands of XMM sources. The XID Database is the main repository of this data and permits easy selection and correlation of XMM X-ray and UV (from Optical Monitor) data with Optical/IR observations. Here we discuss the methodology and some preliminary results of statistical classification and identification of X-ray sources using the data from XID Database. We show that in the medium range of X-ray fluxes and optical/UV magnitudes most of XMM sources are AGNs in agreement with previous observations. Moreover, AGNs are mostly concentrated in a small area of (U/g-r)-HR2/HR3 plane. At present the confirmed identifications are too scarce to permit statistical identification of individual sources without taking their spectra. Nonetheless, these types of investigation help to better understand general characteristics of classes of astronomical objects in X-ray and its relation with optical/IR ones. 
Houri Ziaeepour and Simon Rosen