The BRASS-SIMBAD cross-correlation and the set of optical identifications presented in this paper show that careful selection on multi-wavelength parameters can help to disentangle the various populations of X-ray sources accounting for the ROSAT survey.
In order to reach the state at which one can really compute probabilities of identification of any source with the main classes of X-ray emitters, large source samples have to be completely identified using catalogue data and proper multi-wavelength observations. In the galactic plane, the level of screening of the extragalactic population by absorption and in general galactic latitude are key parameters. Ideally, selected test samples should be accumulated at various latitudes in order to properly handle likelihoods of identification such as for instance outlined in Sterzik et al. (1995).
Among the 93 selected sources, we find a likely counterpart to the X-ray source in 76 cases. With 39 identifications, active coronae again dominate source count. However, X-ray selection enhances the number of non-coronal identifications and we report on 25 new AGN, 6 new CVs, 2 new white dwarfs and a new Be/X-ray binary.
Our programme of optical identification of X-ray selected RGPS sources is going on and new identifications will be reported in a forthcoming paper. Statistics of identifications in the various selected samples will also be presented at this occasion.
Copyright The European Southern Observatory (ESO)