Despite the identification of counterparts in the 2MASS survey, nothing can be definitely said regarding the classification of these sources. Nevertheless some deductions can be made from the plots. Comparing Figure 4.10 with Figure 4.9 we can see that most of the unidentified sources lie within the central QSO ‘zone’ defined by 0.5 < W1 – W2 < 1.8 and 2.25 < W2 – W3 < 4. Now looking at the identified hard x-ray sources from the same region it can be seen that almost all of the sources are BLAGN with the exception of a single star and two NELG. Now if we consider the region 1.0 < W1 – W2, it can be seen that all the x-ray sources in that region are BLAGN (Broad Line Active Galactic Nuclei). So it can be said with fair certainty that the unidentified sources in that region are BLAGN as well. As for the sources outside the locus it can’t be said with any degree of certainty about their classification without the available spectra.
