WISE color-magnitude diagrams (top panels) and color–color diagrams (bottom panels) for WISE objects within the field of view of XMM-Newton (~16′ from ρ Ophiuchi). Symbols are described in the legend in top left panel.In particular, we indicate by squares the objects with X-ray emission, and with crosses the objects with colors typical of normal photospheres (thus not classified as Class I, II or DD objects) that have X-ray detection and [4.6] < 12 mag. Their number are 22 and are associated with Class III stars.Cuts in magnitudes and colors are indicated by dotted lines, these correspond to: [4.6] − [12] = 0.8 mag, [3.4] − [12] = 1.1 mag, and [3.4] − [4.6] = 0.3 mag.Very few Class I and Class II YSOs compared to Class III stars are found in the FOV of XMM-Newton (cf. Fig. A.1).