K_s vs. H − K_s diagram of the near-IR counterparts with measurements in the H and K_s bands. The open triangle refers to Mir-4 in DNS and the rest of the symbols are as in Fig. 3. For reference, the almost vertical solid line delineates the zero-age main sequence (ZAMS; Drilling & Landolt 2000) for d = 1.34 kpc and A_V = 1.0.The dashed lines are the reddening vectors of length A_V = 40 for B0 ZAMS stars. The arrow represents the average slope of the near-IR emission excess caused by disks around YSOs, as determined by López-Chico & Salas (2007).