Close binary components of T 26 (left) and T 31 (middle), i.e., the southern component in both panels, could not be spatially resolved with NACO K_s -band imaging despite the good FWHM of ~0070. From the apparent elongation we estimate that the separation of T 26 BaBb is not much larger than 005 and just at the FWHM for T 31 BaBb. The K_s -band image of T 33 (right) shows the newly discovered faint tertiary component close to T 33 B. The physical association of all three components is discussed in Sect. 3.5. Image stretches and orientation are the same as in Fig. 1.