1999A&A...346..481T

We report on a high dynamical range (>10^m) and high angular resolution (down to 0.2") search for low-mass components of early-type primaries in 7 intermediate-age (5Myr) multiple systems with the ESO 3.6 m telescope and the adaptive optics system ADONIS. The images were obtained in the J and SK bands with and without a coronographic mask of 2" diameter. The census is nearly complete in the angular separation range 1"-6", corresponding to linear separations of 200-1200AU, which have remained unstudied so far due to the intrinsic brightness of the massive primaries. The best detection limits are around K=15^m at 1" and K=19^m at 5" separation from the primary. In 13 fields of 12.5"x12.5" 6 new faint stars were detected. Their magnitudes and colours indicate that 2 of them can be physical low-mass components. The bright (K=11.2, J-K=1.2) companion to HD 108250 C at 2.17" has an IR excess and deserves further study. Several fields were explored without a mask; somewhat surprisingly, no new components at sub-arcsecond separations down to 0.2" were detected. The first order stability analysis indicates that the studied multiple systems are hierarchical at spatial scales of 40-1000AU. The data are briefly discussed in the light of the formation and evolution of multiple systems with massive primaries.