A Multiplicity Survey of the Rho Ophiuchi Molecular Clouds
  We present a volume-limited multiplicity survey with magnitude cutoff (K =< 10.5 mag) of 158 young stellar objects located within or in the vicinity of the Rho Ophiuchi Dark Cloud. With exception of eleven already well observed objects, all sources have been observed by us in the K-band with 3.5m telescopes by using speckle techniques. The separation range covered by our survey is [0.13'',6.4''], where the lower limit is given by the diffraction limit of the telescopes and the upper limit by confusion with background stars. The multiplicity survey is complete for flux ratios => 0.1 (=< 2.5 mag) at the diffraction limit. After taking the background density into account the degree of multiplicity is 29.1%+-4.3% and thus only marginally higher than the value 23.5%+-4.8%derived for the given separation range for the main-sequence solar-like stars in the solar neighbourhood (Duquennoy & Mayor 1991). We discuss the implications of these findings. 
Thorsten Ratzka (1), Rainer Koehler (1,2), Christoph Leinert (1) ((1)   Max-Planck-Institute for Astronomy Heidelberg, (2) S...