A LUNAR OCCULTATION AND DIRECT IMAGING SURVEY OF MULTIPLICITY IN THE OPHIUCHUS AND TAURUS STAR-FORMING REGIONS

We present an IR lunar occultation and direct imaging search for compa nions in the Ophiuchus star-forming region and update a similar search of the Taurus region. The search is sensitive to companions in the an gular separation range 0.005-10 ''. In Ophiuchus we surveyed 35 young star targets; this sample contains at least 10 binaries, two triples, and one quadruple. Ten of the companion stars are newly discovered. In Taurus, the survey now includes 47 systems among which there are at l east 22 binaries and four triples. Only two companion stars are newly identified because there is strong overlap with prior work. All the tr iples and quadruple are hierarchical. The observed binary frequency in Ophiuchus, in the 3-1400 AU range of separations, is at least 1.1 +/- 0.3 that of the nearby solar-like stars. This value is a lower bound because we make no corrections for incompleteness. In Taurus, in the s ame range of separations, the observed binary frequency is at least 1. 6 +/- 0.3 that of the nearby solar-like stars. This value extends Ghez et al.'s (1993) and Leinert's et al.'s (1993) determination of an exc ess binary frequency to 3 AU separation. We used the WT/TT type and th e K-L color index to distinguish between systems with and without inne r disks. We find no convincing difference in the binary frequency or d istribution of separations of the systems with and without inner disks . The 1.3 mm continuum emission of the single systems exceeds that of the multiples suggesting that their extensive outer disks are more mas sive. The specific angular momenta of the binaries overlap those of mo lecular cloud cores measured by Goodman et al. (1993).