  We have analyzed photometric and spectroscopic data of a sample of 14
spatially resolved pre-main-sequence binaries (separations 0.6" to 1.7") in the
nearby (150 pc) low-mass star-forming regions of Chamaeleon, Lupus, and rho
Ophiuchi. The spectroscopic data have been obtained with the ESO New Technology
Telescope (NTT) at La Silla under subarcsec seeing conditions. All binaries
(originally unresolved) were identified as pre-main-sequence stars based on
their strong H-alpha emission -- which classifies them as classical T Tauri
stars -- and their association with dark clouds. One of the presumed binaries
turned out to be a likely chance projection with the `primary' showing neither
H-alpha emission nor Li absorption. Using the spectral A index (as defined by
Kirkpatrick et al. 1991), which measures the strength of the CaH band at
697.5nm relative to the nearby continuum, as a luminosity class indicator, we
could show that the classical T Tauri stars in our sample tend to be close to
luminosity class V. Eight out of the 14 pairs could be placed on an H-R
diagram. A comparison with theoretical pre-main-sequence evolutionary tracks
yields that for all pairs the individual components appear to be coeval within
the observational errors. This finding is similar to Hartigan et al. (1994) who
detected that two third of the wider pairs with separations from 400 AU to 6000
AU are coeval. However, unlike Hartigan et al. for the wider pairs, we find no
non-coeval pairs among our sample. Thus, the formation mechanism for a
significant fraction of the wider pre-main-sequence binaries might be different
from that of closer pre-main-sequence binaries. All of the latter appear to
have formed simultaneously.
