ARE WIDE PRE-MAIN-SEQUENCE BINARIES COEVAL

We have observed a sample of 39 wide (projected separations 400-6000 A U) pre-main-sequence binary pairs spectroscopically and with optical a nd near-infrared images. The observations enable us to place 26 of the pairs in an H-R diagram and to determine masses and ages of the prima ry and secondary according to three sets of pre-main-sequence evolutio nary tracks. In two-thirds of the cases the primary and secondary lie along the same isochrone to within the observational errors. However, real age differences appear for about one-third of our sample pairs-th ere is no set of nonintersecting theoretical isochrones that can make the primary and secondary have the same age for all pairs in our sampl e. In the cases where there are significant age differences between th e component stars, the less massive star is usually younger than the m ore massive star. There is no correlation of the age differences with the presence or absence of accretion disks around the young stars. Hen ce, while disk accretion may affect the evolutionary tracks of the pre -main-sequence stars H-R diagram, we see no clear evidence of this eff ect among the pairs in our sample. The age differences also do not dep end systematically on the apparent separation, the mass ratio, or the ages of the stars.