Synchronization in binaries and age.

Analyzing the published data on field binary systems, we found that the periods below which the orbital and rotational motions are synchronized are systematically longer for evolved mainsequence stars than for ones near the zero-age main sequence. This is interpreted as showing that part of the tendency for tidal interaction to achieve synchronization occurs during the main-sequence lifetime of stars; the remainder occurred during contraction to the zero-age main sequence. Subject headings: stars: binaries - stars: evolution - stars: rotation