Astronomy and astrophysics vol:359 issue:2 pages:552-562
Using the model by Keppens (1997), we investigate the angular momentum (AM) evolution in asymmetric binary star systems from Zero-Age Main Sequence times until at least one component has ascended the giant branch. We concentrate on stars ranging in mass from 0.9 M. - 1.7 M. in almost synchronous, short period systems (P-orb < 9 days). We address synchronization and circularization by tidal interaction, allowing for structural evolution and stellar winds. A Weber-Davis prescription is used to quantify the wind influence, thereby accounting for changes in its acceleration mechanism from the interplay of the evolving thermal-magneto-centrifugal effects. We identify a scenario for fast in-spiraling components with d In P-orb/dt similar or equal to -O(10(-8)) which is primarily driven by fast structural evolution as the heaviest component ascends the giant branch. This leads to the formation of contact systems, which ultimately coalesce and form FK Comae-like objects on relatively short timescales due to the continuing expansion of the primary.