2007MNRAS.378..961P

The contact binary AW UMa has an extreme mass ratio, with the more-massive component (the current primary) close to the main sequence, while the low-mass star at q ~ 0.1 (the current secondary) has a much larger radius than a main-sequence star of a comparable mass. We propose that the current secondary has almost exhausted hydrogen in its centre and is much more advanced in its evolution, as suggested by St{ecedil}pie{nacute}. Presumably the current secondary lost most of its mass during its evolution with part of it transferred to the current primary. After losing a large fraction of its angular momentum, the binary may evolve into a system of FK Com type.