Context. Origin and evolution of blue stragglers in globular clusters is
still a matter of debate. Aims. The aim of the present investigation is to
reproduce the evolutionary history of four binary blue stragglers in four
different clusters, for which precise values of global parameters are known.
Methods. Using the model for cool close binary evolution, developed by one of
us (KS), progenitors of all investigated binaries were found and their
parameters evolved into the presently observed values. Results. The results
show that the progenitors of the binary blue stragglers are cool close binaries
with period of a few days, which transform into stragglers by rejuvenation of
the initially less massive component by mass transfer from its more massive
companion overflowing the inner critical Roche surface. The parameters of V209
from \omega Cen indicate that the binary is substantially enriched in helium.
This is an independent and strong evidence for the existence of the helium rich
subpopulation in this cluster.Comment: Accepted by Astronomy and Astrophysic
