We investigate the distribution of Blue Straggler
stars in the field of three open star clusters.
The main purpose is to highlight the crucial role played by
general Galactic disk fore-/back-ground field stars, which
are often located in the same region of the Color Magnitude
Diagram as Blue Straggler stars.
We analyze photometry taken from the literature of 3 open clusters of
intermediate/old age rich in Blue Straggler stars, and which are
projected in the direction of the
Perseus arm, and study their spatial distribution and the Color
Magnitude Diagram.
As expected, we find that a large portion of the Blue Straggler
population in these clusters are simply young field stars belonging
to the spiral arm. This result has important consequences on the theories
of the formation and statistics of Blue Straggler stars in different
population environments: open clusters, globular clusters or dwarf galaxies.
As previously emphasized by many authors, a detailed membership
analysis is mandatory before comparing the Blue Straggler population
in star clusters against theoretical models. Moreover, these
sequences of young field stars (blue plumes) are potentially
powerful tracers of Galactic structure which require further consideration.