  The central regions of six Galactic Globular Clusters (GGCs) (M3, M80, M10,
M13, M92 and NGC 288) have been imaged using HST-WFPC2 and the ultraviolet (UV)
filters (F255W, F336W). The selected sample covers a large range in both
central density and metallicity ([Fe/H]). In this paper, we present a direct
cluster-to-cluster comparison of the Blue Stragglers Stars (BSS) population as
selected from (m_{255},m_{255}-m_{336}) Color Magnitude Diagrams (CMDs). We
have found:(a) BSS in three of the clusters (M3, M80, M92) are much more
concentrated toward the center of the cluster than the red giants; because of
the smaller BSS samples for the other clusters we can only note that the BSS
radial distributions are consistent with central concentration; (b) the
specific frequency of BSS varies greatly from cluster to cluster.
  The most interesting result is that the two clusters with largest BSS
specific frequency are at the central density extremes of our sample: NGC 288
(lowest central density) and M80 (highest). This evidence together with the
comparison with theoretical collisional models suggests that both stellar
interactions in high density cluster cores and at least one other alternate
channel operating low density GGCs play an important role in the production of
BSS. We also note a possible connection between HB morphology and blue
straggler luminosity functions in these six clusters.

Astrophysics