A Detailed Look into the Blue Stragglers of the Old Open Cluster NGC 188

The WIYN Open Cluster has completed an extensive radial-velocity study of the 7 Gyr open cluster NGC 
188, providing 10,000 measurements of 1200 stars, including 21 blue stragglers. We have found for the blue 
stragglers: a hard binary frequency of 76%, a typical orbital period of 1000 days, a typical secondary mass of 
0.5 Mo, modestly rapid rotation, and a bimodal spatial distribution. We suggest that these results all point to a 
primary formation channel of mass transfer from asymptotic branch giants. We also discuss specific cases 
with signatures of dynamical influences and perhaps collision origins. Finally we will present initial results 
from Hubble Space Telescope ultraviolet imaging of these blue stragglers in search of white dwarf 
companions.