Characterization of blue straggler stars in the galactic field

Blue straggler stars (BSS) are main sequence stars that exhibit an apparent evolutionary delay over the 
region where they are found. They were initially identified in the main sequence of globular clusters above the 
turnoff point. Since then, they have been found in many different stellar environments: globular and open 
clusters, near dwarf galaxies, and also in the field of the Galaxy. The main goal of this work is to build a large 
sample of BSS in the galactic field region. In order to accomplish this task, classical methods of separation 
of BSS from BHB stars were compared with new proposed restrictions based on their atmospheric 
parameters, which are estimated by the SEGUE Stellar Parameter Pipeline (SSPP). The latter procedure 
allowed to include stars with magnitudes g > 18, not handled by traditional methods when <S/N> ratio is 
smaller than 9. The selection methods gathered a sample of BS 8001 stars. These stars were kinematically 
analyzed through their radial velocities. The results suggest that many of them (~1000) can have 
extragalactic origin, associated with Sagittarius stream.