A VIMOS spectroscopy of photometric variables and straggler candidates   in omega Centauri
  We report a spectroscopic study of 19 photometric variables and 55 blue, yellow and red straggler candidates in the field of omega Centauri. We confirm the cluster membership of 18 variables and 54 straggler candidates. Velocity variations are detected in 22 objects, and another 17 objects are classified as suspected of being velocity-variable. Velocity data of 11 photometric variables phase with their photometric periods, however none of these objects has a mass function indicating the presence of a massive degenerate component. Based on both photometric and spectroscopic data we find that the fraction of binaries among blue stragglers may be as high as 69 per cent. 
M. Rozyczka, J. Kaluzny, P. Pietrukowicz, W. Pych, M. Catelan and C.   Contreras
astro-ph.SR