We report 272 radial velocities for 19 RR Lyrae variables. For most of the stars we have complete pulsation cycle. These data are used to determine robust center--of--mass that been compared values from literature in a search evidence binary systems. Center--of--mass were determined each star using Fourier Series and Template fits velocities. Our uncertainties $\pm0.16$ km s$^{-1}$ $\pm$2.5 s$^...

Burer has shown that completely positive relaxations of nonconvex quadratic programs with nonnegative and binary variables are exact when the binary variables satisfy a so-called key assumption. Here we show that introducing binary variables to obtain an equivalent problem that satisfies the key assumption will not improve the semidefinite relaxation, and only marginally improve the doubly nonn...