Radial velocities and membership in Pal 13

We triple the number of spectroscopically confirmed members, including many repeat velocity measurements. Palomar 13 is the only known globular cluster with possible evidence for dark matter, based on a Keck/High Resolution Echelle Spectrometer 21 star velocity dispersion of {sigma}=2.2+/-0.4km/s.

We reproduce this measurement, but demonstrate that it is inflated by unresolved binary stars. For our sample of 61 stars, the velocity dispersion is {sigma}=0.7^+0.6^_-0.5_km/s. Combining our DEIMOS data with literature values, our final velocity dispersion is {sigma}=0.4^+0.4^_-0.3_km/s.