The binary nature of the CH stars

Radial velocity observations are presented that indicate that many CH stars are binary systems. This is an important result for several reasons. (1) CH stars are Population II objects and found on the giant branches of several globular clusters; these are populations usually thought of as deficient in binary systems. (2) Their binary nature probably links them to the Population I Ba II stars which are also binaries. (3) Stars used to determine a mass-to-light ratio of the Draco dwarf spheroidal galaxy are probably CH stars which may give a spuriously high velocity dispersion. (4) CH stars are found only in relatively loosely concentrated systems, probably linking central concentration of clusters with their ability to retain soft binaries.