Comparison of CEMP stars (filled symbols) and CH stars (open symbols) in the period – eccentricity (P − e) diagram. Dwarf carbon stars are represented by circles, giant carbon stars by squares (CEMP stars with unknown gravities in Table 4 are assigned giant status by default). For comparison, the sample of low-metallicity giants studied by Carney et al. (2003) is represented with red triangles.