Are all metallic-line stars binaries? Observations of three stars in Coma.

A radial-velocity study at coude' dispersion of three metallic-line stars in Coma shows 17 Com B to be a spectroscopic binary with a period of 68.290 days. No evidence is found for duplicity in the two other stars observed. Five Am stars in Coma have now been studied at high dispersion, and only two of these have been detected as binaries. Thus there are strong grounds for believing that at least a few Am stars are single; a conclusion consistent with the suggestion that slow rotation alone is the necessary and sufficient condition for the Am phenomenon. Subject headings: binaries - metallic-line stars - open clusters