Rotational velocities of marginal metallic-line stars.

Projected rotational velocities are estimated for the 44 marginal metallic-line stars (Am:) listed by Cowley et al. These rotational velocities are slightly larger than for the more pronounced Am stars. The frequency distribution of equatorial rotational velocities of Am: stars shows little overlap with that of normal A5-A9 IV, V stars, and the overlap can be explained by differences in spectral classification. Thus rotation velocity will determine whether a star will have a normal (A5-A9) or abnormal (Am or Am:) spectrum, but will not determine whether the abnormality will be marked (Am) or marginal (Am:). Analysis of published data on binaries indicates that the Am: stars have the same high frequency of short-period binaries as do the Am stars and that in both cases the low rotational velocities are caused mostly by tendencies toward synchronous rotation in binaries. Subject headings: binaries - metallic-line stars - rotation, stellar