Erratum: Studies of Stellar Rotation. I. Comparison of Rotational Velocities in the Hyades and Coma Clusters.

Abstract

The quantity {V sin i), which gives the mean projected rotational velocity as a function of absolute magnitude, is derived for the Hyades and Coma clusters, based on single stars and members of binary systems with periods over 10 days The color-magnitude diagrams for both clusters are considered de novo, and are based only on single stars, the primary components of single-lined spectroscopic binaries, and resolved visual binaries Rotational velocities are obtained with high spectral resolution for virtually all stars down to spectral type GO V. The following conclusions are reached: (1) The frequency of binaries and of Am stars is approximately the same in the two clusters. (2) The function {V sin î) is the same for both clusters when the two Ap stars of Coma are omitted. (3) Allowing for evolutionary and abundance effects, one finds that the rota-tional velocities of Hyades (and Coma) stars do not differ significantly on the average from those of the field stars. Further work at high resolution for field F-type stars is needed, however. In connection with these results, the following questions are also discussed: (1) Is there a preferential direction of rotational axes for stars in clusters? (2) What is the shape of the frequency distribution about the mean for rotational velocities of stars in the Hyades and Coma? (3) How is the rotational angular momentum per unit mass distributed as a function of mass, and is it the same in the two clusters? It is possible to give fairly definite answers to these questions, except for the last part of No. 3, which requires a definitive determination of the mass-luminosity relation for Coma.