The manganese stars

Abstract

Ultraviolet spectrograms of 194 middle and late B-type stars were obtained in a search for Mn stars. The 24 Mn stars found in this search lay within the limited temperature range from 0.33 to 0.48. Their observed rate of incidence and rotational velocity distribution substantiate the hypothesis that the Mn stars constitute a considerable fraction of the slowly rotating stars in this temperature range. If the atmospheres of these stars are sufficiently stable for diffusion processes to be effective, then it also becomes possible to account for the temperature range in which the Mn overabundance occurs.