PublisherThe University of Arizona.
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AbstractFifty-five spectra at 39 Å/mm are used to determine rotational velocities for 25 stars in the galactic cluster Messier 7 (NGC 675). Compared to field stars, the brighter (-1.4 < Mᵥ < +1.0) cluster stars have very low rotational velocities ( ≈ 91 km /sec), whereas the fainter ( +1.2 < Mᵥ < +2.3) stars have a rather high of about 196 km /sec. The sample is probably incomplete at the fainter magnitude ranges. The frequency of spectroscopic binaries among the earlier type stars is believed to be high, but the of the brighter group remains low even after removal of known binaries. Three Ap or composite stars are found. The rotational velocity characteristics of Messier 7 are compared with those of other clusters. Low for brighter cluster stars is not a unique phenomenon.
Degree ProgramGraduate College