Late Type Stars in the Michigan Spectral Catalogue: Conflation of Luminosity Classes IV and V

Abstract

While computing a comprehensive set of mean values and uncertainties for key stellar parameters, particularly absolute V magnitudes and (B − V)0 colors, for main sequence stars drawn from the Michigan Spectral Catalogue (MSC), we discovered a significant co-mingling between luminosity classes IV and V in spectral types G8 and later. Indeed, among the ∼200 nearby K0 dwarfs examined, as many 20% may be misclassified subgiants. We present data to substantiate this view and offer some commentary on the observed conflation of these two luminosity classes. We conclude that while the MSC is a unique and largely reliable database for spectral classifications of predominantly southern hemisphere HD stars across the H-R diagram, it does contain some ambiguities in the assignment of luminosity classes IV and V among the late G and early K stars of which users should be aware.