The Distribution of Absolute Magnitudes among Stars Brighter than the Sixth Apparent Magnitude

i. The distribution of visual absolute magnitudes among stars of spectral types B, A, F, G, K, and M brighter than the sixth visual apparent magnitude is gixen in Table I. Variable stars and faint companions of binaries have been excluded from the analysis. The methods used in deriving the absolute-magnitude distribution are out- lined in Mt. Wilson Contr. Nos. 395 and 410. The distribution, when all spectral types are combined, is also given in Table I. The same data are shown graphically in Fig. i, in the form of twelve distribution-curves all reduced to equal numbers of stars. 2. Data are given by which the visual absolute magnitude can be reduced to bolo- metric absolute magnitude, or expressed in total power output. Fig. 2 shows the distribu- tion-curves expressed in bolometric absolute magnitudes. 3. Evidence is given for the existence of five chains or sequences connecting the differ- ent values of the absolute magnitude for which the frequencies have maximum values. These five chains are denoted by the terms main sequence, normal giants, faint giants, bright giants, and supergianis. Two gaps exist in the diagrams: the well-known gap sep- arating giants from dwarfs among the later types; the other separating the normal giants or the main sequence stars from the bright giants and extending from spectral type B3 to about G8. The latter gap represents possibly a region of instability con- nected with Cepheid variation and outbursts of novae