Photoelectric Studies.IV. Color-Luminosity Array for Stars in the Region of the Sun.

introduction.-Magnitudes and colors of 180 stars have been deterinined with the photomultiplier photometer attached to the Lick Observatory 12-inch refractor; an additional 8 stars have been observed with the Crossley reflector. Observations of the nearest stars.-The results of 245 observations of 78 stars within 14 parsecs of the sun are listed in Table 3. The color4uminosity array for these stars, derived from trigonometric parallaxes, is shown in Fignre 1. extension of the bright-dwarf sequence.-The mean absolute photographic magnitude of 17 subgiants is +3.60+0.13(A.D.) and is apparently independent of the color C2,, which ranges from +0.32 to +0.97 mag. It appears that the secondary components of Algol-type eclipsing stars are subgiants. Dwarf and sequences.-The dwarf and subdwarf sequences intersect twice, once near C2, = +OW55andagainnearC2, = + . Blite-dwarf and bright blue-dwarf sequences.-It appears that at least some of the fine structure in that portion of the color-luminosity array populated by the A-type stars probably is reflected in the spectra of these stars. Rotational velocity.-The bright blue-dwarfs, which include the spectrum variables, appear to rotate more slowly, in the mean, than do the blue-dwarfs. Conclnding re'narks.-The stars near the sun populate the same sequences in the color-luminosity array that are found in the four galactic clusters, Hyades, Pleiades, Coma Berenices, and Ursa Major.