Radial Velocities, Spectral Types, and Luminosity Classes of 820 Stars.

Abstract

Radial velocities and spectral and luminosity classes are given for 820 stars of types F-M in the HD photographic magnitude range of 8.58.6. The velocities were determined with a one-prism dispersion of 75 A/mm and were reduced to the Lick system by means of observations of 260 brighter stars having velocities based on three-prism Mills spectrograms. Two plates were obtained for two-thirds of the stars, and three plates for most of the remaining stars. The average probable error is + 3.6 km/sec for one plate of unit weight. Comparison of velocities in common with Victoria and Mount Wilson determinations indicates that the systematic errors are satisfactorily small, of the order of 1 km/sec or less. The spectral-class estimates agree well with the I'D, Yerkes, and Mount Wilson classifications, except among the early F stars, where the Lick estimates average somewhat later. The luminosity- assignments are on the Yerkes system, and those for the bright-star velocity standards show no appreciable deviation from the classes given by Morgan, Keenan, and Kellman in thefr Atlas of Stellar Spectra. Because of the basis for selection, statistically significant data on the luminosity function are obtained only for the class IV stars (subgiants). The frequency maximum for these stars appears to be at , and practically no stars are found later than K1 or K2, as previously noted by several other investigators. Solar-motion solutions for giants (III), subgiants (IV), and main-sequence dwarfs (V) give results that show hardly any real differences depending on luminosity: solar motions of 24, 23, and 19 km/sec for class III, IV, and V stars, respectively, toward essentially the same apex at ao = 280 and s = +4421 . No significant K-terms were found, and the mean residual velocities show the usual tendency to increase with advancing spectral class. Two solutions including a galactic-rotation term were made for the giants. The first, for 348 class III stars (including a few Il-Ill and III-W) and with assumed values of K = 0 and L0 = 325 , gave rA = 4.2 + 1.9 km/sec. The second, for 147 class III stars in the galactic zone limited by b = +20 and based on the residual velocities, gave = 6.7 1 1.5 km/sec and L0 = 7 . These results show that the giants included in this material participate in the differential galactic rotation characteristic of the region around the sun.