MK SPECTRAL TYPES FOR 185 BRIGHT STARS

Abstract

A program has been initiated at the Yerkes Observatory to determine more accurately the mean direction of the interstellar magnetic field in the vicinity of the sun by observing the interstellar polarization of bright nearby stars in the direction of the galactic poles and in the galactic plane. Spectroscopic parallaxes are needed for the program stars. Spectrograms have been taken therefore for those stars for which no MK spectral types are given either in the Catalogue of Bright Stars (HofBeit 1964) or the Catalogue of Stellar Spectra Classified in the Morgan-Keenan System (Jaschek, Conde, afnd de Sierra 1964). Since accurate spectral types in the MK system may be useful for other investigations as well, the spectral classifications are published in advance of the extended polarimetrie program. All spectrograms were obtained on Kodak Ila-O plates with the Cassegrain spectrograph and the 110-mm camera on the 82-inch reflector at the McDonald Observatory. The dispersion was about 120 A/mm at Hy. Spectrograms of 54 standard stars of the MK system from the revised list of 1953 were obtained during the same observing period. The standard spectra and the criteria of the Yerkes Atlas of Stellar Spectra (Morgan, Keenan, and Kellman 1943) were used to determine the spectral types. When the line ratios were intermediate between those of two standards, interpolated spectral types were given. No attempt was made to determine luminosity classes for peculiar spectra. Spectra with only slight deviation from standard spectra were labeled (p)- The luminosity of these (p)-stars is assumed to be not much different from ordinary stars of corresponding spectral type. The results of the classification are given in Table I. An asterisk following the HR number refers to a remark on the classification at the end of the table.