THIRTY-SEVEN NEW PECULIAR AND METALLIC-LINE A STARS

Abstract

A survey of fifty objective-prism plates taken with the Curtis Schmidt telescope at The University of Michigan has revealed a number of hitherto unrecognized peculiar and metallic-line A stars. The majority of the plates covers a band in Cygnus about 12° wide lying along the galactic equator from lu = 70° to· lu = 90°. A few additional plates not in this region have also been examined. Each plate has a diameter of 5° with high-quality images to the extreme edge. The 10° prism was used, giving a dispersion of 110 Â/mm at Ηγ. Finally several stars, previously suspected by one of us1 as peculiar on the basis of very low-dispersion objective-prism spectra have been included when appropriate. Slit spectrograms were obtained for all stars suspected of being either of type Ap or Am with either the classification spectrograph on the 40-inch refractor at Yerkes Observatory or the 110-mm Cassegrain spectrograph on the McDonald Observatory 82-inch reflector. Both spectrographs give a dispersion of 125 Â/mm at Ηγ. No peculiar stars other than A stars have been included in this paper. Table I lists the metallic-line A stars found, together with their positions and magnitudes as given in the Henry Draper Catalogue. Stars too faint to be listed in the HD are designated by Β D numbers and magnitudes. The peculiar A stars are listed in Table II. In both tables the semicolon indicates weak characteristics of the type indicated. In a few cases several objective-prism plates of the peculiar stars showed marked variations and these are indicated as probable spectrum variables. Numerous stars listed by Walther2 and Slettebak3 were noticed but are not included in this tabulation.