The Spectra and Rotational Velocities of the Bright Stars of Draper Types B8-A2.

Abstract

view Abstract Citations (175) References Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS The Spectra and Rotational Velocities of the Bright Stars of Draper Types B8-A2. Slettebak, Arne Abstract Spectral types and rotational velocities of 179 stars of Draper types B8-A2 brighter than the fifth magnitude have been determined. Spectral types and luminosity classes were assigned to all normal stars on the Morgan-Keenan-Kellman system of classification. Equatorial rotational velocities multiplied by the sine of the inclination of the axis of rotation (v sin i) were determined for all stars by comparing observed profiles of the Mg II 4481 line in each star with a set of profiles computed by the graphical method of Shajn and Struve. The B8-A2 stars divide into a number of subgroups from the point of view of axial rotation: the supergiant, metallic-line, and peculiar A stars have small axial rotation; the normal stars of intermediate luminosity have moderate axial rotation (v = 93 km/sec); and the normal main-sequence stars have the largest axial rotation (v = 177 km/sec). The only comparison of the B8-A2 main-sequence stars with stars of other spectral types possible at this time is with the Be stars: the latter have about twice the average axial rotation of the B8-A2 main-sequence stars. A number of emission-line stars and spectroscopic binaries included in this study are discussed. The variation of equlvalent width of Mg II 4481 with spectral type is shown. Three stars were found to exhibit a general weakening of the spectral lines; it is suggested that these stars lie somewhat below the main sequence. Publication: The Astrophysical Journal Pub Date: January 1954 DOI: 10.1086/145804 Bibcode: 1954ApJ...119..146S full text sources ADS | data products SIMBAD (181)