Rotational velocities of B8-A2 stars.

Abstract

view Abstract Citations References Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS Rotational velocities of B8-A2 stars. Slettebak, Arne Abstract As a part of a larger program of measuring rotational velocities for the brighter early-type stars, spectrograms of B8-A2 stars brighter than the fifth magnitude are now being obtained at the Perkins Observatory. The object of this investigation is to provide a catalogue of rotational velocities and make a statistical study of axial rotation in stars of this group. Spectrograms of over three-fourths of the 150 stars included have been obtained with the two- prism spectrograph attached to the Perkins 6~-inch, giving a dispersion of 25 A/mm at H~. The graphical method of Shajn and Struve,' in which a line contour from a non-rotating star is used to derive rotationally-broadened line profiles, is being employed. Comparison of the contour as observed in a rotating star with the set of computed contours gives a lower limit to the star's rotational velocity. In this investigation, the N4481 line of MgII has been chosen, with Sirius as the standard non-rotating star. At least two spectrograms of each star are being taken, and the internal consistency of the measures appears to be good. The agreement between the Perkins rotational velocities and those obtained by Elvey,2 for 13 stars, is satisfactory, the Perkins results running generally somewhat higher because of the inclusion of limb darkening in the construction of the computed line profiles. The largest rotational velocity measured to date in this group is 340 km/sec for the B8 main-sequence star a Leonis. The shell star 14 Comae Berenices, underlying star of spectral type A~, which is presumably close to the critical rotational velocity at which material is thrown off at the star's equator, has a measured V sin ~ of 220 km/sec, relatively small as compared with the B-type shell stars. A number of giants among the early A's exhibit relatively large axial rotation, among them the standard A3 Il-Ill star, ~ Ursae Minoris, which has a measured rotational velocity of 180 km/sec. I.M. N. 89, 222, 1929. 2.Ap. J. 71, 221, 1930. Perkins Observatory, Delaware, Ohio. Publication: The Astronomical Journal Pub Date: April 1951 DOI: 10.1086/106599 Bibcode: 1951AJ.....56Q.141S full text sources ADS |