On the axial rotation of stars.

Abstract

view Abstract Citations (47) References Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS On the axial rotation of stars. Struve, O. Abstract Broad and shallow absorption lines in stellar spectra are shown to be due to axial rotation. The evidence is based upon the following facts: (a) the broadening depends upon wave-length, as required by the Doppler principle; (b) in spectroscop'ic binaries there is a distinct correlation between line width on one side and period and amplitude on the other; and (c) as was shown by Elvey, the contours of "dish-shaped" lines agree well with the theoretical shapes of lines of rapidly rotating stars. A survey of the spectra of stars of various types shows that rapid rotation is peculiar to the earliest spectral classes. The B- and A-stars display the greatest tendency toward rapid rotation. In the F's the proportion of rapidly rotating stars is smaller, and in classes G, K, and M no cases of rapid rotation have been observed in single stars. The effect of rotation upon the contours of components of spectroscopic binaries is discussed. In a Virginis the stronger component is found to rotate with an equatorial velocity of 200 km/sec., while for the fainter component the rotational velocity is not more than about 50 km/sec. This indicates a marked difference in the size of the com- ponents. The ratio of the radii is roughly 4 to i. The contours of lines in i~ Ursae Majoris suggest an equatorial velocity of about 200 km/sec. This single star is thus similar to the stronger component of a Virginis. Both stars are found to be stable, but the characteristic quantity w2/27r~yp is not far from the critical value where the Maclaurin ellipsoids of rotation lose stability. It is suggested that there is a transition between close s~ectroscopic binaries and rapidly rotating single -stars in the earliest spectral classes. Observations do not establish the direction in which this transition proceeds Publication: The Astrophysical Journal Pub Date: July 1930 DOI: 10.1086/143256 Bibcode: 1930ApJ....72....1S full text sources ADS |