A Spectroscopic Study of Two Southern B-Type Variables

Abstract

New spectra of the β CMa variable α Lupi taken in 1965 show an outflow of hydrogen relative to He I and metal lines in nearly all phases. This outflow, however, is found to be smaller by a factor of 3 than the reported outflow in 1960. Furthermore, the velocity amplitude has decreased to about 16 km/s. The velocity of β Cen varies with a very short period of between 3 and |$3\frac12$| hours (with the amplitude varying between 10 and 20 km/s) as well as with one which may be more than a year. Together with the spectral type (B2 II) this suggests a β CMa star in a binary system. The extreme width of the spectral lines is unusual for a β CMa star, and the period is very short for a β CMa star. It is postulated that β Cen is intermediate in type between the usual β CMa variables and ‘normal’ B stars.