Combined Light and Velocity Measurements of the Variable Star 12 Lacertae  

Abstract

DURING the summer and autumn of 1956, fifteen observatories co-operated in securing brightness and radial velocity measurements of the variable star 12 Lacertae. The variable belongs to the group of Beta Canis Majoris stars, consisting of about a dozen known members, which vary in light and radial velocity. Stars of this group have spectral types B2, B3, and luminosity classification II–IV, and their periods range between 0.15d. and 0.25d. The amplitudes of the light curves are small, of the order of some tenths of a magnitude. The light and radial-velocity curves are often not quite regular, showing that they are the result of several components. Thus the star 12 (DD) Lacertae has a principal period of 4h. 38m. and a secondary period of 4h. 44m., while recently a third component of 3h. 45m. has been found, and a fourth one of 3.9h. has been suggested. The periods occur in the variation of both the light and the radial velocity. The presence of components with closely similar periods and amplitudes of the same order produces the beat phenomenon, characteristic of a number of stars of the Beta Canis Majoris group. The occurrence of this relatively large number of components produces the observed complexity of the light and velocity curves.