Contribution a l'etude des spectres composites. III. Les binaires spectrales, classe intermediaire entre les binaires visuelles et les binaires spectroscopiques ?

The results of a study of distribution of the logarithm of the semi-major axis of the relative orbits of 180 visual binaries are presented. The study was undertaken to establish the existence of an intermediate class of binaries between spectroscopic and visual binaries. The binaries examined were all within 33 pc from the sun. A Gaussian distribution was obtained for the visual and atrometric binaries, while an irregular distribution was present with the spectroscopic binaries. Least squares calculations produced an average separation of 2.4 AU. It is suggested that the small separation distance creates difficulties in detecting spectroscopic binaries, although speckle interferometric techniques may be developed enough to determine if a significant number of the objects are located near the earth.