On the mass-ratio distribution of spectroscopic binaries with solar-type primaries

We use the radial-velocity complete study of the nearby G-type stars of Duquennoy and Mayor (1991) to derive the mass-ratio distribution of the short-period binaries. We include in the analysis only binaries with periods less than 3000 days and are left, therefore, with 23 systems. To analyze the data, we apply the recently published algorithm of Mazeh and Goldberg (1992). The result seems to fit with a uniform distribution, while the linear fit rises moderately toward high mass ratio. The analysis ignores any possible local features because of the small number of binaries in the sample. This work suggests that the mass-ratio distribution of the short-period binaries is substantially different from the distribution of the long-period binaries. Moreover, the mass distribution of the secondaries of the present sample is very different from the mass distribution of the single stars.