We report infrared spectroscopic observations of a large , well-defined sample of main-sequence , single-lined spectroscopic binaries in order to detect the secondaries and derive the mass ratio distribution of short-period binaries .
The sample consists of 51 Galactic disk spectroscopic binaries found in the Carney & Latham high-proper-motion survey , with primary masses in the range of 0.6–0.85 M _ { \odot } .
Our infrared observations detect the secondaries in 32 systems , two of which have mass ratios , q = M _ { 2 } / M _ { 1 } , as low as \sim 0.20 .
Together with 11 systems previously identified as double-lined binaries by visible light spectroscopy , we have a complete sample of 62 binaries , out of which 43 are double-lined .
The mass ratio distribution is approximately constant over the range q = 1.0 to 0.3 .
The distribution appears to rise at lower q values , but the uncertainties are sufficiently large that we can not rule out a distribution that remains constant .
The mass distribution derived for the secondaries in our sample , and that of the extra-solar planets , apparently represent two distinct populations .