What a local sample of spectroscopic binaries can tell us about the field binary population.

We study a volume-limited sample of spectroscopic binaries (SBs) to find, in absolute terms, the period P, primary mass m1, and mass ratio q (=m2/m1) distributions of the local population of field binaries. The sample was collated using the Batten 8th catalogue of SBs, other data of R F Griffin, and the Hipparcos catalogue (for distances and to refer numbers of objects to fractions of the local stellar population as a whole). We use the better-known group of double-lined SBs (SB2s) to calibrate a refined Monte-Carlo approach to modelling the q distribution of the single-lined SBs (SB1s) from their mass function f(m) and primary mass m1. The total q distribution is then found by adding the observed SB2 q distribution to the Monte Carlo SB1 q distribution. By comparing subsamples of different ranges in parameter space, we also address the important questions of completeness and parameter-specific biases. Our results confirm a clear peak in the q distribution of field binaries near unity. We also note a substantial fraction of systems with intermediate to long periods. These are objects that will interact when the primary evolves onto the RGB or AGB, with statistically significant consequences for the mass distribution of white dwarfs