Orbital parameters of 341 new binaries

Across periods of 100-1500d and at q>0.1, we measure the binary fraction of current A/F primaries to be 15.4%+/-1.4%, though we find that a large fraction of the companions (21%+/-6%) are white dwarfs in post-mass-transfer systems with primaries that are now blue stragglers, some of which are the progenitors of Type Ia supernovae, barium stars, symbiotics, and related phenomena. Excluding these white dwarfs, we determine the binary fraction of original A/F primaries to be 13.9%+/-2.1% over the same parameter space.

Combining our measurements with those in the literature, we find the binary fraction across these periods is a constant 5% for primaries M_1_<0.8M_{sun}_, but then increases linearly with logM_1_, demonstrating that natal discs around more massive protostars M_1_>~1M_{sun}_} become increasingly more prone to fragmentation. Finally, we find the eccentricity distribution of the main-sequence pairs to be much less eccentric than the thermal distribution.