Assigned mass ratio of the 45 confirmed SB1s and estimated mass ratio of the 18 confirmed SB2s versus orbital period. For the SB1s we assumed an isotropic inclination distribution (see text). Bottom panel: period histogram. The solid red line shows the log-normal fit reported by Raghavan et al. (2010) to the period distribution of stellar binaries, scaled to best fit the histogram. Right panel: mass-ratio histogram.