Key points are not available for this paper at this time.
Surveys of M dwarfs within 20 pc are examined to determine the incidence of stellar companions. Observational data are drawn from high-quality surveys, including IR-array imaging, precise velocities, IR speckle interferometry, and visual imaging, and their respective incompleteness is determined. The number of companions per AU of semimajor axis is computed and found to decline monotonically toward larger semimajor axes. The period distribution exhibits a unimodal broad maximum with a peak in the range 9-220 yr, corresponding to separations of 3-30 AU, similar to that for G dwarf binaries. Fifty-eight percent of nearby M dwarf primaries are found to be single, and 42 +/- 9 percent have companions. The M-dwarf binary frequency is lower than that for G dwarfs (about 57 percent), owing partly to the smaller range of companion masses included, i.e., companions less massive than the M- or G-type primary.
Fischer et al. (Tue,) studied this question.