Multi-Epoch Radial Velocities of a Volume-Complete Sample of Mid-to-Late M Dwarfs Within 15 Parsecs

The nearest mid-to-late M dwarfs represent a tremendous opportunity to study the internal structure and magnetic field generation of fully convective stars, and are also the only viable targets for near-future studies of the atmospheres of transiting terrestrial exoplanets. For the past 6 years we have gathered multi-epoch, high-resolution spectra of a volume-complete sample of 413 mid-to-late M dwarfs (masses 10-30% that of the Sun) that lie within 15 parsecs. We report systemic radial velocities, as well as measurements of rotational broadening and H-alpha equivalent widths. Our radial velocities provide the missing element to complement astrometric data and calculate true space motions. We find that 20% of our targets have vsini > 10 km/s. Using our multi-epoch spectroscopy we discovered a number of new spectroscopic binaries and characterized their orbits. We calculate a 22% multiplicity rate for the primaries in our sample and report that 6% of these 413 mid-to-late M dwarfs have M-dwarf, brown-dwarf, or white-dwarf companions at orbital periods of less than 3 years. Our survey has more than tripled the number of these stars with a complete set of high-resolution spectroscopy and trigonometric parallaxes.