Presentation #204.03 in the session “Evolution of Stellar Multiples”.
M dwarf stars make up 75% of the solar neighborhood’s members, and it is now well known that 25-30% of these are in multiple-star systems. Diving deeper into this group, we are conducting a thorough census of the sizes and shapes of the orbits of M dwarfs in multi-star systems. With ~120 orbits observed through long-term astrometry, high-resolution imaging, and radial velocities, we are establishing their distributions of orbital period, eccentricity, semimajor axis, and mass ratios, each of which is a vital clue to the formation and dynamical evolution of these systems. The targets are all M dwarfs within 25 pc with orbital periods up to 30 years, and observations are primarily being conducted through (1) the RECONS astrometry program at the CTIO/SMARTS 0.9m telescope and (2) speckle interferometry with HRCam+SAM at SOAR, supplemented by (3) radial velocity and additional high-resolution imaging results available in the literature. Preliminary results indicate a paucity of circular orbits with periods >10 years, suggesting the M dwarf binaries do not form circular orbits, or dynamically evolve toward higher eccentricities after formation.