The Solar Neighborhood LIV: 54 Orbits of M Dwarf Multiples within 30 Parsecs with Speckle Interferometry at SOAR

We present 1066 speckle measurements of M dwarf multiples observed over 2021-2024, all taken with HRCam on the Southern Astrophysical Research 4.1 m telescope. Among these, 900 observations resolve companions in 212 pairs, with separations spanning 17 milliarcseconds to 3.4 arcsec and brightness differences ranging from 0 to 4.9 magnitudes in the I filter. We have characterized the orbits of 54 of these companions, spanning periods of 0.67-30 yr, by combining our data with literature astrometry, radial velocities, and, in four cases, Hipparcos-Gaia accelerations. Among the orbits presented here are 28 that are the first-ever such characterizations for their systems, and 26 that revise previously-published orbits, thus providing a significant update to the observed dynamics of M dwarfs in the solar neighborhood. From these orbits, we provide new and updated dynamical total masses for these systems, precise to 0.7-7% in nearly all cases. Future mass derivations for components in these systems will contribute to efforts in refining the mass-luminosity relation for the smallest stars, and will enhance investigations of age, magnetism, and metallicity effects on luminosities at a given mass.