Mann, Andrew W.Dupuy, TrentKraus, A LGaidos, EricAnsdell, MeganIreland, MichaelRizzuto, Aaron C.Hung, Chao-LingDittmann, JasonFactor, SamuelFeiden, GregoryRuiz-Rodriguez, Dary2022-05-022022-05-020004-637Xhttp://hdl.handle.net/1885/264197The mass–luminosity relation for late-type stars has long been a critical tool for estimating stellar masses. However, there is growing need for both a higher-precision relation and a better understanding of systematic effects (e.g., metallicity). Here we present an empirical relationship between MKS and M* spanning 0.075 Me < M* < 0.70 Me. The relation is derived from 62 nearby binaries, whose orbits we determine using a combination of Keck/NIRC2 imaging, archival adaptive optics data, and literature astrometry. From their orbital parameters, we determine the total mass of each system, with a precision better than 1% in the best cases. We use these total masses, in combination with resolved KS magnitudes and system parallaxes, to calibrate the MKS–M* relation. The resulting posteriors can be used to determine masses of single stars with a precision of 2%–3%, which we confirm by testing the relation on stars with individual dynamical masses from the literature. The precision is limited by scatter around the best-fit relation beyond measured M* uncertainties, perhaps driven by intrinsic variation in the MKS–M* relation or underestimated uncertainties in the input parallaxes. We find that the effect of [Fe/H] on the MKS–M* relation is likely negligible for metallicities in the solar neighborhood (0.0% ± 2.2% change in mass per dex change in [Fe/H]). This weak effect is consistent with predictions from the Dartmouth Stellar Evolution Database, but inconsistent with those from MESA Isochrones and Stellar Tracks (at 5σ). A sample of binaries with a wider range of abundances will be required to discern the importance of metallicity in extreme populations (e.g., in the Galactic halo or thick disk).A.W.M. was supported through Hubble Fellowship grant 51364 awarded by the Space Telescope Science Institute, which is operated by the Association of Universities for Research in Astronomy, Inc., for NASA, under contract NAS 5-26555. T.J.D. acknowledges research support from Gemini Observatory. This work was supported by a NASA Keck PI Data Award (award nos. 1554237, 1544189, 1535910, and 1521162), administered by the NASA Exoplanet Science Instituteapplication/pdfen-AU© 2019. The American Astronomical Society.binaries: visualstars: late-typestars: low-massstars: luminosity functionmass function Supporting material: machine-readable tablesHow to Constrain Your M Dwarf. II. the Mass-Luminosity-Metallicity Relation from 0.075 to 0.70 Solar Masses201910.3847/1538-4357/aaf3bc2020-12-27