How to Constrain Your M Dwarf. II. The Mass–Luminosity–Metallicity Relation from 0.075 to 0.70 Solar Masse

Andrew W. Mann, Trent Dupuy, Adam L. Kraus, Eric Gaidos, Megan Ansdell, Michael Ireland, Aaron C. Rizzuto, Chao-Ling Hung, Jason Dittmann, Samuel Factor, Gregory Feiden, Raquel A. Martinez, Dary Ruiz-Rodriguez, Pa Chia Thao

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The 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 M K and M * spanning 0.075 M ⊙ < M * < 0.70 M ⊙. 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 K S magnitudes and system parallaxes, to calibrate the M K–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 M K–M * relation or underestimated uncertainties in the input parallaxes. We find that the effect of [Fe/H] on the M K–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).
Original languageEnglish
Article number63
Number of pages41
JournalAstrophysical Journal
Issue number1
Publication statusPublished - 22 Jan 2019


  • astro-ph.SR


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