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Title: A Mass–Magnitude Relation for Low-mass Stars Based on Dynamical Measurements of Thousands of Binary Star Systems

Stellar mass is a fundamental parameter that is key to our understanding of stellar formation and evolution, as well as the characterization of nearby exoplanet companions. Historically, stellar masses have been derived from long-term observations of visual or spectroscopic binary star systems. While advances in high-resolution imaging have enabled observations of systems with shorter orbital periods, measurements of stellar masses remain challenging, and relatively few have been precisely measured. We present a new statistical approach to measuring masses for populations of stars. Using Gaia astrometry, we analyze the relative orbital motion of >3800 wide binary systems comprising low-mass stars to establish a mass–magnitude relation in the GaiaGRPband spanning the absolute magnitude range 14.5 >MGRP> 4.0, corresponding to a mass range of 0.08MM≲ 1.0M. This relation is directly applicable to >30 million stars in the Gaia catalog. Based on comparison to existing mass–magnitude relations calibrated forKsmagnitudes from the Two Micron All Sky Survey, we estimate that the internal precision of our mass estimates is ∼10%. We use this relation to estimate masses for a volume-limited sample of ∼18,200 stars within 50 pc of the Sun and the present-day field mass function for stars withM≲ 1.0M, which we find peaks at 0.16M. We investigate a volume-limited sample of wide binary systems with early-K dwarf primaries, complete for binary mass ratiosq> 0.2, and measure the distribution ofqat separations >100 au. We find that our distribution ofqis not uniform, rather decreasing towardq= 1.0.

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DOI PREFIX: 10.3847
Date Published:
Journal Name:
The Astronomical Journal
Medium: X Size: Article No. 164
["Article No. 164"]
Sponsoring Org:
National Science Foundation
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