CM Draconis and YY Geminorum: Agreement between Theory and Observation

We present new evolutionary models which accurately reproduce the observed masses, radii, and luminosities of the eclipsing binary systems CM Draconis and YY Geminorum. Our calculations include new equation of state and atmosphere models appropriate for low-mass stars. The models yield not only an accurate determination of the age, the helium abundance, and the heavy element content of these objects, but also their absolute magnitude and their distance. The agreement between theory and observation assesses the validity of the present evolutionary models and the related mass-luminosity relation for M dwarfs, a cornerstone to derive accurate mass functions for low-mass stars from the observed luminosity functions.