STELLAR MODELS FOR VERY LOW-MASS MAIN-SEQUENCE STARS - THE ROLE OF MODEL ATMOSPHERES

We present very low-mass stellar models as computed using non-grey mod el atmospheres for selected assumptions about the stellar metallicitie s. The role of atmospheres is discussed and the models are compared wi th models based on the Eddington approximation, and with similar model s that have appeared in the recent literature. Theoretical predictions concerning both the HR diagram location and the mass-luminosity relat ion are presented and discussed in terms of expectations in selected p hotometric bands. Comparison with available observational data concern ing both galactic globular clusters and dwarfs in the solar neighbourh ood reveals a satisfactory agreement together with the existence of so me residual mismatches.