ON SOME PROPERTIES OF VERY METAL-RICH STARS

An analysis of some properties of stellar models as a function of meta llicity Z (and helium content Y) is presented, with special attention to those stars with metallicities higher than twice or three times sol ar. It is shown that the stellar properties as a function of Z are mai nly determined by the effects of the opacities at subsolar metalliciti es, and by the effects of the mean molecular weight and stellar mass l oss at higher metallicities. As a result, very metal-rich stars (Z gre ater than or similar to 0.05) exhibit properties that deviate from wha t is expected from the known characteristics at lower metallicities. I n particular, they are more luminous and hotter than those at Z less t han or similar to 0.05 due to the effect of the mean molecular weight. They have main sequence lifetimes much shorter (60% shorter at Z = 0. 1 than at Z = 0.02) than those at solar metallicity due to their lower initial hydrogen content. Finally, the high mass loss rates at high m etallicities affect significantly the population synthesis of massive stars in very metal-rich regions. An analysis of expected Wolf-Rayet a nd supernovae populations in such conditions is briefly presented.