MASS AND AGE-DETERMINATION FOR 21-LAMBDA-BOOTIS-TYPE STARS

Newly published theoretical grids of stellar models are used to evalua te masses and ages of 21 stars with proven lambda Bootis characteristi cs. Basic input parameters as effective temperature and luminosity for each star are calculated from their uvby beta indices. Masses thus es timated are in the range of 1.6-2.7 solar masses, the evolutionary age s are between 10(7) and 10(9) years. In terms of stellar evolution, mo st of the studied lambda Bootis stars are in the middle of their main sequence evolution. Only a few of them are young enough to fulfill the requirements of the ''diffusion/accretion'' model. Masses and ages of the examined stars are compared with already published [Fe/H] data. I ron is less deficient in more massive lambda Bootis stars. There is no evidence for significant change in the chemical composition of consid ered lambda Bootis type stars during their evolution on the main seque nce.