ABUNDANCE DETERMINATION IN THE CP-STAR 21-CANUM-VENATICORUM BY MEANS OF SPECTRUM SYNTHESIS

An elemental abundance analysis of the marginal chemically peculiar st ar 21 CVn used coadded 0.85 nm mm-1 photographic spectrograms. Altoget her 15 spectrograms were coadded by means of crosscorrelation. T(eff) = 11 100 K and log g = 4.0 were derived from the comparison of observe d and theoretical profiles of Hgamma and Hdelta. Synthetic spectrum an d theoretical equivalent widths were computed for the Kurucz AT-LAS9 m odel labelled as 11 000, 4.0 and two helium-deficient models of the sa me effective temperature and surface gravity. With the microturbulent velocity set equal to zero, abundances of 14 out of 16 identified elem ents are normal, while He and Sc are deficient. The star is a cool ver sion of the helium-weak type.