Abondances anormales d'éléments dans les étoiles Ap

From the data in Babcock's catalogue of magnetic stars and the data compiled by Bertaud, the proportion of Ap stars showing striking overabundancies of Si, Cr, Mn, Sr and Eu is deduced in terms of the spectral type. However this correlation with the spectral class originates at least as much from variations of the visibility of the lines with temperature than from a real dependance of the abundance anomalies on the spectral type. The abundance factors in the Ap stars in regard to the normal ones increase in the average more or less exponentially with the atomic number or the atomic mass.