Evolutionary changes in the chemical composition of υSgr

An analysis is made of the chemical composition of the atmosphere of the bright component of the close binary system υ Sgr, which lost a hydrogen envelope as a result of mass transfer. Besides the deficit of hydrogen, an excess of helium, and changes in the abundances of carbon, nitrogen, and oxygen due to hydrogen burning into helium through the CNO cycle and partly of helium into carbon through the triple α process, excesses in the abundances of many other elements are found. The abundances of the elements from hydrogen to nickel are similar to those obtained for a number of other stars with extremely large helium excesses, although in the case of υ Sgr there are some differences due to its binary nature. For elements with Z > 30 there is a tendency for the excess to increase with increasing atomic number, similar to what is observed for Am stars