Chemical composition of the s-Cepheids

The following results have been obtained: 1) all Cepheids (excluding only EU Tau) have solar-like abundances of {alpha}- and iron-group elements, 2) Na is over abundant for all program stars, 3) the carbon deficiency found for EU Tau, DT Cyg, V440 Per and nitrogen overabundance (DT Cyg), show that these s-Cepheids are not crossing the instability strip for first time, 4) s-process elements are slightly enhanced in the program stars, 5) V1162 Aql does not show any changes in C and N abundances.

The most plausible explanation is that this star is a normal Cepheid (C{delta}), but it is firstly crossing the instability strip toward the giant branch. This conclusion is also confirmed by its position on the evolutionary diagram.